Chapter 18

Question 1

The pH at which a sample of amino acids has equal numbers positive and negative charges

Answer 1

Isoelectric point

Question 2

What does an amino acids isoelectric point influence?

Answer 2

Protein solubility and determines which amino acid in enzymes participate in enzyme reactions

Question 3

Amino acids that can form crystals, have high melting points, are soluble in water but not hydrocarbon solvents are what?

Answer 3

Pure amino acids

Question 4

Amino acids that accept proteins of their basic COO- group to leave only a positively charged NH3+ are what?

Answer 4

Low pH amino acids

Question 5

Amino acids that lose protons from their acidic NH3+ group to leave only negatively charged COO- groups are what?

Answer 5

High pH amino acids

Question 6

How many amino acids are chiral? Which ones aren’t?

Answer 6

19 are chiral, glycine isn’t (it’s identical)

Question 7

Do right or left handed enantiomers make proteins

Answer 7

Left handed enantiomers

Question 8

The sequence in which amino acids are linked by peptide bonds in a protein

Answer 8

Primary structure

Question 9

T or F

Primary structures form ridged planar peptide units

Answer 9

True

Question 10

Regular and repeating structural patterns created by hydrogen binding between backbone atoms in neighboring segments of protein chains

Answer 10

Secondary structure

Question 11

What are the two kinds of repeating patterns of secondary structures?

Answer 11

Alpha helix and beta sheets

Question 12

Do alpha helixes and beta sheets hydrogen bond?

Answer 12

Yes to keep backbone in place

Question 13

Overall 3- dimensional shape that results from the folding of a single protein chain

Answer 13

Tertiary structure

Question 14

The way in which two or more protein chains aggregate to form large ordered structures

Answer 14

Quaternary structure

Question 15

What are the two protein types of secondary structure?

Answer 15

Fibrous protein and globular protein

Question 16

Tough insoluble protein whose protein chains form fibers/ sheets is globular or fibrous protein?

Answer 16

Fibrous

Question 17

Water soluble protein whose chain is folded in compact shape with hydrophilic groups on outside is globular or fibrous protein?

Answer 17

Globular

Question 18

Extremely stable structure where protein chain forms right handed coil stabilized by hydrogen bonds between peptide groups along its backbone

Answer 18

Alpha helix

Question 19

Protein structure where adjacent protein chains in same/ different molecules are held together by hydrogen bonds along its backbone forming a flat sheet structure

Answer 19

Beta sheets

Question 20

What protein is fibrous and makes up about 30% total proteins?

Answer 20

Collagen

Question 21

Protein hydrolysis is where peptides turn into _____

Answer 21

Amino acids

Question 22

Is an acidic or basic solution better for hydrolysis and why?

Answer 22

Acidic because a basic solution can destroy some amino acids

Question 23

What is a protein with the shape in which it exists naturally in living organisms? What type of protein structure is it?

Answer 23

Native structure, can be any 1-4 protein structures

Question 24

A disruption in the shape of the protein that does not affect the order of amino acids within a protein chain

Answer 24

Denaturation

Question 25

Which structures are and are not affected by denaturation

Answer 25

Only primary protein structures not lost Other structures lost because of non covalent interactions or disulfide bonds leaving

Question 26

Denaturation can be caused by heat, ______, ________, organic compounds, ___, or _________.

Answer 26

Mechanical agitation Detergents Organic compounds pH changes Inorganic salts

Question 27

Can renaturation happen?

Answer 27

Possibly but not usually

Question 28

peptides and proteins are always written with the ___ terminal on the left and the ___ terminal on the right

Answer 28

N C

Question 29

The C terminal amino acid has a free ____ group at the end of the protein

Answer 29

-COO group

Question 30

The N terminal amino acid has a free _____ group that’s at the end of the protein

Answer 30

-NH3+

Question 31

Individual amino acids joined in the polypeptide chain are called what?

Answer 31

Residues

Question 32

Why are proteins usually least soluble in water at their isoelectric point?

Answer 32

At isoelectric point their neutral which makes them least soluble (charged proteins are more soluble)

Question 33

What type of bonding is responsible for secondary structures?

Answer 33

Hydrogen bonding

Question 34

Is hydrogen bonding covalent or noncovalent?

Answer 34

Noncovalent

Question 35

Are alpha helixes usually fibrous or globular?

Answer 35

Fibrous (hair, nails, wool)

Question 36

Are B-sheets usually fibrous or globular?

Answer 36

Globular

Question 37

Spontaneous folding into correct tertiary structures is caused by _____ residues interacting with aqueous environments and _____ residues folding away and into each other

Answer 37

Hydrophilic Hydrophobic

Question 38

What is a conjugated protein?

Answer 38

Protein with one or more non protein molecules

Question 39

Why is cysteine such an important amino acid for defining tertiary structure of some proteins?

Answer 39

Disulfide bonds stabilize tertiary structure

Question 40

Which structure coils and fold the entire protein chain?

Answer 40

Teritary

Question 41

Which structure orients segments of polypeptides into patterns?

Answer 41

Secondary

Question 42

What type of bonds hold amino acids together in primary structure?

Answer 42

Peptide bonds

Question 43

What is the minimum number of polypeptide chains necessary for quaternary structures to exist?

Answer 43

2

Question 44

Myoglobin is an example of a ____ protein

Answer 44

Conjugated

Question 45

______ functions to carry oxygen in red blood cells

Answer 45

Hemoglobin

Question 46

What type of bonds connect insulin?

Answer 46

Disulfide bonds

Question 47

What is the difference between protein digestion and denaturation?

Answer 47

Digestion= protein —> amino acids Denaturation= 4 protein —> 1 protein and loss of function

Question 48

Does protein hydrolysis end with the amino acids losing function?

Answer 48

No loss of function