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Enzymes, Cell Membranes and all that Jazz……..
1. What environmental conditions affect enzyme activity?
Use the graph at the right to answer questions 2-5
2. Why did the reaction rate for enzyme J drop when
the temperature exceeded 50C?
3. What is the optimal temperature for enzyme J?
4. How do you know this is the optimal temperature?
5. Could enzyme J be an enzyme found in the human body?
Why or why not?
Use the graph at the right to answer questions 6-8
6. What is the optimal pH for:
Enzyme K?
Enzyme M?
Enzyme L?
7. Which letter represents the activity of an enzyme
that could be found in the stomach?
8. What happens to enzyme activity when the pH is
higher or lower than the optimal pH? Why does this happen?
9. Match the structure with the correct letter from the diagram:
_______ cholesterol
______ cytoskeleton
______ glycolipid
______ glycoprotein
______ hydrophilic end of
phospholipids
______ hydrophobic end of
phospholipids
______ integral protein
______ lipid bilayer
______ peripheral proteins
10. What component(s) of the cell membrane contribute to the fluid quality of the cell
membrane?
11. List possible functions of membrane proteins (Give at least three possible functions)
12. Complete the following chart describing the role of cholesterol in the cell membrane.
Temperature
Role of Cholesterol
Effect on Membrane
Fluidity
Warm
Cold
13. How is winter wheat able to survive the cold temperatures of winter without serious
cell damage?
14. What is the role of carbohydrates on the surface of cell membranes? What are two
reasons why this is important?
15. What is the role of transport proteins in biological membranes?
16. A semipermeable sac containing 4% NaCl, 9% glucose, and 10% albumin is
suspended in a solution with the following composition: 10% NaCl, 10% glucose and 40%
albumin. Assume the sac is permeable to all substances except albumin. Use the key
provided to determine how each substance will move.
_____ Glucose
_____ Albumin
_____ Water
_____ NaCl
A. Moves into the sac
B. Moves out of the sac
C. Does not move
17. The diagrams below show three microscopic fields (A-C) containing red blood cells.
Arrows indicate the direction of water movement. Answer the following questions.
a. Which microscopic field shows a hypertonic environment?_____
b. Which microscopic field shows a cell hypertonic to its environment? _____
c. Which microscopic field shows an isotonic environment? _____
d. Describe what is happening to the cells in Field C and explain why this is happening.
18. Examine the drawing at the left. The tube, filled with 10% sucrose solution was placed
in a 5% sucrose solution. The membrane covering the bottom of the tube is impermeable
to sucrose.
a. In what direction does water flow?
b. Explain why in terms of osmotic pressure.
c. Is the tube’s content hypertonic, hypotonic or isotonic
d. Is the solution outside the tube hypertonic, hypotonic or
isotonic?
19. Complete the following chart comparing the different transport processes.
20. Match the description/definition/example with the correct transport.
A. Active transport
B. Diffusion
C. Endocytosis
D. Exocytosis
E. Facilitatied diffusion
F. Osmosis
G. Phagocytosis
H. Pinocytosis
_____The movement of water across a semipermeable membrane down its concentration
gradient
____ The movement of materials across a semipermeable membrane down their
concentration gradients with the assistance of transport proteins.
____ The movement of materials down their concentration gradient
____ Pumping of materials across a membrane against their concentration gradients
____ Intake of small droplets of liquid by endocytosis
____ Occurs when a vesicle/vacuole fuses with the cell membrane releaseing the contents
to the outside
____ Intake of solids by endocytosis
____ Occurs when a small region of the plasms membrane invaginates, pinches off and
forma a vesicle/vacuole
____ Sodium/potassium pump
_____Transport proteins are used to transport glucose ot amino acids down their
concentration gradients into the cell
_____ White blood cells engulf a harmful bacterium
_____ Drinking water causes the loss of water from cells lining the digestive tract
Any questions? Anything that needs more explanation? Jot your notes here!!