Protein Stability

Question 1

These are spherical proteins that serve functional roles and are generally water-soluble

Answer 1

Globular proteins

Question 2

These proteins are typically elongated (sheet-like) and hydrophobic. They serve structural roles

Answer 2

Fibrous proteins

Question 3

These proteins are attached to plasma membrane

Answer 3

Membrane proteins

Question 4

Which has a higher entropy unfolded or folded protein?

Answer 4

Unfolded

Question 5

Hydrophilic solvents lose entropy when they form a ____________ _________ around hydrophobic side chains

Answer 5

Solvation layer

Therefore, minimal contact = maximum entropy

Question 6

Protein folding is driven by what interactions?

Answer 6

Hydrophobic interactions

Question 7

After protein folding, this has minimal interaction with external environment

Answer 7

Hydrophobic core

Question 8

After protein folding, this interacts with the external environment and is composed of polar amino acids and side chains

Answer 8

Hydrophilic shell

Question 9

Protein folding is favorable despite the decrease in entropy of the folded protein because

Answer 9

The increase in entropy of the solvents (surroundings) is much greater

Question 10

In proteins, the unfolding or loss of higher-level structure is known as what?

Answer 10

Denaturation

Question 11

Loss of non-primary protein structure

Answer 11

Protein denaturation

Non- primary: secondary, tertiary, and quartenary

Question 12

Denatured protein has what structure

Answer 12

It is a primary protein- existing as a linear chain of amino acids

Question 13

Denatured protein has what structure

Answer 13

It is a primary protein- existing as a linear chain of amino acids

Question 14

T or F. Denaturation breaks the primary, secondary, tertiary, and quartenary structure until all is left is a linear chain of amino acids

Answer 14

Denaturation breaks proteins to its primary level which is a linear chain of amino acids

Question 15

Amino acids are held by what bonds? Which atoms are bound by this bond?

Answer 15

Peptide bonds between Carbon and Nitrogen

Question 16

Which are stronger? Intermolecular bonds or intramolecular bonds

Answer 16

Intramolecular bonds

Question 17

What type of bonds can be found in primary, secondary, and tertiary/ quaternary protein structures

Answer 17

Primary: covalent (peptide) bonds
Secondary: hydrogen bonds
Tertiary/ quaternary:non-covalent side-chain interactions, disulfide bonding

Question 18

Example of denaturing agents

Answer 18

Temperature, pH Extremes, Detergents, and Reducing Agents, specific compounds (ex. Urea)

Question 19

Effect on proteins by high temperatures

Answer 19

Disrupt the non-primary interactions that hold a folded protein together

Question 20

Effect of proteins by low temperatures

Answer 20

Can decrease protein activity or enzyme activity

Question 21

Most human proteins are designed to optimally function at what temperature

Answer 21

Around body temp: 37.6 C or 98.6 F

Question 22

pH extremes effect on proteins

Answer 22

Can disrupt charge-based interactions in tertiary and quaternary structure such as salt bridges

Question 23

These denaturing agents are part-polar, part-nonpolar. It can disrupt hydrophobic interactions- largely stripping the protein of its higher-level protein folding

Answer 23

Detergents

Question 24

Give a well known detergent used in a lab technique.

Answer 24

SDS (sodium dodecyl sulfate) used in SDS PAGE

Question 25

T or F. Denaturation of proteins are reversible

Answer 25

False. Some are reversible (denaturing agent: urea) some are irreversible (denaturing agent: heat)

Question 26

These break apart protein primary structure by catalyzing the hydrolysis of peptide bonds

Answer 26

Proteases

Question 27

These denaturing agents disrupt covalent bonds between sulfur atoms (disulfide bonds)

Answer 27

Reducing agent

*remember that disulfide bonds are formed via oxygenation and therefore is broken via reduction

Question 28

These proteases use the hydroxyl group of a serine residue to catalyze protein cleavage. Give an example

Answer 28

Serine proteases

Ex. Digestive enzyme trypsin

Question 29

Trypsin cleave at what terminal

Answer 29

C

Question 30

Aminopeptidases cleave from what terminal?

Answer 30

N-terminal

Question 31

Carboxypeptidases cleave at which terminal

Answer 31

C terminal