BY 123 SI Session 09-24-14
Chapter 7
What’s amphipathic mean?
Having hydrophobic and hydrophilic regions (phospholipid and membrane proteins)
1. Who proposed the sandwich model (phospholipid bilayer between two layers of
hydrophilic proteins)?
Davson and Danielli
2. Who proposed the fluid mosaic model?
Singer and Nicholson
3. What’s the fluid mosaic model? What research experiment allows us to accept this
hypothesis?
Proteins are a mosaic in the cell membrane. They did a freeze fracture and split the cell
membrane in between phospholipids
4. What can we say about polarity within regions of the membrane proteins?
Nonpolar in the middle and polar on the ends touching water
5. All of the following molecules are part of the cell membrane except
A) lipids.
B) nucleic acids.
C) proteins.
D) phosphate groups.
E) steroids.
6. Can phospholipids move? What’s the function of cholesterol in the plasma membranes of
some animals?
Yes, laterally, and flip-flopping; cholesterol lends to fluidity of the membrane
7. What’s the relationship between temperature and membrane lipid composition?
cold environment = many unsaturated fats; hot environment = many saturated fats
8. What’s the function of glycoproteins and glycolipids sticking out the cell?
Cell-cell recognition
Know Figure 7.12
Membrane proteins and lipids are synthesized in the ER -> carbs, and proteins can be
joined together and sent to the Golgi -> glycoproteins undergo further carb modification
and lipids acquire carbohydrates, becoming glycolipids -> these glycoproteins, glycolipids,
and secretory proteins are transported to vesicles to the plasma membrane -> release
through exocytosis
9. What are transport proteins and give me two examples.
Carrier and channel proteins help carry hydrophilic molecules across the cell membrane
10. Give me examples when channel proteins are gated or ungated.
Aquaporins are ungated; different ion channels are gated
11. What type of change happens for carrier proteins to function properly?
conformational
12. Passive transport consists of what three terms?
Simple diffusion, osmosis, facilitated diffusion
13. Simple diffusion characteristics explained in class?
Passive, no ATP needed, and goes down concentration gradient
14. Explain isotonic, hypertonic, and hypotonic solutions in terms with water. Know Figure
7.15
key thing to know after studying: water flows from the hypotonic (less solute; more free
water molecules) to the hypertonic solution (more solute; more BOUND water
molecules)********
15. What is facilitated diffusion?
Passive transport with help of transport protein
16. The solutions in the two arms of this U-tube are separated by a membrane that is
permeable to water and glucose but not to sucrose. Side A is half filled with a solution of 2
M sucrose and 1 M glucose. Side B is half filled with 1 M sucrose and 2 M glucose. Initially,
the liquid levels on both sides are equal.
Initially, in terms of tonicity, the solution in side A with respect to that in side B is
A) hypotonic.
B) plasmolyzed.
C) isotonic. (3M each side)
D) saturated.
E) hypertonic.
After the system reaches equilibrium, what changes are observed?
A) The molarity of sucrose and glucose are equal on both sides.
B) The molarity of glucose is higher in side A than in side B.
C) The water level is higher in side A than in side B. (glucose travels from B to A which
makes a tonicity difference where A is now hypertonic to B)
D) The water level is unchanged.
E) The water level is higher in side B than in side A.
17. What happens if you add unionized (distilled) water to blood? What’s hypotonic
comparatively?
blood lyses because unionized water is HYPOTONIC to blood
18. Which of the following statements correctly describes the normal tonicity conditions for
typical plant and animal cells?
A) The animal cell is in a hypotonic solution, and the plant cell is in an isotonic solution.
B) The animal cell is in an isotonic solution, and the plant cell is in a hypertonic solution.
C) The animal cell is in a hypertonic solution, and the plant cell is in an isotonic solution.
D) The animal cell is in an isotonic solution, and the plant cell is in a hypotonic solution.
E) The animal cell is in a hypertonic solution, and the plant cell is in a hypotonic solution.
19. What is active transport? Know Figure 7.18.
use of energy to go against the concentration gradient
20. Know the sodium-potassium pump and the proton pump (plants, fungi, and bacteria)?
3 na+ out, 2 k+ in
21. What is cotransport?
Use of that active transport concentration gradient to transport molecules back into the cell
(H+/SUCROSE COTRANSPORT)
22. 3 types of exocytosis are Figure 7.22.
A cell (concentration .8 M glucose and .01 M sucrose) with a semi-permeable membrane
only to water is placed in a solution with .7 M glucose, .01 M sucrose, and .2 M fructose.
Where will water flow?
TO THE SOLUTION
Molarity = moles/liters
A problem could give you TWO unknowns: grams, molarity, moles, and liters. They
can give you grams because given grams, it’s easy to find to amount of moles!
Grams = molecular weight (g/mol) X moles
Moles = grams/molecular weight