Biology 189 Unit 4 Study Guide Flashcards

Question-and-answer flashcards covering aerobic respiration, fermentation, energy pathways, cell cycle regulation, mitosis, meiosis, chromosomal errors, and prokaryotic reproduction.

What are the four main stages of aerobic cellular respiration (in order)?

Glycolysis, pyruvate oxidation, Krebs (citric acid) cycle, and electron transport chain/oxidative phosphorylation.

During which stages of cellular respiration is CO2 released?

Pyruvate oxidation and the Krebs cycle.

Which metabolic pathway of cellular respiration generates the most ATP?

The electron transport chain coupled to oxidative phosphorylation.

Approximately how many ATP are produced per glucose in complete aerobic respiration?

About 32-38 ATP.

What is the principal role of NAD⁺ in cellular respiration?

It acts as an electron carrier, accepting electrons to become NADH and delivering them to the electron transport chain.

Where in the cell does glycolysis occur?

In the cytoplasm (cytosol).

What are the inputs and outputs of glycolysis (per glucose)?

Input: glucose (6C), 2 NAD⁺, 2 ADP + 2 P. Output: 2 pyruvate (3C each), 2 NADH, 2 net ATP.

How many net ATP are gained in glycolysis?

2 ATP.

Does glycolysis require molecular oxygen (O₂)?

No, it is anaerobic.

Where in the cell does pyruvate oxidation take place?

In the mitochondrial matrix.

What are the inputs and outputs of pyruvate oxidation (per pyruvate)?

Input: pyruvate, CoA, NAD⁺. Output: acetyl-CoA, CO₂, NADH.

Is oxygen directly required for pyruvate oxidation?

Not directly, but the reaction ceases without the ETC’s use of O₂.

Where does the Krebs (citric acid) cycle occur in eukaryotes?

In the mitochondrial matrix.

What are the main outputs of the Krebs cycle per acetyl-CoA?

3 NADH, 1 FADH₂, 1 ATP (or GTP), and 2 CO₂.

How many ATP (or GTP) does the Krebs cycle make directly per glucose?

2 ATP (1 per acetyl-CoA).

Where is the electron transport chain located in eukaryotic cells?

In the inner mitochondrial membrane (cristae).

What molecule is the final electron acceptor of the ETC?

Molecular oxygen (O₂).

How is water formed during cellular respiration?

O₂ accepts electrons and protons at the end of the ETC, forming H₂O.

What is oxidative phosphorylation?

ATP synthesis powered by the proton-motive force generated by the ETC.

Roughly how many ATP are produced by oxidative phosphorylation per glucose?

About 26–28 ATP.

Under anaerobic conditions, how many ATP are produced per glucose by fermentation?

2 ATP (from glycolysis).

What is the purpose of fermentation for the cell?

To regenerate NAD⁺ so glycolysis can continue producing ATP in the absence of O₂.

What are the end products of lactic acid fermentation?

2 lactate molecules (lactic acid) and 2 NAD⁺.

What are the end products of alcohol fermentation?

2 ethanol, 2 CO₂, and 2 NAD⁺.

Why do muscles fatigue during prolonged anaerobic exercise?

Accumulating lactate and limited ATP production reduce pH and energy supply, leading to fatigue.

Give two major differences between aerobic respiration and fermentation.

Aerobic respiration uses O₂ and yields ~30–32 ATP; fermentation occurs without O₂ and yields only 2 ATP and specific organic end products.

Where do NADH molecules generated in glycolysis normally go under aerobic conditions?

They are shuttled into mitochondria to donate electrons to the ETC.

How can polysaccharides feed into cellular respiration?

They are hydrolyzed to glucose or other sugars that enter glycolysis.

How can lipids be utilized in cellular respiration?

Glycerol enters glycolysis; fatty acids undergo β-oxidation to acetyl-CoA for the Krebs cycle.

How are proteins used to generate ATP in cellular respiration?

Amino acids are deaminated; the carbon skeletons feed into glycolysis, acetyl-CoA, or the Krebs cycle.

What is gluconeogenesis?

The synthesis of glucose from non-carbohydrate precursors such as pyruvate, lactate, or amino acids.

Which yields more ATP per glucose: aerobic respiration or fermentation?

Aerobic respiration.

What are the two types of reproduction?

Asexual reproduction (single parent, genetically identical offspring) and sexual reproduction (two parents, genetic recombination).

Define mitosis.

The division of a eukaryotic nucleus followed by cytokinesis, producing two identical diploid daughter cells.

Define meiosis.

A two-stage nuclear division that reduces chromosome number by half, producing haploid gametes.

What are gametes?

Reproductive cells (sperm and eggs) that are haploid.

What are somatic cells?

All body cells except gametes; they are diploid in humans.

What is chromatin?

DNA and associated proteins in a relaxed, threadlike form found during interphase.

What is a chromosome?

A condensed, threadlike structure of DNA and proteins visible during cell division.

What are homologous chromosome pairs?

Two chromosomes of the same length and gene sequence, one inherited from each parent.

Define haploid (n).

Having one set of chromosomes.

Define diploid (2n).

Having two sets of homologous chromosomes.

What is fertilization?

The fusion of haploid gametes to form a diploid zygote.

What is a zygote?

The diploid cell resulting from fertilization.

What are the main phases of the eukaryotic cell cycle?

Interphase (G1, S, G2) and the M phase (mitosis + cytokinesis).

What are the three phases of interphase and a key event in each?

G1: cell growth; S: DNA replication; G2: preparation for mitosis (organelle duplication, spindle formation).

What is the cell-cycle control system?

A network of regulatory proteins that coordinates the timing of key events in the cell cycle.

What is a checkpoint?

A control point where stop/go-ahead signals regulate the cycle’s progression.

What is the restriction point (G1 checkpoint)?

The point after which the cell commits to the full cycle in the absence of external signals.

What is the G0 phase?

A non-dividing state a cell may enter from G1.

What are growth factors?

External proteins that stimulate cell division.

What are cyclin-dependent kinases (CDKs)?

Enzymes that, when bound to cyclins, phosphorylate target proteins to drive the cell cycle.

What are cyclins?

Regulatory proteins whose levels fluctuate with the cell cycle and activate CDKs.

What is the overall function of mitosis?

Growth, tissue repair, and asexual reproduction by producing genetically identical cells.

What organisms perform mitosis?

All eukaryotic organisms (plants, animals, fungi, protists).

What is a duplicated chromosome?

A chromosome consisting of two sister chromatids joined at a centromere.

What is the centromere?

The region where sister chromatids are most tightly joined and where kinetochores form.

What is a kinetochore?

Protein complex on the centromere where spindle microtubules attach.

What are spindle fibers?

Microtubules that orchestrate chromosome movement during mitosis/meiosis.

What is a daughter chromosome?

A chromatid that has separated and is moving to opposite poles during anaphase.

In animal cells, what structure pinches the cell in two during cytokinesis?

The contractile ring that forms the cleavage furrow.

What is the cell plate?

A precursor to the new cell wall that forms during plant cell cytokinesis.

What happens during prophase of mitosis?

Chromatin condenses, nucleolus disappears, mitotic spindle begins to form, and centrosomes move apart.

What happens during metaphase of mitosis?

Chromosomes line up at the metaphase plate with kinetochores attached to spindle fibers from opposite poles.

What happens during anaphase of mitosis?

Sister chromatids separate and are pulled toward opposite poles.

What regulates progression through mitosis?

Cyclin-CDK complexes (especially M-phase–promoting factor) and spindle checkpoints.

What is the end result of mitosis in terms of ploidy and genetic identity?

Two genetically identical diploid daughter cells.

What is the primary event of meiosis I?

Separation of homologous chromosomes, reducing the cell from diploid to haploid.

What is the primary event of meiosis II?

Separation of sister chromatids, similar to mitosis.

What is crossing over?

Exchange of genetic material between nonsister chromatids of homologous chromosomes.

What is a tetrad?

A paired set of homologous chromosomes, each composed of two sister chromatids (4 chromatids total).

What is a chiasma?

The visible site where crossing over has occurred.

What are recombinant chromosomes?

Chromosomes that carry genes from both parents due to crossing over.

What is independent assortment and when does it occur?

Random orientation of homologous pairs on the metaphase I plate, leading to genetic variation.

What happens during metaphase I of meiosis?

Homologous pairs align side-by-side at the metaphase plate, each pair attached to opposite poles.

What is the final product of meiosis starting from one diploid cell?

Four genetically diverse haploid cells (gametes).

What is nondisjunction?

Failure of homologs or sister chromatids to separate properly during meiosis or mitosis.

What is aneuploidy?

An abnormal number of chromosomes (extra or missing).

What is monosomy?

A type of aneuploidy with only one copy of a particular chromosome.

What is trisomy?

A type of aneuploidy with three copies of a particular chromosome.

What is translocation in chromosomes?

A segment of one chromosome becomes attached to a non-homologous chromosome.

What is binary fission?

Asexual cell division in prokaryotes producing two identical cells.

How is binary fission different from mitosis?

It lacks a mitotic spindle and involves circular DNA replication followed by membrane/cell-wall ingrowth.

How do spermatogenesis and oogenesis differ?

Spermatogenesis produces four equal sperm continuously; oogenesis yields one large ovum and polar bodies, and is discontinuous.

What is bacterial conjugation?

Direct transfer of DNA between bacteria through a pilus-formed conjugation bridge.

What is a conjugation bridge?

A cytoplasmic connection via sex pilus that allows DNA transfer between bacteria.

What is a plasmid?

A small, circular, self-replicating DNA molecule separate from chromosomal DNA.

What is recombination in bacteria?

The incorporation of transferred DNA into the recipient’s chromosome, producing new gene combinations.