Plasma Membranes
This is the primary structural framework of the plasma membrane, composed of two layers of lipid molecules.
What is the phospholipid bilayer?
A solution that has the same solute concentration as the inside of a cell is called…
What is isotonic?
The resting membrane potential of a typical neuron is approximately…
What is –70 mV?
This pigment absorbs light energy to excite electrons in Photosystem II.
What is chlorophyll a?
Linear electron flow stops (no NADPH), oxygen production stops, but cyclic electron flow can still generate ATP.
What is RuBP (ribulose bisphosphate)?
This describes the plasma membrane as a flexible layer with proteins embedded like tiles.
What is the fluid mosaic model?
A plant cell is placed in a solution, and it becomes turgid. This solution is…
What is hypotonic?
If the threshold potential of a neuron is –55 mV, and a stimulus brings the membrane potential to –50 mV, what occurs? Explain why.
What is an action potential is triggered because the threshold is surpassed; voltage-gated Na⁺ channels open, causing rapid depolarization.
The primary purpose of the electron transport chain in the light reactions is to produce a proton gradient used to synthesize this molecule.
What is ATP?
For every three molecules of CO₂ fixed, one molecule of this 3-carbon sugar exits the Calvin cycle.
What is G3P (glyceraldehyde-3-phosphate)?
Proteins that help molecules move down their concentration gradient without energy use are involved in this process.
What is facilitated diffusion?
Water moves across cell membranes through these specialized proteins.
What are aquaporins?
Myelin sheaths increase the speed of action potentials by allowing the signal to jump between gaps called…
What are nodes of Ranvier?
During linear electron flow, electrons travel from Photosystem II to Photosystem I and ultimately reduce this molecule.
What is NADP⁺ (to form NADPH)?
C₄ plants physically separate carbon fixation and the Calvin cycle between these two types of cells.
What are mesophyll cells and bundle sheath cells?
Cells expel large molecules or wastes using this vesicle-mediated transport process.
What is exocytosis?
A freshwater protist has a contractile vacuole that constantly pumps out water. Explain why this adaptation is necessary in terms of osmosis and tonicity.
What is: the freshwater environment is hypotonic relative to the protist’s cytoplasm, so water continuously enters the cell by osmosis. The contractile vacuole prevents the cell from bursting.
Tetrodotoxin (from pufferfish) blocks voltage-gated Na⁺ channels. Predict the effect on neuron signaling.
What is action potentials cannot occur, so nerve signals are blocked?
The specific chlorophyll in PSII is this, while the specific chlorophyll in PSI is this.
What is P680 and P700?
The Calvin cycle does not directly require light, yet it cannot run in the dark for long. Explain why.
It depends on ATP and NADPH from the light reactions, and Rubisco and other enzymes require light-activated conditions (high pH, Mg²⁺ levels, thioredoxin activation).
This type of active transport uses a single protein to move two substances in one direction whereas this n this type of active transport, this protein will move one substance in while another moves out at the same time.
What is a symporter and antiport?
If a plant cell is in a hypertonic solution, the cell membrane pulls away from the cell wall in a process called…
What is plasmolysis?
Explain how the Na⁺/K⁺ pump contributes indirectly to repeated firing of action potentials even though it is not directly involved in the rapid depolarization phase.
What is the pump restores resting ion gradients over time, maintaining the concentration differences necessary for future action potentials?
Protons accumulate in this part of the chloroplast during the light reactions, creating the gradient used for ATP synthesis.
What is the thylakoid lumen or thylakoid space?
This phase of the Calvin cycle uses both ATP and NADPH to convert 3-PGA into G3P.
What is the reduction phase?
The sodium-potassium pump moves sodium and potassium in opposite directions. Which direction are sodium ions pumped and how many? Which direction are potassium ions pumped and how many?
What is 3 sodium ions out of the cell and 2 potassium ions into the cell?
Pure water has a water potential of 0. A cell has Ψs = –0.7 MPa and Ψp = +0.3 MPa. If placed in pure water, will water enter or leave the cell?
What is water will enter the cell because the cell’s Ψ= –0.4 MPa, which is lower than pure water (Ψ= 0).
Compare and contrast the effects of a local anesthetic that blocks voltage-gated Na⁺ channels versus a toxin that blocks K⁺ channels on action potentials.
Blocking Na⁺ channels prevents depolarization → action potentials cannot fire. Blocking K⁺ channels slows repolarization → prolonged action potentials, but signals can still propagate.
Why is the splitting of water at Photosystem II referred to as photolysis, and why does it occur on the lumen side of the membrane?
Light energy drives the oxidation of water; it occurs on the lumen side to directly contribute protons to the lumen for the H⁺ gradient.
C₄ and CAM plants avoid photorespiration using this first stable 4-carbon compound.
What is oxaloacetate?
List the 6 main functions of membrane proteins.
What are 1. transport, 2. Cell-Cell recognition, 3. Enzymatic activity, 4. Signal transduction, 5. Intercellular joining, and 6. Attachment for extracellular matrix or cytoskeleton
A plant cell is placed in a solution with solute concentration slightly higher than its cytoplasm. Predict the effect on turgor pressure and explain why the cell does not immediately plasmolyze completely.
What is water will leave the cell, reducing turgor pressure. The cell wall resists complete collapse, so plasmolysis is partial; the cell maintains some structure until equilibrium is approached.
A demyelinating disease damages the myelin on an axon. Predict how this affects action potential propagation.
Conduction slows or may fail; signals may dissipate between nodes because saltatory conduction is impaired.
Predict the effect of disabling Photosystem II while keeping Photosystem I functional.
Linear electron flow stops (no NADPH), oxygen production stops, but cyclic electron flow can still generate ATP.
ATP:NADPH usage in the Calvin cycle is not equal. Predict why cyclic electron flow increases during high Calvin cycle activity.
The Calvin cycle uses more ATP than NADPH, so cyclic electron flow supplements ATP production without generating additional NADPH.