Protein Folding, Misfolding, and Denaturation

Question 1

A specific 3D conformation is called a

Answer 1

native fold

Question 2

The native fold has a _____ ______ of ________ ______ within the protein.

Answer 2

large number of favorable interactions

Question 3

What is the final folded configuration/shape of a protein determined by?

Answer 3

its amino acid sequence

Question 4

Proteins that fail to be properly folded are ultimately

Answer 4

targeted for destruction

Question 5

What are the steps to create a protein?

Answer 5

Nascent polypeptide –> folding and cofactor binding (non-covalent interactions) –> covalent modification by glycosylation, phosphorylation, acetylation, etc. –> binds to other protein subunits –> a mature functional protein is created

Question 6

The 5 favorable interactions in proteins are:

Answer 6

1. ionic bonds
2. H-bonds
3. van der waal’s forces
4. hydrophobic effect
5. disulfide bridges

Question 7

What are the 3 types of non-covalent bonds needed to stabilize protein folding?

Answer 7

ionic bond
hydrogen bond
van der Waals

Question 8

When is a protein considered misfolded?

Answer 8

if it cannot achieve its normal native state

Question 9

Protein misfolding can be due to:

Answer 9

• mutations in the amino acid sequence

- a disruption of the normal folding process by external factors

Question 10

Misfolded proteins typically contain

Answer 10

B-sheets that are organized in a supramolecular arrangement known as a cross-B structure

Question 11

These B sheets rich assemblies are very ______ , very _______, and genreally _______ to ________.

Answer 11

stable
insoluble
resistant to proteolysis

Question 12

What can increased levels of aggregated proteins in the cell lead to?

Answer 12

the formation of amyloid-like structures which can cause degenerative disorders and cell death

Question 13

Aggregated proteins are associated with ______-_______ illnesses such as bovine ________ ________ (mad cow disease) or _______-related illnesses such as Alzheimer’s disease.

Answer 13

prion-related
spongiform encephalopathy
amyloid

Question 14

A failure to fold properly can lead to

Answer 14

protein aggregation

Question 15

To denature a protein is to

Answer 15

remove its natural characteristics

Question 16

Denaturation is a process in which proteins or nucleic acids lose the

Answer 16

quaternary, tertiary, and secondary structure which is present in their native state

Question 17

A protein is subject to change depending on its:

Answer 17

temperature
pH
exposure to chemicals

Question 18

The weak attractions between amino acids may

Answer 18

alter the shape of the protein

Question 19

Although the amino acid sequence ( a protein’s primary structure) ______ ____ _______ the protein’s shape may change so much that it becomes _________, in which case the protein is considered _________.

Answer 19

does not change
dysfunctional
denatured

Question 20

When a protein becomes denatured, some of its

Answer 20

bonds begin to break, and it unfolds

Question 21

During denaturization, bonds that held the folding ________

and bonds that created the spiral and pleats _______.Covalent bonds that held the amino acids together ______.

Answer 21

weaken
weaken
remain

Question 22

In this unfolded state,the protein doesn’t

Answer 22

have it’s original nature and characteristics

Question 23

Since a protein’s function is dependent on its _____, a denatured protein is no longer _________.

Answer 23

shape

functional

Question 24

A denatured protein is not _________ active, and can’t perform its ________ function.

Answer 24

biologically

natural

Question 25

Denaturation:
Renaturation:

Answer 25

loss of biological activity

regains activity

Question 26

Normal protein –> denatured protein

Denatured protein –> normal protein

Answer 26

denaturation

renaturation

Question 27

What can happen if the denaturing was very gentle?

Answer 27

when the denaturing agent is removed, the original attractions between the amino acids reshape the protein and it can resume its function

Question 28

Protein Thermal Irreversible Denaturation

Answer 28

native albumen –> denaturation –> cross linking

Question 29

Usually, denaturation is so extreme that it can’t be _______. Proteins that have _______ can not become _______.

Answer 29

reversed
coagulated
renatured

Question 30

Proteins in a slightly beaten egg can ______

Proteins in a cooked egg _______.

Answer 30

refold

can’t

Question 31

pH’s effect on denaturation

Answer 31

denaturation is brought about by controlling pH

Question 32

heat’s effect on heat

Answer 32

when an egg white is heat @ 600 C , the protein ovalbumin gets denatured
as temp increases, coagulation takes place and the egg white separates out as a solid

Question 33

Salts and Chemical’s effect on denaturation

Answer 33

when present in a high concentration, it precipitates proteins out of solutions and disperses them
e.g. cured ham bake in egg whites

Question 34

Not all proteins react

Answer 34

alike

Question 35

Heating foods can make them

Answer 35

safer to eat

Question 36

Acidic juice keeps

Answer 36

gelatin from setting

Question 37

Acidic tenderizers can help make meat

Answer 37

more tender

Question 38

Another agent of denaturation includes

Answer 38

alcohol/organic solvents

Question 39

How does hand sanitizer work?

Answer 39

it kills germs by denaturing the proteins in them

Question 40

Key Point 1:

Proteins change their shape when ………..

Answer 40

exposed to different pH or temperatures

Question 41

Key Point 2

The body strictly regulates pH and temperature to ………..

Answer 41

prevent proteins such as enzymes from denaturing

Question 42

Key Point 3:

Some proteins can refold after denaturation while

Answer 42

others cannot