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Questions and Answers
What does the law of segregation state about alleles during gamete formation?
What does the law of segregation state about alleles during gamete formation?
What is the term for a heritable feature that varies among individuals?
What is the term for a heritable feature that varies among individuals?
Which statement about a homozygous organism is true?
Which statement about a homozygous organism is true?
What occurs during meiosis that is different from most cell division processes?
What occurs during meiosis that is different from most cell division processes?
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How does the segregation of alleles correspond to chromosomal behavior during meiosis?
How does the segregation of alleles correspond to chromosomal behavior during meiosis?
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What is the primary structure of microtubules?
What is the primary structure of microtubules?
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Which protein subunit is a dimer found in microtubules?
Which protein subunit is a dimer found in microtubules?
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What function do microtubules primarily serve in cells?
What function do microtubules primarily serve in cells?
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Which component is NOT a type of cell junction?
Which component is NOT a type of cell junction?
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What role do integrins play in the extracellular matrix?
What role do integrins play in the extracellular matrix?
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Which type of cell junction prevents fluid from moving across layers of cells?
Which type of cell junction prevents fluid from moving across layers of cells?
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What is the main function of the centrosome?
What is the main function of the centrosome?
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What structural component is common in both cilia and flagella?
What structural component is common in both cilia and flagella?
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Which of the following is a major component of the extracellular matrix?
Which of the following is a major component of the extracellular matrix?
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What type of protein is dynein?
What type of protein is dynein?
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What primarily regulates the eukaryotic cell cycle?
What primarily regulates the eukaryotic cell cycle?
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What happens to a cell if it does not receive a go-ahead signal at the G1 checkpoint?
What happens to a cell if it does not receive a go-ahead signal at the G1 checkpoint?
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Which checkpoint is considered the most important for many cells in the cell cycle?
Which checkpoint is considered the most important for many cells in the cell cycle?
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What role do cyclin-dependent kinases (Cdks) play in the cell cycle?
What role do cyclin-dependent kinases (Cdks) play in the cell cycle?
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What initiates a cell's transition from G2 phase into M phase?
What initiates a cell's transition from G2 phase into M phase?
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How do external factors influence cell division?
How do external factors influence cell division?
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What is MPF an example of?
What is MPF an example of?
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Which of the following statements about cancer cells is true?
Which of the following statements about cancer cells is true?
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What happens to the activity of Cdks throughout the cell cycle?
What happens to the activity of Cdks throughout the cell cycle?
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During which phase do cells ensure all chromosomes are properly attached to the spindle?
During which phase do cells ensure all chromosomes are properly attached to the spindle?
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What is the role of acetyl CoA in cellular respiration?
What is the role of acetyl CoA in cellular respiration?
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How many ATP molecules are generated by one turn of the citric acid cycle?
How many ATP molecules are generated by one turn of the citric acid cycle?
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What happens to electrons as they move through the electron transport chain?
What happens to electrons as they move through the electron transport chain?
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What is the primary function of NADH and FADH2 in cellular respiration?
What is the primary function of NADH and FADH2 in cellular respiration?
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Where does chemiosmosis occur during cellular respiration?
Where does chemiosmosis occur during cellular respiration?
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What process generates most of the ATP in cellular respiration?
What process generates most of the ATP in cellular respiration?
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What is the initial product formed when acetyl CoA combines with oxaloacetate?
What is the initial product formed when acetyl CoA combines with oxaloacetate?
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What does the electron transport chain consist mostly of?
What does the electron transport chain consist mostly of?
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Which of the following statements about glycolysis is correct?
Which of the following statements about glycolysis is correct?
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What connects glycolysis to the citric acid cycle?
What connects glycolysis to the citric acid cycle?
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What is the final electron acceptor in the electron transport chain?
What is the final electron acceptor in the electron transport chain?
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Why is chemiosmosis important for ATP production?
Why is chemiosmosis important for ATP production?
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Which component of the mitochondrion is responsible for the electron transport chain?
Which component of the mitochondrion is responsible for the electron transport chain?
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What is the main purpose of the citric acid cycle?
What is the main purpose of the citric acid cycle?
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What is the primary function of helicase in DNA replication?
What is the primary function of helicase in DNA replication?
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What is the role of single-strand binding proteins during DNA replication?
What is the role of single-strand binding proteins during DNA replication?
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Which enzyme is responsible for correctively relieving overwinding ahead of replication forks?
Which enzyme is responsible for correctively relieving overwinding ahead of replication forks?
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In which direction do DNA polymerases add nucleotides during replication?
In which direction do DNA polymerases add nucleotides during replication?
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What are Okazaki fragments associated with in DNA replication?
What are Okazaki fragments associated with in DNA replication?
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What problem does DNA polymerase face with linear DNA during replication?
What problem does DNA polymerase face with linear DNA during replication?
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What is the primary role of telomerase in eukaryotic cells?
What is the primary role of telomerase in eukaryotic cells?
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What do telomeres do for chromosomes?
What do telomeres do for chromosomes?
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Which component is responsible for synthesizing RNA primers?
Which component is responsible for synthesizing RNA primers?
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What is the main limitation of the replication machinery in eukaryotes regarding DNA ends?
What is the main limitation of the replication machinery in eukaryotes regarding DNA ends?
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What direction does the leading strand synthesize during DNA replication?
What direction does the leading strand synthesize during DNA replication?
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How does DNA ligase function in DNA replication?
How does DNA ligase function in DNA replication?
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Which statement about the antiparallel structure of DNA is true?
Which statement about the antiparallel structure of DNA is true?
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Why is shorter DNA molecules a problem in eukaryotic chromosomes?
Why is shorter DNA molecules a problem in eukaryotic chromosomes?
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Study Notes
Cell Structure and Function
- The extracellular matrix (ECM) of animal cells is made of glycoproteins like collagen, fibronectin, and a proteoglycan complex. ECM proteins bind to integrins in the plasma membrane.
- The cytoskeleton is a network of microtubules, microfilaments, and intermediate filaments; it provides support and motility, maintaining cell shape.
- Microtubules (tubulin polymers) are hollow tubes (25 nm diameter with 15 nm lumen), the thickest cytoskeletal fibers. Tubulin is a dimer of α- and β-tubulin. Functions include maintaining cell shape, cell motility (cilia, flagella), chromosome movement, and organelle movement. Centrosomes contain centrioles with nine microtubule triplets. Cilia and flagella have a microtubule core, a basal body, and the motor protein dynein.
- Peroxisomes perform oxidation reactions; their relation to other organelles is not fully understood.
Cell Junctions
- Tight junctions prevent fluid movement across cell layers.
- Desmosomes are anchoring junctions.
- Gap junctions (communicating junctions) provide cytoplasmic channels between cells; they are found in epithelial tissues.
Cellular Respiration
- Glycolysis occurs with or without oxygen.
- Pyruvate is converted to acetyl CoA before the citric acid cycle. This is catalyzed by a multienzyme complex.
- The citric acid cycle (Krebs cycle) completes pyruvate breakdown to CO2, producing 1 ATP, 3 NADH, and 1 FADH2 per turn. It involves eight enzyme-catalyzed steps; acetyl CoA combines with oxaloacetate, and citrate is decomposed back to oxaloacetate.
- Oxidative phosphorylation generates most of the ATP (≈90%) via redox reactions, using the electron transport chain and chemiosmosis. Glycolysis and the citric acid cycle produce smaller amounts of ATP by substrate-level phosphorylation.
- The electron transport chain is located in the inner mitochondrial membrane (cristae). Electrons are passed through protein complexes, including cytochromes, ultimately to O2 forming H2O. ATP is not directly generated here.
- Chemiosmosis uses the H+ gradient (generated by electron transport) to drive ATP synthesis via ATP synthase.
Mitosis and Cell Cycle
- The cell cycle is regulated by a molecular control system; cell division frequency varies by cell type.
- Cancer cells escape usual cell cycle controls.
- Cytoplasmic signals drive the cell cycle.
- The cell cycle has checkpoints (G1, G2, M) where it stops until a “go-ahead” signal is received. The G1 checkpoint is often the most important. Cells in G0 are non-dividing.
- The cell cycle control system involves cyclins and cyclin-dependent kinases (Cdks). Cdk activity depends on cyclin concentration.
- MPF (maturation-promoting factor), a cyclin-Cdk complex, triggers passage past the G2 checkpoint.
- Internal signals (e.g., chromosome attachment to the spindle) and external factors (e.g., growth factors like PDGF) influence cell division.
Mendelian Genetics
- A character is a heritable feature; a trait is a character variant.
- The law of segregation: two alleles for a character separate during gamete formation.
- Homozygous: two identical alleles; heterozygous: two different alleles.
Meiosis
- Meiosis is a specialized cell division producing sperm and egg cells with half the genetic information of the parent cell.
Key Players in DNA Replication
- Helicase: Unwinds the parental DNA double helix at replication forks.
- Single-strand binding proteins: Stabilize single-stranded DNA until it's used as a template.
- Topoisomerase: Relieves strain ahead of replication forks by breaking, swiveling, and rejoining DNA strands.
- Primase: Synthesizes RNA primers needed to initiate DNA synthesis.
- DNA polymerase III: Adds nucleotides to the growing DNA strand using the parental DNA as a template.
- DNA polymerase I: Removes RNA primers and replaces them with DNA nucleotides.
- DNA ligase: Joins Okazaki fragments on the lagging strand and seals gaps in the leading strand.
Antiparallel Elongation
- DNA polymerase adds nucleotides only to the free 3' end of a growing strand (5' to 3' direction).
- Leading strand synthesis is continuous in the direction of the replication fork.
- Lagging strand synthesis is discontinuous, producing Okazaki fragments.
Replicating the Ends of DNA Molecules
- DNA polymerase cannot replicate the 5' ends of linear DNA molecules, leading to shortening with repeated replication.
- This is not a problem for prokaryotes with circular chromosomes.
Telomeres
- Specialized nucleotide sequences at eukaryotic chromosome ends.
- Protect genes near the ends from erosion during replication.
- Telomere shortening is linked to aging.
- Telomerase lengthens telomeres.
Steps in DNA replication
- The provided text does not detail the steps in DNA replication.
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Description
This quiz explores the essential components of cell structure and the function of various organelles. It covers topics such as extracellular matrix, cytoskeleton, and cell junctions, providing insight into how these structures contribute to cellular integrity and operations. Test your understanding of cellular architecture and its significance in biological processes.
