Exam 4 Review – Cellular Respiration, Genetics & Cell Division

These flashcards review enrollment rules, aerobic respiration (equations, steps, yields, and enzymes), fermentation, ATP synthesis, bacterial genetics, cell-cycle phases, meiosis vs. mitosis, and chromosomal disorders to prepare for Exam 4.

What is the overall chemical equation for cellular respiration?

C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + energy (ATP & heat).

What is the main end-product of one turn of the citric acid cycle (multiple-choice slide)?

CO₂ is released (along with NADH, FADH₂ and ATP).

Which stage of cellular respiration does NOT make NADH?

Oxidative phosphorylation (electron-transport chain) does not generate new NADH.

Which phases of cellular respiration make ATP by substrate-level phosphorylation?

Glycolysis and the citric acid (Krebs) cycle.

What is the other way cells synthesize ATP besides substrate-level phosphorylation?

Oxidative phosphorylation driven by chemiosmosis.

Which step of respiration uses oxidative phosphorylation?

The electron-transport chain/chemiosmosis stage.

Which stage of respiration yields the greatest number of ATP molecules?

Oxidative phosphorylation (ETC + chemiosmosis).

How many net ATP are produced by glycolysis per glucose molecule?

2 ATP (4 made, 2 used).

How many ATP are produced directly (substrate-level) in the citric acid cycle per glucose?

2 ATP (1 per turn × 2 turns).

Approximately how many ATP are made by oxidative phosphorylation per glucose?

About 24–32 ATP, depending on shuttle efficiency and proton leak.

What happens during the first (energy-investment) half of glycolysis?

2 ATP are spent to phosphorylate glucose and split it into two 3-carbon molecules.

What happens during the second (energy-payoff) half of glycolysis?

ATP and NADH are produced; glyceraldehyde-3-phosphate is converted to pyruvate.

Where in the cell does the link (pyruvate oxidation) reaction occur?

In the mitochondrial matrix.

For pyruvate to be oxidized in the link reaction, what molecule is reduced?

NAD⁺ is reduced to NADH.

In which compartment is pyruvate initially generated?

The cytosol (during glycolysis).

How is pyruvate transported into the mitochondrial matrix?

Active transport through a transport protein across both mitochondrial membranes.

What gaseous by-product is released during pyruvate oxidation?

CO₂.

What does coenzyme A deliver into the Krebs cycle?

A 2-carbon acetyl group (acetyl-CoA).

How many carbons are in the acetyl group carried by CoA?

Two carbons.

With what molecule does the acetyl group combine at the start of the Krebs cycle, and what is formed?

It joins oxaloacetate to form citrate (citric acid), a 6-carbon compound.

How many CO₂ molecules are released per acetyl-CoA in the Krebs cycle?

Two CO₂ per cycle (four per glucose).

How many different high-energy molecules are generated in one turn of the Krebs cycle?

Three types: NADH, FADH₂, and ATP (or GTP).

How many NADH, FADH₂ and ATP are made per Krebs cycle turn?

3 NADH, 1 FADH₂, and 1 ATP.

What is the primary purpose of the NADH produced during respiration?

To carry high-energy electrons to the electron-transport chain for ATP production.

List the four major stages of aerobic respiration in order.

1) Glycolysis 2) Pyruvate oxidation (link reaction) 3) Citric acid cycle 4) Oxidative phosphorylation.

What molecule shuttles electrons between complexes I/II and III in the ETC?

Ubiquinone (coenzyme Q).

Which small protein performs a role similar to ubiquinone, transferring electrons between complexes III and IV?

Cytochrome c.

Give an example of a dietary source rich in glucose.

Starchy foods such as bread, pasta, or rice.

Are carbohydrates the only macromolecules that can feed into ATP production?

No—lipids and proteins can also be catabolized for energy.

What is the general term for extracting energy from macromolecules other than carbohydrates?

Catabolism of alternative fuels (lipid and protein catabolism).

How are lipids utilized for cellular respiration?

Glycerol enters glycolysis; fatty acids undergo β-oxidation to form acetyl-CoA.

Where does glycolysis occur and does it require oxygen?

In the cytosol; it does not require O₂.

What are the inputs and key outputs of pyruvate oxidation per glucose?

Inputs: 2 pyruvate; Outputs: 2 acetyl-CoA, 2 NADH, 2 CO₂.

Where is the electron-transport chain located in eukaryotic cells?

On the inner mitochondrial membrane (cristae).

What is the terminal electron acceptor in aerobic respiration?

Molecular oxygen (O₂).

During fermentation, what acts as the terminal electron acceptor?

An organic molecule (e.g., pyruvate or acetaldehyde).

Name two differences between lactic acid fermentation and alcohol fermentation.

Lactic acid fermentation produces lactate and no CO₂ using lactate dehydrogenase; alcohol fermentation releases CO₂ and produces ethanol using pyruvate decarboxylase and alcohol dehydrogenase.

Why does fermentation occur in cells?

To regenerate NAD⁺ when oxygen is absent so glycolysis can continue producing ATP.

In which cellular compartment does fermentation take place?

The cytosol.

Where does ATP synthase obtain the energy to phosphorylate ADP?

From the proton motive force generated by chemiosmosis across the inner mitochondrial membrane.

If the inner mitochondrial membrane became leaky to H⁺ ions, what would happen to ATP production?

ATP synthesis would fall sharply because the proton gradient would be dissipated.

List two main ways bacteria generate genetic diversity.

Random mutations and horizontal gene transfer (transformation, conjugation, transduction).

Define bacterial transformation.

Uptake of naked DNA from the surrounding environment and incorporation into the genome.

What is bacterial conjugation?

Direct transfer of DNA from a donor to a recipient cell through a sex pilus.

Define transduction in bacteria.

Transfer of bacterial DNA from one cell to another via a bacteriophage.

Name the three stages of interphase.

G₁ (growth), S (DNA synthesis), and G₂ (preparation for mitosis).

A healthy cell not preparing to divide is typically in which cell-cycle phase?

G₁ phase of interphase (often termed G₀ when quiescent).

During which division (mitosis or meiosis) do homologous chromosomes pair and crossing over occur?

Meiosis I.

What key event characterizes prometaphase of mitosis?

The nuclear envelope breaks down and spindle microtubules attach to kinetochores on chromosomes.

What is the point where crossing over occurs between homologous chromosomes called?

A chiasma (plural: chiasmata).

What is the biological purpose of crossing over?

To increase genetic diversity by exchanging DNA between homologous chromosomes.

Which other meiotic mechanism generates diversity similar to crossing over?

Independent assortment of homologous chromosomes during metaphase I.

Differentiate between homologous chromosomes and sister chromatids.

Homologous chromosomes are maternal and paternal versions of the same chromosome; sister chromatids are identical copies of one chromosome created during DNA replication.

Define ploidy.

The number of complete sets of chromosomes in a cell (n, 2n, etc.).

What is the ploidy of human somatic cells and gametes?

Somatic cells are diploid (2n); gametes are haploid (n).

Where are human gametes produced?

Sperm are produced in the testes; eggs are produced in the ovaries.

Name the male germ cell that enters meiosis to form sperm.

A primary spermatocyte derived from a spermatogonium.

Name the female germ cell that enters meiosis to form an egg.

A primary oocyte derived from an oogonium.

What is nondisjunction?

Failure of homologous chromosomes or sister chromatids to separate properly during meiosis (or mitosis).

Trisomy 13 causes which genetic disorder?

Patau syndrome.

Trisomy 18 results in what condition?

Edwards syndrome.

Which human trisomy is generally least severe and is known as Down syndrome?

Trisomy 21.

What are Brushfield spots and with which condition are they commonly associated?

Small white spots on the iris, often seen in individuals with Down syndrome.