BIO EXAM 3

What is the main purpose of meiosis?

Reduce chromosome number and produce haploid cells.

In humans, how many chromosomes does a diploid cell contain?

46 chromosomes.

How many chromosomes does a normal human gamete contain?

23 chromosomes.

What are homologous chromosomes?

Chromosomes with the same genes in the same locations, but possibly different alleles.

What happens to each chromosome before meiosis begins?

It replicates.

After DNA replication, what does each chromosome consist of?

Two sister chromatids.

What is the pairing of homologous chromosomes during prophase I called?

Synapsis.

What is the structure formed when homologous chromosomes pair called?

Bivalent.

Between which chromatids does crossing over occur?

Non-sister chromatids of homologous chromosomes.

What are chiasmata?

Sites where homologous chromosomes remain connected after crossing over.

What happens during metaphase I?

Homologous chromosome pairs line up at the metaphase plate.

What happens during anaphase I?

Homologous chromosomes separate.

What are the daughter cells like at the end of meiosis I?

Haploid with replicated chromosomes.

Why is meiosis I called a reduction division?

Chromosome number is reduced from diploid to haploid.

Does DNA replication occur between meiosis I and meiosis II?

No. False.

What happens during anaphase II?

Sister chromatids separate.

How many haploid cells does one diploid parent cell normally produce after meiosis?

Four.

During which types of cell division do sister chromatids separate?

Mitosis and meiosis II.

What are homologous chromosomes?

A maternal and paternal pair with the same genes in the same locations, but possibly different alleles.

What are sister chromatids?

Replicated copies of the same chromosome.

What is one process during meiosis that increases genetic variation by exchanging DNA?

Crossing over.

What process increases genetic variation through random chromosome alignment?

Independent assortment.

How do homologous chromosome pairs align during metaphase I?

Randomly.

How does independent assortment increase genetic variation?

It produces different combinations of maternal and paternal chromosomes in gametes.

What happens during crossing over?

Corresponding DNA segments are exchanged between non-sister chromatids of homologous chromosomes.

How does crossing over increase genetic variation?

It produces new combinations of alleles.

If a species has 2n = 8 chromosomes, how many chromosomes are in a normal gamete?

4 chromosomes.

What phase occurs when homologous chromosome pairs align across the center of the cell?

Metaphase I.

What happens to homologous chromosome pairs during metaphase I?

They align together at the metaphase plate.

What is the error called when homologous chromosomes fail to separate correctly?

Nondisjunction.

How is a gamete with one extra chromosome represented?

n + 1.

How is a gamete missing one chromosome represented?

n − 1.

Put the four major stages of cellular respiration in the correct order.

1. Glycolysis; 2. Pyruvate processing; 3. Krebs cycle; 4. Electron transport and oxidative phosphorylation.

What is the major purpose of cellular respiration?

To produce ATP from energy stored in molecules such as glucose.

What is the overall equation for aerobic cellular respiration?

Glucose + 6 O₂ → 6 CO₂ + 6 H₂O + energy.

Where does glycolysis occur in a eukaryotic cell?

Cytosol.

What six-carbon molecule enters glycolysis?

Glucose.

How many ATP molecules are initially used in glycolysis?

2 ATP.

How many ATP molecules are produced during glycolysis?

4 ATP.

What is the net ATP gain from glycolysis?

2 ATP.

How many pyruvate molecules are produced from one glucose during glycolysis?

2 pyruvate.

How many NADH molecules are produced during glycolysis?

2 NADH.

How many net ATP molecules are produced during glycolysis?

2 ATP.

What type of ATP production occurs directly during glycolysis?

Substrate-level phosphorylation.

Which enzyme is an important regulator of glycolysis?

Phosphofructokinase.

What happens to phosphofructokinase when ATP levels are high?

ATP binds to a regulatory site and inhibits phosphofructokinase.

Why does glycolysis slow down when ATP levels are high?

The cell already has abundant ATP and does not need to break down glucose as rapidly.

Where does pyruvate processing occur in a eukaryotic cell?

Mitochondrial matrix.

What is the reaction for one pyruvate during pyruvate processing?

Pyruvate + NAD⁺ + CoA → CO₂ + NADH + acetyl-CoA.

How many CO₂ molecules are released per pyruvate during pyruvate processing?

1 CO₂.

What electron carrier is reduced during pyruvate processing?

NAD⁺ → NADH.

What two-carbon product enters the Krebs cycle?

Acetyl-CoA.

How many acetyl-CoA molecules are produced per glucose during pyruvate processing?

2 acetyl-CoA.

How many CO₂ molecules are produced per glucose during pyruvate processing?

2 CO₂.

How many NADH molecules are produced per glucose during pyruvate processing?

2 NADH.

What enzyme complex regulates pyruvate processing?

Pyruvate dehydrogenase.

What happens to pyruvate dehydrogenase when products are abundant?

It is phosphorylated, changes shape, and becomes inhibited.

Where does the Krebs cycle occur in a eukaryotic cell?

Mitochondrial matrix.

What molecule combines with the acetyl group from acetyl-CoA at the start of the Krebs cycle?

Oxaloacetate.

What molecule is formed when the acetyl group combines with oxaloacetate?

Citrate.

How many CO₂ molecules are produced per turn of the Krebs cycle?

2 CO₂.

How many NADH molecules are produced per turn of the Krebs cycle?

3 NADH.

How many FADH₂ molecules are produced per turn of the Krebs cycle?

1 FADH₂.

How many ATP/GTP molecules are produced per turn of the Krebs cycle?

1 ATP/GTP.

How many CO₂ molecules are produced per glucose in the Krebs cycle?

4 CO₂.

How many NADH molecules are produced per glucose in the Krebs cycle?

6 NADH.

How many FADH₂ molecules are produced per glucose in the Krebs cycle?

2 FADH₂.

How many ATP/GTP molecules are produced per glucose in the Krebs cycle?

2 ATP/GTP.

What happens to Krebs cycle reaction rates when ATP and NADH are scarce?

Reaction rates are high.

What happens to Krebs cycle reaction rates when ATP and NADH are abundant?

Reaction rates are low.

What type of inhibition regulates the Krebs cycle?

Feedback inhibition.

Which two reduced electron carriers deliver electrons to the ETC?

NADH and FADH₂.

What is the final electron acceptor during aerobic cellular respiration?

Oxygen.

What molecule forms when oxygen accepts electrons and protons?

Water (H₂O).

What does the electron transport chain pump, and in which direction?

H⁺ (protons) from the mitochondrial matrix into the intermembrane space.

What enzyme allows H⁺ to move down its gradient?

ATP synthase.

Where do H⁺ ions move during oxidative phosphorylation?

From the intermembrane space into the mitochondrial matrix.

What molecules combine to produce ATP?

ADP + Pi → ATP.

What is the movement of protons through ATP synthase called?

Chemiosmosis.

Which stage produces the majority of ATP during cellular respiration?

Oxidative phosphorylation.

Where does glycolysis occur?

Cytosol.

What are the major inputs of glycolysis?

Glucose, ATP, and NAD⁺.

What are the major outputs of glycolysis?

Pyruvate, NADH, and net ATP.

How is glycolysis regulated?

Phosphofructokinase; high ATP inhibits the enzyme.

Where does pyruvate processing occur?

Mitochondrial matrix.

What are the major inputs of pyruvate processing?

Pyruvate, NAD⁺, and CoA.

What are the major outputs of pyruvate processing?

Acetyl-CoA, NADH, and CO₂.

How is pyruvate processing regulated?

Pyruvate dehydrogenase; phosphorylation inhibits it.

Where does the Krebs cycle occur?

Mitochondrial matrix.

What are the major inputs of the Krebs cycle?

Acetyl-CoA, NAD⁺, FAD, and ADP/GDP.

What are the major outputs of the Krebs cycle?

CO₂, NADH, FADH₂, and ATP/GTP.

Where does the ETC/oxidative phosphorylation occur?

Inner mitochondrial membrane.

What are the major inputs of ETC/oxidative phosphorylation?

NADH, FADH₂, O₂, and ADP + Pi.

What are the major outputs of ETC/oxidative phosphorylation?

H₂O, ATP, NAD⁺, and FAD.

How is ETC/oxidative phosphorylation regulated?

Depends on electron supply, final electron acceptor, and proton gradient.

What is the primary purpose of fermentation?

To regenerate NAD⁺ so glycolysis can continue.

Where does fermentation occur in eukaryotic cells?

Cytosol.

What happens to the electron transport chain when a final electron acceptor is unavailable?

The ETC stops.

What molecule builds up when the ETC stops?

NADH.

What molecule does the cell begin to run out of when the ETC stops?

NAD⁺.