Question 1

Which of the following best describes the structure of a DNA molecule?

Accepted Answer

A double helix composed of two antiparallel polynucleotide strands held together by hydrogen bonds between complementary bases.

Question 2

Which of the following base sequences is complementary to the DNA strand 5'-TAGGCCT-3'?

Accepted Answer

3'-ATCCGGA-5'

Question 3

A mutation changes a cytosine (C) to a thymine (T) in a DNA strand. Which of the following is a possible consequence at the molecular level?

Accepted Answer

The complementary strand will have an adenine (A) instead of a guanine (G) at that position.

Question 4

Which of the following statements about phospholipids in the plasma membrane is correct?

Accepted Answer

The hydrophilic heads face the aqueous environment, while the hydrophobic tails are oriented toward the interior of the bilayer.

Question 5

Which of the following best explains why cell membranes are described as 'fluid mosaics'?

Accepted Answer

Membranes consist of a fluid phospholipid bilayer with proteins and other molecules drifting laterally within it.

Question 6

A scientist is studying a membrane protein that spans the lipid bilayer and forms a hydrophilic channel. Which function is this protein most likely performing?

Accepted Answer

Transport of specific molecules across the membrane

Question 7

Which of the following is a key difference between DNA and RNA molecules?

Accepted Answer

DNA contains deoxyribose sugar, while RNA contains ribose sugar.

Question 8

Which of the following best describes the directionality of a polynucleotide strand?

Accepted Answer

It has a free 5' phosphate group at one end and a free 3' hydroxyl group at the other.

Question 9

Which of the following is an example of active transport across a cell membrane?

Accepted Answer

Movement of sodium ions against their concentration gradient using ATP

Question 10

A patient is found to be resistant to HIV infection due to a genetic mutation. Which membrane protein is most likely affected?

Accepted Answer

The CCR5 co-receptor on immune cells

Question 11

Which of the following best describes the role of membrane carbohydrates?

Accepted Answer

They function as markers to distinguish cell types and are involved in cell-cell recognition.

Question 12

Which of the following statements about the synthesis and orientation of membrane proteins is correct?

Accepted Answer

Membrane proteins have a specific orientation, with glycoproteins and glycolipids facing the extracellular side.

Question 13

Which of the following best explains why cholesterol is important in animal cell membranes?

Accepted Answer

Cholesterol helps regulate membrane fluidity across temperature changes.

Question 14

A cell is placed in a solution and water moves into the cell by osmosis. Which of the following must be true about the solution?

Accepted Answer

The solution is hypotonic to the cell.

Question 15

Which of the following best describes the process of transcription?

Accepted Answer

The synthesis of messenger RNA (mRNA) from a DNA template.

Question 16

Which of the following is a correct statement about the base pairing rules in DNA?

Accepted Answer

Adenine pairs with thymine, and cytosine pairs with guanine.

Question 17

Which of the following best describes the difference between facilitated diffusion and active transport?

Accepted Answer

Facilitated diffusion moves substances down their concentration gradient without energy input, while active transport moves substances against their gradient using energy.

Question 18

A researcher observes that a certain protein is only found on the extracellular side of the plasma membrane. Which of the following best explains this observation?

Accepted Answer

The protein is a glycoprotein that was oriented during synthesis in the endoplasmic reticulum and Golgi apparatus.

Nucleic Acids and Membrane Structure: Key Concepts in General Biology

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