1. AP BIO EXAM REVIEW: CELLS

2. CELL THEORY
The cell is the basic unit of life
All living things are composed of cells
Cells can ONLY come from pre-existing cells

3. TYPES OF CELLS Prokaryotic Eukaryotic Cells are limited in their size
Prokaryotic cells, in general, are smaller and considered more primitive.
Genomic DNA is smaller with no histone proteins and forms a circle of DNA.
These cells are found in the domains Archaea and Bacteria.

4. WHAT’S THE DIFFERENCE? PROKARYOTES EUKARYOTES
No membrane bound organelles
DNA in nucleoid
Rod shape
Bacteria & Archaea
EUKARYOTES
Membrane bound organelles
DNA in nuclear membrane
Plants, animals, fungi
larger
Multiple but key points
They both have mitochondria

5. ORGANELLES smooth ER mitochondria rough ER chloroplast cytoskeleton
cell wall
large central vacuole
microtubules
nucleous
mitochondria
chloroplast
ribosome
lysosome
nucleus
golgi complex
cell membrane
mito-breaks down food molecules to make energy available (ATP)
chlor- capture energy from the sunlight and use it to produce food for the cell
Rib- where proteins are made
Lys- digests food particles, wastes, cell parts, and foreign invaders
Nuc- the control center of the cell; it contains the nucleolus
Golgi-processes and transports proteins and other materials out of the cell
Cell memb- thin, flexible barrier around a cell, it regulates what enters and leaves the cell
Smooth- Synthesis of lipids, metabolism of carbs, Ca2+storage, and detoxification of drugs and poisons
Rough- Aids in synthesis of secretory and other proteins from bound ribosomes, adds carbs to glycoproteins , and produces new membrane
Cyto- Structural support and mobility and signal transmission for the cell
Cell wall- prevent cells from bursting
Vac- Digestion, storage, waste disposal, water balance, cell growth, and protection
Microtub- Are used to move organelles (like a monorail) and chromosomes.
nucleo-The nucleolus is dark staining object in the nucleus. It contains DNA which codes for the production of ribosomal RNA.

6. CELL MEMBRANES

7. WHAT IS IT?
The cell membrane is a dynamic and intricate structure that regulates material transported across the membrane
It is semi-permeable
The cell membrane is a dynamic and intricate structure that regulates material transported across the membrane. The membrane is selectively permeable (or semi-permeable) meaning that certain molecules can cross the membrane and others cannot.

8. Phospholipids have hydrophilic heads and hydrophobic tails Two layers
WHAT IS IT MADE OF?
Phospholipid bilayer
Phospholipids have hydrophilic heads and hydrophobic tails
Two layers
All cells have plasma membranes and many of their organelles also have membranes. All membranes are made from a bilayer of phospholipids.
Hydrophilic head is attracted to water and the hydrophobic tails are attracted to one another as the tails are hydrocarbons and nonpolar so they do not mix with water. The cell membrane has two layers of phospholipids. The hydrophilic heads are facing an aqueous environment and the hydrophobic tails are facing one another.

9. CHOLESTEROL
It is found in the cell membranes of animals but not plants. It affects the fluidity of the membrane
Cholesterol functions in the following ways: It can weakly bind to hydrocarbon tails making it more difficult for smaller molecules to cross membrane. If the phospholipids are saturated, it prevents them from being packed too closely, making the membrane more fluid. However - if the phospholipids are unsaturated there are kinks in the tails where the cholesterol molecules can fill in and anchor them making the membrane less fluid.

10. PROTEINS IN THE MEMBRANE
Transport Proteins
Aquaporins
Enzyme
Receptor Site
Cell to Cell Recognition
Intercellular Joining
Attachment to the cytoskeleton and extracellular matrix (ECM only in animal cells)
Transport proteins, or permeases, transport molecules across the membrane. Aquaporins are special protein channels used to move water across the membrane.

11. PLASMA MEMBRANE SYNTHESIS
The size of the plasma membrane is increased and decreased with the interaction of vesicles
The size of the plasma membrane is increased and decreased with the interaction of vesicles. Vesicles bringing material to the membrane to be secreted increase the surface area of the plasma membrane; and through the process of endocytosis, the surface area of the cell membrane decreases.

12. CELL TRANSPORT

13. PASSIVE DIFFUSION
The red molecules are initially more concentrated on side B. These molecules have more free energy.
The net movement of the red molecules is from side B to side A, or from a higher concentration to a lower concentration.
The water molecules (blue) are equally distributed and will move across at the same rate. Passive diffusion- the membrane is permeable to the molecules involved (CO2, O2, etc). Predicting the net movement is as if there was no membrane at all. The molecules move from high to low concentration.

14. FACILITATED DIFFUSION
The molecule is impermeable to the membrane.
The transport of the molecule requires a carrier protein or channel protein
It requires no ATP. The driving force is an increase in entropy. The molecules are moving from an area of higher concentration to lower concentration or from higher free energy to lower free energy
Facilitated diffusion- the membrane is not permeable to the smaller molecules involved (glucose, amino acids etc.). These molecules need a transport protein to transport the molecule across the membrane. Predicting the net movement of the molecules is like predicting the movement of molecules during passive diffusion. The net movement of the molecules is from an area of higher concentration to an area of lower concentration. The protein carriers (permeases) may take the form of a channel that allows certain molecules with a certain shape to enter the cytoplasm and others may take the form of a carrier protein that changes conformational shape to move the molecules across. Facilitated diffusion and passive diffusion are also called passive transport since no energy in the form of ATP is needed.

15. ACTIVE TRANSPORT Membrane is impermeable to the molecule
Molecules are moving against a concentration gradient (from low to high) or from low free energy to high free energy
Transport protein and ATP are both needed

16. SODIUM POTASSIUM PUMP
This is the sodium-potassium pump which is vital to the nervous system. Starts with three Na+ attaching to the permease (transport protein) The permease is phosphorylated by ATP The permease becomes unstable which causes it to change its shape or conformation This allows the three Na+ to be released but on the other side of the membrane. This second conformation favors the attachment of two K+ ions and the release of the phosphate group. This change favors the proteins to return to its original conformation and the two K+ ions are released to the inside of the cell.

17. ELECTROGENIC PUMP
Pumps ions against a concentration gradient AND a charge gradient
Create a separation of charge across the membrane
Sometimes an electrogenic pump is combined with another protein carrier involved in facilitated diffusion.
The driving force moving the H+ ions is the concentration gradient (high concentration to low concentration) and the attraction of the positive H+ ions to the negative charges on the other side of the membrane.

18. OSMOSIS
Osmosis is a special case of diffusion involving the movement of water. When the membrane is impermeable to certain molecules and they are not in equilibrium, water will move across the membrane “to help reach equilibrium.” Water is moving from high free energy to low free energy.
"Water likes to dilute".

19. OSMOSIS IN PLANTS & ANIMAL CELLS
Concentration refers to the amount of solute molecules dissolved in a given amount of solvent.
Cell submerged in a hypotonic solution-The solution outside the cell is less concentrated than the solution inside the cell and therefore the solution outside the cell is said to be a hypotonic solution.
If cells are submerged in a hypotonic solution like pure water, the net movement of water is into the cells. Animal cells may not be able to accommodate the water and subsequently burst. Plant cells become turgid because of a back pressure from the cell wall. Then the rate of the movement of water will be equal in both directions. (Point out that relative to the solution outside the cell, the solution inside the cell is hypertonic).
Isotonic- Two solutions found inside the cell and outside the cell have equal amounts of solutes on both sides of the membrane. Water moves across the membrane at the same rate. The cells are at equilibrium.
Cells submerged in a hypertonic solution-The solution outside the cells is more concentrated than the solution inside the cells and therefore the solution outside the cell is called a hypertonic solution.
If cells are submerged cells in a hypertonic solution like syrup, the net movement of water is out of the cells. Both types of cells will decrease in volume. The plasma membrane of plant cells will pull away from the cell wall or plasmolysis will occur. Then the rate of the movement of water will be equal in both directions. (Point out that relative to the solution outside the cell, the solution inside the cell is hypertonic).

20. ENDOCYTOSIS
The movement of larger particles into the cell by use of membrane vesicles
Three types
Phagocytosis
Pinocytosis
Receptor Mediated Endocytosis

21. PHAGOCYTOSIS “Cell Eating”
Larger molecules or particles are brought into the cell by engulfing them into a plasma membrane vesicle
Ex. White blood cells engulfing bacteria

22. PINOCYTOSIS “Cell Drinking”
Dissolved molecules are brought into the cell by engulfing them into a plasma membrane vesicle

23. RECEPTOR MEDIATED ENDOCYTOSIS
Receptors on the outside of cell membrane allow for the attachment of a particular molecule
When a certain number of receptor sites are filled, endocytosis occurs

24. EXOCYTOSIS Opposite of endocytosis
Material that needs to be secreted moves through Golgi apparatus where it may be modified
The material is then surrounded by membrane forming a vesicle

25. QUESTIONS?

26. ANSWERS TO HANDOUT