Bio Chem -- Proteins and Enzymes

Question 1

primary protein structure

Answer 1

linear AA sequence
covalent bonds joining AAs
covalent disulfide bonds (join two sides of chain at different locations)

Question 2

secondary protein structure

Answer 2

alpha-helices and beta-pleated sheets
can be prevented by size/composition of R group
H-bonds (between carboxyl of one and amino of another)

Question 3

how and when are proteins folded?

Answer 3

by chaperones, when protein is just formed or after partial denaturation

Question 4

tertiary structure

Answer 4

interaction of side groups of single protein

creates domains

Question 5

quaternary structure

Answer 5

interaction between multiple proteins

Question 6

what can cause protein to lose function?

Answer 6

change in structure, such as by pH or Temp

Question 7

compare interactions involved in different protein structures

Answer 7

primary–covalent

all others–non-covalent (usually)

Question 8

shape that protein assumes in water

Answer 8

lowest energy shape, with groups capable of H-bonding on outside

Question 9

7 functions of proteins

Answer 9

transport (hemoglobin)
immunity (IgG)
signaling/receptors (G protein)
control of gene expression
cell structure
catalysis (enzymes)
cell/organism motion/locomotion (contractile proteins in muscle)

Question 10

enzyme function

Answer 10

speeding up (catalysis) of spontaneous reaction

Question 11

post-translational modification

Answer 11

covalent attachment of sugars or phosphates to a protein after translation

Question 12

O-linkage

Answer 12

kind of glycoprotein linkage

covalent attachment of carbohydrate to hydroxyl group of amino acid’s R group

Question 13

N-linkage

Answer 13

kind of glycoprotein linkage

covalent attachment of carbohydrate to amino group of amino acid’s R group

Question 14

glycosylation vs glycation

Answer 14

glycosylation: enzymatic linkage of sugars (kind of post-translational modification)
glycation: spontaneous reaction between sugars and proteins

Question 15

phosphorylation of proteins

Answer 15

kind of post-translational modification
addition of phophate group, catalyzed by kinases
(removal of phosphate is catalyzed by phophatases)

Question 16

mechanism of enzyme catalysis

Answer 16

enzyme binds to substrate
non-covalent for quick release
very specific action (one enzyme catalyzes one, maybe two-three rxns)
coenzymes (organic) and cofactors (inorganic) complete enzyme so it fits substrate

Question 17

enzyme reaction rate factors

Answer 17

substrate concentration (incr. concentration = incr. rate, until saturation)
inhibition
competitive (inhibitor competes with substrate for same active site on enzyme)
non-competitive (inhibitor binds to site other than active site–doesn’t compete with substrate for active site)
temp (incr. in temp incr. rate until denaturation–peak temp is optimum temp)
pH (incr. in pH incr. rate until denaturation)

Question 18

enzyme kinetics

Answer 18

Vmax: max rxn rate (occurs at saturation point)
Km: substrate concentration at 1/2 Vmax (lower Km = higher affinity of enzyme for substrate)

Question 19

Lineweaver-Burke Plot

Answer 19

plot of reciprocals of Michaelis-Menten plot
turns curves into straight lines
easy calculation of Vmax and Km

Question 20

enzymes are usually a type of __________

Answer 20

protein

Question 21

translation of amino acids

Answer 21

peptide bond formed between AAs via dehydration rxn

Question 22

properties of aromatic AAs

Answer 22

pretty nonpolar (Tyr less so)
absorb UV light

Question 23

amino acid acids and bases

Answer 23

acids: second carboxylic acid group; neg. charge makes them soluble in water
bases: second amino group; pos. charge makes them soluble in water

Question 24

sulfur-containing amino acids

Answer 24

disulfide bonds

hydrophobic

Question 25

enzyme kinetics

Answer 25

competitive inhibition: Vmax same (if enough substrate added); Km higher (less affinity of enzyme for substrate)
non-competitive inhibition: lower Vmax, higher Km

Question 26

enzyme regulation

Answer 26

inactive precursors

allosteric regulation

Question 27

allosteric regulation

Answer 27

activation: activator binds at “other” site, conformation of active site changed, substrate can now bind
inhibition: inhibitor binds at “other” site, conformation of active site is changed, substrate can no longer bind

Question 28

inactive precursors

Answer 28

aka zymogens
inactive form of enzyme
activated by cleavage
examples: pepsinogen (becomes pepsin); trypsinogen (becomes trypsin)