Keystone Test Biology: Cell Processes/Transport 3 — Questions and Answers
Question 1: Facilitated diffusion differs from simple diffusion because it requires which of the following?
- ATP energy
- A concentration gradient reversal
- Protein channels or carriers (Correct answer)
- The Golgi apparatus
Correct answer: Protein channels or carriers
Facilitated diffusion uses transport proteins (channels or carriers) to help substances cross the membrane, but still moves substances down their concentration gradient without ATP.
Question 2: During lactic acid fermentation in human muscle cells, what happens to pyruvate?
- It enters the Krebs cycle
- It is converted to lactic acid to regenerate NAD+ (Correct answer)
- It is broken down into CO2 and water
- It is converted to ethanol
Correct answer: It is converted to lactic acid to regenerate NAD+
In lactic acid fermentation, pyruvate accepts electrons from NADH and is reduced to lactic acid, regenerating NAD+ so glycolysis can continue.
Question 3: Which of the following BEST describes the function of the sodium-potassium pump?
- It moves Na+ and K+ down their concentration gradients
- It uses ATP to move 3 Na+ out and 2 K+ into the cell (Correct answer)
- It allows free diffusion of ions across the membrane
- It transports glucose into the cell
Correct answer: It uses ATP to move 3 Na+ out and 2 K+ into the cell
The sodium-potassium pump uses ATP to actively transport 3 sodium ions out of and 2 potassium ions into the cell, maintaining the electrochemical gradient.
Question 4: A plant cell placed in a hypertonic solution will undergo plasmolysis. What does this mean?
- The cell membrane ruptures from excess water
- The cell wall breaks down
- The cell membrane pulls away from the cell wall as water leaves (Correct answer)
- The chloroplasts stop photosynthesizing
Correct answer: The cell membrane pulls away from the cell wall as water leaves
Plasmolysis occurs when water exits a plant cell placed in hypertonic solution, causing the cell membrane to shrink and pull away from the rigid cell wall.
Question 5: Which waste product of cellular respiration is removed from the body through the lungs?
- Oxygen
- Water only
- Carbon dioxide (Correct answer)
- Lactic acid
Correct answer: Carbon dioxide
Carbon dioxide is produced when carbon atoms from glucose are fully oxidized during the Krebs cycle and is expelled through exhalation.
Question 6: What is the role of NADH and FADH2 in cellular respiration?
- They directly produce ATP in glycolysis
- They carry electrons to the electron transport chain (Correct answer)
- They break down glucose into pyruvate
- They absorb light energy for the cell
Correct answer: They carry electrons to the electron transport chain
NADH and FADH2 are electron carriers that deliver high-energy electrons to the electron transport chain, where their energy drives ATP synthesis.
Question 7: Which characteristic makes the cell membrane selectively permeable?
- Its rigid cellulose structure
- Its phospholipid bilayer with embedded proteins (Correct answer)
- Its single layer of proteins
- Its connection to the cytoskeleton only
Correct answer: Its phospholipid bilayer with embedded proteins
The phospholipid bilayer's hydrophobic core blocks most polar molecules while embedded proteins create selective channels for specific substances.
Keystone Test Biology: Cell Processes/Transport 3
Facilitated diffusion differs from simple diffusion because it requires which of the following?