Chapter 11
A membrane contains mostly saturated fatty acid tails and is exposed to a sudden drop in temperature. Which change would best prevent the membrane from becoming excessively rigid?
What is increasing cholesterol?
A positively charged ion has a high concentration outside a cell, while the inside of the cell is electrically negative. Both forces favor movement into the cell. What type of gradient determines this movement?
What is the electrochemical gradient?
Define the different gating mechanisms for ion channels.
Ion channel gating is the process by which integral membrane proteins switch between closed, open, and inactivated conformational states to control the passive flow of ions across cell membranes
what provides the strongest support for the endosymbiotic theory?
Mitochondria and chloroplasts possess circular DNA and bacterial-like 70S ribosomes.
Explain the role of Acetyl-CoA and pyruvate dehydrogenase complex.
The pyruvate dehydrogenase complex (PDC) is a large multienzyme group in the mitochondrial matrix that links glycolysis to the citric acid (TCA) cycle by converting pyruvate into acetyl-CoA. Acetyl-CoA then acts as a central carbon fuel source that enters the TCA cycle to drive cellular respiration and ATP production.
A protein contains a long stretch of mostly nonpolar amino acids that is approximately the thickness of a lipid bilayer. What type of membrane association is most likely?
What is an integral membrane protein?
The Na⁺/K⁺ pump uses __ hydrolysis to move ___ and ____,
The Na⁺/K⁺ pump uses ATP hydrolysis to move 3 Na⁺ outward and 2 K⁺ inward
Identify the basic components of a nerve cell.
Which molecule is the ultimate electron donor in the light-dependent reactions of oxygenic photosynthesis?
Water is split during photolysis in the light-dependent reactions to replace the electrons lost by chlorophyll and releases oxygen as a byproduct.
one process that result in CO2 production.
Cellular Respiration: Plants, animals, and microorganisms combine glucose and oxygen to produce energy, releasing \(\text{CO}_{2}\) and water vapor
A scientist observes a membrane protein that can move laterally within one region of the membrane but cannot cross into an adjacent region. What structure most directly explains this restriction?
What is tight junctions
Suppose voltage-gated Na⁺ channels could open normally but could never inactivate. What major effect would this have on an action potential?
prolonged Na⁺ influx and impaired termination of depolarization?
Describe how an action potential propagates along an axon.
An action potential is propagated down an axon when an influx of sodium ions in one active segment depolarizes the neighboring membrane section, triggering a fresh action potential in a repeating, self-sustaining wave
A scientist isolates a thylakoid membrane and exposes it to light. Which combination of machinery would be expected to be present in this membrane?
Photosystems, electron transport machinery, and ATP synthase
contrast cellular respiration and fermentation.
Fermentation and cellular respiration are both ways that cells break down glucose to make energy, but cellular respiration needs oxygen and makes much more energy, while fermentation does not need oxygen and makes less energy.
A researcher uses a detergent to disrupt a membrane. Unlike phospholipids, the detergent does not form a bilayer. What structural feature of the detergent explains this difference?
What is a single hydrophobic chain?
A neuron has a normal resting membrane potential and normal Na⁺/K⁺ gradients, but its voltage-gated K⁺ channels fail to open after voltage-gated Na⁺ channels activate. Predict the effect on the action potential and explain the underlying ion movements.
Repolarization would be impaired or delayed because K⁺ normally exits through voltage-gated K⁺ channels after the Na⁺-dependent depolarization phase. Without that outward K⁺ movement, the membrane would remain depolarized longer.
contrast simple diffusion, facilitated diffusion and active transport
Simple diffusion, facilitated diffusion, and active transport are the three main ways substances move across cell membranes, differing primarily in their energy requirements, direction relative to concentration gradients, and need for protein helpers
An uncoupling molecule allows H⁺ to cross the inner mitochondrial membrane without passing through ATP synthase. Which outcome would be expected?
Dissipation of the proton gradient and decreased ATP production through oxidative phosphorylation
identify the location for glycolysis, fermentation, citric acid cycle and oxidative
phosphorylation
Why can an ion move against its concentration gradient during secondary active transport even though the transporter itself may not directly hydrolyze ATP?
What is coupling to the favorable movement of another solute?
An action potential reaches the axon terminal, but voltage-gated Ca²⁺ channels are blocked. What step in synaptic transmission is directly disrupted?
What is Ca²⁺-dependent synaptic vesicle fusion?
Explain the difference between a channel and transporter.
A channel and a transporter (or carrier protein) are both membrane proteins that help move substances across the cell membrane, but they work in very different ways
A researcher disrupts the inner mitochondrial membrane while leaving all electron transport proteins structurally intact. Which outcome is most likely?
Electron transfer can continue, but formation of a productive proton gradient is disrupted, greatly reducing ATP synthesis.
A 3-carbon molecule enters the mitochondrion under aerobic conditions. Before entering the citric acid cycle, it loses one carbon as CO₂, transfers electrons to NAD⁺, and attaches its remaining 2-carbon acetyl group to this molecule.
What is Coenzyme A (CoA), forming acetyl-CoA?
Pyruvate is oxidized by the pyruvate dehydrogenase complex. The reaction produces acetyl-CoA, CO₂, and NADH.