Question 1

Which of the following best explains why the oxygen released during photosynthesis comes from water and not from carbon dioxide?

Accepted Answer

Because water is oxidized, losing electrons and producing oxygen during the light reactions.

Question 2

A scientist exposes a plant to light with a wavelength of 700 nm. Based on the absorption spectrum of chlorophyll a, what is the expected effect on the rate of photosynthesis?

Accepted Answer

The rate will decrease because 700 nm is outside the optimal absorption range for chlorophyll a.

Question 3

Which equation correctly represents the energy of a photon, and what does each variable represent?

Accepted Answer

$$E = h c / \lambda$$, where $$E is $$photon energy, $$h is $$Planck's constant, $$c is $$the speed of light, and $$\lambda is $$wavelength.

Question 4

A mutation disables the enzyme PEP carboxylase in a C₄ plant. What is the most likely consequence for the plant under hot, sunny conditions?

Accepted Answer

The plant will experience increased photorespiration and reduced photosynthetic efficiency.

Question 5

Which of the following best describes the difference between linear and cyclic electron flow in the light reactions of photosynthesis?

Accepted Answer

Linear electron flow produces ATP, NADPH, and oxygen; cyclic electron flow produces only ATP and does not release oxygen.

Question 6

A plant is genetically engineered to lack ATP synthase in its thylakoid membranes. Which process will be directly affected?

Accepted Answer

The synthesis of ATP from ADP and $$P_i$$ via chemiosmosis.

Question 7

Which of the following scenarios illustrates the principle of signal amplification in cell signaling?

Accepted Answer

A single ligand binds to a receptor, which activates multiple G proteins, each of which activates several adenylyl cyclase enzymes, resulting in the production of many cAMP molecules.

Question 8

A mutation causes a G protein to be unable to hydrolyze GTP to GDP. What is the most likely cellular consequence?

Accepted Answer

The G protein will remain active, continuously stimulating downstream signaling pathways.

Question 9

Which of the following best explains why steroid hormones can regulate gene expression directly?

Accepted Answer

Steroid hormones are lipid-soluble and can cross the plasma membrane to bind intracellular receptors that act as transcription factors.

Question 10

A researcher adds a drug that inhibits protein phosphatases to a cell culture. What is the most likely effect on cell signaling?

Accepted Answer

Proteins will remain phosphorylated longer, potentially prolonging or amplifying the signal.

Question 11

During which stage of mitosis do sister chromatids separate and move toward opposite poles of the cell?

Accepted Answer

Anaphase

Question 12

A cell is observed to have condensed chromosomes aligned at the metaphase plate, with spindle fibers attached to kinetochores. Which checkpoint must be satisfied before the cell can proceed to the next stage?

Accepted Answer

Spindle (M) checkpoint

Question 13

Which of the following best describes the role of cyclin-dependent kinases (CDKs) in the cell cycle?

Accepted Answer

CDKs phosphorylate target proteins to regulate progression through the cell cycle.

Question 14

A cell line is found to lack functional p53 protein. Which of the following is a likely consequence?

Accepted Answer

The cell may fail to arrest the cell cycle or undergo apoptosis in response to DNA damage.

Question 15

Which of the following best explains why cancer cells can continue to divide even when they are densely packed and not attached to a substrate?

Accepted Answer

They have lost normal responses to density-dependent inhibition and anchorage dependence.

Question 16

A patient is diagnosed with a tumor that has spread to the liver from the colon. Which term best describes this process?

Accepted Answer

Metastasis

Question 17

Which of the following is a direct product of the Calvin cycle that can be used to synthesize glucose and other carbohydrates?

Accepted Answer

Glyceraldehyde-3-phosphate (G3P)

Question 18

Which of the following best describes the role of caspases in apoptosis?

Accepted Answer

They cleave specific target proteins to coordinate cell dismantling.

Question 19

A cell is exposed to a growth factor that binds to a receptor tyrosine kinase (RTK). Which sequence of events is most likely to occur?

Accepted Answer

The RTK dimerizes and autophosphorylates, activating downstream signaling pathways.

Question 20

Which of the following best explains why C₄ and CAM plants are more efficient than C₃ plants in hot, arid environments?

Accepted Answer

They have mechanisms to concentrate CO₂ around RuBisCO, reducing photorespiration.

Photosynthesis, Cell Communication, and the Cell Cycle: Structured Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard