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Critical Thinking Questions- Biology A
Unit Two: Cells
1. A mature human red blood cell has no nucleus or mitochondria. It consists
primarily of a membrane surrounding hemoglobin, the protein molecule that
carries oxygen. Suggest an advantage of the simple organization of human red
blood cells. (HR4)
2. Livestock in the western United States often die after eating a locoweed, such as
Astragalus toanus. The chemical that the plant contains is also poisonous to
plants. How does locoweed keep from poisoning itself? (HR4)
3. There is a higher concentration of air molecules of air molecules inside an inflated
balloon than there is outside the balloon. Because of their concentration random
motion, the molecules inside press against the balloon and keep it taut. How is the
pressure exerted by these air molecules similar to turgor pressure? How is it
different? (HR5)
4. Sometimes water seeps through the concrete wall of a basement after a heavy
rain, and the homeowner must remove it with a sump pump. How can this
situation be compared to the action of a unicellular organism that lives in a pond?
(HR5)
5. When a cell takes in substances through endocytosis, the cell membrane forms an
inside-out vesicle. That is, the outside of the cell membrane becomes the inside of
the vesicle. What might this suggest about the structure of the cell membrane?
(HR5)
6. If a cell were exposed to a poison that blocked the cell’s ability to manufacture
ATP, what effect would that have on the cell membrane’s transport processes?
(HR5)
7. Some plant cells have carrier proteins that transport sugar molecules and
hydrogen ions into the cytosol at the same time. These carrier proteins move sugar
molecules up their gradient as hydrogen ions move down their gradient. How
would the transport of sugar into these cells affect the pH of the cells’ external
environment? What would happen to the transport of sugar if hydrogen ions were
removed from the external environment? (HR5)
8. A gelatin block is prepared with a chemical indicator that turns pink in the
presence of a base. The block is enclosed in a membrane and placed in a beaker of
ammonium hydroxide solution. After half an hour, the block begins to turn pink.
Account for the gelatin’s pink color. (HR5)
Critical Thinking Questions- Biology A
Unit Two: Cells
Rate of transport of glucose
9. The two curves below show the rate at which glucose is transported across a cell
membrane versus the concentration gradient of glucose. One curve represents the
diffusion of glucose through the lipid bi-layer, and the other curve represents the
transport of glucose by facilitated diffusion. Which curve corresponds to
facilitated diffusion? Explain your reasoning. (HR5)
X
Y
Glucose concentration gradient
10. One of the accessory pigments used in photosynthesis is beta-carotene, a
carotenoid found in high concentration in carrots. When one molecule of betacarotene is split by an enzyme, two molecules of vitamin A are produced.
Removal of a hydrogen atom from vitamin A produces retinal, the pigment
involved in vision. Explain why eating carrots is important for good vision.
11. All of the major components of the light reactions, including the pigment
molecules clustered in photosystem I and II are located in the thylakoid
membrane. What is the advantage of having these components confined to the
same membrane rather than dissolved in the stroma or the cytosol?
12. When a thick forest, clouds, dust from a volcanic eruption, or smoke from a large
fire block the sun’s rays, what effect do you think this has on photosynthesis?
How might it affect the levels of atmospheric carbon dioxide and oxygen? What
experimentation could scientist conduct in the laboratory to test your prediction?
13. How does the folding of the inner mitochondrial membrane benefit aerobic
respiration?
14. Yeast can produce ATP through either fermentation or aerobic respiration,
depending on whether oxygen is present. If oxygen is present, yeast cells consume
glucose much more slowly than if oxygen is absent. How can you explain this
observation?
Critical Thinking Questions- Biology A
Unit Two: Cells
15. A person will breathe deeply and rapidly for some time after a period of very
strenuous exercise. The longer and more intense the exercise was, the longer the
deep breathing will continue after the exercise stops. Using your understanding of
cellular respiration, explain why strenuous exercise stimulates deep breathing that
continues after the end of exercise.
16. Find a recipe for making leavened, or raised, bread and a recipe for making
unleavened bread. What ingredient that is present in the recipe for leavened bread
is missing from the recipe for unleavened bread? Explain why that ingredient is
omitted from the recipe.