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MCB 3010 > EXAM 3: Glycolysis I > Flashcards

EXAM 3: Glycolysis I Flashcards

1
Q

four major pathways of glucose utilization

A

storage

glycolysis

pentose phosphate pathway

synthesis of structural polysaccharides

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2
Q

four major pathways of glucose utilization:

storage

A

if the cell has enough energy, plenty of glucose is stored

can be stored in the polymeric form (starch, glycogen)

when [glucose] and [ATP] is high, glucose is stored

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3
Q

four major pathways of glucose utilization:

glycolysis

A

start of breaking down glucose for energy

generates energy via oxidation of glucose to ATP

short-term energy needs

can link to other pathways to generate more energy; end product is pyruvate

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4
Q

four major pathways of glucose utilization:

pentose phosphate pathway

A

generates NADPH via oxidation of glucose

for detoxification and the biosynthesis of lipids and nucleotides

product is critical for making nucleotides

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5
Q

four major pathways of glucose utilization:

synthesis of structural polysaccharides

A

cellulose, chitin in cell walls of bacteria, fungi, plants

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6
Q

importance of glycolysis

A

sequence of enzyme-catalyzed reactions by which glucose is converted into pyruvate (3C)

some of the free energy from oxidation is captured by synthesis of ATP and NADH

(NADH can help produce ATP through oxidative phosphorylation if oxygen is available)

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7
Q

summary of glycolysis

A

used: 1 glucose, 2ATP, 4ADP, 2Pi, 2NAD+
made: 2 pyruvate, 4ATP, 2NADH

NET:
1 glucose + 2ADP +2 Pi + 2NAD+
=
2 pyruvate + 2NADH + 2H+ +2ATP

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8
Q

why is glycolysis heavily regulated?

A

ensures proper use of nutrients

ensures production of ATP only when needed

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9
Q

dG for glycolysis

A

-146 kJ/mol for breakdown of glucose and 61 KJ/mol for synthesis of 2 ATP

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10
Q

getting monosaccharides for glycolysis

A

glucose can be transported into the cell via glucose transporter

glucose molecules can be cleaved from glycogen or starch (to get glucose-1P; must be converted to glucose-6P for glycolysis)

disaccharides can be hydrolyzed into monosaccharides

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11
Q

maltose

A

two glucose

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12
Q

lactose

A

glucose, galactose

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13
Q

sucrose

A

glucose, fructose

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14
Q

fructose, galactose, mannose

A

enter glycolysis at different paths

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15
Q

glycolysis overview

A

goal: extract energy without oxygen

first: activate glucose by phosphorylation
second: collect energy from high energy metabolites

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16
Q

3 irreversible reactions in glycolysis

A

very negative dG’*

point of regulation so glycolysis only goes forward when necessary – allosteric and reversible covalent regulation

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17
Q

GLYCOLYSIS: Step 1

A

phosphorylation of glucose

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18
Q

GLYCOLYSIS: Step 1, phosphorylation of glucose

A

traps glucose inside the cell

lowers intracellular [glucose] to allow further transport by glucose transporter

uses ATP

hexokinase

thermodynamically favorable, irreversible

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19
Q

GLYCOLYSIS: Step 1 phosphorylation of glucose

HEXOKINASE

A

glucose to glucose 6-phosphate

nucleophilic oxygen at C6 of glucose attacks last (gamma) phosphate of ATP

irreversible

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20
Q

GLYCOLYSIS: Step 2

A

phosphohexase isomeriaztion

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21
Q

GLYCOLYSIS: Step 2 phosphohexase isomerization

A

C1 of fructose is easier to phosphorylate in next step

allows for symmetrical cleavage of aldolase

unfavorable, reversible

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22
Q

GLYCOLYSIS: Step 2

phosphohexokinase isomerase

A

glucose 6-P to fructose 6-P

changing product concentrations allows reverse reaction

product concentration kept low to drive forward

unfavorable, reversible

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23
Q

GLYCOLYSIS: Step 3

A

2nd priming reaction

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24
Q

GLYCOLYSIS: Step 3 2nd priming reaction

A

Further activation of fructose

phosphofructokinase-1

first committed step of glycolysis

uses ATP

favorable, irreversible

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25
GLYCOLYSIS: Step 3 2nd priming reaction PHOSPHOFRUCTOKINASE-1
Fructose 6-P to fructose 1,6-bisphosphate irreversible, favorable first committed step of glycolysis
26
how is phosphofructokinase-1 tightly regulated?
tightly regulated by ATP, fructose-1,6-bisphosphate and other metabolites prevents burning of glucose when there is plenty of ATP
27
why is the 2nd priming reaction with phosphofructokinase-1 the first committed step of glycolysis?
fructose 1,6-bisphosphate must continue through glycolysis where as prior products may be utilized in other pathways
28
GLYCOLYSIS: Step 4
aldol cleavage of fructose-1,6-bisphosphate
29
GLYCOLYSIS: Step 4 aldol cleavage
cleavage of 6 carbon sugar into two three carbon sugars aldolase cleaves C-C bond between C3 and C4 in fructose-1,6-bisphosphate makes glyceraldehyde-3P (ald) and dihydroxyacetone-phosphate (ket) unfavorable, reversible
30
GLYCOLYSIS: Step 4 aldol cleavage ALDOLASE
fructose-1,6-bisphosphate to glyceraldehyde-3P and dihydroxyaceone-phosphate unfavorable, reversible G3P concentration kept low to drive reaction DHAP converted to G3P in a separate reaction so product concentration is kept low
31
GLYCOLYSIS: Step 5
triose phosphate interconverstion
32
GLYCOLYSIS: Step 5 triose phosphate interconversion
allows glycolysis to proceed by one pathway dihydroxyacetone phosphate to glyceraldehyde 3-phosphate via triose phosphate isomersase unfavorable, reversible END OF PREPARATORY PHASE
33
GLYCOLYSIS: Step 5 triose phosphate interconversion TRIOSE PHOSPHATE ISOMERASE
dihydroxyacetone phosphate to glyceraldehyde-3P unfavorable reversible
34
Glycolysis: preparatory phase
phosphorylation of glucose and its conversion to glyceraldehyde-3-phosphate first priming reaction (hexokinase, phosphohexase isomerase) second priming reaction (phosphofructokinase 1) cleavage of 6 carbon sugar into 2 3 carbon sugars isomerase
35
Glycolysis: payoff phase
oxidative conversion of glyceraldehyde 3-P to pyruvate and the coupled formation of NADH and ATP
36
Where are 2 ATPs used in glycolysis?
prep phase: hexokinase to phosphorylation glucose phosphofructokinase 1 to make fructose-1,6-bisphosphate
37
where are 4 ATPs made in glycolysis?
payoff phase: 1 ATP per phosphoglycerate kinase (2 total) 1 ATP per pyruvate kinase (2 total)
38
GLYCOLYSIS: Step 6
oxidation and phosphorylation of glyceraldehyde 3P
39
GLYCOLYSIS: Step 6 oxidative phosphorylation of glyceraldehyde 3P
generates high energy phosphate compound via incorporation of inorganic phosphate (NOT ATP) allows for production of ATP in next step oxidation of aldehyde (into carboxyl) and reduction of NAD+ (to NADH) phosphorylation makes a phosphorylated carboxyl group unfavorable, reversible; coupled to next reaction to pull glyceraldehyde 3phosphate dehydrogenase
40
GLYCOLYSIS: Step 6 oxidative phosphorylation of glyceraldehyde 3P GLYCERALDEHYDE -3P DEHYDROGENASE
glyceraldehyde -3P + Pi to 1,3 bisphosphoglycerate
41
GLYCOLYSIS: Step 7
phosphoryll transfer to ATP substrate-level phosphorylation to make 2 ATP 1,3-bisphosphoglycerate donates phosphate group from C1 to ADP phosphoglycerate kianse favorable, reversible
42
GLYCOLYSIS: Step 7 phosphoryl transfer to ATP PHOSPHOGLYCERATE KINASE
1,3-bisphosphoglycerate + ADP to 3-phosphoglycerate + ATP 2 times
43
GLYCOLYSIS: Step 8
migration of phosphate
44
GLYCOLYSIS: Step 8 | migration of phosphate
phosphoglycerate mutase catalyzes change in position of phosphate functional group within the molecule 3-phosphoglycerate to 2-phosphoglycerate unfavorable, reversible
45
GLYCOLYSIS: Step 8 migration of phosphate PHOSPHOGLYCERATE MUTASE
3-phosphoglycerate to 2-phosphoglycerate - enzyme is phosphorylated - donates phosphate to C2 before removing phosphate at C3 - 2,3-bisphosphoglycerate intermediate - phosphate from substrate ends up bound to enzyme at the end of reaction reactant concentration kept high by phosphoglycerate kinase to push phosphoglycerate mutase reaction
46
GLYCOLYSIS: Step 9
dehydration of 2-phosphoglycerate to phosphoenolpyruvate
47
GLYCOLYSIS: Step 9 | dehydration of 2-phosphoglycerate to PEP
generates high energy compound slightly unfavorable, reversible product concentration kept low enolase
48
GLYCOLYSIS: Step 9 ENOLASE
2-phosphoglycerate to phosphoenolpyruvate
49
GLYCOLYSIS: Step 10
2nd production of ATP
50
GLYCOLYSIS: Step 10 | 2nd production of ATP
substrate-level phosphorylation to make ATP loss of phosphate from phosphoenolpyruvate yields an enol, tautomerizes into a ketone favorable, irreversible pyruvate kinase
51
GLYCOLYSIS: Step 10 PYRUVATE KINASE
PEP + ADP to pyruvate and ATP 2 total regulated by ATP, divalent metals, other metabolites
52
tautomerization in step 10
changes molecule with high free energy to molecule with low free energy (favorable) effectively lowers concentration of reaction product drives reaction towards ATP formation responsible for half of dG*' = -61.9 kJ/mol
53
fates of pyruvate: hypoxic or anaerobic conditions
2 ethanol + 2CO2 fermentation to ethanol in yeast
54
fates of pyruvate: aerobic conditions
``` 2 acetyl-CoA + 2CO2 | citric acid cycle | 4CO2 + 4H2O ``` animal, plant, microbial cells under aerobic conditions; all carbons oxidized, many NADH, FADH2
55
fates of pyruvate: hypoxic or anaerobic conditions
2 lactate fermentation to lactate in contracting muscle, erythrocytes, microorganisms
56
glycogen phosphorylase
first enzyme breaks a1-4 linkages between glucose molecules via phosphorolysis cleaves until 4 glucoses remain before a branch point product: glucose-1P
57
phosphorolysis
uses inorganic phosphate instead of water in hydrolysis to break bond
58
glycogen debranching enzyme
second enzyme transferase activity glucosidase activity
59
glycogen debranching enzyme transferase activity
transfers 3 of 4 remaining glucoses of one branch to another branch
60
glycogen debranching enzyme glucosidase activity
cleaves off remaining glucose that is attached a1-6 as glucose via hydrolysis
61
phosphoglucomutase
third enzyme converted glucose-1P into glucose6P which can feed into glycolysis
62
glucose-6-phosphatase
in liver cleaves off phosphate so glucose can be transported in to the blood for other organs
63
maltase
cleaves maltose hydrolysis
64
lactase
cleaves lactose hydrolysis
65
sucrase
cleaves sucrose hydrolysis
66
fructose route 1
hexokinase + ATP can make fructose 6 phosphate second reaction to make fructose 1,6-bisphosphate to go into glycolysis
67
fructose route 2
fructokinase + ATP: makes fructose 1 phosphate fructose 1 phosphate aldolase: cleaves fructose-1-phosphate to make dihydroxyacetone phosphate and glyceraldehyde trios kinase + ATP phosphorylates glyceraldehyde so it can enter glycolysis
68
galactokinase
synthesizes galactose-1P from galactose using ATP
69
UDP-glucose galactose-1-phosphate uridylyltransferase
trades groups UDP from UDP-glucose to C1 on galactose Phosphate from galactose-1P to C1 on glucose glucose 1P becomes glucose 6P via phosphoglucomutase
70
UDP glucose 4 epimerase
switches OH on chiral carbon 4 of galactose portion of UDP-galactose to make UDP-glucose
71
anaerobic glycolysis: fermentation
generation of ATP without consuming oxygen final reaction reduces pyruvate to another product to produce NAD+ process is used in production of food
72
lactic acid fermentation
animals, some bacteria reversible reduction of pyruvate to lactate glycogen in muscle becomes glucose becomes lactate. lactate transports to liver to be converted to glucose using ATP glucose sent back to muscle to restore glycogen stores erythrocytes do lactic acid fermentation bc no mitochondria
73
cori cycle
cycle with lactate and liver
74
lactate dehydrogenase
reduces pyruvate to lactate and oxidizes NADH to NAD+
75
ethanol fermentation
yeast pyruvate to acetaldehyde = irreversible pyruvate decarboxylase alcohol dehydrogenase CO2 produces in first step = carbonation, dough rising
76
pyruvate decarboxylase
pyruvate to acetaldehyde humans don't have this
77
alcohol dehydrogenase
acetaldehyde to ethanol humans have this for ethanol metabolism (reverse of fermentation)

MCB 3010 (12 decks)

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