Membranes and Molecules
What type of transport moves molecules down their concentration gradient without directly using ATP?
Passive transport
What molecule is the cell's immediate, usable energy currency?
ATP
What is the main purpose of the light reactions of photosynthesis?
To capture light energy and produce ATP and NADPH for the Calvin Cycle.
What is the typical resting membrane potential of a neuron?
-70mV
Which organelle modifies, sorts, and packages many proteins for transport?
The golgi apparatus
What type of bond forms when atoms share electrons?
A covalent bond
Where does glycolysis occur in a cell?
The cytosol
In which part of the chloroplast does the Calvin Cycle occur?
The stroma
Which part of the neuron typically integrates graded potentials to determine whether threshold is reached?
The axon hillock
Which organelle is the main site of protein synthesis by translation?
Ribosomes
A cell is placed in a solution with a higher solute concentration than its cytoplasm. Predict the movement of water.
Water moves out of the cell by osmosis, so the cell loses water and shrinks.
A cell's oxygen supply suddenly drops. Which stage of aerobic respiration is most directly affected first, and why?
The ETC because oxygen serves as its final electron acceptor.
A plant receives plenty of light, but a chemical prevents it from making NADPH. Which process would be directly limited?
The Calvin Cycle, because it uses NADPH to help reduce carbon compounds during glucose production
During the rising phase of an action potential, which ion moves through voltage-gated channels and in which direction?
Na+ moves into the neuron, causing depolarization.
A cell can make a protein, but cannot efficiently secrete it outside the cell. Name one organelle or structure in the secretory pathway that could be malfunctioning.
The rough ER, Golgi apparatus, or transport/secretory vesicles.
A membrane protein uses ATP to move Na+ out of a cell against its concentration gradient. What type of transport is occuring?
Primary active transport
A mitochondrion's inner membrane becomes freely permeable to H+. What happens to ATP production by ATP synthase?
It decreases because the proton gradient dissipates, removing the driving force of chemiosmosis.
A plant is exposed to green light instead of red or blue light. Why might its photosynthetic rate decrease?
Chlorophyll absorbs green light less effectively than red and blue light, so less light energy is captured
A toxin prevents voltage-gated K+ channels from opening. Predict what happens to repolarization.
Repolarization is impaired because K+ cannot leave through those channels as expected.
What is the main idea of the endosymbiotic theory?
Mitochondria and chloroplasts originated from free-living bacteria that were engulfed by ancestral cells and formed a lasting relationship.
A membrane is much more permeable to K+ than Na+. If K+ permeability increases further, which way will the resting membrane potential shift, and why?
It shifts toward K+ equilibrium potential (about -90mV), becoming more negative because K+ has a greater influence on the membrane potential.
A cell has functioning glycolysis, but a blocked ETC. Explain why the cell can make some ATP, but cannot maintain normal aerobic ATP production.
Glycolysis produces a small amount of ATP by substrate-level phosphorylation, but the blocked ETC prevents normal oxidative phosphorylation and disrupts NADH recycling.
A toxin stops the electron transport chain in the thylakoid membrane. Predict TWO effects on the light reactions and explain why.
ATP production through chemiosmosis and NADPH production would decrease or stop because electron transport is needed to establish the proton gradient and supply electrons for NADP+ reduction.
A drug prevents voltage-gated Na+ channels from inactivating. What effect could this have on the neuron's electrical activity?
The neuron may remain depolarized longer or fire more action potentials because Na+ entry is not shut off normally.
A cell has abundant rough ER and Golgi Apparatus. What does this suggest about the cell's function, and why?
It likely produces and secretes substantial amounts of protein because the rough ER supports the synthesis of many secreted proteins and the Golgi modifies and sorts them.