Free BACE Cells Questions and Answers 2 — Questions and Answers
Question 1: What is the primary function of the cell membrane?
- To synthesize proteins for export
- To regulate what enters and exits the cell by acting as a selectively permeable barrier (Correct answer)
- To produce energy through oxidative phosphorylation
- To store genetic information for cell division
Correct answer: To regulate what enters and exits the cell by acting as a selectively permeable barrier
The cell membrane is selectively permeable, allowing certain molecules to pass while blocking others, regulating the internal environment of the cell.
The plasma membrane is a phospholipid bilayer with embedded proteins. Its selective permeability is achieved through: the hydrophobic core that blocks polar molecules and ions, channel proteins that allow specific ions to pass, carrier proteins that transport specific molecules, and receptor proteins that respond to external signals. This control over cellular contents is fundamental to maintaining homeostasis.
Question 2: Which organelle is responsible for producing ATP through cellular respiration in eukaryotic cells?
- Nucleus
- Ribosome
- Mitochondria (Correct answer)
- Endoplasmic reticulum
Correct answer: Mitochondria
Mitochondria carry out oxidative phosphorylation, producing the majority of ATP used by eukaryotic cells through the electron transport chain.
Mitochondria perform aerobic cellular respiration: glycolysis products enter the mitochondria, are processed through the citric acid cycle, and the electron transport chain uses electron carriers to pump protons across the inner mitochondrial membrane, driving ATP synthase. Each glucose molecule ultimately yields approximately 30-36 ATP molecules.
Question 3: What is the difference between prokaryotic and eukaryotic cells?
- Prokaryotes have a nucleus; eukaryotes do not
- Eukaryotes have a membrane-bound nucleus and organelles; prokaryotes lack these structures (Correct answer)
- Prokaryotes are larger and more complex than eukaryotes
- Eukaryotes lack cell walls while prokaryotes always have them
Correct answer: Eukaryotes have a membrane-bound nucleus and organelles; prokaryotes lack these structures
Eukaryotic cells have a true membrane-bound nucleus and specialized organelles; prokaryotic cells (bacteria and archaea) lack a membrane-bound nucleus and membrane-bound organelles.
Prokaryotes have no membrane-bound nucleus, no membrane-bound organelles, 70S ribosomes, and are typically 0.1-10 µm. Eukaryotes have a membrane-bound nucleus, organelles (mitochondria, ER, Golgi, lysosomes), 80S ribosomes, and are typically 10-100 µm. This distinction is fundamental in biotechnology as different cell types are used for different applications.
Question 4: What is the role of ribosomes in a cell?
- To store genetic information as DNA
- To synthesize proteins by translating mRNA sequences into amino acid chains (Correct answer)
- To transport molecules across the cell membrane
- To package proteins for export from the cell
Correct answer: To synthesize proteins by translating mRNA sequences into amino acid chains
Ribosomes are the sites of protein synthesis — they read mRNA sequences (translation) and link amino acids together to form polypeptide chains.
Ribosomes are complexes of rRNA and proteins that catalyze translation. Free ribosomes in the cytoplasm synthesize proteins destined for the cytoplasm. Membrane-bound ribosomes (on rough ER) synthesize proteins destined for the secretory pathway. Biotechnology exploits ribosomes extensively in recombinant protein production.
Question 5: What is cell cycle arrest and in what context is it relevant in biotechnology?
- The permanent death of a cell due to DNA damage
- The temporary or permanent pausing of the cell cycle at specific checkpoints in response to internal or external signals (Correct answer)
- The conversion of a cell from proliferative to differentiated state
- The process by which cells stop dividing after reaching 100% confluency in culture
Correct answer: The temporary or permanent pausing of the cell cycle at specific checkpoints in response to internal or external signals
Cell cycle arrest is the pausing of cell cycle progression at checkpoints in response to DNA damage, nutrient deprivation, or signaling, preventing damaged cells from dividing.
Cell cycle checkpoints ensure genomic integrity: G1 checkpoint monitors cell size, nutrients, and DNA integrity; G2/M checkpoint ensures DNA replication is complete; spindle assembly checkpoint ensures chromosomes are properly attached before separation. In biotechnology, cell cycle synchronization is used to study phase-specific processes and to maximize recombinant protein yield in certain production systems.
Question 6: Which type of cell junction in epithelial tissues prevents molecules from passing between adjacent cells?
- Gap junctions
- Desmosomes
- Tight junctions (zonula occludens) (Correct answer)
- Adherens junctions
Correct answer: Tight junctions (zonula occludens)
Tight junctions seal adjacent epithelial cells together, preventing paracellular transport of molecules between cells and maintaining distinct compartments.
Tight junctions consist of claudin and occludin proteins that form a seal between adjacent epithelial cells, restricting paracellular transport of ions, water, and macromolecules. They are critical in maintaining polarized epithelial barriers. Desmosomes provide mechanical strength. Gap junctions allow direct cell-to-cell communication. In cell culture models, tight junction integrity is assessed by transepithelial electrical resistance (TEER).
Free BACE Cells Questions and Answers 2
What is the primary function of the cell membrane?