Question 1

Which of the following best explains why scientists can use non-human cells, such as yeast or E. coli, to study fundamental aspects of human cell biology?

Accepted Answer

All present-day cells share conserved molecular mechanisms inherited from a common ancestor.

Question 2

A researcher wants to study the genetic basis of multicellular development and cell differentiation. Which experimental model would be most appropriate for this study?

Accepted Answer

Caenorhabditis elegans

Question 3

Stanley Miller’s experiment was significant because it demonstrated which of the following?

Accepted Answer

Organic molecules can form spontaneously under conditions thought to exist in Earth’s early atmosphere.

Question 4

Which of the following statements about the RNA World Hypothesis is correct?

Accepted Answer

RNA can serve as both a template for replication and a catalyst for chemical reactions.

Question 5

Which process is believed to have led to the origin of mitochondria and chloroplasts in eukaryotic cells?

Accepted Answer

Endosymbiosis

Question 6

A molecule with both hydrophilic and hydrophobic regions, such as a phospholipid, is described as:

Accepted Answer

Amphipathic

Question 7

Which type of bond is responsible for joining monosaccharides together in polysaccharides such as starch and glycogen?

Accepted Answer

Glycosidic bond

Question 8

Cellulose is more difficult to break down than starch because:

Accepted Answer

Cellulose is composed of glucose monomers joined by $$\beta-1$$,4 glycosidic bonds, forming rigid microfibrils.

Question 9

Which of the following correctly describes the difference between DNA and RNA?

Accepted Answer

DNA is usually double-stranded and contains thymine; RNA is usually single-stranded and contains uracil.

Question 10

Which bond is responsible for linking nucleotides together in a nucleic acid polymer?

Accepted Answer

Phosphodiester bond

Question 11

Which of the following is a purine base found in nucleic acids?

Accepted Answer

Adenine

Question 12

Which level of protein structure is defined by the specific sequence of amino acids in a polypeptide chain?

Accepted Answer

Primary structure

Question 13

Which type of bond stabilizes both the alpha helix and beta sheet structures in proteins?

Accepted Answer

Hydrogen bond

Question 14

A prion is best described as:

Accepted Answer

A misfolded protein capable of self-replication and inducing misfolding in normal proteins.

Question 15

Which of the following statements about enzyme catalysis is correct?

Accepted Answer

Enzymes lower the activation energy ($$E_A) $$required for a reaction to proceed.

Question 16

Allosteric regulation of an enzyme involves:

Accepted Answer

A regulatory molecule binding to a site distinct from the active site, inducing a conformational change.

Question 17

Which of the following best describes the role of cholesterol in the plasma membrane?

Accepted Answer

Cholesterol acts as a fluidity buffer, decreasing fluidity at high temperatures and increasing it at low temperatures.

Question 18

Which of the following membrane proteins can be dissociated from the membrane by high salt or polar reagents without disrupting the bilayer?

Accepted Answer

Peripheral membrane proteins

Question 19

Which type of membrane transport requires energy input, often from ATP hydrolysis, to move molecules against their concentration gradient?

Accepted Answer

Active transport

Question 20

The selectivity filter of a potassium ($$K^+) $$channel allows $$K^+$$ ions to pass but excludes $$Na^+$$ ions. This is primarily because:

Accepted Answer

The carbonyl oxygen atoms in the filter are spaced to coordinate $$K^+$$ ions but are too far apart to coordinate the smaller $$Na^+$$ ions.

Cell Biology: Experimental Models, Biomolecules, Membranes, and the Cytoskeleton

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