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Biochemistry > [2] Class 7: Glycolysis And Gluconeogenesis > Flashcards

[2] Class 7: Glycolysis And Gluconeogenesis Flashcards

1
Q

3 components to monosaccharide:

A
  1. Carbon number
  2. Functional group
  3. Stereoisomer form
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2
Q

Only 5 carbon sugar to know:

A

D-ribose

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3
Q

3 carbon sugars to know:

A

Dihydroxyacetone

D-glyceraldehyde

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4
Q

6 carbon ketose sugar?

A

D-fructose

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5
Q

Major component of DNA

A

Deoxyaldose

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6
Q

Theyre components of glycoproteins and glycolipids: cell signaling and adhesion

A

Acetylated amino sugars

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7
Q

Glycosaminoglycans and proteoglycans. Present in cell membrane and ECM

A

Acidic sugars

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8
Q

Constituted the gangliosides in oligodendrocyte of the NS

A

Sugar esters

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9
Q

Food additives, gains importance in uncontrolled diabetes leading to cataracts and peripheral neuropathy, used in synthesis of lipids

Sorbitol, mannitol

A

Sugar alcohols

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10
Q

Ex of sugar alcohols:

A

Sorbitol, mannitol, and xylitol

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11
Q

Sugar alcohols that can be converted to fructose and metabolized normally, their slow metabolism is what helps reduce calories and weight gain.

A

Sorbitol, mannitol, and xylitol

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12
Q

Non-sugar based artificial sweeteners trick the receptors on tongue and aren’t metabolized like sugar. How does this effect endocrine?

A

Disrupts insulin signaling

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13
Q

Giving a phosphate generally…

A

Activates

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14
Q

Disaccharide

A

2 monosaccharides glycosidic linkage

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15
Q

Starch amylose

A

Polysaccharide of glu residues w/ alpha-1,4 glycosidic bonds

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16
Q

Amylopectin

A

Amylose w/ addition of alpha-1,6 glycosidic branch points

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17
Q

A major plant polysaccharide

Unbranded polymer of glucose residues joined by beta-1,4 linkages, allowing to form very long and straight chains

Dietary fiber

A

Cellulose

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18
Q

Metabolizes one molecule of glucose to 2 molecules of pyruvate w/ 2 net ATP

A

Glycolysis

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19
Q

Glycolysis and oxygen

A

Anaerobic

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20
Q

Glucose is the only fuel that: 2 things…

A

The brain uses under nonstarvation conditions and the only fuel that red blood cells can use at all.

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21
Q

How can pyruvate and lactate be salvaged?

A

By being resynthesized to glucose in gluconeogenesis

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22
Q

Sources of glucose in diet:

A

Starch, glycogen, disaccharides (esp. sucrose and lactose)

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23
Q

Complete oxidation efficiency > …

A

Anaerobic glycolysis

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24
Q

The only insulin dependent glucose uptake GLUT4

A

In skeletal, muscle, heart, adipose

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25
Q

Why would GLUT 2 [main transporter for liver] have a low affinity for glucose uptake:

A

The liver doesnt want to store glu. It wants to maintain it throughout body.

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26
Q

Ubiquitous but high in RBC’s and brain

High affinity for glucose

A

GLUT1

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27
Q

The main glucose transporter in neurons

A

GLUT3

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28
Q

How many stages to glycolysis?

A

3;

1st is 6 carbons-investment

2nd: is converting into 3 carbons and conversion of DHAP to G3P
3rd: converting to pyruvate- gaining ATP

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29
Q

Traps glucose in the cell

A

Hexokinase

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30
Q

Which stage in glycolysis, the conversion of glucose to fructose 1,6-bisphosphate

A

Stage 1

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31
Q

Strategy to stage 1 glycolysis:

A

Traps the glucose in cell, for a A compound that can be readily cleaved into 2 phosphorylated 3- carbon units

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32
Q

What enzyme does liver use to convert glucose into glu-6-P?

A

Glucokinase

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33
Q

What are the 2 steps involving energy investment in stage 1 glycolysis?

A

Glucose->G6P by hexokinase/glucokinase

F6P-> F1,6BP by phosphofructokinase

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34
Q

What regulates hexokinase?

A

Negative feedback inhibition by product- G6P

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35
Q

Regulation of glucokinase:

A

Stimulated by glucose, F-1P, and insulin

Inhibited by glucagon and F6P

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36
Q

Regulation of phosphofructokinase

A

Stimulated by AMP and F2,6-BP

Inhibited by ATP and Citrate

37
Q

Which stage of glycolysis?

Fructose 1,6-BP into 2 3-C fragments by Aldolase reaction
And isomerase
Products are readily interconvertible

A

Stage 2

38
Q

What conditions represent high energy? (3)

A

High ATP

High NAD+

Low NADH

39
Q

When there’s high energy which of the products of stage 2, DHAP and GAP (G3P) is favored?

A

DHAP is favored under high energy conditions b/c it is converted to glycerol 3 phosphate- that way it can form triacylglycerols -FAT

40
Q

What percentage of f1,6BP becomes GAP, usually?

A

Usually, 99% becomes GAP to continue glycolysis….in the event of high energy conditions the reaction will regress to DHAP for fat storage

41
Q

Glyceraldehyde 3-P creates:

A

NADH (x2) that will be used in oxidative phosphorylation

42
Q

1,3-BPG is converted to 3-PG by

A

Phosphoglycertae kinase and this forms the first ATP (x2) of glycolysis

43
Q

2-PG is converted to_______ by:

A

Phosphoenolpyruvate by dehydration rxn by enolase

44
Q

Phosphate is removed from phosphoenolpyruvate by:_________ creating:

A

Pyruvate kinase;

Pyruvate (x2)

45
Q

Pyruvate is what type of molecular structure?

A

Stable ketone

46
Q

3 irreversible steps of glycolysis:

A

1- glu-G6P

3-F6P-F1,6BP

10-PEP- Pyruvate

47
Q

Regulation of pyruvate kinase:

A

Stimulated by insulin and Fructose 1,6-BP

Inhibited by Alanine, ATP, and glucagon

48
Q

After glycolysis, aerobic:

Anaerobic?

A

Pyruvate to TCA;

Pyruvate to lactate–then, hopefully cori cycle…

49
Q

Disaccharide of glucose and fructose makes=

A

Sucrose

50
Q

Disaccharide composed of glucose and galactose =

A

Lactose

51
Q

Fructose and galactose are converted to:

A

Glycolysis intermediates

52
Q

In times of high energy, fructose quickly turns to:

A

FAT

53
Q

Why would fructose quickly turn to fat in times of high energy?

A

Remember that GAP is readily interconvertible w/ DHAP, and although GAP is formed 99% of the time…this isn’t the truth when there is high energy conditions b/c the GAP is converted to DHAP which becomes triacylglycerols- it is the backbone of fat.

54
Q

3 regulated steps in glycolysis for ATP need

A

Hexokinase

PFK

Pyruvate kinase

55
Q

Main organ in glucose regulation

A

Liver

56
Q

NO hexokinase in liver: it is glucokinase….how is this regulated?

A

Glucose is permanently trapped in liver cell.

It is not inhibited by G3P (product of glucokinase)

57
Q

What type of regulation is used for pyruvate kinase:

A

Allosteric effectors and covalent modification

58
Q

Pyruvate kinase is more ________ when phosphoirylated

A

Inactive- under conditions of low BG

59
Q

Pyruvate kinase is more ________ when dephosphorylated

A

ACTIVE - under conditions of high BG

60
Q

Glucokinase has a ____ Km

A

High

= low affinity

61
Q

Hexokinase Km is significantly ________ than glucokinase

A

Lower

62
Q

Fates of pyruvate

A

Lactate

TCA

-other micoorganisms can convert pyruvate to ethanol

63
Q

What must occur before pyruvate can enter TCA cycle?

A

Pyruvate must undergo oxidative carboxylation to form acetyl CoA

64
Q

Pyruvate can be reduced to lactate w/ the regeneration of:

A

NAD+

65
Q

Precursor for pentose phosphate pathway

A

glucose-6-phosphate

66
Q

Which organ(s)depends on glucose as primary fuel or only fuel

A

Brain and

RBCs- only use glucose

67
Q

Brains daily glucose req’ment amt.:

Whole body req’ment:

A

120 g

160g

68
Q

Glucose always has ____ g in body fluids, but there’s about _____g available from glycogen

A

20 g;

190 g

69
Q

How long would glucose reserves last a person?

A

About a day or so.

70
Q

What bodily process is important during a long period of fasting or starvation?

A

Gluconeogenesis

71
Q

Synthesis of glucose from noncarbohydrate precursors

Major precursors are lactate, AA’s, and glycerol (but not FA’s)

Pathways convert pyruvate to glucose

Pathway is not a reversal of glycolysis

A

Gluconeogenesis

72
Q

Enzymes of irreversible reactions in the liver:

A

Glucokinase

Phosphofructokinase

Pyruvate kinase

73
Q

What are the 4 enzymes used in gluconeogenesis to ‘bypass’ irreversible steps of glycolysis:

A

Pyruvate carboxylase (pyruvate->OAA)

Phosphoenolpyruvate carboxykinase (OAA->PEP)

Fructose-1,6-BPtase (F-1,6-BP->F-6-P)

Glucose-6-phosphatase (G-6-P->glu)

74
Q

Regulation of pyruvate kinase:

A

Stimulated by insulin and F-1,6-BP

Inhibited by alanine, ATP, and glucagon

75
Q

Stimulation of glucose-6-phosphatase

A

Stimulated by cortisol

76
Q

Regulation of fructose-1,6-BPtase:

A

Stimulated by citrate and cortisol

Inhibited by AMP and F-2,6-BP

77
Q

Regulation of PEP carboxylase

A

Stimulated by cortisol, glucagon, thyroxine

78
Q

Regulation of pyruvate carboxylase

A

Stimulated by acetyl CoA and cortisol

Inhibited by ADP

79
Q

First step of gluconeogenesis:

A

Pyruvate is converted to OAA

80
Q

Source of OAA in gluconeogenesis:

How about pyruvate:

A

Some AA’s source of OAA and pyruvate

Lactate also is a source of pyruvate

81
Q

Generation of free glucose

For glucose to leave the liver the phosphate must be removed from glucose-6-phosphate

Which reaction? Enzyme?

A

G-3-P to glucose

Glucose 6-phosphatase

82
Q

Where is glucose-6-phosphatase located?

A

In the lumen of the endoplasmic reticulum

83
Q

G3P is transported to the ER by

A

A specific protein (T1) and another protein (T2) then transports glucose back to the cytoplasm

84
Q

Glycolysis __________ ATP;

Gluconeogenesis __________ ATP

A

Generates;

Consumes

85
Q

What is the best way to determine which pathway will be most active btw glycolysis and gluconeogenesis:

A

Energy charge (ATP/ADP ratio)

86
Q

Gluconeogenesis and glycolysis are _____________ regulated

A

Reciprocally

87
Q

Lactate produced in skeletal muscle and RBC’s can be converted back to pyruvate in the liver

A

Cori cycle

88
Q

What is the benefit of the cori cycle?

A

Since lactate is able to be converted back to pyruvate, the pyruvate can be used in gluconeogenesis to form glucose in times of low energy.

Biochemistry (13 decks)

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