Question 1

A human somatic cell in G1 phase contains 46 chromosomes. After DNA replication in S phase, how many chromosomes and DNA molecules (chromatids) does the cell contain?

Accepted Answer

46 chromosomes and 92 DNA molecules

Question 2

During which phase of the cell cycle does DNA replication occur, and what is the consequence for chromosome structure?

Accepted Answer

S phase; each chromosome consists of two sister chromatids

Question 3

A cell with 12 X-shaped chromosomes at metaphase undergoes anaphase. Immediately after the sister chromatids separate, how many chromosomes are present in the cell?

Accepted Answer

24 chromosomes

Question 4

Which structure attaches spindle microtubules to chromosomes during mitosis?

Accepted Answer

Kinetochore

Question 5

In animal cell cytokinesis, what structure is responsible for physically dividing the cell, and what is it composed of?

Accepted Answer

Cleavage furrow; contractile ring of actin microfilaments

Question 6

Which of the following best explains why cells exit the cell cycle into G0 from G1 phase rather than from S, G2, or M phase?

Accepted Answer

Exiting from G1 avoids incomplete or excess DNA replication

Question 7

Which of the following drugs would most specifically prevent chromosomes from aligning at the metaphase plate without affecting other stages of mitosis?

Accepted Answer

A drug that inhibits kinetochore function

Question 8

In the experiment marking microtubules during anaphase, what was observed and what does it reveal about microtubule dynamics?

Accepted Answer

Microtubules shorten at the kinetochore end, not the centrosome end

Question 9

Which of the following best describes binary fission in prokaryotes?

Accepted Answer

Replication of a single circular chromosome followed by division without mitosis

Question 10

Which of the following is the correct order of events in aerobic cellular respiration?

Accepted Answer

Glycolysis → pyruvate oxidation → citric acid cycle → electron transport chain

Question 11

What is the immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation?

Accepted Answer

The proton-motive force (H$$^+$$ gradient) across the inner mitochondrial membrane

Question 12

Which molecule donates electrons to the electron transport chain at the highest energy level?

Accepted Answer

NADH

Question 13

Why does anaerobic respiration produce less ATP than aerobic respiration?

Accepted Answer

The final electron acceptors in anaerobic respiration are less electronegative than O$$_2$$, so less energy is released per electron

Question 14

Which process regenerates NAD$$^+ in $$the absence of oxygen, allowing glycolysis to continue?

Accepted Answer

Fermentation

Question 15

Which of the following is a key difference between mitosis in animal cells and binary fission in bacteria?

Accepted Answer

Mitosis involves a mitotic spindle and nuclear envelope breakdown; binary fission does not

Question 16

Which of the following best describes the role of NAD$$^+ in $$cellular respiration?

Accepted Answer

It acts as an oxidizing agent, accepting electrons and becoming reduced to NADH

Question 17

Which checkpoint is considered the most important for regulating cell division in mammalian cells, and what happens if a cell does not pass this checkpoint?

Accepted Answer

G1 checkpoint; the cell enters G0 and stops dividing

Question 18

Which of the following best explains why glycolysis is considered one of the earliest metabolic pathways to have evolved?

Accepted Answer

It does not require oxygen or organelles and is present in most organisms

Question 19

A patient is treated with a chemotherapy drug that disrupts microtubule polymerization. What is the most likely effect on dividing cancer cells?

Accepted Answer

They cannot complete mitosis and die due to failed chromosome segregation

Question 20

Which of the following is a real-world example of substrate-level phosphorylation?

Accepted Answer

ATP production during glycolysis

Cell Division, Chromosomes, Cell Cycle, Mitosis, and Cellular Respiration: Study Guide

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