Note 7 -Protein (Structures)

Question 1

What is the meaning of - protein shape equals protein function?

Answer 1

Shape determines whether protein can interact with other proteins.

Question 2

Structural proteins

Answer 2

Muscle, tendons, hair etc

Question 3

Functional proteins

Answer 3

-Carry out vital functions

-Enzymes, hormones, antibodies etc.

Question 4

Name the levels of protein structure

Answer 4

primary, secondary, tertiary, quaternary

Question 5

What does the primary structure consist of?

Answer 5

-polypeptide chain

Question 6

What is a polypeptide chain?

Answer 6

Chain of amino acids linked together by peptide bonds

Question 7

How many polypeptide chains make up proteins

Answer 7

1 polypeptide chain (not all)

Question 8

Peptide bonds

Answer 8

Bonds that link amino acids

Question 9

How is the sequence and number of amino acids in polypeptide chain determined?

Answer 9

Encoded in DNA (unique to each protein)

Question 10

What causes loss of protein function?

Answer 10

Gene variant that alters the primary structure that causes it to fold incorrectly (misshapen)

Question 11

What are the components that make up an amino acid?

Answer 11

1 - nitrogen containing amino group

2- central carbon

-carboxyl group

-side “R” chain (functional group)

Question 12

Significance of the “R” chain

Answer 12

Amino acids have same base structure, but each amino acid has a unique side chain “R”.

Question 13

Ways side chains differ (2)

Answer 13

1 - Charge

2 - Hydrophilic/Hydrophobic

Question 14

What is the common structure of an amino acid?

Answer 14

Central carbon, Amino group, carboxyl group, r group

Question 15

Difference between essential and nonessential amino acid

Answer 15

essential: CANNOT make “R” group

nonessential: CAN make “R” group.

Question 16

What is a functional group of an amino acid?

Answer 16

a variable side chain that influences the function of amino acid.

Question 17

Describe the primary structure of a protein and what determines the sequence and number of amino acids. How can a gene variant alter the shape of the protein?

Answer 17

Structure: polypeptide chain linked by peptide bonds
Sequence: Encoded in DNA (gene structure)
Variant: Causes it to fold incorrectly (misshapen)

Question 18

How is the secondary structure of a protein formed?

Answer 18

-Positive charge of amino acids + negative charge of carboxyl groups.

-Attractions cause primary structure to fold in organized/predictable patterns

Question 19

What holds secondary structure together?

Answer 19

Hydrogen bonds

Question 20

What are the 2 common folding patterns of the secondary structure?

Answer 20

Alpha helix and beta helix

Question 21

How is the tertiary structure of a protein formed?

Answer 21

-Interactions of R-groups of amino acids (+/- charges)
-Interactions between R-groups and the surroundings (hydrophobic/hydrophilic)
-Interactions cause protein to bend to form 3-D shape.

Question 22

What forms the quaternary structure of a protein?

Answer 22

-multiple polypeptides (exists in proteins with 2 or more polypeptide chains)

Question 23

Do all proteins have quaternary structure?

Answer 23

No - only those with 2 or more polypeptide chains.

Question 24

What happens when a protein is denatured?

Answer 24

• The 3-D shape of a proteins is altered (unfolds) = function is altered.

Question 25

How does denaturing happen?

Answer 25

-Weak bonds responsible for maintaining 3-D structure disrupted (secondary and tertiary) and protein unfolds.
-Most situations they become dysfuntional

Question 26

When a protein is denatured, is the primary structure altered? Why?

Answer 26

No, because peptide bonds not disrupted.

Question 27

What are denaturing agents?

Answer 27

-Heat
-pH
-Heavy metals

Question 28

What happens to denatured proteins in food.

Answer 28

Nothing, they retain their nutritional value.

Question 29

What is the proteolytic enzymes (proteases)?

Answer 29

Enzymes that break down protein (protein digestion)

Question 30

How do proteolytic enzymes work?

Answer 30

hydrolyze peptide bonds with protein digestion

Question 31

What is a zymogen?

Answer 31

-Inactive enzyme precursors that require a biochemical change to become active.
-proteolytic enzymes synthesized as inactive zymogen

Question 32

What is the function of zymogen?

Answer 32

prevent unwanted protein degradation.

Question 33

Where are different Protease enzymes needed for digestion found?

Answer 33

1) Stomach
- pepsinogen (pepsin)
2) Pancreas
- trypsinogen (trypsin)
-Chymotrypsinogen (chymotrypsin)
-Procarboxypeptidase (carboxypeptidase)
3) Small intestime (brush border)
-Enterokinase (enteropeptidase)

Question 34

What are the steps of protein digestion?

Answer 34

Protein enters stomach -> gastrin (hormone) released -> Gastric juice (HCl) denatures food proteins -> peptide bonds hydrolyzed by enzymes.

Question 35

Where and hoe does enzymatic digestion of protein begin?

Answer 35

-In the stomach
-Pepsin

Question 36

Function of pepsin

Answer 36

Hydrolysis peptide bonds = multiple polypeptide chains

Question 37

Function of gastrin

Answer 37

Stimulates the release of gastric juice.

Question 38

How are zymogens activated. What forms do they change?

Answer 38

-Exposed to gastric juice (HCl)
-Pepsinogen (zymogen) -> pepsin

Question 39

How is protein digested in the small intestine?

Answer 39

By pancreatic protease enzymes

Question 40

How do the pancreatic protease enzymes work to digest protein in the SI?

Answer 40

Trypsinogen - converted into trypsin by brush boarder enzyme (enterokinase)

Trypsin -
converts chymotrypsinogen -> chymotrypsin and
procarboxypeptidase -> carboxypeptdiase

Completely hydrolyze polypeptides -> amino acids (happens on brush boarder)

Question 41

Where are the amino acids absorbed after protein digestion?

Answer 41

enterocytes