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Biochemistry > Chapter 14 > Flashcards

Chapter 14 Flashcards

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1
Q

Many organisms use glucose to generate what things?

A
  • amino acids (by breaking glucose down into pyruvate then use pyruvate)
  • membrane lipids
  • nucleotides in DNA and RNA
  • cofactors necessary for metabolism
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2
Q

Gluconeogenesis is the synthesis of glucose from simpler precursors like ______ and ______

A

pyruvate and lactate

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3
Q

What pathway is an alternative pathway for glucose oxidation?

A

the pentose phosphate pathway

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4
Q

Glucose can be efficiently stored in what form?

A

Polymeric (starch, glycogen)

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5
Q

What two things can happen to pyruvate after glycolysis?

A
  1. pyruvate can be further aerobically oxidized
  2. pyruvate can be used as a precursor in biosynthesis
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6
Q

How many ATP molecules are consumed in the preparatory phase of Glycolysis (steps 1-5)

A

2 molecules of ATP

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7
Q

In the payoff phase of glycolysis, how many pyruvate molecules are created for each molecule of glucose

A

2 pyruvate per 1 glucose

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8
Q

What are the reactants for glycolysis?

A

Glucose + 2(NAD+) + 2ADP + 2Pi

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9
Q

What are the products of glycolysis?

A

2 pyruvate + 2NADH + 2H +2ATP + 2H20

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10
Q

The conversion of glucose to pyruvate is (endergonic or exergonic) ?

A

exergonic = favorable
delta G = -146jk/mol

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11
Q

Under standard cellular conditions, glycolysis is (reversible or irreversible) ?

A

irreversible

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12
Q

energy stored in pyruvate can be extracted in which two processes?

A

aerobic and anaerobic processes

Aerobic: oxidative reactions in Krebs, oxidative phosphorylation

Anaerobic: reduction to lactate, reduction to ethanol

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13
Q

What is the purpose of the first step in glycolysis?

A

To trap glucose inside the cell & to lower intracellular glucose levels so that further glucose uptake can occur

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14
Q

Which steps in glycolysis require ATP?

A

steps 1 and 3

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15
Q

Which steps in glycolysis PRODUCT ATP?

A

steps 7 and 10 (substrate level phosphorylations)

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16
Q

Which steps in glycolysis are carried out by isomerases?

A

steps 2 and 5

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17
Q

What are the functions of phosphoryl groups in glycolysis?

A
  • to prevent glycolytic intermediates from leaving the cell
  • to serve as essential components in the enzymatic conservation of metabolic energy
  • to lower the activation energy and to increase the specificity of the enzymatic reactions
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18
Q

In what step of glycolysis does an aldose isomerize into a ketose via an enediol intermediate?

A

Step 2- Isomerization of glucose (an aldose) to fructose (a ketose) via enzyme phosphohexose isomerase

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19
Q

What is the mechanism of the phosphohexose isomerase mechanism in the isomerization of glucose to fructose?

A

General acid-base catalysis

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20
Q

What is the first committed step of glycolysis?

A

Step 3 - The Second Phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate

**fructose 1,6-bisphosphate is committed to becoming pyruvate

**irreversible reaction

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21
Q

What is the least energetically favorable step of the preparatory phase?

A

Step 4 - Aldol cleavage

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22
Q

In step 6, DHAP must be oxidized to _____ via triose phosphate isomerase

A

DHAP OXIDIZED TO GAP

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23
Q

What step completes the preparatory phase of glycolysis?

A

step 5- triose phosphate isomerization

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24
Q

Enzymes that transfer phosphate groups between ATP and various substrates

A

Kinases

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25
Define substrate-level phosphorylation
The formation of ATP by phosphoryl group transfer from a substrate
26
Why does glycolysis need to be regulated?
To ensure proper use of nutrients and to ensure ATP is only produced when it is needed
27
What two molecules is glucose cleaved from?
Glycogen and Starch
28
In step 6 of glycolysis, each molecule of glyceraldehyde-3-phosphate is oxidized and phosphorylated by ________ to form 1,3 Bisphosphoglycerate
Inorganic Phosphate (Pi)
29
What is the purpose of step 2 in glycolysis?
makes the next steps in the reaction require less energy - the isomerization of glucose-6-phosphate to fructose-6-phosphate moves the carbonyl to C-2 : a prerequisite for steps 3 and 4 --C1 of fructose is easier tot phosphorylate by PFK , allows for symmetrical cleavage by aldolase
30
What is the purpose of step 3 in glycolysis?
the 2nd phosphorylation converts fructose-6-phosphate to fructose-1,6-bisphosphate -- this is the first committed step of glycolysis...b/c fructose 1,6 bisphosphate is committed to becoming pyruvate
31
What is the purpose of step 4 in glycolysis?
Step 4 is the aldol cleavage of a 6-carbon sugar into two 3-carbon sugars GAP and DAP
32
What is the purpose of step 5 in glycolysis?
This step completes the preparatory phase of glycolysis - allows glycolysis to proceed to the payoff phase by a single chemical pathway conversion of dihydroxyacetone phosphate to GAP (glyceraldehyde-3-phosphate)
33
What is the purpose of step 6 in glycolysis?
The oxidation of GAP produces a high-energy acyl phosphate compound -- incorporates inorganic phosphate -- the first energy-yielding step in glycolysis, produced NADH
34
What is the purpose of step 7 in glycolysis?
Substrate level phosphorylation to make ATP
35
Purpose of step 8 in glycolysis?
The migration of a phosphate group from C-3 to C-2, sets up for the final steps of the pathway
36
Purpose of step 9 in glycolysis?
Dehydration activates the phosphoryl for transfer to ADP in the last step
37
Purpose of step 10 in glycolysis?
Production of the 2nd ATP
38
For both phosphorylations in the preparatory phase of glycolysis, what is the phosphoryl group donor?
ATP serves as the phosphoryl group donor
39
Which process in glycolysis is endergonic?
The formation of ATP from ADP and Pi
40
What is anaerobic glycolysis called
Fermentation
41
What is lactic acid fermentation?
the reduction of pyruvate to lactate
42
What is ethanol fermentation?
the two-step reduction of pyruvate to ethanol
43
What is the CO2 produced in the first step of ethanol fermentation used for?
carbonation in beer and dough rising
44
Gluconeogenesis
Pathway that converts pyruvate (and its related 3 and 4 carbon compounds) to glucose
45
Is any ATP produced during gluconeogenesis?
No
46
What molecules in gluconeogenesis are permeable to the mitochondrial membrane...which are impermeable
Permeable molecules = Malate, PEP, pyruvate IMpermeable = oxaloacetate
47
What is oxaloacetate converted to in order to allow for transport to the cytosol for gluconeogenesis?
oxaloacetate can be converted to PEP or malate
48
A reason why gluconeogenesis is physiologically necessary
The brain, NS, and red blood cells can only generate ATP from glucose
49
What can animals produce glucose from, what can they not produce glucose from?
Animals CAN produce glucose from certain sugars (pyruvate, lactate, oxaloacetate) and from the amino acids capable of being converted to Kreb's cycle intermediates (al but Leucine and Lycine) Animals CANNOT produce glucose from fatty acids b/c the product off fatty acid degradation is acetyl-coA
50
What are hexokinase I,II and III all inhibited by?
Their product, glucose-6-phosphate
51
What is hexokinase IV inhibited by?
Hexokinase IV is inhibited by Fructose-6-phosphate which is an allosteric effector
52
When is pyruvate converted to PEP?
when fatty acids are available
53
What are the molecular costs of gluconeogenesis?
4 ATP, 2 GTP, 2 NADH
54
During fermentation (anaerobic glycolysis). ATP is generated without consuming ______ or ______
generation of ATP without consuming oxygen or NAD+
55
In mammals, where is the main site of gluconeogenesis
liver
56
What are the three bypass points (steps) in gluconeogenesis?
Pyruvate --> phosphoenolpyruvate (PEP) Fructose 1,6 bisphosphate ---> fructose 6-phosphate Glucose 6-phosphate --> glucose
57
How is phosphofructokinase-1 (PFK-1) regulated?
PFK-1 is regulated by the binding of ATP to an allosteric site - this occurs when there is an excess in ATP Citrate inhibits PFK-1 by increasing the inhibitory effects of ATP -- causes a smaller concentration of ATP to seem like more
58
How is (FBPase) fructose 1,6 bisphosphate ALLOSTERICALY regulated (inhibited)
high concentrations of AMP (which corresponds to low concentrations of ATP) inhibit FBPase --> thus slowing glucose synthesis high ATP concentrations slows glycolysis and speeds up gluconeogenesis
59
What molecule mediates the rapid hormonal regulation of glycolysis and gluconeogenesis?
FRUCTOSE 2,6-BISPHOSPHATE
60
How does fructose 2,6-bisphospate regulate PFK-1 (phosphofructokinase-1)
Binds to PFK-1 and increases its affinity for fructose-6-phosphate
61
How does fructose 2,6-bisphospate regulate FBPase-1 (fructose 1,6-bisphosphate)
binds to FBPase-1 and reduces its affinity for its substrate
62
What molecule catalyzes the formation of FBPase-1 ?
PFK-2 (phosphofructokinase-2)
63
What molecules catalyze the BREAKDOWN of FBPase-1?
FBPase-2
64
What are the main products of the Pentose Phosphate Pathway?
NADPH and ribose-5-phosphate
65
A process by which cells continue using glycolysis to extract energy in anaerobic conditions
Fermentation
66
Pentose phosphates can be regenerated into _______ which requires no ATP
glucose-6-phosphate
67
A process by which cells can generate pentose phosphates & NADPH
pentose phosphate patway
68
Ribose-5-phosphate is a biosynthetic precursor of _______?
nucelotides
69
Under aerobic conditions what does pyruvate become?
pyruvate gets oxidized to acetyl-coA
70
In the reduction of pyruvate to ethanol, pyruvate decarboxylase requires what two cofactors?
Mg2+ and thiamine pyrophosphate (TPP)
71
Tumor cells cause an increased expression of what?
LDH (lactate dehydrogenase)

Biochemistry (10 decks)

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