Q: A solution is prepared by dissolving 0.5 moles of NaCl in enough water to make 1 liter of solution. What is the molarity ($$M) of $$the solution? Use the formula $$M = \frac{\text{moles of solute}}{\text{liters of solution}}.$$

$$M = \frac{0.5}{1} = 0.5\ \text{M}$$

Question 1

Which of the following best explains why ice floats on water, and why is this property important for aquatic life in cold climates?

Accepted Answer

Ice is less dense than liquid water due to hydrogen bonding, so it floats and insulates the water below, allowing aquatic life to survive.

Question 2

A scientist wants to test the effect of a new fertilizer on plant growth. She sets up two groups: one receives the fertilizer, and the other does not. All other conditions are kept constant. What type of experiment is this, and what is the independent variable?

Accepted Answer

This is a controlled experiment; the independent variable is the presence or absence of fertilizer.

Question 3

Which of the following best describes the difference between a hypothesis and a scientific theory?

Accepted Answer

A hypothesis is a testable, tentative explanation for an observation, while a theory is a well-supported, broad explanation for a wide range of phenomena.

Question 4

Which of the following molecules would most easily cross a cell membrane by simple diffusion?

Accepted Answer

Oxygen (O2)

Question 5

A solution is prepared by dissolving 0.5 moles of NaCl in enough water to make 1 liter of solution. What is the molarity ($$M) of $$the solution? Use the formula $$M = \frac{	ext{moles of solute}}{	ext{liters of solution}}.$$

Accepted Answer

$$M = \frac{0.5}{1} = 0.5\ 	ext{M}$$

Question 6

Which level of protein structure is directly determined by the sequence of amino acids and stabilized by peptide bonds?

Accepted Answer

Primary structure

Question 7

A patient is unable to break down certain macromolecules in their cells, leading to accumulation of waste. Which organelle is most likely malfunctioning?

Accepted Answer

Lysosome

Question 8

Which of the following best describes the main difference between exergonic and endergonic reactions?

Accepted Answer

Exergonic reactions release energy and are spontaneous, while endergonic reactions require energy input and are non-spontaneous.

Question 9

Which of the following is an example of an anabolic pathway?

Accepted Answer

Photosynthesis

Question 10

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

Accepted Answer

Anaphase

Question 11

A genetic cross between two heterozygous pea plants (Aa x Aa) results in which genotypic ratio among the offspring?

Accepted Answer

1:2:1 (AA:Aa:aa)

Question 12

Which enzyme is responsible for joining Okazaki fragments during DNA replication?

Accepted Answer

Ligase

Question 13

Which of the following statements about the sodium-potassium pump is correct?

Accepted Answer

It moves sodium and potassium ions against their concentration gradients using ATP.

Question 14

Which of the following best describes the function of the tryptophan operon in bacteria?

Accepted Answer

It is a repressible operon that is turned off when tryptophan is present.

Question 15

Which of the following best explains why cells are typically small in size?

Accepted Answer

Small cells have a higher surface area-to-volume ratio, allowing efficient exchange of materials with their environment.

Question 16

Which of the following is a property of water that allows it to dissolve many substances, making it the 'universal solvent'?

Accepted Answer

Water is polar and forms hydrogen bonds with solutes.

Question 17

Which of the following best describes the difference between structural isomers and enantiomers?

Accepted Answer

Structural isomers differ in the arrangement of atoms, while enantiomers are mirror images of each other.

Question 18

Which of the following best describes the role of enzymes in biological reactions?

Accepted Answer

Enzymes lower the activation energy, speeding up reactions.

Question 19

Which of the following statements about the lytic and lysogenic cycles of viruses is correct?

Accepted Answer

In the lysogenic cycle, viral DNA integrates into the host genome and can later enter the lytic cycle.

Question 20

A mutation causes a cell to produce a receptor protein inside the cytoplasm instead of on the plasma membrane. Which type of signaling molecule would still be able to activate this receptor?

Accepted Answer

A hydrophobic ligand such as a steroid hormone

Biology Study Guide: Foundations of Life, Cells, and Genetics

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