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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