Chp. 18 Protein Structure/Function

Question 1

What does the term ‘protein’ mean?

Answer 1

Of first importance

Question 2

List the biological functions of proteins

Answer 2

• Enzymes
• Defense proteins
• Transport proteins
• Regulatory proteins
• Structural proteins
• Movement proteins
• Nutrient proteins

Question 3

What is the general structure of an α-amino acid?

Answer 3

Contains both an amine and an acid

Question 4

How many common α-amino acids are found in nature?

Answer 4

20
19/20 stereoisomers, not glycine

Question 5

What is a zwitterion?

Answer 5

A neutral molecule with equal number of + and − charges

Question 6

What is the isoelectric point?

Answer 6

The pH point at which there is no net charge on the zwitterions

Question 7

Which amino acid is not chiral?

Answer 7

Glycine

Question 8

What are the classes of amino acids based on their R groups?

Answer 8

• Hydrophobic amino acids
• Hydrophilic amino acids
• Polar, neutral amino acids
• Negatively charged amino acids
• Positively charged amino acids

Question 9

What is the peptide bond?

Answer 9

Linkage between the carboxyl group of one amino acid and the amino group of another

Question 10

What is the primary structure of proteins?

Answer 10

The amino acid sequence of the polypeptide chain; A result of covalent bonding between the peptide bonds (amino acids)

Question 11

What results in the formation of secondary structure in proteins?

Answer 11

Hydrogen bonding between amide hydrogens and carbonyl oxygens of the peptide bonds (how they fold in a repeated primary sequence)

Question 12

What is the most common type of secondary structure?

Answer 12

α-Helix

Question 13

Describe the structure of an α-helix

Answer 13

• Coiled, helical
• Right-handed (clockwise)
• 3.6 amino acids per turn
• Carbonyl O links with Amide H: 4 amino acids away

Question 14

What is the second most common type of secondary structure?

Answer 14

β-Pleated sheet

Question 15

What defines tertiary structure in proteins?

Answer 15

The overall 3-D folding of the entire polypeptide chain

Question 16

List the types of interactions that maintain tertiary structure

Answer 16

• Disulfide bridges
• Salt bridges
• Hydrogen bonds
• Hydrophobic interactions

Question 17

What is quaternary structure?

Answer 17

The arrangement of subunits or peptides that form a larger protein; tertiary structures coming together

Question 18

What types of proteins require prosthetic groups?

Answer 18

• Nucleoproteins
• Lipoproteins
• Glycoproteins
• Phosphoproteins
• Hemoproteins
• Metalloproteins

Question 19

What is the role of myoglobin?

Answer 19

Oxygen storage protein of skeletal muscle

Question 20

What causes denaturation of proteins?

Answer 20

Extremes of temperature and pH

Question 21

What is the difference between denaturation and hydrolysis?

Answer 21

Denaturation is the loss of organized structure; hydrolysis breaks proteins into smaller peptides or amino acids

Question 22

What are essential amino acids?

Answer 22

Amino acids that cannot be made in the body

Question 23

What are nonessential amino acids?

Answer 23

Amino acids that can be made in the body

Question 24

List the essential amino acids

Answer 24

• Isoleucine
• Leucine
• Lysine
• Methionine
• Phenylalanine
• Threonine
• Tryptophan
• Valine
• Histidine (for infants)

Question 25

List the nonessential amino acids

Answer 25

* Alanine * Arginine (conditionally essential) * Asparagine * Aspartate * Cysteine (conditionally essential) * Glutamate * Glutamine * Glycine * Proline * Serine * Tyrosine (conditionally essential)

Question 26

What is the primary effect of increasing temperature on proteins?

Answer 26

Increases the rate of molecular movement

Question 27

How does changing pH affect protein structure?

Answer 27

Interferes with salt bridges and hydrogen bonds stabilizing the tertiary structure

Question 28

Protein Biological Function: Enzymes Example?

Answer 28

Biological Catalyst

Question 29

Protein Biological Function: Defense Proteins Example?

Answer 29

Antibodies: produced by the immune system in response to antigens

Question 30

Protein Biological Function: Transport Proteins Example?

Answer 30

Hemoglobin: carries oxygen from the lungs to the tissues/organs

Question 31

Protein Biological Function: Regulatory Proteins Example?

Answer 31

Glucose Regulation

Question 32

Protein Biological Function: Structural Proteins Example?

Answer 32

Actin: gives structure/shape in the cytoskeleton

Question 33

Protein Biological Function: Movement Proteins Example?

Answer 33

Actin & Myosin Proteins work together to create movement inside the cell

Question 34

Protein Biological Function: Nutrient Proteins Example?

Answer 34

Food from Diet (further broken down into amino acids for energy)

Question 35

Amino Acid Configuration Isolated From Proteins is

Answer 35

L- (most oxidized end of the molecule: carbonyl is at the top when drawing)

Question 36

What is a dipeptide?

Answer 36

A dipeptide is a molecule formed from two amino acids linked by a peptide bond.

Question 37

True or False: Dipeptides are the simplest form of peptides.

Answer 37

True

Question 38

Fill in the blank: A dipeptide consists of __ amino acids.

Answer 38

2

Question 39

Which type of bond connects the amino acids in a dipeptide?

Answer 39

Peptide bond

Question 40

What Produces a Dipeptide

Answer 40

Condensing/Dehydrating 2 amino acids

Question 41

N-terminal Amino Acid

Answer 41

Amino Acid with a free α-NH3+ group

Question 42

C-terminal Amino Acid

Answer 42

Amino Acid with a free -COO (carboxyl) group

Question 43

β-Pleated Sheet

Answer 43

*All of Carbonyl O and Amide H are involved in H bonding *Parallel if the N termini are head to head *Perpendicular (antiparallel) if the N-terminus of one chain is aligned with the C-terminus of the other

Question 44

Globular Proteins

Answer 44

*Formed Spontaneously *Maintained by interactions among the side chains/R-groups *Apart of tertiary structure of proteins

Question 45

Tertiary Structure: Disulfide Bridges

Answer 45

Between 2 cysteine Residues ex. Curling/Straightening Hair

Question 46

Tertiary Structure: Salt Bridges

Answer 46

Between ionic side chains -COO and NH3+ (carboxyl and amine)

Question 47

Tertiary Structure: Hydrogen Bonds

Answer 47

Between polar residue side chains

Question 48

Tertiary Structure: Hydrophobic Interactions

Answer 48

2 nonpolar groups are attracted by a mutual repulsion of water

Question 49

prosthetic groups

Answer 49

a special tool that gets attached to a protein, and it helps the protein do its job better. It's not made of protein itself, but it sticks to the protein really tightly

Question 50

Fibrous Protein Functions

Answer 50

*Mechanical strength *Structural Components (actin, keratin) *Movement (actin, myosin)

Question 51

Globular Protein Functions

Answer 51

*Transport: nonpolar, hemoglobin, myoglobin *Regulatory: polar insulin *Enzymes

Question 52

Hemoglobin

Answer 52

oxygen transport protein of higher animals

Question 53

Denature Agents

Answer 53

*Organic Solvents -interfere w/ hydrophobic interactions *Detergents -polar head and hydrophobic tail & interferes w/ hydrophobic interactions *Heavy Metals -bind to (-) charged amino acid & interfere w/ disulfide bridges *Mechanical Stress -lots of force on proteins break weak interactions

Question 54

Myoglobin

Answer 54

oxygen storage protein of skeletal muscle