Mitosis
What ensures that each new cell gets an identical set of chromosomes during mitosis?
Spindle fibers attach to centromeres and pull sister chromatids apart evenly.
What is the main purpose of meiosis compared to mitosis?
To produce genetically unique gametes with half the chromosome number.
During glycolysis, a cell uses 2 ATP to start the process but ends with 4 ATP. Why is this called a “net gain†of 2 ATP?
Because 2 ATP are invested and 4 are produced, resulting in a net gain of 2 ATP.
Why do plants close their stomata on hot, dry days, and what effect does that have on photosynthesis?
To prevent water loss, but it also limits COâ‚‚ intake and slows photosynthesis.
Where in the cell do transcription and translation occur in eukaryotes?
Transcription in the nucleus, translation in the cytoplasm (ribosome).
A cell fails to form spindle fibers correctly. What phase will it likely be stuck in?
Metaphase, because chromosomes can’t align or separate.
Crossing over happens during which phase, and why is it important?
Prophase I; it increases genetic variation by exchanging DNA segments.
If oxygen suddenly becomes unavailable, what process allows cells to keep generating ATP, and what byproduct builds up?
Anaerobic fermentation; lactic acid (in animals) or ethanol + COâ‚‚ (in yeast).
What would happen to the Calvin cycle if the light reactions stopped?
What would happen to the Calvin cycle if the light reactions stopped?
It would halt because it needs ATP and NADPH from the light reactions.
What would happen if mRNA was transcribed without a stop codon?
The ribosome would keep reading until it hit the mRNA end, producing a faulty, nonfunctional protein.
How is cytokinesis different in plant and animal cells?
Animal cells form a cleavage furrow; plant cells form a cell plate.
A nondisjunction occurs during meiosis II. Predict the chromosome numbers in the resulting gametes.
Two normal gametes, one with an extra chromosome, and one missing one.
The electron transport chain (ETC) depends on NADH and FADHâ‚‚. What would happen to the ETC if the Krebs cycle stopped?
The ETC would slow or stop because no NADH/FADHâ‚‚ would be available to supply high-energy electrons.
A scientist grows two identical plants—one in normal air and one in an environment with no carbon dioxide but plenty of sunlight and water. After several days, the second plant begins to wilt. Explain why this happens even though it still receives light energy.
Without CO₂, the Calvin cycle can’t make sugars, so the plant runs out of stored chemical energy. Even though light reactions still produce ATP and NADPH, they can’t be used efficiently, leading to energy imbalance and reduced growth, causing the plant to weaken and wilt.
A mutation changes a codon from UAU to UAA. What type of mutation is this and what happens to translation?
Nonsense mutation; translation stops early, creating a shortened protein.
Why does mitosis need to be tightly regulated in multicellular organisms?
Uncontrolled mitosis leads to tumor growth or cancer.
If a diploid cell with 16 chromosomes undergoes meiosis, how many chromosomes will each gamete have?
8 chromosomes - gametes are haploid.
Cyanide blocks the last step of the ETC. Predict what would happen to ATP production and to NADH/FADHâ‚‚ levels.
ATP production would drop drastically, and NADH/FADH₂ would accumulate since they can’t offload electrons.
If a plant is exposed only to green light, predict the effect on its rate of photosynthesis.
It would drop significantly because green light is mostly reflected, not absorbed.
If a tRNA carrying methionine (AUG) can’t bind to the ribosome, what happens to protein synthesis?
Translation cant start because methionine is the start codon.
If a cell has 12 chromosomes at the start of mitosis, how many chromosomes will each daughter cell have after division?
12 chromosomes — mitosis produces identical diploid cells.
How do independent assortment and crossing over work together to increase diversity?
Independent assortment mixes whole chromosomes, while crossing over mixes genes within chromosomes.
Some bacteria use nitrate (NO₃â») instead of oxygen as the final electron acceptor. What kind of respiration is this and how does its ATP yield compare?
Anaerobic respiration; produces less ATP than aerobic because nitrate yields less energy than oxygen.
In photorespiration, oxygen binds to RuBisCO instead of COâ‚‚. Explain why this is wasteful.
It uses ATP and releases COâ‚‚ instead of fixing it, reducing sugar production efficiency.
A scientist finds a cell that produces mRNA but no proteins. Which process is most likely malfunctioning and where?
Translation; malfunction likely in the ribosome or tRNA binding.