the building blocks of life: cells history of cells until recently, the oldest fossils on earth were...
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The Building Blocks of Life: Cells
History of Cells
Until recently, the oldest fossils on earth were little more than 600 million years old.
The world is estimated to be 4.5 billion years old.
Within the last few years, the electron microscope has allowed scientists to discover that life may have possibly existed 3.5 billion years ago.
Fleas, whales, flowers and Douglas firs all come from the same single ancestral cell.
History of Cells
Every human spent about half an hour as a single cell
Every square inch of the human body has an average of 32 million bacteria on it.
The History of the Cell: Part II By the early 1800s improvements to the
microscope allowed scientists to investigate structures within a cell.
These improvements led to the development of the cell theory
Using an electron microscope, scientists can see things that are 0.0000001m in size.
Bacteria on the head of a pin.
Here is a fly…up close
The Cell Theory
Three Parts:
1. All living things are made up of one or more cells.
2. The cell is the functional unit of life.
3. All living cells come from pre-existing cells.
The Theory
Before the development of this theory people believed that living things could come from non-living things. (i.e. insects from a raindrop)
Seeing that the cell theory was uniform scientists could look for a general explanation of life processes as opposed to looking at the life processes of specific organisms.
A Cell
Think of a cell as self-contained city. The city imports certain materials to maintain
itself. It also exports certain materials that it
produces. There is a central control of the city
(Municipal Hall, Provincial Government) Specific parts of the city have specific
functions.
Common features of all cells They all have a cell membrane (this is what
encloses a cell) They all have a cytoplasm (the interior fluid of
all cells) They all have DNA in them
Cell Membrane
Cytoplasm
DNA
How DNA is held in a cell
• Some cells have their DNA free in the cytoplasm
• These kind of cells are the most primitive and simple
• Most cells have their DNA enclosed in a membrane.
• These are more advanced and complex cells.
DNA free in the cytoplasm DNA inside the nucleus
Cells are very small Cells are larger
Very few other structures Many other structures
Examples : Bacteria Examples : Plant and Animal cells
Primitive Cells Advanced Cells
Prokaryotic Cells Eukaryotic Cells
Science 9 Review (woo-hoo!)
Cells need nutrients to grow and repair Where do these nutrients come from?
DIGESTION!
What parts of the cell are you already familiar with? (hands up!) Can you recall their function?
The cell membrane
• A phospholipid bi-layer composed of 50% phospholipids and 50% embedded proteins.
Phospholipids…
Phospholipids are the main structural components of membranes
They each have a hydrophilic head and two hydrophobic tails
Draw one and label
Cell Membrane
In water, phospholipids form a stable bilayer The heads face outward and the tails face inward
DRAW IT!!
Three main functions of cell membranes
1. The cell membrane is the outer boundary of the cell.
2. The cell membrane is selectively permeable and controls what enters and leaves a cell.
3. Recognition markers on the outside of the cell membrane are for cell to cell identification.
The Brain: The nucleus
The largest organelle. Separated from the
cytoplasm by the nuclear membrane.
The nucleus is the ‘brain’ of the cell: it contains the DNA, and controls the cell activities.
The nucleus and the nuclear membrane
Chromatin and the nucleolus
Chromatin long strands of DNA
(genetic information) that float around within the nucleus.
The nucleolus a dark area within the
nucleus where ribosomes are made.
Chromatin
Nucleolus
Pore
NUCLEUS
Nuclear membrane
DRAW IT!!
More about Cells….The Cytoplasm
Cytoplasm:
All the contents of a cell, including the plasma membrane, but not including the nucleus.
“Soupy” mixture that contains a variety of cell structures called organelles.
continuous with the nuclear membrane
Rough Endoplasmic Reticulum (RER)
ribosomes attached at tiny holes (making it ‘rough’) The function of the Rough Endoplasmic
Reticulum is to synthesize and export proteins and glycoproteins.
Chromatin
Nucleolus
Pore
NUCLEUS
Nuclear membrane
ROUGHENDOPLASMICRETICULUM
Ribosomes
Smooth endoplasmic reticulum
connected to the RER (and nucleus), but has no attached ribosomes
smooth ER makes lipids (fat)
DRAW IT!!
Products leave the ER in vesicles:
1
Vesiclebuds off from ER
RibosomeProtein inside vesicle
ROUGH ERProtein created
DRAW IT!!DRAW IT!!
Vacuole
In plant cells, vacuoles are larger, act as storage areas, and help regulate water
When vacuoles fill with water, they get larger What happens to a plant cell when this takes
place? The vacuole pushes against the cell wall
The firmness makes veggies crisp and plants stand up!
In animal cells, vacuoles are called vesicles…
Vesicles Vesicles have a simple structure. Liquid filled sacs surrounded by a single
membrane. Package liquids containing a wide variety of
substances and carry these materials to other parts / outside of the cell.
Vesicles also form around material (liquid or solid) that are brought into the cell.
Vesicles are the shipping containers within cells.
Ribosomes
Where proteins are synthesized. May be free, or attached to the RER. Where the information that DNA contains is
transformed into protein.
Lysosomes
Contain digestive enzymes Digest worn out organelles, food particles,
viruses and bacteria Cell janitors – keep the cytoplasm clean
the Golgi complex is a stack of membranous sacs, like a stack of pancakes
these receive and modify products of the ER, then send them on to other organelles or to the cell membrane.
think of it like a distribution company, with a “shipping and receiving” function
The Golgi complex
The Golgi complex
“Receiving” side ofGolgi complex
Vesiclefrom ER
Newvesicleforming
Transport vesiclefrom the Golgi
Golgi apparatus
“Shipping”side of Golgicomplex
Mitochondria
The “power-house” of the cell. This is the structure where cellular respiration
occurs. (i.e. where food is converted into energy)
In everyday language: glucose (sugar) + oxygen carbon dioxide +
water + energy
The mitochondrion (mitochondria)
Note: Folds/Creases
Note: Double Membrane
Cell appendages
Cilia: thin, tail-like projections that beat in one direction or have sensory functions
Flagella: long, whip-like projection used for movement
Plant vs Animal Cells…Round 1 Animal cells have centrioles Centrioles are protein fibres that aid cell
division by helping to move chromosomes
Animal cells take round 1!
Plant vs Animal Cells…Round 2 Plant cells have a cell wall The cell wall protects that plant cell and helps
maintain the cell’s shape Made of cellulose Plant cells take round 2!
Round 3…the final blow
Chloroplasts are found in plant cells only They carry out photosynthesis, which
converts sun’s energy into nutrients Carbon dioxide + water + sunlight glucose
+ oxygen Without chloroplasts, we would have no
oxygen and no sugar
What makes plants green?
Ok, smarty pants… Why are plants green?
Chloroplasts contain chlorophyll, which absorbs sunlight
If chlorophyll is green, then what colors of light (ROYGBIV) do they absorb?
Common structures in plant and animal cells:
Organelles found in plant cells
Cell wall – made of cellulose, gives cell strength and protection
Larger vacuoles – store water and keep cell rigid
Chloroplasts – make sugar from CO2 and sunlight - photosynthesis
Organelles found in animal cells
Centrioles – attachment for the cytoskeleton, organise spindle fibres during cell division
Plant Cells Animal cells
Have a cell wall Do not have a cell wall
Have chloroplasts Do not have chloroplasts
Have large vacuoles Have small vacuoles
No visible centrioles Centrioles visible
IMPORTANT SLIDE!!!