Question 1

Which type of bond links amino acids together in a polypeptide chain, and what is a key property of this bond?

Accepted Answer

Peptide (amide) bond; it is resistant to hydrolysis

Question 2

In the $$eta-$$sheet secondary structure, how are the polypeptide strands typically arranged?

Accepted Answer

They can be antiparallel, parallel, or mixed

Question 3

Which of the following best describes the driving force for the formation of tertiary structure in water-soluble proteins?

Accepted Answer

Hydrophobic interactions between interior residues

Question 4

A protein is found embedded in a membrane. Which arrangement of amino acids is most likely for its tertiary structure?

Accepted Answer

Hydrophobic amino acids on the surface, hydrophilic amino acids in the interior

Question 5

Which statement about quaternary structure is correct?

Accepted Answer

It involves the assembly of multiple polypeptide chains into a single protein

Question 6

Trehalose is a disaccharide that helps some organisms survive desiccation. What is its proposed biochemical role?

Accepted Answer

It replaces hydrogen bonds that biomolecules normally form with water

Question 7

Tardigrades can survive desiccation without trehalose. What molecule is primarily responsible for their survival under these conditions?

Accepted Answer

Intrinsically disordered proteins (TIDP)

Question 8

If a protein has a high ratio of hydrophilic to hydrophobic amino acids, which shape is it most likely to adopt?

Accepted Answer

A spherical shape with a high surface-to-volume ratio

Question 9

Which of the following is true regarding the directionality of polypeptide chains?

Accepted Answer

Sequences are written from the amino to the carboxyl terminus

Question 10

Which of the following best explains why proteins can refold efficiently after being unfolded under certain conditions?

Accepted Answer

The amino acid sequence contains all the information needed for folding

Question 11

In an $$eta-$$sheet, what type of bond connects the strands together?

Accepted Answer

NH-to-CO hydrogen bonds

Question 12

Which of the following is a consequence of the hydrophobic effect in protein folding?

Accepted Answer

Hydrophobic amino acids are buried in the protein interior

Question 13

A mutation deletes a TIDP gene in tardigrades. What is the most likely outcome after dehydration and rehydration?

Accepted Answer

Drastically reduced survival after rehydration

Question 14

Which of the following is NOT a feature of the tertiary structure of water-soluble proteins?

Accepted Answer

Hydrophobic amino acids on the surface interacting with water

Question 15

Which equation best represents the ratio used to predict protein folding based on amino acid composition?

Accepted Answer

$$\frac{	ext{hydrophilic amino acids}}{	ext{hydrophobic amino acids}}$$

Question 16

Which of the following statements about peptide bonds is correct?

Accepted Answer

Peptide bonds are resistant to hydrolysis, contributing to protein stability

Question 17

Which structural level of a protein is directly determined by the sequence of bases in a DNA molecule?

Accepted Answer

Primary structure

Question 18

Which of the following is a correct description of an $$	ext{\alpha}-$$helix?

Accepted Answer

A tightly packed rod-like structure stabilized by hydrogen bonds between the CO group of one amino acid and the NH group four residues ahead

Question 19

Which of the following is a plausible reason why trehalose prevents protein denaturation during desiccation?

Accepted Answer

It forms hydrogen bonds with proteins, replacing those lost from water

Question 20

A protein subunit is found to have more hydrophobic than hydrophilic amino acids. What is the most likely explanation for its location in a tetrameric protein?

Accepted Answer

Its hydrophobic amino acids interact with those of other subunits, shielding them from water

Biochemistry: A Short Course 3

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