Protein Functions - 3b

Question 1

What functional groups are present in all amino acids?

Answer 1

An amino group (-NH₂) and a carboxyl group (-COOH), along with an R group (side chain).

Question 2

How many amino acids occur naturally and how many are typically found in proteins?

Answer 2

Over 700 occur naturally, but only 20 are standard amino acids found in proteins.

Question 3

How are amino acids classified based on their side chains?

Answer 3

Into four categories:
* Non-polar (hydrophobic)
* Polar neutral
* Polar acidic (negatively charged)
* Polar basic (positively charged)

Question 4

What are proteins made of?

Answer 4

Proteins are polymers of amino acids linked by peptide bonds.

Question 5

What are essential amino acids?

Answer 5

Amino acids that the body cannot synthesize and must be obtained from the diet.

Question 6

What’s the difference between complete and incomplete proteins?

Answer 6

Complete proteins contain all essential amino acids (e.g., animal sources). Incomplete proteins lack one or more essential amino acids (e.g., plant sources).

Question 7

What are the four levels of protein structure?

Answer 7

Primary, Secondary, Tertiary, Quaternary.

Question 8

What defines the primary level of protein structure?

Answer 8

Amino acid sequence.

Question 9

What characterizes the secondary level of protein structure?

Answer 9

Alpha helices and beta-pleated sheets (hydrogen bonding).

Question 10

What defines the tertiary level of protein structure?

Answer 10

3D shape due to R group interactions.

Question 11

What is the quaternary level of protein structure?

Answer 11

Interaction between multiple polypeptide chains.

Question 12

What types of bonds stabilize the tertiary structure?

Answer 12

Covalent bonds, electrostatic attractions, hydrogen bonds, and hydrophobic interactions.

Question 13

What is protein denaturation?

Answer 13

Disruption of secondary, tertiary, and quaternary structures, leading to loss of function.

Question 14

How are proteins classified by composition?

Answer 14

Simple and Conjugated (complex).

Question 15

What are examples of conjugated proteins and their prosthetic groups?

Answer 15

Lipoproteins (lipid: HDL), Glycoproteins (carbohydrate: Interferon), Metalloproteins (metal: Ferritin).

Question 16

How are proteins classified by shape?

Answer 16

Fibrous and Globular.

Question 17

What are examples of fibrous proteins?

Answer 17

Structural, insoluble, strong (e.g., collagen).

Question 18

What are examples of globular proteins?

Answer 18

Metabolic, soluble, weaker (e.g., enzymes).

Question 19

How are proteins classified by function?

Answer 19

Structural, Regulatory, Contractile, Immunological, Transport, Catalytic, Transmembrane, Storage, Nutrient, Buffer, Fluid-balance, Messenger.

Question 20

What are enzymes?

Answer 20

Protein catalysts that speed up specific chemical reactions.

Question 21

How are enzymes named?

Answer 21

Based on the reaction/substrate, usually ending in -ase or -in for some digestive enzymes.

Question 22

What are the components of conjugated enzymes?

Answer 22

Apoenzyme (protein part) and Cofactor (non-protein part).

Question 23

What are types of cofactors?

Answer 23

Simple ions and Coenzymes.

Question 24

What are enzyme-substrate and enzyme-product complexes?

Answer 24

Temporary complexes formed during reactions before the final products are released.

Question 25

What are the two models of enzyme-substrate interaction?

Answer 25

Lock and key, Induced fit.

Question 26

What are the levels of enzyme specificity?

Answer 26

Absolute, Group, Linkage.

Question 27

What controls enzyme activity?

Answer 27

Gene regulation, environmental conditions, and presence of inhibitors or activators.

Question 28

What are types of enzyme inhibition?

Answer 28

Reversible competitive, Reversible non-competitive, Irreversible.

Question 29

What are allosteric enzymes?

Answer 29

Enzymes with multiple subunits and regulatory sites.

Question 30

How are inactive enzymes activated?

Answer 30

By removing part of the peptide chain to change structure.

Question 31

What is an integral (transmembrane) protein?

Answer 31

A protein that spans the membrane and may have channels for substances.

Question 32

What is a peripheral protein?

Answer 32

A protein attached to the membrane surface, easily removable, and does not span the membrane.

Question 33

Here is a photo of Protein Structures

Answer 33

Question 34

What is a peptide?

Answer 34

A short chain of amino acids linked by peptide bonds.

Question 35

How is a peptide bond formed?

Answer 35

Through a condensation reaction between the carboxyl group of one amino acid and the amino group of another, releasing a molecule of water.

Question 36

What is a dipeptide?

Answer 36

A molecule made of two amino acids joined by a single peptide bond.

Question 37

What is a polypeptide?

Answer 37

A longer chain of amino acids, usually containing 10 or more residues.

Question 38

What determines a polypeptide’s primary structure?

Answer 38

The sequence of amino acids in the chain, coded by DNA.

Question 39

At what point is a polypeptide considered a protein?

Answer 39

When it folds into a functional 3D shape, often involving multiple polypeptide chains or complex structures.

Question 40

Are all polypeptides proteins?

Answer 40

No. A polypeptide becomes a protein only when it is properly folded and functional.

Question 41

What is the difference between a peptide and a protein?

Answer 41

Size and complexity: Peptides are shorter and simpler, often with fewer than 50 amino acids. Proteins are longer, folded polypeptides that carry out specific biological functions.

Question 42

What are some functions of peptides in the body?

Answer 42

Hormones (e.g., insulin), neurotransmitters (e.g., endorphins), and signaling molecules.

Question 43

Can peptides act as hormones?

Answer 43

Yes! Many hormones like oxytocin and vasopressin are small peptides.