Biology

A Tour of the Cell

http://www-micro.msb.le.ac.uk/MBChB/bloodmap/Blood.gif

Introduction to Cells

https://vimeo.com/37107992?ref=em-share

https://www.brainpop.com/science/cellularlif

eandgenetics/cells/

• A cell is the smallest unit of life.

• They can vary in size, shape and function (structure determines function).

• The light microscope led the way to knowledge of the cell.

http://www.microscope-microscope.org/basic/microscope-

images/138-microscopes-lg.jpg

http://www.smithsonianchannel.com/sc/web/show/3379126/aliens-inside-us

Microscopes:

• A light (COMPOUND)

microscope magnifies objects (specimens) ~1000x their size. Most cellular structures CANNOT be seen.

• You will work with a light microscope in the lab.

http://www.dsbn.edu.on.ca/schools/Westlane/Scien

ce/simon/SBI3C1/micro.gif

• Electron microscopes give more detail and

magnify a million times the object’s size.

• However, the organism dies when using an

electron microscope.

There are 2 types of electron microscopes:

• A scanning electron microscope (SEM) gives

a 3D image of a specimen/object.

• A transmission electron microscope (TEM)

transmits electrons to view the interior of an

object.

http://w3.salemstate.edu/~pkelly/sem/image003.jpg

http://www.nims.go.jp/htm21/MA/tem.jpg

SEM

http://img72.imageshack.us/img72/2392/071003100546198ddedh5.jpg http://www.st-andrews.ac.uk/~dclogan/Fig3.jpg

CELL THEORY

https://www.khanacademy.org/science/biology/structure-of-a-

cell/introduction-to-cells/v/cell-theory

A history lesson:

• Robert Hooke (1665) named the cell after looking at cork under the microscope.

http://www.google.com/imgres

• Anton van Leeuwenhoek (LAY-von-hohk) (1670’s) developed a simple light microscope & discovered unicellular organisms and called them “little beasties”.

• Rudolf Virchow (1855) stated that all cells came from pre-existing cells (a.k.a. Cell Theory).

http://www.google.com/imgres

The Cell Theory (Virchow) has 3 basic

principles:

1. Cells are the basic

units of life.

2. All organisms are

made of 1 or more

cells.

3. All cells arise from

existing cells.

http://www.leksikon.org/images/virchow_rudolf.jpg

http://www.dmturner.org/Teacher/Pictures/Cell%20reproduction.jpg

Cell Structures:

• All cells have an enclosure called a cell, or plasma membrane.

• This functions as the gate keeper and controls what enters and exits the cell.

• It is mainly composed of phospholipids and proteins. http://www.google.com/imgres

• Within the cell is the cytoplasm. This is a semifluid substance that contains the organelles.

• The organelles are small structures that have specific functions within the cells.

http://www.google.com/imgres

• The cytoskeleton is a protein network within the cytoplasm that helps support the cell and helps the cell maintain or change its shape. It also

– Anchors organelles

– Enables the cell to move

– Allows materials to move throughout the cell

– Composed of microtubules & microfilaments

http://www.google.com/imgres

• The nucleus is the control center of the cell

– It is surrounded by the nuclear envelope

– It contains the chromosomes. There are 46 chromosomes in the human nucleus (in every cell of the human body). The chromosomes are the DNA (genetic material).

• The nucleus is only found in eukaryotic cells!

http://www.google.com/imgres

• The nucleus

contains the

nucleolus

(if more than 1,

nucleoli).

• Nucleolus:

makes

ribosomes

• Ribosomes

make proteins.

http://www.google.com/imgres

2 Types of Cells Prokaryotic Cells

• Bacteria

• NO organelles

(membrane-bound

structures)

• Contained w/in cell

membrane & cell wall,

contain ribosomes, 1

circular chromosome in

nucleoid region (NO

nucleus) & plasmids

(extra pieces of DNA)

Eukaryotic Cells

• Protists, Fungi, Plants,

& Animals

• Contained w/in cell

membrane (may have a

cell wall)

• Contain nucleus &

other membrane-bound

organelles

• Means ‘true kernel’

There are 2 types of cells:

1. Prokaryotes:

These are bacteria

(in Kingdoms

Archaebacteria

and Eubacteria).

– They are unicellular

organisms.

– These were the first

cells. They are very

small cells and are

very simple cells.

http://www.singleton-associates.org/gifs/cell.jpg

2. Eukaryotes: found in

all other kingdoms.

– These have a nucleus

(as well as a cell

membrane and the

majority of the

organelles being

discussed, depending

on the type of

organism).

http://www.google.com/imgres

ANIMAL CELLS:

http://viewpure.com/cj8dDTHGJBY?start=0&end=0

Animal Cell: http://www.animalport.com/img/Animal-Cell.jpg

PLANT CELLS:

http://viewpure.com/9UvlqAVCoqY?start=0&end=0

http://micro.magnet.fsu.edu/cells/plants/images/plantcell.jpg

• Ribosomes make proteins from amino acids;

can be found suspended within the

cytoplasm or attached to the endoplasmic

reticulum. (not really organelles; these are

cellular components)

• The endoplasmic reticulum (ER) is a network

of membrane that produces materials for the

cell. There are 2 types:

– The rough ER contains ribosomes and functions

in protein synthesis and makes new cell

membrane.

– The smooth ER makes lipids, process

carbohydrates and breaks down toxins.

http://www.google.com/imgres

• The golgi apparatus is composed of flat

membranous save that modify, package and

distribute molecules (warehouse of the cell).

http://www.google.com/imgres

• Vacuoles are membrane-

bound organelles that

have various functions.

– Some store food, water,

proteins, ions, or wastes.

Generally these are large

and centralized.

• Lysosomes contain

digestive enzymes that

break down large

molecules and old

organelles that the cell no

longer needs.

Vacuole

http://www.google.com/imgres

• Chloroplasts, double-membrane-bound organelles, perform photosynthesis.

– This is the process of making sugar (synthesis) in the presence of light (photo).

– Plants (some bacteria & protists) make their own food (a.k.a. autotrophic).

http://www.daviddarling.info/images/chloroplast.jpg

• The mitochondrion is the “powerhouse of the cell” b/c it changes stored enter from food into useable chemical energy (ATP) for chemical reactions.

– ATP = adenosine triphosphate (energy ‘currency’ of cells)

– The chemical reactions are cellular respiration.

http://scienceblogs.com/worldsfair/Mitochondria.jpg

• Cilia are short hair-

like projections

that are in the

surface on the cell

usually in large

number. (NOT

organelles)

– Beat in unison and

aid in the cell’s

movement or in the

movement of fluid

over the cell.

Cellular Structures

http://www.google.com/imgres

• Flagella are long tail-like

projections that are on

the surface of the cell.

(NOT organelles)

– Usually 1 to 3 of these.

– In prokaryotic cells, they

spin like propellers.

– In eukaryotic cells, they

move like whips.

http://www.google.com/imgres

Plants differ from animal

cells. In plants:

• A cell wall surrounds the

cell membrane.

• The cell wall is a rigid outer

covering that protects and

maintains the shape of the

plant cell.

• Fungi, algae (a type of

protist) and bacteria also

have cell walls but the

composition is different.

Cell Wall

http://www.google.com/imgres

• Plants LACK lysosomes and centrioles.

• Animals are heterotrophic, meaning

they must consume food.

Animal cells:

• LACK a cell wall but have cytoskeletons

for structural support.

• LACK chloroplasts

• Contain small vacuoles (instead of a

large centralized one)

• Have lysosomes

BOTH Animal and Plant Cells Contain:

• Organelles previously mentioned

(nucleus, ER, mitochondria, ER,

ribosomes, etc)

• Cell membranes

• DNA (in chromosomes)

REVIEW:

http://www.cellsalive.com/cells/cell_mod

el.htm

SEMI-PERMEABLE MEMBRANE • Cell/plasma

membrane is composed of a phospholipid bilayer (2 layers of phospholipids) with proteins interspersed.

• Phospholipids have a hydrophilic head & hydrophobic tail

• Fluid & flexible

http://www.bioteach.ubc.ca/Bio-

industry/Inex/graphics/phospholipid.gif

http://www.hallym.ac.kr/~de1610/histology/cell-3.jpg

Cell Membrane

Membrane Functions • Cell membranes are semipermeable. This

means that some things pass through the membrane while others cannot pass through (this depends on the size & charge of the molecule).

• Passive transport is the movement of a substance across a membrane without energy input.

• Active transport is the movement of a substance across a membrane with the input of energy.

• http://www.sumanasinc.com/webcontent/animations/content/diffusion.html

• Concentration=[ ].

• Molecules move from a higher [ ] gradient to a lower [ ]

gradient.

• A [ ] gradient is the difference between the [ ] of a particular

molecule in 1 area and its [ ] in an adjacent area.

• The rate of diffusion depends on temperature and size of

molecules involved (molecules move faster at higher temperatures

and smaller molecules move faster than larger molecules).

• Once molecules are dispersed evenly, DYNAMICequilibrium is

reached and diffusion stops.

CLICK ON LINK:

http://highered.mheducation.com/sites/007249585

5/student_view0/chapter2/animation__how_diffu

sion_works.html

• Diffusion is the movement of molecules from

a higher concentration to a lower

concentration.

Passive Transport

http://www.google.com/imgres

• Facilitated diffusion is the diffusion of

molecules with the help of a carrier

protein embedded within a cell

membrane. CLICK ON LINK:

• http://highered.mheducation.com/sites/00

72495855/student_view0/chapter2/animat

ion__how_facilitated_diffusion_works.htm

http://www.google.com/imgres

• Osmosis is the diffusion of water.

• Diffusion, facilitated diffusion and osmosis

are all type of passive transport. These do

NOT require energy (occur spontaneously).

http://www.biologycorner.com/resources/osmosis.jpg

• Active transport in cells usually occurs

with the help of carrier proteins but

REQUIRE energy. An example is the

sodium-potassium pump (Na+/K+ pump).

http://web.ahc.umn.edu/~mwd/cell_www/images/Na-Kpump.png

• When comparing 2 solutions with a membrane between them, there are 3 types of solutions:

• Hypertonic: the fluid outside a cell has a higher [solute] than the cytoplasm inside the cell. In this case, water diffuses out of the cell.

• Isotonic: the [solute] outside the cell= the [solute] inside the cell. In this case, no osmosis will occur.

• Hypotonic: the fluid outside a cell has a lower [solute] than the cytoplasm inside the cell. In this case, water will move inside the cell.

http://kentsimmons.uwinnipeg.ca/cm1504/Image130.gif

http://road-to-rn.tumblr.com/post/127238852030/hypotonic-

hypertonic-isotonic-solutions-videos

Bulk Transport:

1. Exocytosis:

exo=exit; cyto=cell

• Wastes and cell

products are

packaged in

vesicles by the

golgi apparatus.

• The vesicles fuse

with the cell

membrane and

leave the cell

http://www.octc.kctcs.edu/gcaplan/anat/images/Image152.gif

2. Endocytosis: endo=within; cyto=cell

• A portion of the cell membrane

surrounds a substance outside of the

cell & pinches off to form a vesicle

• The vesicle moves inward and fuses

with other organelles

• This includes

– Pinocytosis: cell drinking

– Phagocytosis: cell eating

http://www.gla.ac.uk/~jmb17n/Teaching/L2teaching/Agpres/Figures/Endocytosis.jpg

https://www.youtube.com/watch?v=xuG4ZZ1GbzI

LIMITS TO CELL SIZE – view link for

SURFACE AREA TO VOLUME RATIO:

https://www.youtube.com/watch?v=URUJD5NEXC8&s

ns=em

DO VENN DIAGRAM after watching:

ENDOSYMBIOSIS Where did mitochondria, centrioles, and chloroplasts come from?

Evidence of Symbiosis

•Mitochondria and chloroplasts contain DNA, which is fairly different from that in the cell’s nucleus and that is similar to that of bacteria (circular and smaller). •They are surrounded by two or more membranes, and the innermost of these shows differences in composition compared to the other membranes in the cell. The composition is like that of a prokaryotic cell membrane. •New mitochondria and chloroplasts are formed only through a process similar to binary fission. •Much of the internal structure and biochemistry of chloroplasts, for instance the presence of thylakoids and particular chlorophylls, is very similar to that of cyanobacteria. •Centrioles are also believed to have developed by endosymbiosis. •The size of these organelles is comparable to bacteria. •These organelles' ribosomes are like those found in bacteria. •Most of this research began in the 1960’s by Lynn Margulis and was confirmed by later research in the 1980’s. (see animation attached )

http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter4/animation_-_endosymbiosis.html

DOMAIN KINGDOM UNICELLULAR or

MULTICELLULAR

AUTOTROPH or

HETEROTROPH

PROKARYOTE or

EUKARYOTE

EUBACTERI

A or

BACTERIA

bacteria U both P

ARCHAEA archaebacteri

a

U both P

EUKARYA protists Mostly unicellular,

some multicellular

algae

both E

EUKARYA fungi Mostly multicellular;

yeasts: unicellular

H E

EUKARYA plants All M A E

EUKARYA animals ALL M H E

CLASSIFICATION - TAXONOMY