Exam Three Flashcards
What is required for enzymatic reactions?
Formation of an ES complex
What is the equation for a first order reaction?
rate = k[A]
What is the equation for a second order reaction?
rate = k[A][B]
What order reaction occurs when the amount of substrate has no effect on the rate?
zero
True or False: the higher the concentration of S, the faster the reaction
False, it is dependent on the amount of enzyme present
True or False: the higher the concentration of E, the faster the reaction
True, although technically there is normally a limited amount of enzyme
________ is an indicator of affinity for a substrate (binding efficiency)
Km
Does a smaller or larger Km indicate better affinity?
smaller
What is Vmax?
The maximum velocity the enzyme can achieve at a given enzyme concentration
What is the kcat equation?
kcat = Vmax / total Enzyme concentration
What value can be thought of as frequency of the reaction?
kcat
what is the measure of both binding and catalytic events?
kcat/Km
Does a larger or smaller value of kcat/Km indicate a better enzyme?
larger
What limits kcat/Km?
time for electron rearrangement, turnover number, and collision
What is the number of kcat/Km that is considered catalytic perfection?
10e8 - 10e9 1/(M*s)
Generally, efficient enzymes have (high/low) Vmax, Km, kcat, kcat/Km?
high Vmax, low Km, high kcat, high kcat/Km
With a lineweaver-burk plot equation, what is the Vmax equal to?
1/y-intercept
With a lineweaver-burk plot equation, what is the Km equal to?
slope/y-intercept
What makes an irreversible inhibitor, irreversible?
it covalently modifies the enzyme so that it cannot return to its active form
What is an example of an irreversible inhibitor?
Serine Protease
Kinetics don’t affect which kind of inhibitor?
irreversible
What are the effects of reversible inhibitors interacting with an enzyme?
lower overall reaction rate, reaction kinetics are changed, and the inhibitor can be released from the enzyme
What kind of inhibitor am I describing: the inhibitor competes with the substrate for the active site
competitive inhibitor
Which inhibitor is considered mutually exclusive?
competitive
For competitive inhibition, what occurs if [s] is much greater than [I]?
no inhibition is observed
What values do competitive inhibitors affect?
Km, not Vmax
(increase in Km)
What kind of inhibitor am I describing: inhibitor binds at a site other than the active site and changes the conformation of the enzyme
mixed inhibitor
What values do mixed inhibitors affect?
Vmax (decreases) and Km (increase or rarely decrease)
What kind of inhibitor is a noncompetitive inhibitor?
mixed
What values do noncompetitive inhibitors affect?
Vmax (decreases), no change in Km
What kind of inhibitor affects only the catalytic activity and not substrate binding?
Uncompetitive inhibitor
What values do uncompetitive inhibitors affect?
Km (decreases) and Vmax (decreases)
What kind of inhibitor is Tamiflu?
competitive inhibitor
What NSAID is irreversible inhibition of both COX-1 and COX-2?
Aspirin
What NSAID is reversible inhibition of both COX-1 and COX-2?
ibuprofen
What NSAID is selective inhibition of just COX-2?
Vioxx and Celebrex
What is the term for the sequential reaction where the order of the substrate matters?
Ordered
What is the term for the sequential reaction where it doesn’t matter which substrate goes first/the order doesn’t matter?
Random
If you have more than one substrate, is there one Km, or does each substrate have its own Km?
Each substrate has a distinctive Km
Does allosteric regulation inhibit or enhance enzyme activity?
It does both! Depends if it’s a positive or negative effector
What is the allosteric effect?
binding of an effector to one subunit affects the active sites of all subunits
What is the negative effector of PFK?
PEP: almost a final product of of the pathway that PFK is regulating
What is the positive effector of PFK?
ADP
Why is ADP the positive effector of PFK?
High concentration of ADP would indicate a need for ATP, which is the product of glycolysis
What form are the majority of natural carbohydrates in?
D form
What are the left and right symbols for D-Glucose?
RLRR
What are the left and right symbols for D-Galactose?
RLLR
Pyran is a ___ - membered ring
6
Furan is a _____ - membered ring
5
Is Beta together or opposite?
together
is Alpha together or opposite?
opposite
Anomeric carbon forms a covalent bond with an alcohol - what is this called?
glycosidic bond
What is a reducing sugar?
sugars with anomeric carbons that have not formed glycosides
What is polymerized by glycosidic bonds?
carbohydrate monomers
Sucrose make up:
alpha-glucose + beta-fructose
Maltose make up:
alpha-glucose + beta-glucose
Lactose make up:
beta-galactose + beta-glucose
Isomaltose make up:
alpha-glucose + alpha-glucose
Cellobiose make up:
beta-glucose + beta-glucose
Which polysaccharide has a linear make up?
cellulose
Which polysaccharide has a branched make up?
starch
Which polysaccharide has a highly branched make up?
glycogen
What cleaves glycogen?
glycogen phosphorylase / glycogen debranching enzyme
What is a glycoprotein?
protein that has some type of carbohydrate attached to it
What kind of carbohydrate is attached to a glycoprotein?
oligosaccharide
At what amino acids are the oligosaccharides attached to the glycoprotein?
Asn (N-glycosidic), Ser (O-glycosidic), or Thr (O-glycosidic)
What is the purpose of the oligosaccharide added to the glycoprotein
helps stabilize the protein and the helps the organism recognize its own protein vs. foreign proteins
Which fatty acids have double bonds?
unsaturated
Which fatty acids don’t have any double bonds?
saturated
What is the saturated 18 C fatty acid
stearic acid CH3(CH2)16COOH
What is the monounsaturated 18 C fatty acid
oleic acid CH3(CH2)7CH=CH(CH2)7COOH
What is the polyunsaturated 18 C fatty acid with two double bonds?
linoleic acid CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH
What is the polyunsaturated 18C fatty acid with three double bonds?
linolenic acid CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH
What is the common name for 18:1n9, trans?
Elaidic Acid
What causes trans unstaturation?
hydrogenation
What makes omega 6 and omega 3 fatty acids “essential”
our body needs them, but cannot make them so we must take them from food
What is the 12 C saturated fatty acid called?
Lauric Acid
What is the 14 C saturated fatty acid called?
Myristic Acid
What is the 16 C saturated fatty acid called?
Palmitic Acid
What is a triacylglycerol?
3 fatty acids on a glycerol backbone
The more double bonds, the ________ the melting point
lower
The longer the acyl chain, the ________ the melting point
higher
What are the 4 kinds of membrane bilayers?
glycerophospholipids, sphingomyelins, cholesterol, and isoprenoids
What is the make up of a glycerophospholipid?
glycerol-3-phosphate + 2 fatty acids
What is a sphingosine?
18 carbon amino alcohol
What is the make up of a ceramide?
sphingosine + N-acyl fatty acid
What is the make up of a sphingomyelin?
ceramide + phosphoryl head group
What is the make up of a cerebroside?
ceramide + single sugar head group
What is the make up of a ganglioside?
ceramide + oligosaccharides (including sialic acid)
What is Tamiflu an analog of?
Sialic acid
What is sterol’s make up?
3 cyclohexanes and 1 cyclopentane
Which vitamins are isoprenoids?
A, D, and K
Vitamins A, D, and K are _______ because of their isoprenoid nature
fat soluble
What is the outer leaflet of the membrane composed of?
sphingolipids and phosphatidyl choline
What is the inner leaflet of the membrane composed of?
phosphatidyl serine
How are the inner and outer leaflets of the membrane’s distinct compositions maintained?
it is thermodynamically unfavorable to flip flop
What enzyme allows the outer and inner leaflets to flip flop?
flippases (or translocases)
What is another term for the flip flop of inner and outer leaflets?
transverse diffusion
What is the more common type of switching in the membrane?
lateral diffusion
What kind of diffusion is the reason the membrane is so flexible?
Lateral Diffusion
Membranes are _________ (structure - wise)
dynamic and fluid
What is the main source of energy in the body?
oxidation of carbons in carbohydrates
All reactions in vivo occur with a net ________ in free energy
decrease
Are metabolic pathways reversible?
No, it is thermodynamically unfavorable to do so
What is the first step of every metabolic pathway called and what is unique about it?
First committed step, Delta G of this step must be negative
What is the catabolic pathway of glycolysis?
gluconeogensis
What are used as energy currency in the cell?
reduced cofactors
Reduced cofactors are produced as a result of what?
catabolic activities
Where do glycosidic bonds have to take place?
at anomeric carbons
What kind of bonds are very unstable/high energy and are therefore favorable to break?
phosphoanhydride
What are the results of the breaking of phosphoanhydride bonds?
more resonance stabilization, more solvation in water, and less ionic repulsion
Hydrolysis of _________ bonds also releases a large amount of free energy and is therefore a favorable reaction.
thioester
What is the oxidized form of NAD?
NAD+
What is the reduced form of NAD?
NADH
What is the oxidized form of FAD?
FAD
What is the reduced form of FAD?
FADH2
What is the oxidized form of Q?
Q
What is the reduced form of Q?
QH2
Which reduced cofactor accepts hydrogen as an element?
FAD and Q
Which reduced cofactor accepts Hydride ion?
NAD
What coenzyme can carry electrons in the membrane?
coenzyme Q
What is the tendency of a substrate to accept electrons/to become reduced?
reduction potential
These are the major functions of which organelle: citric acid cycle, electron transport and oxidative phosphorylation, fatty acid oxidation, and amino acid breakdown
mitochondrion
These are the major functions of which organelle: glycolysis, pentose phosphate pathway, fatty acid biosynthesis, and many reactions of gluconeogenesis
cytosol
These are the major functions of which organelle: DNA replication and transcription, RNA processing
nucleus