Finals Flashcards
(99 cards)
1
Q
Why is glycolysis the most important metabolic pathway?
A
- found in nearly all cells
- starts catabolism of glucose
- sole course of ATP and NADH for some cells/condition
2
Q
How many steps does glycolysis have?
A
10 steps to oxidize glucose to pyruvate
3
Q
How many important products does glycolysis have?
A
3 important products:
- 2 pyruvate
- 2 ATP
- NADH
4
Q
What are the two phases in glycolysis?
A
- preparatory phase
- payout phase
5
Q
What happens in the preparatory phase?
A
2 ATP consumed in steps 1 and 3
6
Q
What happens in the payout phase?
A
4 ATP produced in steps 7 and 10
2 NADH produced in step 6
7
Q
What is the Net in Glycolysis?
A
- 2 ATP generated
= 4 payout - 2 preparatory - 2 NADH generated
= 2 payout
8
Q
What is step 1 in glycolysis?
A
- phosphorylation of glucose to glucose 6P
- uses ATP
- traps glucose inside cell
9
Q
What is the enzyme that phosphorylates glucose into Glucose 6- phosphate?
A
hexokinase
10
Q
What happens during phosphorylation?
A
once phosphorylated it will be trapped in the cell
11
Q
What happens in step 2 in glycolysis?
A
- isomerization of Glucose -6P
- rearranges molecules to make step 3 easier
12
Q
What enzyme used during the process of isomerization of glucose-6P to fructose 6-phosphate?
A
phosphohexose isomerase
13
Q
What happens in step 3 in glycolysis?
A
- phosphorylation of fructose-6P
- uses ATP
- first committed step of glycolysis
14
Q
what enzyme is used during the phosphorylation of fructose -6P to Fructose 1,6-biphosphate
A
phosphofructokinase -1 (PFK-1)
15
Q
Why is step 3 the first committed step in glycolysis?
A
- earlier intermediates can be used in other pathways
- highly regulated (e.g inhibited by ATP)
= signals the cell that it does not need more ATP
16
Q
What happens in step 4 in glycolysis?
A
- cleavage of fructose 1,6P2
- creates two triose phosphates
- phosphate sugars with 3 carbons
- Lysis step that gives pathway its name
17
Q
What enzyme is used during the cleavage of fructose 1,6P2 to the following:
Dihydroxyacetone phosphate
Glyceeraldehyde 3-phosphate
A
aldolase
18
Q
What does lysis mean?
A
molecules that are broken down into two
19
Q
What happens in step 5 in glycolysis?
A
- isomerization of dihydroxyacetone-P
- Only glyceraldehyde-3P can be used in later steps
= dihydroxyacetone - P must be converted to it.
20
Q
what enzyme is used in isomerization of dihydroxyacetone -P to Glyceraldehyde 3- phosphate?
A
triose phosphate isomerase
21
Q
What step does payout phase start?
A
step 6
22
Q
What happens in step 6 in glycolysis?
A
- phosphorylation and oxidation glyceraldehyde-3P
- uses Pi, NOT ATP
- allows for later ATP production, with no ATP investment
- produces NADH
- 1 per glyceraldehyde-3P
- 2 per glucose
23
Q
What enzyme is being used during phosphorylation and oxidation of glyceraldehyde -3P to 1,3 Biphosphoglycerate
A
Glyceraldehyde 3-phosphate dehydrogenase
24
Q
What happens in step 7 of glycolysis?
A
- transfer of phosphoryl group to ADP
- 1st production of ATP
- 1 per 1,3-biphosphoglycerate
- 2 per glucose
- enzyme name (phosphoglycerate kinase) is confusing
- named fro reverse reaction (phosphorylation of 3-phosphoglycerate)
This is the first time getting ATP back
25
What happens in step 8 of glycolysis?
- isomerization of 3-phosphoglycerate
- moves phosphoryl group to position better for later steps
(shifting phosphoryl group to a better location)
- performed by phosphoglycerate mutase
- involves an intermediate with two phosphoryl groups (2,3-biphosphoglycerate)
26
What enzyme is used during isomerization of 3-phosphoglycerate to 2-phosphoglycerate?
phosphoglycerate mutase
27
What happens in step 9 of glycolysis?
- dehydration of 2-phosphoglycerate
- creates a compound with high phosphoryl group potential
-∆rG'˚ for PEP hydrolysis = 61.0 kj/mol = really favorable
- makes it possible to synthesize ATP in step 10
28
What enzyme is used during the dehydration of 2-phosphoglycerate to phosphoenolpyruvate
enolase
29
what happens in step 10 in glycolysis?
- transfer of phosphoryl group to ADP
- 2nd production of ATP
- 1 per PEP
- 2 per glucose
- production of pyruvate
- 1 per PEP
- 2 per glucose
30
what enzyme is used during the transfer of phosphoenolpyruvate to pyruvate?
pyruvate kinase
31
Glycolysis has energetically favorable and unfavorable steps. Give examples :)
- some steps are highly favorable (∆ rG' <<0) = easy to carry out
- example: phosphorylation of glucose (step 1; ∆rG' =-33 kj/mol)
- other steps are not (∆rG' ~ 0) = difficult to carry out
- example: isomerization of glucose-6P ; ∆rG' ~ 0 kj/mol)
32
_______ speeds up during cancer?
Glycolysis
33
Why does glycolysis speed up during cancer?
- cancerous tissues have 10x faster glycolysis
- warbug effect
- provides pyruvate faster to support anabolism
- detectable by PET scan
- detects tissues taking up glucose analog (FdG)
- high uptake -> cancer
34
Why does glycolysis speed up during cancer?
- cancerous tissues have 10x faster glycolysis
- warbug effect
- provides pyruvate faster to support anabolism
- detectable by PET scan
- detects tissues taking up glucose analog (FdG)
- high uptake -> cancer
35
What continues the catabolism of glucose?
Pyruvate metabolism and TCA cycle
36
why is pyruvate metabolism and TCA cycle continue catabolism of glucose important to take note of?
- completes oxidation of pyruvate (from glycolysis) to CO2
- produces most NADH and FADH2 available to cell
- used to generate ATP by oxidative phosphorylation
- present in all cells that respire (use O2 during catabolism)
37
_______ has a single step with two important products?
Pyruvate metabolism
38
Pyruvate metabolism is a single step with two important steps
- connects glycolysis with the TCA cycle
- pyruvate is oxidized to acetyl - CoA
39
What are the two important products of pyruvate metabolism?
1 Acetyl - CoA
1 NADH
40
What enzyme is used during the oxidization of pyruvate to acetyl - CoA?
pyruvate dehyrdogenase complex (E1+ E2 + E3 )
41
What is the center of metabolism?
Acetyl -CoA
- catabolized during TCA cycle but is also used in anabolism
42
How many steps are there in the TCA cycle?
8 steps to oxidize 1 acetyl-CoA to 2 CO2
43
How many important products are there in the TCA cycle?
3 important products
- 3 NADH
- 1 FADH
- 1 GTP
44
What is step 1 in the TCA cycle?
- condensation of acetyl-CoA (2 carbons) with oxaloacetate (4 carbons)
- product (citrate) is 6 carbons
45
what enzyme is being used during the condensation of acetyl-coa and oxaloacetate?
citrate synthase
46
what is step 2 in the TCA cycle?
-isomerizarion of citrate to isocitrate
- involves intermediate cisaconitrate
- sometimes it is considered in two separate steps
47
what enzyme is used during the isomerization of citrate to isocitrate?
citrate -> aconitae -> (intermediate ) cis-aconitrate ->aconitase -> isocitrate
48
what is step 3 in the TCA cycle?
- oxidation and carboxylation of isocitrate
-forms NADH or NADPH
-one isoenzyme forms NADH, and another form NADPH
- product (∂- ketoglutarate) is 5 carbons
49
what enzyme is being used in the oxidation and carboxylation of isocitrate to ∂ ketoglutarate
isocitrate dehydrogenase
50
What is step 4 in the TCA cycle?
- oxidation and decarboxylation of ∂-ketoglutarate
- forms NAGH
-product (succinyl - CoA) is 4 carbons
- no more carbons are lost during cycle
51
What enzyme is being used during the oxidation and decarboxylation of ∂ - ketoglutarate?
∂- ketoglutarate dehydrogenase complex
52
what is step 5 of TCA cycle?
- conversion of succinyl-CoA to succinate
- from GTP or ATP
- depending on isoenzyme used!!!!!
- only step that directly forms NTP
- rest are formed during oxidative phosphorylation
bacteria = atp not gtp
53
what enzyme is used during the conversion of succinyl - CoA to succinate?
- succinyl-CoA synthethase
54
what is step 6 in the TCA Cycle?
- oxidation of succinate
- forms FADH2
- remains bound to enzyme (unlike NADH)
- enzyme is part of respiratory chain in oxidative phosphorylation
55
What enzyme is being used during the oxidation of succinate to fumarate?
succinate dehydrogenase
56
what is step 7 in TCA Cycle?
hydration of fumarate
- product is L- malate not D- malaate (stereospecific)
57
What enzyme is being used in the hydration of fumarate to L-malate?
fumarase
fumarate -> carbanion transition state -> L-malate
58
what is step 8 in the TCA cycle?
- oxidation of malate
- forms NADH
- product is oxaloacetate which is the substrate for first step
- completes the cycle
59
what enzyme is used during the oxidation of L-malate to oxaloacetate?
L-malate dehydrogenase
60
T/F: TCA cycle generates large numbers of reduced enzymes
True because it does the following:
- generates more than other steps of glucose catabolism
- fate of reduced coenzyme is oxidative phosphorylation
- Or fermentation (in anaerobic organisms)
61
What are the other roles of the TCA cycle?
- involved in the catabolism of other nutrients
- amino acids
- fatty acids
- anything else that produces acetyl-CoA
- involved in anabolism
- intermediates are siphoned off for anabolic pathways
- amino acid synthesis
62
How does oxidative phosphorylation complete glucose catabolism?
- oxidizes reduced coenzymes (NADH and FADH2), completing catabolism of glucose
- generates most ATP available to cell
- Present in all cells that respire (use O2 during catabolism)
- Reason why we breath oxygen :))))))
63
How many protein complexes do oxidative phosphorylation involve?
5 protein complexes in total
- first 4 complexes
+ oxidize reduced coenzyme (e- donors) with O2
+ generate H+ gradient
- Last complex (ATP synthase)
+ uses H+ gradient to synthesize ATP
64
Where does the Oxidative phosphorylation occur?
+ Mitochondria
- protein complexes are in inner membrane
- TCA cycle enzymes are in the matrix
- Glycolysis enzymes are the cytosol (not in the mitochondria)
65
What are the two different paths of oxidative phosphorylation?
NADH is the electron donor
I-III-IV-V
FADH2 (succinate) is the electron donor
II-III-IV-V
66
NADH pathway: what happens in complex I?
- oxidizes NADH
-Reducs quinone (Q), forming QH2
- Builds up gradient of 4 H+
- 4H+ pumped out of the matrix into the intermembrane space
- An additional 2H+ is consumed during quinone reduction, but this is canceled out by 2H+ released by dehydrogenases
67
NADH pathway: what happens in complex II?
SKIPPED
68
NADH & FADH2pathway: what happens in complex III?
- Oxidizes QH2
- reduces cytochrome C (Cyt c)
- builds up gradient of 2H+
- 2H+ pumped out
69
NADH & FADH 2pathway: what happens in complex IV?
- oxidizes Cyt c
-Reduced O2 to water
- Builds up gradient of 4 H+
- 2H+ pumped out
- 2H+ consumed with water formation
70
NADH pathway: what happens in complex V?
- ATP synthase (complex V)
- synthesizes ATP from H+ gradient
- 1 ATP/ 4H+
= 2.5 ATP / 1 NADH
71
NADH pathway summary
- complexes I, III, IV
- oxidize NADH with O2
- pump/consume 10H+
COMPLEX II = NOT INVOLVED
ATPase
- synthesizes 2.5 ATP/NADH
72
FADH2 pathway: what happens in complex I?
SKIPPED
73
FADH2 pathway: what happens in complex II?
- succinate reduces FAD+ to FADH2
- FADH2 reduces Q to QH2
- part of TCA cycle (succinate dehydrogenase)
74
FADH2 pathway: what happens in complex V?
- Same as NADH but H+ gradient is smaller
-- 6H+ FADH2 vs 10 H+ NADH
- less ATP is synthesized
- 1.5 ATP/ 1 FADH2
75
FADH2 pathway summary
- complexes I1, III, IV
- oxidize NADH with O2
- pump/consume 6H+
COMPLEX I = NOT INVOLVED
ATPase
- synthesizes 1.5 ATP/NADH
76
How many ATPs are yielded in the whole catabolism of glucose?
~32
77
What are the other roles of oxidative phosphorylation?
Involved in catabolism of other nutrients
- Amino Acids
- Fatty Acids
- Anything else that produces NADH or FADH2
78
What are the two ways to synthesize ATP?
- Electron transport phosphorylation
- Substrate level phosphorylation
79
What is Electron Transport Phosphorylation?
ATP formed by ATP synthase
Example: ATP synthase in oxidative phosphorylation
80
What is substrate-level phosphorylation?
ATP formed by via substrate with phosphoryl group
example: pyruvate kinase in glycolysis
81
In glucose catabolism how many ATPs are from oxidative phosphorylation vs substrate level phosphorylation?
- 28 ATP from oxidative phosphorylation
- 4 ATP from substrate level phosphorylation
=== We breathe O2 to make most of our ATP
82
Why is fermentation important in absence of O2?
- No O2 as final electron acceptor = cells cant perform oxidative phosphorylation
- reduced coenzymes (NADH and FADH2) from glycolysis and TCA cycle quickly build up
- Oxidized coenzyme (NAD+ and FAD+) are quickly depleted
- metabolism cant continue
- fermentation is an alternative
- used pyruvate or other organic compounds as electron acceptor
83
why is fermentation to lactate important in many organisms?
- pyruvate reduced to lactate in single step using lactate dehydrogenase
- consumes 1NADH/pyruvate
- allows glycolysis to continue with no O2
- Glycolysis produces 1 NADH/pyruvate
84
why is fermentation to lactate important in animals
- muscles during intense exercise
- not enough O2 to sustain oxidative phosphorylation
- erythrocytes
- lack mitochondria for TCA cycle
- cancerous cells
-Warburg effect
85
why is fermentation to lactate important in microbes?
- bacteria in yogurt and other fermented products
- microbes from cow rumen during lactic acidosis
- produce lactate when quickly changed to high grain
- lower rumen pH to dangerous levels (< 5.2)
- can kill host
86
why is fermentation to ethanol important to microbes?
- pyruvate reduced to ethanol in two steps
- consumes glycolysis to continue with no O2
- same as lactate
- important to microbes
- yeast = used in production of most alcohol
- Zymomonas mobilis = bacterium used in production of tequila
87
why is fermentation to VFA important to cattle?
- Volatile Fatty Acids (VFA)
- Acetate
- Propionate
- Butyrate
- formed by microbes in the rumen of cattle from feed carbohydrate
- absorbed and metabolized by cow
- fulfill up to 70% of total energy needed by host
88
VFA: what is propionate
- formed by phosphoenilpyvruate in 9 steps
- consumes NADH (NAD red)
- also produces ATP
(TCA cycle in reverse)
89
VFA: what is acetate
- formed from pyruvate in 3 steps
- produces ATP
- produces reduced ferredoxin (Fd red)
- does not consume NADH
- does not have the same role as other fermentation pathways
- can be formed using a second pathway
- forms. some products as first pathway, but last two enzymes differ
90
VFA: what is butyrate?
- formed from pyruvate in 7 steps
- produces ATP
- Consumes NADH and produces reduces ferredoxin
91
What are the industrial importance of other fermentations
- fermentation to produce biofuels and chemicals
-- ethanol
-- butanol
-- acetone
- dome with microbes at a large scale in tanks
92
what are the other alternatives to oxidative phosphorylation?
- anaerobic respiration
-- respiration without O2
--- uses inorganic electron acceptors other than O2
+ Nitrate (forms nitrite)
+ Sulfate ( forms sulfide)
+ CO2 (forms methane)
--- important in microbes
methanogen = type of microbe in the rumen that forms CO2
93
what are the two important sources of glucose?
-gluconeogenesis and glycogen
94
why are the two important sources of glucose important?
- some organs can use only glucose, not other nutrients
-- example : brain
- glucose can come from die, but used up within hours of fasting
-body used two glucose sources to meet needs
-- glycogen (polysaccharide of glucose)
-- gluconeogenesis (glucose synthesis)
95
_______ is mobilized to and from glycogen
Glucose
96
What is glucose degradation?
- mobilizes glucose during fasting
- also called glycogenolysis
- glycogen phosphorylase breaks (∂1->1) bonds
-- release glucose 1P
--- conserves 1 ATP equivalent by releasing glucose - 1P, not glucose
-- stops when near branch point with (∂1->6) bond
- debranching enzyme breaks (∂1->6) bonds
-- also has a transferase activity shown
-- sets up glycogen phosphorylase to break remaining (∂1-->4) bonds
97
what is glycogen synthesis?
- replenishes stores of glycogen during well-fed state
- also called glycogenesis
98
what happens during glycogen synthase elongates (∂1->4) chains
-- uses UDP-glucose as precursor
-- requires an input of 2 ATP equivalents
99
what happens during the glycogen-branching enzyme forms (∂1->6) bonds
- makin more non-reducing ends
--- increases sites for synthesis and degradation
- makes glycogen more water-soluble
