Unit 2 Review AP Biology

Chapter 4 CellsChapter 5 Cell Membrane and

Signaling

1. Calculate surface area to volume ratio

10 um 20 um 100 um

Surface Area 600 um2 2400 um2 60,000 um2

Volume 1000 um3 8000 um3 1000000 um3

Surface Area to Volume Ratio

3:5 3:10 3:50

Reduced 0.6 : 1 0.3 : 1 0.06 : 1

Surface Area = 6 X length squaredVolume = length x length =x length

2. Which size cell would be the first to get a toxin in the middle?

• The smallest cell would be first • Why?• The smallest cell has the greatest surface area

relative to its volume. • The toxin would have greater opportunity to

enter the cell because of this ratio

3. Explain how prokaryotes carry out enzymatically catalyzed biochemical

conversions without organelles?

• There are proteins in the cytoplasm moving around.

• This motion ensures that reactions are taking place at a rate sufficient for the cell to survive.

• There are also enzymes in the cytoplasm to catalyze reactions.

4. Explain whether ribosomes are present only in eukaryotes, only in prokaryotes, or

in both.

• Both• Ribosomes make proteins and proteins are

essential in all living things

5. Describe the structure and function of as many cellular organelles as you can in regard to the synthesis and secretion of protein signals.• RER – proteins are synthesized on the

ribosomes and then delivered to Golgi• SER – stores Ca+ that trigger the secretion of

proteins that are secreted by cells• Golgi Body – concentrates, packages, sorts

and modifies proteins to send them to their destination

• Ribosomes – make proteins from amino acids

6. Label the membrane.

7. Explain how the structure of the phospholipid is amphipathic and can form a bilayer that is nonpolar

in middle and polar on the outsides

• Middle is hydrophobic due to the fatty acids• Outside is hydrophilic due to the phosphate

groups.

8. What are the 2 primary factors that influence membrane fluidity?

• Lipid composition and temperature

9. Explain how the ink diffused through the gel even though there were no currents.

• By diffusion its random and it will go until equilibrium.

10. Describe 2 differences between passive and active transport

Passive• Moves materials from high

to low• No energy needed

Active• Moves materials from low

to high• Requires energy• All require proteins

11. Define and provide a description

• Isotonic – Equal solute concentrations on each side of

membrane– No net movement of water in/out of cell

• Hypotonic– Low solute concentration outside the cell– Causes enlargement of cells

• Hypertonic– High solute concentrations outside the cell– Causes shrinking of cells

12. Is facilitated diffusion active or passive transport? Explain why.

• Passive transport• No energy is required even though there are

proteins involved.

13. Explain how cells are involved in the transition from wilted to normal.

• Wilted hypertonic resulting in a flaccid appearance

• When a wilted plant is watered, water moves in to the shrunken cells, expanding them. Cells become plump again and has turgor pressure.

19. Complete table.

Simple Diffusion

Osmosis Facilitated Diffusion

Active transport

Cellular Energy required?

No No No Yes

Driving force? Concentration Gradient

Concentration Gradient

Concentration Gradient

ATP hydrolysis

Membrane protein required?

No Yes for some cells, No for others

Yes Yes

Directional? No No No Yes

Specificity? No No Yes Yes

20. Explain the Na+K+ Pump

• 3 sodium ions get pumped OUT• 2 potassium ions get pumped IN• Requires 1 ATP – ATP gets broken down into

ADP + inorganic phosphate

16. Explain how phagocytosis and pinocytosis are similar and different

Similar• Both forms of endocytosis• Both involve the folding of

the plasma membrane• Both active transport• Both bring materials into

the cell

Different• Phagocytosis is bringing in

large particles/cells• Pinocytosis is bringing in

fluids and dissolved substances

17. Describe each step of cell signaling

• Signal– Signal arrives at target. Signal molecule may be a

specific molecule or a physical stimulus.• Receptor– Signal molecule fits into the receptor protein and

binding occurs• Response– Receptor changes its 3D shape and this initiates a

cellular response

18. If a cell had no proteins, will it be able to respond to any environmentally stimuli? Explain

• No• Cells must have specific receptors to any

environmental stimuli and receptors are always made of protein

19. Why doesn’t caffeine enter the cell?

• Caffeine is large• Caffeine is polar (see

nitrogens)• It is unlikely to diffuse

through the plasma membrane so it likely will bind to a receptor on the surfaces of nerve cells in the brain

20. All cells have

• Cytoplasm• Plasma membrane• ribosomes

21. Animals HAVE (and plants don’t)

• Lysosomes• Centrioles• Flagella• Cilia• More rounder shape• Smaller and more vacuoles

22. Plants HAVE & animals don’t

• Cell wall• Chloroplast• Square shape• Central vacuole

23. Prokaryote vs. Eukaryote

Pro• Older• No nucleus (nucleiod)• No organelles• Simpler ribosomes• Bacteria is an example

Euk• Younger• Nucleus and nuclear

membrane• Organelles• Complex ribosomes• Plants, animals, fungi and

protists are examples

Exam:• 20 multiple choice – cells (chapter 4)• 9 chapter 5• 3 cell signalling ch 4• Short Answer– Labeling Chapter 4– Calculate % change in mass– Calculate SA:V ratio– Calculate solute potential– Calculate standard deviation

• 10 point essay