cell biology - student notes 2017 · topic 1 – cell biology . 1 1.1 – introduction to cells...
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CELL BIOLOGY
TOPIC 1
1.1 – INTRODUCTION TO CELLS ............................................. 1 1.2 – ULTRASTRUCTURE OF CELLS ..................................... 10 1.3 – MEMBRANE STRUCTURE ............................................ 22 1.4 – MEMBRANE TRANSPORT ............................................ 28 1.5 – THE ORIGIN OF CELLS .................................................. 37 1.6 – CELL DIVISION ................................................................. 45 SAMPLE QUESTIONS ............................................................... 55
TOPIC 1 – CELL BIOLOGY
1
1.1 – INTRODUCTION TO CELLS
CELL THEORY •
•
• Evidence: • With the invention of _____________________
(Janssen) scientists could see cells (Hooke, Leeuwenhoek)
• _____________________________________ demonstrated that cells couldn’t grow in _____________________ conditions (disproved abiogenesis)
• _____________________ (structures within cells) and _____________________ cannot carry out all of the characteristics of other living things
• _____________________ _____________________ is _____________________ under a microscope
Looking for trends and discrepancies • Although most organisms conform to cell theory, there are
exceptions. Exceptions to the cell theory: 1 Striated muscle 2 Erythrocytes (red blood cells) 3 Giant algae 4 Aseptate fungal hyphae • Striated muscle:
- Skeletal muscle is composed of muscle fibres that are _____________________ than a single cell.
- The muscle fibres are _____________________, containing several hundred nuclei.
2
CELL THEORY
• Erythrocytes (red blood cells): - Once they have _____________________, they ______________________________. - This prevents them from carrying out many _____________________
_____________________ from this point of their life cycle.
• Giant algae: - The single cells of some large algae are _____________________, remaining in a
“_____________________”-like state. - They _________________________________ so that they can form
__________________________________________.
• Aseptate fungal hyphae: - Hyphae are long _____________________. - In aseptate or nonseptate hyphae, these threads have _____________________
_____________________, but the cells are ______________________________ by cell walls.
3
FUNCTIONS OF LIFE
• Unicellular organisms carry out all the functions of life:
- M _____________________ - R _____________________ - S ____________________________________ - C ____________________________________ - G _____________________ - R _____________________ - E _____________________ - N _____________________
• Unicellular organisms carry out all the functions of life:
- M _____________________ - R _____________________ - H _____________________ - G _____________________ - R _____________________ - E _____________________ - N _____________________
• More details… - M _______________________________________________________________ - R _______________________________________________________________ - H _______________________________________________________________ - G - R _______________________________________________________________ - E _______________________________________________________________ - N _______________________________________________________________
4
FUNCTIONS OF LIFE
Examples to learn: 1 Paramecium 2 Chlorella
• Paramecium:
- _____________________ organisms in the kingdom of _____________________
- Small but _____________________ with the naked eye (~_____________________)
- They are _____________________, meaning that they are surrounded by tiny _____________________ structures
- Cilia are used to _____________________ particles towards their _____________________________________
- Use _____________________ _____________________ to _____________________ to changing _____________________ in their environment
• Chlorella:
- _____________________ _____________________ - Spherical in shape, _____________________ in diameter - Come together in __________________________________
to form _____________________. - Contains _____________________,
allowing it to _____________________. - Photosynthesis provides the _____________________ and
_____________________ to __________________________________________. - It __________________________________________, producing _____________________ each
time.
5
CELL SIZE
Relative sizes: • Use your logic to put these in the correct order!
- Bacteria ________ - Cell membrane thickness ________ - Cells ________ - Molecules ________ - Organelles ________ - Virus ________
• Watch this: http://learn.genetics.utah.edu/content/cells/scale/ Magnification:
• Measurements need to be in the ________________________! 1mm = ________________ • Complete relevant practice Qs beginning on Page 55 Limitations: • Cells _______________________________________________________________. • They reach a _____________________ size and then they may _____________________. • If a cell becomes too large, it would develop _____________________. • These problems may include….? • The rate of _____________________ varies with a cell’s _____________________ • The rate of _____________________ _____________________ varies with a cell’s
_____________________ _____________________ • When a cell grows, _____________________ grows _____________________ than
_______________________________ and the cell must ____________________________
• Many cells contains structures to _____________________ the ratio of their surface area to their volume (_____________________) - eg. _____________________
6
BECOMING MULTICELLULAR
• Unicellular organisms are in the Kingdom Protoctista (_____________________) • They evolved _____________________ years ago. • They remained the dominant life form until 600 million years ago. • Unicellular organisms are able to carry out all of the typical cellular processes within their
single cell!
• Kingdom _____________________, _____________________ and _____________________ are all composed of _____________________ cells
• They are _____________________ organisms – made up of many cells together. • These cells _____________________ (_____________________) so that all energy in the cell is not
taken up by performing all cellular functions. • These cells group into _____________________, _____________________ and
_____________________ making us far more _____________________ than a single bacterial cell. Cell differentiation: • Differentiation:
• Cells in multicellular organisms share the same genetic info (cf. cell division, reproduction, formation of blastocyst)
• What is different between cells is _____________________ _____________________ • _____________________ _____________________ lead to _____________________ gene expression
and thus _____________________ of cells Emergent properties: • The _____________________ of _____________________ _____________________ can give rise to
emergent properties in _____________________ organisms • Means that the _____________________ _____________________ is _____________________ than
the _____________________ of _____________________: - because of the _________________________________________________________ - because of the _________________________________________________________
7
STEM CELLS • Stem cells _____________________ the _____________________ to _____________________ • They are _____________________ • They have the _____________________ to differentiate
along _____________________ _____________________ Therapeutic use of stem cells: • Stem cells have the potential for _____________________ _____________________ and can
theoretically treat a variety of _____________________ conditions
• In 1968, doctors performed the first successful bone marrow transplant. • Bone marrow contains _____________________ stem cells. It is transplanted routinely to treat a
variety of blood and bone marrow diseases, blood cancers, and immune disorders. • More recently, __________________________________________ stem cells (from the blood
stream) and __________________________________________ stem cells have been used to treat some of the same blood-based diseases.
Examples to learn: 1 Stargardt’s disease 2 *one other*
• Stargardt’s disease
- a _____________________ eye disorder - it is a type of _____________________ _____________________ affecting the
_____________________ at the back of the eye
- causes _____________________ loss of ____________________________________ in both eyes - recent stem cell research has involved using _____________________
_____________________ _____________________ (RPE) - can use _____________________ stem cells to generate RPE - first human therapeutic trials were conducted in _____________________, improving vision
in the patients receiving the treatment - Australian researchers are now focusing on the use of _____________________ for the
treatment of similar disorders - Read this: http://www.newscientist.com/article/dn26381-stem-cells-improve-vision-
enough-for-horse-riding.html#.VJpIvAAA
8
STEM CELLS
• Parkinson’s Disease, MS, strokes - all involve loss of _____________________ or other cells in the _____________________
_____________________ - could potentially use stem cells to _____________________ them
• Leukaemia
- a cancer of _____________________ blood cells or _____________________ - __________________________ is normally used to kill the abnormal cells; however, a
___________________________________________________________ is needed if it doesn't work.
1 The patient's existing bone marrow and abnormal leukocytes are first _____________________ using chemotherapy and _____________________.
2 A sample of _____________________ bone marrow containing _____________________, _____________________ stem cells is _____________________ into the patient's bloodstream.
3 If the transplant is successful, the stem cells will _____________________ into the patient's bone marrow and begin _____________________ new, healthy leukocytes to replace the abnormal cells.
• Burn treatment - _____________________ _____________________ can be used to _____________________
_____________________ in burns victims - Use the _____________________ from the required cell to generate new cells with the
______________________________________________________________ – eg. skin cells - See Topic 3.5 for detailed process
9
STEM CELLS
• Stem cell research has depended on the work of teams of scientists
in many countries who share results thereby speeding up the rate of progress.
• However, national governments are influenced by local, cultural and religious traditions that impact on the work of scientists and the use of stem cells in therapy.
Ethics of stem cell use: • There is _____________________ _____________________ in the therapeutic use of these cells. • The _____________________ of these cells is ___________________________________ to
_____________________, reducing some of the associated ethical concerns – eg. _____________________ SC, _________________________ SC, ______________.
• Some religious groups _____________________ SC research if embryos are not involved. • Some groups still oppose SC research, _____________________ of where the SC are sourced
from, as it goes against the laws of _____________________. • Complete relevant practice Qs beginning on Page 57
10
1.2 – ULTRASTRUCTURE OF CELLS
PROKARYOTIC CELLS What differences can you see?
• •
• • •
•
• •
•
11
PROKARYOTIC CELLS
• Prokaryotic cells were the first to _____________________ • Perform all functions of life
- Remember: MR H GREN? M ___________________ R ____________________ H ____________________ G ___________________ R____________________ E ____________________ N____________________
• They have _____________________ • They have _______________________________________________________________
- ie. no ____________________________
• Prokaryotic cells _________________ by _________________ _________________ • Basically, one cell splits into two! • __________________________________ and attaches to cell membrane • __________________________________ pulls DNA loops apart (_________________) • __________________________________ between loops separates cell into two.
12
PROKARYOTIC CELLS
13
PROKARYOTIC CELLS
Cell wall _________________ the cell and _________________ the cell from _________________ or _________________ if internal pressure is high
Cell membrane __________________________________ barrier that controls the __________________________________________ of substances into and out of the cell
Cytoplasm _____________________ component which _____________________ _____________________ needed for ____________________________________; also contains the _____________________ _____________________
Nucleoid Region of the cytoplasm which _____________________ the _____________________; DNA is “_____________________” (without proteins)
Plasmid Additional _____________________; can exist and _____________________ _____________________ & can be transmitted between cells
Ribosome _____________________ _____________________ (prokaryotic ribosomes _____________________ than eukaryotic - ______)
Slime Capsule Protects against _________________ (drying out) and _________________
Flagella (sing. flagellum )
Long, slender projection which spins like a _________________, enabling _________________
Pili (sing. pilus)
_____________________ extensions which can serve for _________________ or _________________.
Attachment pili: Shorter in length, allow _________________ to other bacteria or surfaces
Communication pili: Longer in length, allow for the _________________________________________________
• Play these games & quizzes to review these terms: http://www.sheppardsoftware.com/health/anatomy/cell/index.htm
14
EUKARYOTIC CELLS
• eg. animal cells, plant cells, protist cells, fungi cells
• Eukaryotic cells have a _________________ and other _____________________________
_________________ • Each organelle performs a _________________ _________________ for the cell • Eukaryotic cells divide by either:
- _________________ (most _________________ cells) - _________________ (forms _________________ only)
Animal cells:
15
EUKARYOTIC CELLS
Example to learn: Electron micrograph (EM) of exocrine gland cells of the pancreas
16
EUKARYOTIC CELLS
Animal cells:
Cell Membrane Semi-permeable barrier that controls the entry and exit of substances; ____________________________________________________________________
Cytosol The fluid portion of the cytoplasm (does not include the organelles or other insoluble materials)
Nucleus Contains _________________ and controls cell activities and division; surrounded by _________________ _________________ (a double membrane)
Nucleolus Site of the production and assembly of _________________ _________________
within the nucleus
Ribosome Protein synthesis (eukaryotic ribosomes _________________ than prokaryotic - _______)
Mitochondria Site of _________________ _________________ _________________
Golgi Apparatus _________________ and _________________ _________________ involved in the sorting, storing and modification of _________________ _________________
Lysosome Site of _________________ / digestion / breakdown of macromolecules
Endoplasmic Reticulum
A system of _________________ involved in the _________________ of materials _________________ _________________:
_________________ ER: _________________ with _________________ and involved in the _________________ and _________________ of _________________ destined for secretion
_________________ ER: Involved in the synthesis and transport of _________________
• Play these games & quizzes to review these terms:
http://www.sheppardsoftware.com/health/anatomy/cell/index.htm
17
EUKARYOTIC CELLS
Plant cells:
Example to learn: Electron micrograph of a palisade mesophyll plant cell
18
EUKARYOTIC CELLS
Plant cells:
Cell wall
A structure _________________ the plasma membrane composed of _________________ that _________________ _____________________________, _________________ excessive _________________ uptake and holds the whole plant up against the force of _________________.
Vacuole A large, permanent structure surrounded by a _________________ that _________________ compounds, helps in plant growth, and plays a role in maintaining the _________________ of the cell.
Chloroplasts Specialised organelles containing _________________, a light sensitive pigment. This enables ________________________ to occur.
• Play these games & quizzes to review these terms: http://www.sheppardsoftware.com/health/anatomy/cell/index.htm
19
CELL COMPARISON
What are the similarities and differences between prokaryotic and eukaryotic cells?
Feature Similarities Differences
Prokaryotes Eukaryotes
Genetic material
Protein synthesis
----
Respiration
Ultrastructure
Reproduction
----
Size
----
20
CELL COMPARISON
What are the differences between plant and animal cells?
Feature Plant Animal
Cell wall
Chloroplasts
Vacuole
Reserve food
Centrioles
Shape
Cholesterol in membrane
21
MICROSCOPES
Developments in scientific research follow improvements in apparatus • The invention of electron microscopes led to greater understanding
of cell structure.
• Microscopes were invented simultaneously in different parts of the
world at a time when information travelled slowly. • Modern-day communications have allowed for improvements in
the ability to collaborate, enriching scientific endeavour. • Zacharias _________________ produced the first microscope in __________.
• Anton ______________________ was the first man to make and use a real microscope in _______. He was the first to see and describe specimens like bacteria and yeast plants.
• The first ______________________ lens was developed in ______ by Hans Busch.
• The first electron microscope prototype was built in ______ by Ruska and Knoll.
• _________________ microscopes have a _________________ _________________ than _________________ microscopes.
• Resolution is the _________________ _________________ that can be distinguished between two points.
• Light microscopes are limited to _________________, while electron microscopes can magnify an object up to _________________.
• Light microscopes show us the _________________ of a cell, while electron microscopes can show us the _________________________ – ie. the parts within the parts!
• Electron microscopes can see specimens that are ___________ in dimension – eg. viruses.
• Complete relevant practice Qs beginning on Page 59
c
22
1.3 – MEMBRANE STRUCTURE
PHOSPHOLIPIDS • Phospho – contains _____________________ • Lipid – contains _____________________
• Also contains _____________________,
which is a _____________________ • Phospholipids have a head and 2 tails
- Head: Ø made from phosphate Ø _____________________ = charged Ø _____________________ = water-loving
- Tails: Ø made from __________________________________________ Ø _____________________ = uncharged Ø _____________________ = water-hating
• These are referred to as the _____________________ _____________________ of phospholipids. • These properties control how the phospholipids are able to _____________________ themselves
in the membrane.
• Phospholipids arrange in a _____________________ • Hydrophobic tail regions face _____________________ • The ______ hydrophilic head regions _____________________ with the _____________________
(cytoplasm) and _____________________ (outside) environments respectively
23
THE FLUID MOSAIC MODEL
Use your space well (⅓–½ page); Use clear, strong lines; Use straight label lines; Make sure lines touch the labelled structure;
No shading or colouring; Use a scale bar if appropriate
• Watch this: http://youtu.be/w9VBHGNoFrY
24
MEMBRANE FLUIDITY & CHOLESTEROL
• Phospholipids are held together by _____________________ _____________________ (weak associations)
• Hydrophilic / hydrophobic layers _____________________ entry and exit of substances • Phospholipids allow for membrane _____________________ / _____________________ (important
for _____________________) • Fluidity allows for the _____________________ / _____________________ of membranes
(exocytosis / endocytosis) • _____________________ is present in
_____________________ cell membranes. • The interactions between it and the phospholipids make
the membrane _____________________ and more rigid. • This makes the membrane ______________
_____________________ to water-soluble molecules. • Cholesterol in the blood has also been associated with
_____________________ disease.
25
MEMBRANE PROTEINS
• Proteins are also found in the membrane.
• _____________________ proteins – are _____________________ in the membrane
• _____________________ proteins – _____________________ to the surface
• Some peripheral proteins are _____________________
• Glycoproteins – have a __________________________________________ attached to them to serve a _____________________ purpose
• eg. TRACIE
• T_________________: Protein _________________ and protein _________________
(eg. Na+/K+ Pump)
• R_________________: Peptide-based _________________ (eg. insulin, glucagon, etc.)
• A_________________: _________________ attachments and __________________________________
• C_________________ _________________: MHC proteins and _________________ used in the immune system
• I_________________ _________________: Tight junctions and _________________________________ in plant cells
• E_________________ _________________: Metabolic pathways (eg. _________________ _________________ _________________ in _________________ _________________)
26
MEMBRANE MODELS
Using models as representations of the real world • eg. James Watson & Francis Crick are credited with discovering the
structure of DNA by piecing together the research from a number of scientists. They made a model to help them achieve this.
• There are a number of different models of membrane structure.
• Hugh _____________________ and James _____________________ proposed a model of the
plasma membrane in _____________________ • Their model suggest that a phospholipid bilayer existed, but that it lay _____________________
two layers of _____________________ – like a _____________________ • The proteins in their model were _____________________________ in the membrane. • The _____________________ would have allowed
the movement of substances whilst still maintaining an effective barrier to others.
27
MEMBRANE MODELS
• The Davson-Danielli model predominated until _____________. • It was supported by evidence from _____________________
_____________________. • The membranes in these images appeared as two dark lines
with a light line between them. • As proteins appear dark, and phospholipids appear light –
the micrographs supported their model.
Falsification of theories with one theory being superseded by another • Evidence falsified the Davson-Danielli model.
• A new technique called __________________________________________ or freeze-
_____________________ was developed. • This technique allowed _____________________ in cell structures to be developed. • It highlighted __________________________________________ in the _____________________ of the
membrane. • The line of weakness was _____________________, indicating structures _____________________
within the layer. • A new model needed to be developed to _____________________ the trans-membrane proteins.
• New discoveries were also made regarding the _____________________ of proteins found in the
membrane. • Different organisms use _____________________ proteins to transport different
_____________________ across their membranes. • All membranes are therefore __________________________________________, as suggested by
the Davson-Danielli model. • The fluid mosaic model was described by _____________________ and
_____________________ in _________. • Complete relevant practice Qs beginning on Page 61
28
1.4 – MEMBRANE TRANSPORT
PERMEABILITY • The phospholipid bilayer is _____________________ _____________________. • This means that it _____________________ the entry and exit of molecules into and out of the
cell.
• Movement will depend on: - _____________________ - _____________________
• Remember that the polar (charged) _____________________ of the phospholipids will
_____________________ other polar molecules – eg. _____________________. • The non-polar _____________________ will _____________________ this movement, therefore it is
sometimes necessary to use a ________________ _____________________ or _____________________ to help move a substance across the membrane.
29
TYPES OF TRANSPORT
PASSIVE TRANSPORT
• Movement can take the form of:
- _____________________ transport:
Ø _____________________ _____________________ – inc. _________________
Ø _____________________ _____________________
- _____________________ transport
Ø _____________________ _____________________
Ø _____________________ _____________________ – inc. __________________________________________
• _______________________________________________________________
• Movement of substances is _____________________ the _____________________ _____________________ (_____________________)
• 2 types of passive transport:
- Simple diffusion (inc. osmosis)
- Facilitated diffusion
Simple diffusion: • The _____________________ net movement of particles from a region of ______________
concentration to a region of _____________ concentration, _____________________ a _____________________ _____________________, _____________________ a ______________________________ _____________________
• Concentration gradient = term given to the _____________________ in concentration between two regions
30
PASSIVE TRANSPORT
• The _____________________ of diffusion through a semi-permeable membrane can be affected by:
- _____________________ _____________________ (as shown above)
- _____________________ _____________________
- _____________________ of the _____________________ _____________________
Osmosis:
• The diffusion of _____________________
• The passive net movement of water molecules from a region of ___________________________ concentration to a region of ___________________________ concentration , _____________________ the gradient, across a semi-permeable membrane
• _____________________ also exist:
- _____________________ _____________________
- designed to _____________________ the movement of water molecules
- can be found in the _________________ within the human _________________
31
PASSIVE TRANSPORT
• Osmotic control: - To _____________________ _____________________ in the cells of tissues and organs
destined for use in _____________________ _____________________, they must be _____________________ in a solution that is the _____________________ _____________________ as the _____________________.
- ie. an _____________________ saline solution
- Examples of use:
Ø Saline _____________________ to rehydrate a patient
Ø Used to _____________________ wounds
Ø Used to keep skin _____________________ before applying skin grafts
Ø Eye drops
Ø _____________________ donor organs for transportation
Facilitated diffusion: • Simple diffusion:
- _____________________, _____________________ molecules can _____________________ diffuse across the membrane
- eg. __________________________________________, glycerol
• Facilitated diffusion: - _____________________, _____________________ substances
__________________________________________ diffuse
- Require the _____________________ _____________________ to facilitate their movement
- eg. _____________________, sucrose, _____________________
32
PASSIVE TRANSPORT
ACTIVE TRANSPORT
Example to learn: Potassium channels in axons
• Channels exist along the _____________________ of _____________________ to allow __________ movement in/out of the cell.
• _____________________ channels in the axon are __________________________________________.
• They _____________________ the movement of ___________________________ – the channels therefore show _____________________.
• The opening of K+ channels during the _____________________ of a _____________________ _____________________ al lows _____________________ the neuron, _____________________ the cell and _____________________ the _____________________ _____________________ within the neuron.
• _______________________________________________________________
• Movement of substances is _____________________ the concentration gradient (_____________________)
• Will only occur in the _____________________ of _____________________
• eg:
- _____________________
- _____________________ _____________________
33
ACTIVE TRANSPORT
Protein pumps: • They use the energy from the _____________________ of ATP to ____________________ the
molecules _____________________ the gradient
• The _____________________ of ATP to ADP causes a the protein pump to _________________________________, resulting in the forced movement of the substance
• Protein pumps are _____________________ for a given molecule
Example to learn: sodium-potassium pumps in axons
• Cycle through a series of _____________________
• Results in _____________________ and _____________________ molecules being “_____________________” for one another
• This swap is _____________________ – _____________________ exchanged for every _____________________
• These pumps are used in the axons of neurons.
• They are used to _____________________ the _____________________ in the neuron and _____________________ _____________________ _____________________.
• Each cycle uses _____________________.
• Watch this: http://www.northland.cc.mn.us/biology/biology1111/animations/transport1.swf
34
ACTIVE TRANSPORT
Vesicular transport: • Proteins _____________________ for ________________
are directed to the _____________________ _____________________
• The protein is transferred to the _____________________ _____________________ via a _____________________, which forms from the _____________________ of the membrane
• The protein moves via vesicles from one side of the golgi to the other and may be _____________________ along the way (eg. glycosylated, truncated, etc.)
• The protein is transferred via a vesicle to the plasma membrane, whereby it is either immediately released or stored for a delayed release
• Vesicular transport is possible b/c:
- Membrane has some _____________________
- Small amounts can be _____________________ or _____________________ without tearing the membrane (endo- & exo- cytosis)
- Membranes of _______________________________ are the same
• Exocytosis: - _____________________ produces proteins
intended for _____________________
- Golgi apparatus _____________________ substances for exocytosis
- Transport vesicle formed from a __________________ of _____________________ from the _________________________________________
- This membrane then _____________________ the _____________________ membrane
- Exocytosis ________________________________!
35
ACTIVE TRANSPORT
• Endocytosis: - Transport vesicle formed from a section of the cell
membrane
- This process ______________________ ____________________ too!
- Used to take up substances that are __________________________ and/or ______________________________ and cant enter on their own
- Requires recognition of the substance by a _____________________ _____________________ _____________________
- Two types of endocytosis:
Ø _____________________
§ when the substance is fluid
§ “_______________________________”
Ø _____________________
§ when the substance is solid
§ “_______________________________”
36
TYPES OF TRANSPORT
Summary:
ATP required Concentration gradient
Diffusion
Facilitated diffusion
Osmosis
Active transport with protein pumps
Endocytosis
Experimental design • Accurate quantitative measurement in osmosis experiments are
essential.
• Practical 2: estimation of osmolarity by bathing potato tissue samples in hypotonic and hypertonic solutions.
• Read this: http://www.nuffieldfoundation.org/print/3132
• Complete relevant practice Qs beginning on Page 62
37
1.5 – THE ORIGIN OF CELLS
PASTEUR’S EXPERIMENTS • Review any of the following animations to help you understand these experiments and the
conclusions made as a result: - http://bcs.whfreeman.com/thelifewire/content/chp03/0302003.html - https://www.youtube.com/watch?v=4zLY_B_2d8w - http://www.sumanasinc.com/webcontent/animations/content/scientificmethod.html
• Aim: to see if _____________________ would _____________________ _____________________ in a _____________________ _____________________ _____________________
• Method: - Experiment 1: one flask _____________________ to the air; one flask
_____________________ - Experiment 2: both flasks sealed
• Results:
- Experiment 1:
- Experiment 2: • Conclusion:
• However….It has to have been able to occur at least once! “There is an unbroken chain of life from the first cells on Earth to all cells in organisms alive today.”
38
FORMATION OF CELLS Cells can only be formed by division of pre-existing cells:
• Cells _____________________ through division
• _____________________ results in genetically _____________________ daughter cells
• _____________________ generates _____________________ (sex cells)
• Further evidence to support this statement:
- Cells are very _____________________
- All examples of _____________________ are the result of ______________________
- The genetic code controlling all cell functions is _____________________
- It consists of 64 codons that signal the use of the ______________________________ _____________________, regardless of the organism
The first cells must have arisen from _____________________ materials.
• There are _____________________ that were needed for the _____________________ _____________________ of life on Earth:
1 non-living synthesis of __________________________________________________
2 assembly of _________________molecules into _________________
3 origin of _________________________________________________ that made _________________ possible
4 packaging of these molecules into _________________
1 Non-living synthesis of simple organic molecules
- The source of the molecules had to be _________________.
- Early Earth had to have all of the _________________ and compounds required.
- _________________ – somehow able to _________________ themselves to make _________________ _________________ _________________.
- Could have come from another source – eg. _________________________________!
39
FORMATION OF CELLS
2 Assembly of simple organic molecules into polymers
- There was __________________________________ in the atmosphere at the time, making _________________ _________________.
- Resulted in a ‘__________________________________’, which would have made __________________________________________________________________________________.
- _________________ – somehow able to _________________ themselves to make _________________ _________________.
- They are thought to have been formed on _________________, _________________ surfaces.
3 Origin of self-replicating molecules allowing inheritance
- ___________________________________________________. It needs _________________ _________________ (formed from it’s own instructions!).
- Some _________________ can self-replicate.
- Utilised _________________ _________________ _________________.
- These RNA molecules are called _________________ and incorporate both the features required of life:
Ø ___________________________________________________
Ø the ability to _________________________________________
4 Packaging of self-replicating molecules into membranes
- Creates a _________________ with a _________________ _________________ _________________ from the _________________ _________________.
- Closed membrane vesicles (_________________ or _________________) can form _________________ from _________________.
- _________________ – somehow formed a “lipid-loop” around the _________________.
- This is thought to have happened ~_________________ years ago.
40
FORMATION OF CELLS
41
THE MILLER-UREY EXPERIMENT
• In 1953, Stanley Miller and Harold Urey worked on trying to confirm some of these ideas regarding _____________________ Earth.
• Set up an _____________________ to _____________________ conditions of early Earth.
• The atmosphere on Earth at this time probably contained a variety of _____________________ molecules:
- Hydrogen
- Nitrogen
- Water vapour
- Methane
- Ammonia
• __________________________ until after _____________________ formed and started _________________________________.
• The conditions on pre-biotic Earth at this time included: - A _________________ _________________ (resulting from the lack of ___________) - _________________ _________________ _________________ - _________________ _________________ (due to __________________________________) - _________________ _________________ _________________ (no _________________ so was
extreme) - _________________ _________________ - _________________ _________________
• Miller and Urey recreated the conditions of pre-biotic Earth in a closed system:
– High temperatures/volcanic activity – a flask of _________________ was _________________ to generate _________________ _________________
– Reducing atmosphere –a _________________ of _________________, _________________ and _________________ was introduced
– Electrical storms – _________________ _________________ were used to simulate lightning
• The mixture was then allowed to _________________.
42
THE MILLER-UREY EXPERIMENT
• After one week, they found some _______________________________________________ in the mixture (_________________ essential AAcs) and ______ of the ________________ present were now in _________________ _________________.
• Based on these findings, it was concluded that
43
THE ENDOSYMBIOTIC THEORY • The oldest fossils of eukaryotic cells have been found to be _________________ years old. • The endosymbiotic theory from Lyn Margulis (_________________) tries to explain the
_________________ of _________________.
• Endosymbiosis:
• ______________________________________________ from this - the cells can no longer live separately from each other
• The theory stipulates that chloroplasts and mitochondria were once ___________________ ____________________: - Mitochondria à _________________ bacteria - Chloroplasts à _________________________ bacteria
• These cells were _________________ by larger _________________ (_________________).
• The nucleus could have developed from _________________ of the plasma membrane around the _________________ _________________.
• The nuclear envelope surrounding the nucleus has a _________________ _________________.
44
THE ENDOSYMBIOTIC THEORY
• Evidence to support the theory includes: - Both mitochondria and chloroplasts _________________________________________
(_________________ and _________________ like bacterial DNA). - They have a _________________ _________________ (own of their own and one from being
engulfed). - They have __________________________________. - They are the _________________________ as bacterial cells. - They can _______________________________________ in a process similar to binary fission. - Chloroplasts are similar in structure to ________________________.
• The four eukaryotic kingdoms are: - _________________ - _________________ - _________________ - _________________
• Eukaryotic cells have some _________________ over prokaryotic cells so the early eukaryotes
_________________ and _________________ • Hence the wide _________________ of species we know today!
• Complete relevant practice Qs beginning on Page 63
45
1.6 – CELL DIVISION
CELL DIVISION
CELL CYCLE
• All cells come from _____________________ cells
• Cells undergo division in order for an organism to _____________________, _____________________ and ________________________________________________
• Cell division must be _____________________ _____________________ by the mechanisms of the cell cycle
• _____________________ form from _____________________ cell division
• Mitosis occurs whenever new cells are required.
• Remember: GATE • Mitosis is used for:
- G_____________________
- A_____________________ _____________________
- T_____________________ _____________________ and
- E_____________________ _____________________
• The cell cycle is a series of _____________________ through which all cells must pass in order to _____________________.
• • Two main stages: - __________________________________
Ø Includes G1, S and G2 stages - __________________________________
Ø Includes stages of _________________
• Cells undergo division in order for an organism to _____________________, _____________________ and ________________________________________________
• Cell division must be _____________________ _____________________ by the mechanisms
46
CELL CYCLE
1 Interphase: • Occurs _________________ _________________ _________________ • Includes 3 distinct stages, whereby:
- the cell _________________ and _________________ (_________), - _________________ its _________________ (_________) and - _________________ for division (_________)
• Cell can _________________ the cell cycle and enter the _________ phase – a _________________ phase
2 M phase: • The periods of _________________ _________________ (_________________) and _________________
_________________ (_________________) • The division of the nucleus creates _____________________________________________
__________________________________
47
CELL CYCLE
• The _________________ of the cell cycle depends on the particular cell. • For example:
- bacterial cells can divide every _________________ under suitable conditions - skin cells divide every _________________ on average - liver cells every _________________ - muscle cells _________________ divide at all after maturing, so remain in the growth
phase for decades Cyclins: • The _________________ though the cell cycle depends on the _________________ of a family of
_________________ called _________________.
• Cells can’t _________________ to the next phase of the cell cycle until a _________________
_________________ reaches a _________________ _________________ • These cyclins _________________ a _________________ of _________________ that ultimately
_________________ a _________________ _________________ in the cell cycle.
48
CELL CYCLE
Serendipity and scientific discoveries • The discovery of cyclin was accidental.
• ________________________ was researching protein synthesis and fertilisation in spawning
_________________ eggs when he discovered cyclin in _________________. • Read these:
- http://www.sciencedirect.com/science/article/pii/S009286740800888X - http://www.nobelprize.org/nobel_prizes/medicine/laureates/2001/presentation-
speech.html Interphase: • Before mitosis, _________________ occurs. • Interphase contains _________________ _________________ to ensure division is viable:
- G1: the cell _________________, _________________ _________________, _________________ _________________ and produces _________________
- S: _________________ is _________________ - G2: the copied DNA is _________________ for fidelity (_________________) and final
metabolic reactions occur • Interphase is an _________________ _________________ in the life of a cell
• Remember: PAID
- P_________________ _________________ (transcription/translation) - A_________________ _________________ (ATP formation) - I_________________ _________________ (mitochondria/chloroplast) - D_________________ _________________ (in S phase)
49
CELL CYCLE
Prophase: • DNA _________________ (chromatin → _________________) • _________________ _________________ _________________ • _________________ move to opposite poles • Centrioles start making _________________ _________________
• Supercoiling:
- Chromosomes within the nucleus _________________ by _________________
- Human cells are _________________ in diameter - Human chromosomes are _____________________
in length - Supercoiling allows the chromosomes to be
_________________ _________________ during division
Metaphase: • Spindle fibres connect to _________________ of each chromosome • Chromosomes _________________ _________________ along _________________
• Anaphase: • Spindle fibres _________________ • Causes _________________ _________________ chromosomes to _________________ into
_________________ _________________ single chromatid chromosomes • Chromosomes move to _________________ _________________
Telophase + Cytokinesis: • _________________ _________________ (chromosome → _________________) • _________________ _________________ _________________ • _________________ _________________ _________________ around chromatin • The _________________ of the cell into ________ _________________ _________________
(cytokinesis) occurs concurrently with telophase
50
CELL CYCLE
• Cytokinesis is the _________________ of the _________________, and therefore the cell itself. • Cytokinesis is very _________________ in plant and animal cells. • This is due to the _________________ of the __________________________. • Animal cells:
- _________________ _________________ (___________________________) inside the plasma membrane pull the membrane in at the _________________
- This produces a _________________ _________________. - When this furrow reaches the centre of the cells, they are able to separate.
• Plant cells: - _________________ _________________ are transported in _________________ to the centre
of the cell during telophase. - This forms the _________________, which eventually connects with the existing cell’s
membrane. - The components of the vesicles are _________________ into the _________________
between the cells, _________________ them together. - Both daughter cells _________________ _________________ to build their walls
51
MITOSIS SKILLS • You are required to _________________ the _________________ of mitosis in cells viewed:
- with a _________________ - in a _________________
• You are also required to _________________ the _________________________________ from a
micrograph:
• Online activity: Follow the instructions and complete the table provided.
http://www.biology.arizona.edu/cell_bio/activities/cell_cycle/cell_cycle.html
• Practical activity: Calculate the mitotic index of fixed onion root tips viewed at 1000x magnification under a light microscope.
52
TUMOURS
• Tumours (cancers) are the result of _________________ cell division. • These can occur in any organ or tissue.
• The cell cycle is controlled by a _________________ control system
- proteins from _________________ _________________ _________________ _________________ cell division
- proteins from __________________________________ _________________ cell division • _________________ to these genes result in uncontrolled cell division, resulting in the formation
of a tumour
Mutagens: • agents that _________________ _________________ _________________ • not all mutations cause cancer, but they all have the _________________ to cause cancer • There are different types of mutagens:
- _________________ mutagens (_________________________) – eg. _________________ linked to lung cancer incidence
- _________________ – eg. _______ radiation linked to skin cancer incidence - _________________ – eg. ________ linked to _________________ cancer incidence
Oncogenes: • genes that _________________ the cell cycle and cell division • mutations in these genes result in uncontrolled cell division • this leads to _________________ _________________ • eg. _________________ oncogenes could cause cells destined for _________________
__________________________ (_________________) to _________________ and _________________
53
TUMOURS
Types of tumours: • _________________ tumours:
- result from _________________ mutations in the _____________________ (very low probability)
- they are _________________ after the _________________ where the abnormal growth first occurred
• _________________ tumours: - result from cancerous cells _________________ other tissues
• _________________:
- name given to the _________________ of cells ______________________________ tumour
• Biologists in laboratories throughout the world are researching into the causes and treatments of cancer.
• For example, the correlation between smoking and the incidence of lung cancer.
Smoking and cancer: • Smoking is linked to a _________________ _________________ of _________________ cancer, as
well as _________________ than _________________ incidences of _________________ and _________________ cancers.
• Other cancers are also more common in smokers: - eg. _________________ cancer
_________________ cancer _________________ cancer
54
TUMOURS
• Discuss the relationship shown here. • What type of correlation is shown? • Is it a strong correlation? • Remember that _________________ is not _________________! • Just because there is a lot of evidence, one can never be _________________ certain that
smoking was the __________________________________ of the cancer observed. • There is a _________________ _________________ _________________ seen in first few decades.
As one _________________, _________________________________________. • However, the correlation is _________________. There is an ________________________ between
the factors here.
• Lung cancer rates in males are actually _________________. • They are _________________ in females.
• Complete relevant practice Qs beginning on Page 64
55
SAMPLE QUESTIONS
INTRODUCTION TO CELLS Cell sizes: Q1 Use the MIA formula triangle to
calculate the magnification of the paramecium shown in this image:
Q2 Use the MIA formula triangle to
calculate the magnification of the Chlorella shown in this image:
56
INTRODUCTION TO CELLS
Q3 Could this organism have been viewed under a light microscope? Q4 Use the scale bar provided to
determine the size of this red blood cell. Then calculate the magnification of this image. HINT: use equivalent fractions first, and then the formula triangle
Q5 A red blood cell is 8μm in diameter. If drawn 100 times larger than its actual size, what diameter will the drawing be in mm?
Q6 If a mitochondrion has a length of 5µm and a student’s drawing of the mitochondrion is 10mm, what is the magnification of the drawing?
Q7 If a Sequoia sempervirens tree is 100m tall and a drawing of it is 100mm tall, what is the
magnification of the drawing?
57
INTRODUCTION TO CELLS
Q8 Which functions of life are carried out by all unicellular organisms?
A. Response, homeostasis, growth and photosynthesis B. Metabolism, ventilation, reproduction and nutrition C. Response, homeostasis, metabolism and growth D. Reproduction, ventilation, response and nutrition
Q9 A botanist measures a leaf and finds it is 24 cm long and 8 cm wide. His drawing of the leaf is 4 cm wide. Which was the magnification and length of his drawing, assuming that the proportions of the drawing were correct?
Scale Length / cm
A. x2 48
B. x2 12
C. x0.5 48
D. x0.5 12 Q10
a. Outline the cell theory. [2]
58
INTRODUCTION TO CELLS
b. Calculate the
magnification of the E. coli shown in the electron micrograph. [1]
59
ULTRASTRUCTURE OF CELLS Q1 The diagram to the right shows a bacterium.
What structure does the part labelled X identify? _________________
Q2 Escherichia coli is a unicellular organism,
so each cell must carry out all of the processes required for life. Outline the functions of each of the structures in the cells of Escherichia coli.
[8 marks]
60
ULTRASTRUCTURE OF CELLS
Q3 Label this hepatocyte:
1 2
3 4
5 6
7 8
9 10
11 12
13 14
15 16
61
MEMBRANE STRUCTURE
Q1 Draw a labelled diagram to show the fluid mosaic structure of a plasma membrane,
indicating the hydrophilic and hydrophobic regions. [5 marks]
62
MEMBRANE TRANSPORT
Q1 What do diffusion and osmosis have in common? [2 marks] Q2 Describe the movement of water across membranes. [2 marks] Q3 Distinguish between active and passive movements of materials across plasma membranes,
using named examples. Hint: Use a table! [5 marks]
63
THE ORIGIN OF CELLS
Q1 The spontaneous origin of life on Earth is thought to have involved the non-living synthesis
of simple organic molecules. a) List two other processes needed for the spontaneous origin of life. [2] ...................................................................................................................................... ......................................................................................................................................
b) Outline the role of prokaryotes in the development of an oxygen-rich atmosphere
on the Earth. [2] ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................
[Total 4 marks] Q2 Discuss the endosymbiotic theory for the origin of eukaryotes. [6 marks]
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64
CELL DIVISION Q1 The diagram below shows a cell during mitosis.
What are the structures (I and II) and the stage of mitosis? [2 marks]
Q2 Cyclins were discovered by Timothy R Hunt in 1982 while studying sea urchins. What is a
function of cyclins? A. Circulation of seawater for gas exchange B. Rotation of tentacles C. Control of the cell cycle D. Recycling of nutrients
Q3 Explain how mitosis produces two genetically identical nuclei. [8 marks] ......................................................................................................................................
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CELL DIVISION
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