BIOL 130 Exam Review: Cell Structure, Membranes, Cellular Energy and Division

Terms in this set (28)

1. Prokaryotic vs eukaryotic cells: key differencesProkaryotes lack a nucleus and membrane-bound organelles, have a circular chromosome and 70S ribosomes. Eukaryotes have a nucleus, internal membrane organelles, linear chromosomes and 80S cytoplasmic ribosomes.
2. What are the main tenets of cell theory?All living things are made of one or more cells, the cell is the basic unit of life, and all cells come from pre-existing cells.
3. Describe the fluid mosaic model of the plasma membrane.A phospholipid bilayer in which lipids and proteins move laterally, with integral and peripheral proteins, cholesterol and carbohydrate chains embedded in or attached to it.
4. How does cholesterol affect membrane fluidity?It acts as a fluidity buffer: at high temperature it restrains phospholipid movement, and at low temperature it prevents tight packing, keeping the membrane from becoming too rigid.
5. How do unsaturated fatty acid tails affect a membrane?Cis double bonds create kinks that prevent tight packing, increasing membrane fluidity and lowering the temperature at which the membrane solidifies.
6. Which molecules cross a lipid bilayer easily without a transporter?Small nonpolar molecules such as O2, CO2 and N2, and to a lesser extent small uncharged polar molecules like water. Ions and large polar molecules need proteins.
7. Passive vs active transportPassive transport moves solutes down their electrochemical gradient with no energy input (simple or facilitated diffusion). Active transport moves solutes against their gradient using ATP or another gradient.
8. What does the Na+/K+ pump do per ATP hydrolyzed?It pumps 3 Na+ out of the cell and 2 K+ into the cell, contributing to the membrane potential and maintaining ion gradients.
9. Secondary active transport (cotransport)A transporter uses the energy of an ion moving down its gradient (often Na+ or H+) to move another solute against its gradient, e.g. Na+/glucose symport.
10. Function of the rough ER vs smooth ERRough ER has ribosomes and makes secretory, membrane and lysosomal proteins. Smooth ER synthesizes lipids, detoxifies drugs and stores Ca2+.
11. What does the Golgi apparatus do?It modifies (e.g. glycosylates), sorts and packages proteins and lipids received from the ER, sending them to the plasma membrane, lysosomes or secretion. Cargo enters the cis face and exits the trans face.
12. Function of lysosomesMembrane-bound organelles with acid hydrolases (active at about pH 5) that digest macromolecules, worn-out organelles (autophagy) and engulfed material.
13. What evidence supports the endosymbiotic origin of mitochondria and chloroplasts?They have double membranes, their own circular DNA, bacteria-like 70S ribosomes, and divide by a fission-like process.
14. Name the three types of cytoskeletal filaments and a main role of each.Microfilaments (actin) for cell shape and movement; intermediate filaments for mechanical strength; microtubules (tubulin) for tracks for transport, the mitotic spindle, cilia and flagella.
15. What are motor proteins kinesin and dynein used for?They walk along microtubules using ATP: kinesin generally moves cargo toward the plus end (cell periphery), dynein toward the minus end (cell centre); dynein also bends cilia and flagella.
16. Write the overall equation for aerobic cellular respiration.C6H12O6 + 6 O2 -> 6 CO2 + 6 H2O + energy (ATP and heat).
17. Where does each stage of cellular respiration occur in eukaryotes?Glycolysis: cytosol. Pyruvate oxidation and citric acid cycle: mitochondrial matrix. Electron transport chain and ATP synthase: inner mitochondrial membrane.
18. Net products of glycolysis per glucose2 pyruvate, 2 ATP (net) and 2 NADH.
19. What is chemiosmosis?The electron transport chain pumps H+ into the intermembrane space; H+ then flows back into the matrix through ATP synthase, and that flow drives ATP synthesis.
20. What is the final electron acceptor in aerobic respiration?Oxygen, which is reduced to water at the end of the electron transport chain.
21. What does fermentation accomplish when oxygen is absent?It regenerates NAD+ from NADH (producing lactate or ethanol plus CO2) so glycolysis can continue to make a small amount of ATP.
22. Competitive vs noncompetitive enzyme inhibitionA competitive inhibitor binds the active site and can be overcome by more substrate (Km rises, Vmax unchanged). A noncompetitive inhibitor binds elsewhere and lowers Vmax.
23. How do enzymes speed up reactions?They lower the activation energy by stabilizing the transition state. They do not change the overall free energy change (delta G) or the equilibrium position.
24. List the phases of the eukaryotic cell cycle in order.G1, S (DNA replication), G2 (together called interphase), then M phase: mitosis (prophase, prometaphase, metaphase, anaphase, telophase) followed by cytokinesis.
25. What happens in anaphase of mitosis?Cohesin holding sister chromatids together is cleaved, and the chromatids are pulled to opposite poles by shortening kinetochore microtubules.
26. What is the role of cyclins and cyclin-dependent kinases (Cdks)?Cyclin levels rise and fall through the cycle; cyclin binding activates Cdks, which phosphorylate targets to drive the cell through checkpoints such as G1/S and G2/M.
27. Mitosis vs meiosis outcomesMitosis produces two genetically identical diploid daughter cells. Meiosis produces four genetically varied haploid cells through two divisions, crossing over and independent assortment.
28. What is apoptosis?Programmed cell death carried out by caspases, in which the cell shrinks and fragments in a controlled way without causing inflammation.