15. glycolysis Flashcards
(103 cards)
1
Q
define metabolism
A
the highly organized/regulated collection of chemical transformations carried out by living cells. Carried out by metabolic pathways
2
Q
what are metabolic pathways
A
a series of sequential reactions. The product of one becomes the substrate for the next
3
Q
what are metabolites
A
small molecules that are intermediates in the degradation or biosynthesis reactions of biopolymers
4
Q
what is intermediary metabolism
A
the study of metabolites throughout metabolic pathways
5
Q
T or F; metabolic pathways can be highly connected and share intermediates
A
true
6
Q
what is anabolism
A
synthesis of small molecules into large molecules
7
Q
what is catabolism
A
breakdown of large molecules into smaller molecules
8
Q
which type of metabolism requires an input of energy
A
anabolic pathways
9
Q
what type of energy does anabolism require an input of
A
ATP (phosphoryl group transfer) and NADH/NADPH/FADH2 (reduced electron carriers)
10
Q
which type of metabolism releases energy
A
catabolic pathways
11
Q
describe the release of energy in catabolism
A
regenerates ATP from ADP and Pi, and regenerates the reduced electron carriers from their oxidized forms (NAD+, NADP+, FAD)
12
Q
what are amphibolic pathways
A
pathways that are either catabolic or anabolic depending on the energy conditions of the cell
13
Q
T or F: most metabolic reactions in cells are at steady state
A
true
14
Q
define steady state
A
the amount of each intermediate is not changing
15
Q
define flux
A
the rate of flow through the pathway
16
Q
T or F: most cells have the enzymes to carry out both the degradation and synthesis of important biomolecules
A
true
17
Q
T or F: feedback can activate or inhibit a metabolic pathway
A
true
18
Q
explain how glucose plays a central role in the metabolism of animals and plants
A
- rich in potential energy (G’o = -2840kj/mol)
- large amounts can be stored
- quick release from storage when needed
19
Q
where does glycolysis occur
A
in the cytosol
20
Q
how many steps is glycolysis
A
10
21
Q
what is the first 5 steps of glycolysis called
A
the preparatory phase
22
Q
what does the preparatory phase produce
A
glyceraldehyde-3-phosphate
23
Q
what is the cost of the preparatory phase
A
2 ATP
24
Q
what is the last 5 steps of glycolysis called
A
the payoff phase
25
what does the payoff phase produce
pyruvate
26
what is the benefit of the payoff phase (ie what's the payoff)
4 ATP
27
what happens to pyruvate after glycolysis
- complete oxidation to CO2 to produce reduced electron carriers for the ETC
- lactic acid fermentation to regenerate NAD+
- ethanol fermentation
28
step 1: what is the reagent and product
glucose --> glucose-6-phosphate
29
step 1: how does it happen
phosphorylation at C6 turns glucose into G6P
30
step 1: what phosphorylates glucose
ATP is the phosphoryl donor
31
step 1: is it reverisble
no
32
step 1: what is the purpose of phosphorylation
it "primes" glucose for subsequent reactions
33
step 1: what effect does phosphorylation have on glucose (hint: think location)
phosphorylation traps glucose in the cell
34
step 1: what enzyme is used for glucose phosphorylation from ATP
hexokinase
35
step 1: describe the G'o
relatively large G'o (because energy in this step was raised)
36
step 1: does hexokinase need a substrate
yes
37
step 1: what substrate does hexokinase (and all the other kinases) need
(MgATP)^2-
38
step 1: since MgATP2- is the substrate for hexokinase, what does that make Mg2+. What is the purpose of Mg2+
it's an essential cofactor. It shields negative charges in the active site
39
step 2: what enzyme is used
phosphohexose isomerase (requires Mg2+)
40
step 2: what is the reagent and product
glucose-6-phosphate --> fructose-6-phosphate
| aldose to ketose
41
step 2: is it reversible
yes
42
step 2: what is the purpose of aldose to ketose
C1 is now able to be phosphorylated just like C6 was
| because the goal is to have glucose as a mirror image
43
step 2: what is required to convert the aldose to the ketose
we need to open the ring in the active site to temporarily revert glucose to linear form, then we can form the ketose
44
step 3: what is the reagent and product
fructose-6-phosphate --> fructose 1,6-bisphosphate
45
step 3: what happens to make the product
F6P is phosphorylated to make the product
46
step 3: where does the phosphate come from to phosphorylate F6P
ATP
47
step 3: what enzyme uses the P from ATP to phosphorylate F6P
phosphofructokinase-1
48
step 3: is it reversible
no! phosphofructokinase-1 commits these carbons to glycolysis
49
step 3: what does phosphofructokinase-1 need for proper kinase activity
Mg2+
50
step 4: what is the reagent and product
fructose 1,6-bisphosphate --> glyceraldehyde 3-phosphate AND dihydroxyacetone phosphate
51
step 4: what is glyceraldehyde 3-phosphate
aldose, phosphorylated version of glyceraldehyde
52
step 4: what is dihydroxyacetone phosphate
ketose, phosphorylated version of dihydroxyacetone
53
step 4: what happens to fructose 1,6-bisphosphate in this step
it is cleaved into the two products, which requires the ring opening
54
step 4: when the ring is opened to make the two products, is there a tetrahedral intermediate
yes
55
step 4: what enzyme is used
aldolase
56
step 5: what is the reagent and product
dihydroxyacetone phosphate --> glyceraldehyde 3-phosphate
57
step 5: how does DHAP become G3P
isomerization
58
step 5: what are we left with + why
2 molecules of G3P, because one was made in this step and one was pre existing from the last step
59
step 5: what enzyme is used
triose phosphate isomerase
60
step 6: what is the reagent and product
glyceraldehyde 3-phosphate --> 1,3-bisphosphoglycerate
61
step 6: how does the conversion of G3P to 1,3BPG occur
oxidation with the help of Pi and NAD+
62
step 6: what enzyme is used
glyceraldehyde 3-phosphate dehydrogenase
63
step 6: other than 1,3BPG, what is produced
2 NADH and 2 H+
64
step 6: what is the role of the electron carrier NAD+
it's a co-substrate of the dehydrogenase enzyme
65
step 6: how are NADH and H+ formed
two electrons and a proton from the oxidation of G3P to 1,3BPG are transferred to the NAD+
66
step 6: what happens to NAD+ levels after this step
NAD+ levels in the cell are very low, so NAD+ is eventually regenerated down the road
67
step 6: endergonic or exergonic
endergonic (non-spontaneous)
68
how do we make step 6 spontaneous (exergonic)
by coupling it with step 7
69
step 7: what is the reagent and product
1,3-bisphosphoglycerate --> 3-phosphoglycerate
70
step 7: how is 3-phosphoglycerate formed
hydrolysis of the high energy phosphoryl group from 1,3BPG
71
step 7: where does the hydrolyzed phosphoryl group go (came from 1,3BPG)
it is transferred to ADP --> ATP
72
step 7: what enzyme is used
phosphoglycerate kinase
73
step 7: how many ATP are produced
2
74
step 7: 1,3BPG was one of the molecules with a large negative G'o from bioenergetics. What does this mean for glycolysis
the products of this step (3-phosphorglycerate) are stabilized (due to ionization and resonance), and this step is super exergonic
75
step 7: what is the term for the transfer of a phosphoryl group from a high energy compound (ie BPG) to ADP by a soluble enzyme in the cytosol
substrate level phosphorylation
76
step 7: does the enzyme require Mg2+
yes
77
what does coupling of steps 6 and 7 achieve
makes the endergonic step 6 into an exergonic step
78
step 8: what is the reagent and product
3-phosphoglycerate --> 2-phosphoglycerate
79
step 8: how is 2-phosphoglycerate made
the phosphoryl group on 3-phosphoglycerate is shifted to C2 from C3 to produce 2-phosphoglycerate
80
step 8: what enzyme is used
phosphoglycerate mutase
81
step 8: does phosphoglycerate mutase require Mg2+
yes
82
step 9: what is the reagent and product
2-phosphoglycerate --> phosphoenolpyruvate
83
step 9: how is phosphoenolpyruvate produced
water is removed from 2-phosphoglycerate to produce phosphoenolpyruvate
84
step 9: what enzyme is used
enolase
85
step 9: phosphoenolpyruvate was one of the molecules with a large negative G'o from bioenergetics. What does this mean for glycolysis
the hydrolysis product (pyruvate) is stabilized by isomerization
86
step 10: what is the reagent and product
phosphoenolpyruvate --> pyruvate
87
step 10: how is pyruvate produced
hydrolysis
88
step 10: what enzyme is used
pyruvate kinase
89
step 10: does pyruvate kinase require Mg2+
yes
90
step 10: what else is produced
ATP
91
step 10: how much ATP is produced
2
92
step 10: how much of the standard free energy is retained in the ATP
half; the other half is released
93
T or F: for all 10 steps, the gibbs free energy is either negative or zero
true
94
describe the delta G value for the overall sum of the reactions
negative
95
which of the 10 reactions has a large negative delta G value
1, 3, and 10
96
for reactions 1, 3, and 10 (ones having large negative G), why are they considered regulatory points in metabolism
they're both metabolically irreversible and regulated
97
describe the feeder pathway for starch
broken down by a-amylases in salivary glands = short oligosaccharides. Pancreatic a-amylases continue = maltose. Maltose is degraded to glucose by intestinal enzymes
98
describe the feeder pathway of dietary glycogen (animal products)
very similar to starch
99
describe the feeder pathway of endogenous glycogen (glucose in our bodies)
broken down via phosphorylases in the liver/muscle. Glucose 1-phosphate is cleaved off, which isomerizes to glucose 6-phosphate
(this is phosphorolysis, not hydrolysis)
100
describe the feeder pathway of sucrose
sucrose is cleaved by sucrases into glucose and fructose. Fructose can enter glycolysis via the muscle and kidney, or by the liver
101
describe the feeder pathway for fructose in the muscle/kidney
fructose is phosphorylated by hexokinase and enters glycolysis
102
describe the feeder pathway for fructose in the liver
fructose is phosphorylated by fructokinase at C1 (not C6). F 1-P is then cleaved into two products that enter glycolysis via G3P
103
describe the feeder pathway for mannose
mannose is phosphorylated by hexokinase to mannose 6-phosphate. M6P is then isomerized to fructose 6-phosphate
