General Biology Flashcards

A cell with a water potential of -0.4 MPa is placed in a solution with a water potential of -0.2 MPa. Water will:

Answer: Move out of the cell

Water moves by osmosis from higher (less negative) to lower (more negative) water potential, so water exits the cell toward the -0.2 MPa solution.

Which stage of cellular respiration produces the most ATP per glucose molecule?

Answer: Oxidative phosphorylation

Oxidative phosphorylation (electron transport chain + chemiosmosis) generates approximately 32-34 ATP per glucose, far more than the other stages.

What is the function of the sinoatrial (SA) node in the heart?

Answer: Initiates the electrical impulse for each heartbeat

The SA node is the heart's natural pacemaker, spontaneously generating electrical impulses that trigger each cardiac contraction.

Which of the following is a characteristic feature of prokaryotic cells?

Answer: 70S ribosomes

Prokaryotes have 70S ribosomes (composed of 50S and 30S subunits), while eukaryotes have 80S ribosomes in the cytoplasm.

Hardy-Weinberg equilibrium requires which of the following conditions?

Answer: Random mating among individuals

One of the five Hardy-Weinberg assumptions is random mating; violations of this or other assumptions cause allele frequencies to change over time.

Which hormone is primarily responsible for stimulating the fight-or-flight response?

Answer: Epinephrine

Epinephrine (adrenaline), released by the adrenal medulla, rapidly triggers the fight-or-flight response by increasing heart rate, dilating airways, and mobilizing energy.

What type of bond holds the two strands of a DNA double helix together?

Answer: Hydrogen bonds

Complementary base pairs (A-T and G-C) between the two DNA strands are held together by hydrogen bonds, which are weak but collectively stable.