Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biochemistry 2300 > Lectures 19/20: Carbohydrate Metabolism > Flashcards

Lectures 19/20: Carbohydrate Metabolism Flashcards

1
Q

Negative deltaG

A

Keq greater than 1
More products than substrates in equilibrium
Exergonic reaction towards products
Favourable reaction towards products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Positive deltaG

A

Keq is less than 1
More substrate than products in equilibrium
Endergonic reaction towards products
Non-favourable reaction towards products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

GLUT

A

Specific glucose transporters that take glucose inside cell
Several forms based on tissue and cell type
Transporters facilitate bidirectional transport of glucose (in and out), always from higher to lower concentration of glucose
Does not transport phosphorylated glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Glucose uptake

A

By GLUT
Reversible, deltaG nearly 0
Direction of glucose transport depends on substrate/product levels
Phosphorylation removes glucose from equilibrium
Entry of glucose depends on GLUT transporters and the activity of hexokinase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Pyruvate

A

Glucose is converted to 2 pyruvate, 2 3-carbon molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Glycolysis

A

Oxidation of glucose to pyruvate
Net yield of 2 ATP
2 ATP are invested, and 4 are made
Electron carriers are reduced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Gluconeogenesis

A

Reverse conversion of pyruvate to glucose
Reversible glycolysis reactions use the same enzyme
Irreversible glycolysis reactions use different enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Phase 1 of glycolysis

A

Energy investment
Steps 1-5
Phosphorylation of glucose and conversion of 2 molecules of glyceraldehyde-3-phosphate
Two ATP are used

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Phase 2 of glycolysis

A

ATP production phase
Steps 6-10
Conversion of glyceraldehyde-3-phosphate to pyruvate and coupled formation of 4 ATP
Reduction of 2NAD+ to 2NADH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Step 1 of glycolysis

A

Hexokinase phosphorylates glucose to glucose-6-phosphate
1 ATP used
Irreversible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Step 2 of glycolysis

A

Isomerization of glucose 6-phosphate to Fructose-6-phosphate

Catalyzed by phosphoglucose isomerase (PGI)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Step 3 of glycolysis

A

Phosphorylation of Fructose-6-phosphate to Fructose-1,5-bisphosphate
1 ATP used
Irreversible
Catalyzed by phosphofructokinase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Phosphofructokinase-1

A

Phosphorylates fructose-6-phosphate to give fructose-1,6-phosphate (more symmetrical)
Allosterically regulated by fructose-2,6-BP
Addition of ATP reduces PFK1 and more F-2,6-BP needed to activate
Addition of AMP increases activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Steps 4 and 5 of glycolysis

A

Cleavage of carbon backbone to dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phsohate (GAP)
Isomermization of DHAP and GAP by triose phosphate isomerase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Triose phosphate isomerase

A

Isomerizes GAP and DHAP (become readily interchangeable, allows glycolysis to proceed using the same enzymes for each)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Step 6 of glycolysis

A

Oxidation and addition of inorganic phosphate to GAP by glyceraldehyde-3-phosphate dehydrogenase
NAD is needed
1,3-biphosphateglycerate (1,3-BPG) and NADH are produced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Glyceraldehyde-3-phosphate dehyrogenase

A

Oxidized and adds phosphate to GAP

Generates 1,3-bisphosphoglycerate and NADH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Step 7 of glycolysis

A

Dephosphorylation and first generation of ATP from 1,3-BPG by phosphoglycerate kinase to generate 3-phosphoglycerate
Direction and flux influenced by ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Step 8 of glycolysis

A

Phosphoglycerate mutate moves phosphate from 3 to 2 position on 3-phosphoglycerate

20
Q

Phosphoglycerate kinase

A

Generates 3-phosphoglycerate from 1,3-BPG

Generates 1 ATP (but occurs twice per glucose molecule)

21
Q

Step 9 of glycolysis

A

Dehydration of 2-phosphoglycerate to phosphoenolpyruvate by enolase
Generates H2O

22
Q

Steps 10 of glycolysis

A

Formation of pyruvate and generation of second ATP
Irreversible
Catalyzed by pyruvate kinase

23
Q

Pyruvate kinase

A

Catalyzes the generation of ATP and pyruvate from phosphoenolpyruvate
Happens twice per glucose molecule to give 2 ATP total

24
Q

Pyruvate

A

Can take many different routes
Aerobic: mitochondrial conversion of pyruvate to acetyl-CoA and oxidation in the TCA cycle
Anaerobic: cytosolic regeneration of NAD+

25
Q

Alcoholic fermentation

A

Yeast regenerates NAD+ by making ethanol

Catalyzed by pyruvate decarboxylase and alcohol dehydrogenase

26
Q

Lactic fermentation

A

Pyruvate and NADH fermentation by lactase dehydrogenase gives lactic acid and NAD+
Lactate is secreted from the cell and acidifies the environment

27
Q

Anaerobic glycolysis

A

Glycolysis followed by conversion of pyruvate to lactate
Generates 2ATP
Full oxidation of pyruvate to CO2 requires oxygen and mitochondria

28
Q

Gluconeogenesis

A

Generation of glucose from various substrates: pyruvate, lactate, glycerol, most amino acids, all citric acid cycle intermediates
Not exact reverse of glycolysis
Unique gluconeogenic enzymes: glucose phosphatase, fructobisphosphatase, phosphoenolpyruvate carboxykinase, pyruvate carboxylase

29
Q

Glucose phosphatase

A

Reverse of hexokinase
Glucose phosphorylation by hexokinase is irreversible and has high -deltaG
If both were coupled, it would have a net cost of 1ATP

30
Q

Oxaloacetate

A

For last step reversal (first step of gluconeogenesis from pyruvate) pyruvate carboxylase catalyses oxaloacetate formation from pyruvate
Requires ATP

31
Q

Pyruvate carboxylase

A

Converts pyruvate to oxaloacetate, using 1ATP

32
Q

Phosphoenolpyruvate carboxykinase

A

Converts oxaloacetate to phosphoenolpyruvate

Uses 1GTP

33
Q

Phosphofructokinase 2

A

Phosphorylates fructose-6P at 2 carbon to generate Fructose-2,6-BP

34
Q

Fructose-2,6-bisphosphate

A

Most potent activator of phosphofructokinase in mammals
Allosteric activator of PFK1
Inhibits fructobisphosphatase: inhibits gluconeogenesis

35
Q

Product inhibition

A

Product of enzyme inhibits enzyme

Does not change reaction, but changes rates

36
Q

Covalent modification

A

Usually catalyzed by other enzyme

Usually phosphorylations and dephosphorylations through kinases and phosphatases

37
Q

Allosteric control

A

Feedback, feedforward within one pathway
Metabolites from other pathways regulate connected pathways
Feedforward interaction is more rare

38
Q

Feedback inhibition

A

Prevents overproduction of product

39
Q

Feedforward activation

A

Ensures completion of the pathway

40
Q

Pentose pathway

A

Provides different intermediates
Intermediates of pathway can be used for synthesis of nucleotides
Highly adaptable to needs of cell
Feeds into glycolysis
Can make 2 fructose-6-P and glyceraldehyde-3-phoshate (GAP)

41
Q

Glycogen

A

Synthesized from monomer of glucose-1-phosphate - isomerized from glucose-6-phoshate

42
Q

UTP

A

Bonds with glucose-1-P to give glucose-UDP and 1P

Glucose added to glycogen polymer though glycogen synthase and release of UDP

43
Q

Glycogen break down

A

Linear chaines broken down via phosphorolysis

Branched chains broken down by hydrolysis

44
Q

Fructose metabolism

A

Usually phosphorylated by hexokinase to fructose-6-phosphate
Does not occur in liver
No feedback mechanism
If liver gets overwhelmed by byproducts, they can enter fat synthesis
Liver transports can only transport a fraction of fructose

45
Q

Fructose metabolism in liver

A

Glucoinase cannot metabolize fructose

Converted to fructose-1-phosphate by fructokinase

46
Q

Fructose-1-Phosphate

A

converted to glyceraldehyde-3-phosphate which enters glycolysis after main regulatory step

Biochemistry 2300 (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions