1. Prokaryotic vs. Eukaryotic Cells
Literally means “before the nucleus”.
They do contain DNA but it is not organized into a nucleus.
The DNA is circular and shorter
The cell is much smaller in size.
The only prokaryotic cells are bacteria.

2. Eukarytotic
Means “true nucleus”, these cells all contain an organized nucleus containing DNA
Eukaryotic DNA is linear and longer
Cells will also contains many other membrane bound structures

3. Comparison of the 2 types of cells:
Structure prokaryotic eukaryotic
cell membrane
chromosomes
nuclear membrane, Golgi
ER, lysosomes, vacuoles
cell wall
ribosomes
mitochondria
chloroplasts
cytoskeleton

4. Endosymbiotic theory:
Means “cell within a cell”
One cell was engulfed by another cell
or it entered as a parasite
Instead of being destroyed it added
energy to the cell and eventually
evolved into a cell structure

5. Evidence for the endosymbiotic theory:
1. They kept their own membrane. These structures have a double membrane now.
2. They both contain their own DNA which is similar to bacterial DNA
3. Mitochondria and chloroplasts can divide independently in the same method as bacteria.
4. They have their own ribosomes.

6. A comparison of plant and animal cells:
Plants have one large vacuole, animals have several small ones
Plants contain plastids, animals don’t
Plants have a cell wall, animals don’t
Plants don’t have lysosomes, animals do
Plants don’t use centrioles to divide, animals to

7. Specialized cells and tissues
Tissue is Latin for “weave”, it is a group of cells with a common structure and function
some are literally woven together
some are held together with a sticky coating called a matrix

8. Cells form tissues which in turn form organs:

9. Fluid mosaic model of the cell membrane:
The cell membrane is a bilayer of phospholipids embedded with proteins, with attached carbohydrate chains and cholesterol
“fluid” means it is asymmetrical and changing-the materials making it up can move
“mosaic” means it is made up of several different materials

10. A closer look at the mosaic parts:
A. The proteins are of 2 types:
1.Transmembrane proteins go through the membrane and may project through the surface
carriers-help carry materials across
channels-allow substances to move through
receptors-bind certain molecules
enzymes-carry out metabolic reactions

11. 2. Peripheral proteins-occur on the surface of the membrane
Anchor to a carbohydrate or a lipid
May link to cytoskeleton on inside or link to matrix on outside

12. C. Cholesterol-found within the bilayer
B. Carbohydrates
serve as fingerprints; sugars are recognized by other cells
transplanted tissue may be rejected because the body doesn’t recognize the markers
Examples: glycoproteins, glycolipids
C. Cholesterol-found within the bilayer
Acts to stabilize
Reduces permeability to small molecules
Found in animal cells only

13. D. Bilayer glycerol linked to 2 fatty acids and a phosphate
hydrophobic ends face inside, hydrophilic end faces outside

14. Permeability-movement across the membrane
The membrane is easily permeable to small, noncharged, lipid soluble molecules.
Large polar molecules and ions do not pass freely.
Membrane is said to be selectively permeable.

15. Types of transport: 1. Passive-requires no energy output by the cell
a. diffusion-based on random motion of molecules
molecules move from high to low concentration (down a concentration gradient) until equilibrium is reached
speed is affected by
gradient steepness
temperature (faster at higher temperatures)
pressure gradients (may differ in each side of membrane)
molecule size (small move faster)
electric gradients (charge differences)

16. How diffusion works:

17. b. Osmosis-diffusion of water across a membrane
pressure develops on the side of the membrane that has a higher concentration of solutes
examples-water absorbed by large intestines, water retention in kidneys, water taken up by blood

18. Differences in amounts of water inside and outside of cells creates tonicity:
Isotonic-the solute concentration (and therefore the water concentration) is the same on both sides. Water moves equally in and out of the cell.
Hypertonic-solution has more solute (and therefore less water) than the cell
water leaves cell and it shrinks
Called “crenation” in animals
Called “plasmolysis” in plants
Hypotonic-the solution has less solute than cell (therefore more water)
water goes into cell causing it to swell and burst
cell wall of plant prevents this (tugor pressure)

19. Animal cells
Plant cells

20. c. Facilitated diffusion
carrier proteins are used to move materials across the membrane.
Proteins are specific-will combine with only one thing
They can only move in the direction of the gradient (high to low) so no energy is used by the cell

21. 2. Active transport-movement of molecules against the concentration gradient—requires energy.
Protein pumps-proteins are used to bind to material and move it across the membrane
sodium potassium pump

22. Endocytosis-taking in large materials by forming vessicles around them.
1. phagocytosis-”cell eating”– is the uptake of large particles. Can be seen in unicellular organisms or WBC.
2. pinocytosis-”cell drinking”– uptake of small particles or liquid. Seen in plant root cells

23. 3. receptor mediated-receptor proteins in membrane fit to a particular molecule, bind it and indent to pull it in.

24. Exocytosis-release of materials (waste) from cell.
Vessicles move to membrane and fuse with it. Membrane opens and contents spill out
This is one way of secreting hormones (like insulin from pancreas into blood), plants use it to secrete material for the cell wall

25. Cell junctions:
Neighboring cells interact and communicate with each other through junctions.
Plant junctions:
plasmodesma-channels in the cell wall of plants that allow cytoplasm to move through and into adjacent cells.

26. Animal cell junctions:
1. Tight junctions-found in cells like
epithelial cells (linings).
Prevents leaking of materials
between cells
2. Desmosome (Adhering) junctions-
joins cells of the skin and heart that
need to stretch. Works like a rivet
3. Gap junctions-links cytoplasm of
neighboring through membrane channels.