Final exam Flashcards
What is the net yield of ATP after glycolysis?
2 ATP
What enzymes catalyzes the transfer of a phosphoryl group from ATP to glucose
hexinose
Phosphofructokinase (PFK) is allosterically activated by _____
AMP
Phosphofructokinase (PFK) is _ inhibited by __
ATP and citrate
What is glucose converted to in the skeletal muscle under anerobic conditions?
lactate
What is the purpose of co-factors chemical teeth?
broaden the range of enzymes’ catalytic properties
What are the two cofactor
metal ions and coenzymes
What are the different types of coenzymes
cosubtrates and Prosthetic groups
Define cosubstrates
loosely bound, cycle on & off
Define prosthetic
tightly/covalently bound
What are some examples of Metabolite coenzymes:
ATP, UDP-glucose, S-adenosylmethionine
What are some examples of Vitamin-derived coenzymes (water soluble)
Vitamins B and C
What are some examples of lipid soluble vitamin-derived coenzymes
vitamins` A, D, E, and K (
Acid-base catalysis
Partial proton donation (general acid catalysis) or abstraction (general base catalysis)
What amino acids participate in acid-base catalysis
Asp, Glu, Lys, Arg, and His
What makes a good catalyst
Good leaving group, reversibiliy of the bond, (how mobile electrons are).
How does covalent catalyst form
Via transient formation of covalent E-S intermediate
What is a covelent catalysis
a nucleophile attacks an electrophile and forms covalent bond with it
There are 2 classes of metal ion catalysis, what are those two classes?
Metalloenzymes and Metal-activated enzymes
What are the differences between Metal-activated enzymes and Metalloenzymes
Metalloenzymes are tightly bound and are transition metals. Metal-activated enzymes are loosely bound and are alkaine
What are the 3 ways that metal ion catalysis act
Bind to substrates (orient properly for reaction).
2. Transiently change redox state (mediate redox reaction).
3. Stabilize/shield negative charges.
What is the proximity and oreintation effects?
Binding to E forces substrate orient in a certain way Rotational, translational motions cease
active groups face each other reaction
Is there a prefential binding for ES
yes, there’s an affinity for E in ES because there’s a higher chance to form product
What is Km ((Michealis constant)
enzyme binding affinity (higher Km=weaker affinity)
What is Vmax
maximum rate of the reaction
Vmax relates
Kcat and [Et] by Vmax = kcat[Et]
What is Kcat
(turnover number or catalytic constant) and the Speed of catalysis
Define kcat/KM
measure of catalytic efficiency of enzyme
What does Kcat measure
product formation, substrate turnover
What is the Michaelis-Menten equation
V = Vmax[S]/(KM+[S])`
When would the Michaelis-Menten equation be haf-maximal
[S] = KM
what is the slope of Lineweaver-Burk plot
or double reciprocal plot
Km/Vmax
What is the y-intercept of the Lineweaver -Burk plot
1/vmax
What is the x-intercept of the Lineweaver
-1/Km
What is the purpose of Lineweaver -Burk
Can determine KM and Vmax graphically
What is competitive inhibition
the inhibtition is structurally similar to the substrate and competes with the substrate for active site binding
What is competitve inhibtion impact on the reaction
reduces the steady state of ES, increases the Km, and no reaction happens if the inhibition binds to the active site
How can the competitve inhibition be overcommed
increase the amount of substrate
What is uncompetitve inhibitor
binds only to ES but not to any free enzyme
What is the impact uncometitve inhibitor has on the reaction
Both KM and Vmax change,Does not change the slope (KM/Vmax), no reaction happens at ESI
Defines Noncompetitive (mixed) inhibition
Binds both E and ES (somewhere, not in the active site)
Non competitve inhibition impact on the reaction
slope becomes steeper
Y-intercept moves up, but X-intercept stays the same.
o Apparent Vmax ↓ but KM stays the same.
What is an example of product inhibition
hexokinase by glucose-6-P
Define feedback inhibition
cellular control mechanism in which an enzyme’s activity is inhibited by the enzyme’s end product.
Where does glycolysis take place?
in the cytosal
What are the products of glycolysis
2 ATP, 2 Pyr, 2 NADH, 4 H+, 2 H20
Pyruvate kinase (step 10) is inhibitied by
ATP and acetyl-CoA
Pyruvate kinase (step 10) is activated by
AMP and fructose-1,6-bisphosphate.
What is the purpose of glycolysis?
provides precursor for aerobic catabolism
(TCA cycle
What are the 2 stages of glycolysis
Investment and activation
What is the product from the stage 1: investment
2 glyceraldehyde-3-phosphate (GAP)
Stage 1 in glycolysis spends how many ATP
2 ATP for glucose activation
What steps consume ATP in glycolysis?
are consumed in steps 1 and 3 by hexokinase (HK) and
phosphofructokinase (PFK)
What steps are ATP synthesized in during glycolysis
steps 7&10 by phosphoglycerate kinase (PGK) and
pyruvate kinase (PK) via substrate-level phosphorylation
What were the 3 irreversible control points in glycolysis
Hexokinase (step 1), Phosphofructokinase (step 3), Pyruvate kinase (step 10)
Step 1 of Glycolysis results in
glucose-6-P
In step 3 what catalyzes fructose-6-phosphate?
phosphofructokinase (PFK
)
Where does the TCA cycle take place
in the mitochondrial matrix
define reduction potential
tendency of a given reacting species to gain e - when paired with a
standard
Positive reduction potential
tendency to attract/accept e- (reduced)
Negative reduction potential
tendency to give up e- (oxidized
What happens in a 2 half cell
e- always spontaneously flow from the half-rxn with more negative E o (donor) to
more positive E o (acceptor)
Mechanims of ATP sysnthese
3 αβ protomers, 3 distinct sites, in 3 different conformations (states)
O state of ATP sysnthase
open, inactive, cannot bind ADP
L State of ATP synthase
loose binding, inactive, can bind ADP & Pi
T state of ATP synthase
tight binding, active,can synthesize ATP
What is the Michaelis-Menten equation
V = Vmax[S]/(KM+[S]
Pyruvate kinase is inhibited by
ATP and acetyl-CoA
Pyruvate kinase is activated
AMP and fructose-1,6-bisphosphate
What steps in glycolysis go through
substrate-level phosphorylation
What is substrate-level phosphorylation
the formation of ATP from ADP and a phosphorylated intermediate,
What activates step 4 of the citric acid cycle?
AMP
What inhibits step 4 of the TCA cycle
NADH and succinyl-CoA
What is being oxidized in step 6 of the Kreb’s cycle
succinate
What is being reduced in step 6 of the citric acid cycle ?
FAD to FADH2
What process is succinate dehydrogenase is apart of besides the TCA cycle
electron transport chain
Where does o
