MCAT Biochemistry

Question 1

What two function groups do amino acids contain?

Answer 1

Amine and carboxyl group

Question 2

What groups are attached to the alpha carbon

Answer 2

amine group, carboxyl group, a hydrogen atom, and an R group (specific to each amino acid)

Question 3

proteinogenic amino acids are…?

Answer 3

The 20 main amino acids that have amino and carboxyl group attached to the alpha carbon (create proteins)

Question 4

Which amino acid is achiral?

Answer 4

glycine

Question 5

Which amino acid has an R configuration?

Answer 5

cysteine

Question 6

Which amino acids have non-polar, non aromatic side chains?

Answer 6

glycine, alanine, valine, leucine, isoleucine, methionine, and proline.

Question 7

Which amino acids have aromatic side chains?

Answer 7

tryptophan, phenylalanine, and tyrosine

Question 8

Which amino acids have polar side chains?

Answer 8

serine, threonine, asparagine, glutamine, and cysteine

Question 9

Which two amino acids have acidic (negatively charged) side chains

Answer 9

asparagine (aspartate specifically) and glutamine (glutamate)

Question 10

Which amino acids have positive side chains?

Answer 10

lysine, arginine, and histidine

Question 11

T/F Hydrophobic amino acids tend to be found on the interior of proteins

Answer 11

True

Question 12

Amphoteric species are

Answer 12

molecules that can either accept or donate a proton, depending on the pH of their environment

Question 13

T/F Ionizable groups tend to lose protons under acidic conditions and gain them in basic conditions

Answer 13

False they gain a proton in acidic conditions and lose a proton in basic conditions

Question 14

If pH is less than the pKa, a majority of the species will be?

Answer 14

pronated

Question 15

If pH is more than the pKa, a majority of the species will be ?

Answer 15

deprotonated

Question 16

Each ionizable proton has its own pKa, at which is it half—____

Answer 16

half-deprotonated

Question 17

Amino acids tend to be ___ charged under very acidic conditions

Answer 17

positively

Question 18

zwitterions are

Answer 18

dipolar (one positive one negative) ions within an amino acid

Question 19

At highly alkaline (basic) pH values, amino acids tend to be ____ charged

Answer 19

negatively

Question 20

When the pH of a solution is approximately equal to the pKa of the solute, the solution acts as a ___-

Answer 20

buffer

Question 21

isoelectric point is the

Answer 21

point in the pH where the molecule is electrically neutral

Question 22

Amino acids with acidic side chains have a pI well ____ 6 and amino acids with a basic side chain have a pI well ____ 6

Answer 22

below, above

Question 23

Peptides are composed of

Answer 23

amino acid subunits (also known as residues)

Question 24

Dipeptides consist of

Answer 24

two amino acid residues

Question 25

Tripeptides consist of

Answer 25

three amino acid residues

Question 26

oligopeptides consist of

Answer 26

up to about 20 residues

Question 27

polypeptides consist of

Answer 27

more than 20 residues

Question 28

resides in peptides are joined together through...

Answer 28

peptide bonds

Question 29

Peptide bond formation is accomplished through

Answer 29

Condensation or dehydration (addition of removal of water)

Question 30

The free amino end is know as the amino terminus, or the ______

Answer 30

N-terminus (left side)

Question 31

The free carboxyl end is the carboxy terminus or the ______

Answer 31

C-terminus (right side)

Question 32

What are proteins?

Answer 32

they are polypeptides that range from a few amino acids in length up to thousands

Question 33

What are the four levels of protein structures

Answer 33

primary, secondary, tertiary, and quaternary

Question 34

What are the two most common secondary structures?

Answer 34

alpha helixes and beta pleated sheets

Question 35

What protein is the alpha helix an important structural component in?

Answer 35

keratin

Question 36

Which amino acid is rarely found in alpha helixes?

Answer 36

proline

Question 37

The tertiary structure of a protein is primary the result of ________ into the interior of the protein

Answer 37

hydrophobic amino acid side chains

Question 38

What bond is an important component in tertiary structures

Answer 38

disulfide bonds

Question 39

When do disulfide bonds form?

Answer 39

when two cysteine molecules become oxidized to form cystine, which creates loops

Question 40

What bonds form from secondary structures to tertiary structures

Answer 40

secondary structure forms, hydrophobic interactions, and then hydrogen bonds to collapse the protein

Question 41

What is the intermediate state between secondary and tertiary structures?

Answer 41

molten globules

Question 42

denaturation is when

Answer 42

a protein (usually tertiary structure), loses its shape/structure and loses its function

Question 43

What forms a solvation layer?

Answer 43

solvent molecules that come in contact with the solute, (forms around the solute)

Question 44

Are negative changes in entropy favorable or unfavorable?

Answer 44

unfavorable, because it makes the process non-spontaneous

Question 45

When do quaternary structures exist

Answer 45

when there is more than one polypeptide chain

Question 46

What proteins have a quaternary structure?

Answer 46

hemoglobin and immunoglobulins

Question 47

Where do conjugated proteins derive their function from?

Answer 47

From the covalent attachment of prosthetic groups

Question 48

Lipoproteins, glycoproteins, and nucleoproteins all have a....?

Answer 48

prosthetic group

Question 49

To reverse protein folding, a protein would need to undergo

Answer 49

denaturation

Question 50

What are the two main causes of denaturation?

Answer 50

heat and solutes

Question 51

why does heat denature a protein?

Answer 51

it overrides the hydrophobic interactions that hold a protein together

Question 52

Why do solutes denature proteins

Answer 52

they break apart disulfide bridges as well as hydrogen bonds that hold the alpha helix and beta sheets together

Question 53

Enzymes are ______

Answer 53

biological catalysts

Question 54

T/F enzymes lower activation energy

Answer 54

true

Question 55

Do enzymes increase or decrease the rate of reaction

Answer 55

increase

Question 56

Do enzymes alter the equilibrium constant?

Answer 56

no

Question 57

Are enzymes changed at all during the reaction?

Answer 57

no

Question 58

Are enzymes pH and temp sensitive?

Answer 58

yes

Question 59

Do enzymes effect the free energy (deltaG) of the reaction?

Answer 59

no

Question 60

Are enzymes specific?

Answer 60

yes

Question 61

Oxidoreductase function is to

Answer 61

catalyze oxidation-reduction reactions

Question 62

Transferase function is to

Answer 62

catalyze the movement of a functional group from one molecule to another

Question 63

Kinases transfer _______

Answer 63

phosphate groups

Question 64

Hydrolases function is to

Answer 64

catalyze the breakdown of a compound into two molecules by adding water

Question 65

Lyases function is to

Answer 65

catalyze the cleavage of a single molecule into two products

Question 66

Isomerases function is to

Answer 66

catalyze the rearrangement of bonds within a molecule

Question 67

Ligases function is to

Answer 67

catalyse addition or synthesis reactions, usually between larger and more similar molecules (require ATP)

Question 68

Endergonic reactions require

Answer 68

energy input

Question 69

Exergonic reactions give off

Answer 69

energy

Question 70

Catalysts such as enzymes help to lower the

Answer 70

activation energy of a reaction

Question 71

Lock and Key Theory suggests that

Answer 71

the enzyme active site is already in the appropriate confirmation for the right substrate to bind

Question 72

Induced fit model

Answer 72

During transitional state, both the substrate and enzyme undergo a conformational change to complement each other (requires energy)