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Principles: biochemistry > The Catabolism of Glucose > Flashcards

The Catabolism of Glucose Flashcards

1
Q

the aim of glucose metabolism is the generate ___

A

ATP

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2
Q

ATP can be used to drive _____ reactions to form other molecules such as amino acids and sugars

A

biosynthetic

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3
Q

which cell types require glucose as an energy source?5

A
  • erythrocytes - exclusively use glucose as an energy source
  • retina
  • renal medulla
  • brain
  • all cancer cells
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4
Q

why can diabetes cause eye damage

A

diabetes can result in the retina being starved of glucose

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5
Q

____ converts oxidised precursors to reduced biosynthetic products using -_____ and __ and generating ___

A

anabolism, NADPH and H+, generating NADP+ (NOT NAD+ like catabolism)

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6
Q

_____ converts reduced fuel into oxidised products using ___- and generating ____ and ___

A

catabolism, NAD, generating NADH and H+(NOT NADPH like anabolism)

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7
Q

oxygen is a very reactive molecule but glucose has a sufficiently stable structure so oxygen can be stored in this -OH bonds.

glucose is like a coiled spring - ready to release energy

The body must metabolise the ___ isoform of glucose

A

D isoform

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8
Q

describe lactose disaccharides

A

galactose beta 1,4- glucose

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9
Q

describe maltose disaccharides

A

glucose alpha 1,4- glucose

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10
Q

describe sucrose disaccharides

A

glucose alpha 1,2 - fructose

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11
Q

describe cellobiose disaccharides

A

glucose beta 1,4- glucose §

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12
Q

____ is the storage form of glucose

A

glycogen

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13
Q

what 4 things can glucose be converted to? what is its fate?

A
  1. glycogen, starch, sucrose, conversion to lipids - STORAGE
  2. pyruvate
  3. lactate
  4. ribose - 5- phosphate
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14
Q

glucose is converted to pyruvate by _____ through ____ ___

A

oxidation through aerobic glycolysis

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15
Q

glucose is converted to lactate by _____ through ____ ___

A

fermentation by anaerobic glycolysis

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16
Q

glucose is converted to ribose - 5 phosphate by _____ through the ____ ___ pathway

A

oxidation through the pentose phosphate pathway

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17
Q

the function of aerobic glucose metabolism is to generate ____ which is then converted to _____

A

pyruvate, acetyl co a

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18
Q

the purpose of the citric acid cycle is to oxidise _____ and generate ___ and ____

A

NADH and FADH2

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19
Q

what are the two mechanisms of glucose transport into cells

A
  1. via Na/glucose symporters - this does not require energy

2. via passive facilitated diffusion glucose transporters (there are 5 GLUT transporters )

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20
Q

The glucose GLUT transporters have different kinetic properties

GLUT1 - present in the \_\_\_\_ 
GLUT2 - present in the \_\_\_\_ and \_\_\_ \_\_\_ 
GLUT3 - present in the \_\_\_\_ 
GLUT4 - present in the \_\_\_\_ and \_\_\_ \_\_\_\_ 
GLUT5 - present in the \_\_\_\_
A

GLUT1 - present in the brain
GLUT2 - present in the liver and beta cells
GLUT3 - present in the brain
GLUT4 - present in the muscle and adipose tissue
GLUT5 - present in the gut

21
Q

the GLUt transporters in the brain have a ___ Km

A

low - can utilise glucose at very low concs

22
Q

the GLUT transporters in the liver and beta cells have a ___ Km

A

high - so they can control glucose

they are insulin dependent

23
Q

the GLUT 4 transporters in muscle and adipose are ____ dependent

A

insulin

24
Q

the GLUT 5 transporters in the gut transport _____

A

fructose

25
Q

glycolysis - overall numbers

glucose + __ADP + __ Pi + __NAD+

——–>

_ pyruvate + _ ATP +_ H2O + _ NADH + _ H+

A

glucose + 2 ADP + 2 Pi + 2 NAD+
——->
2 pyruvate + 4 ATP +2 H2O + 2 NADH + 2 H+

26
Q

what are the two important intermediates between glucose and pyruvate?

A

glucose first converted to fructose - 1- 6 bisphosphate using 2 ATP in the process

this is converted to 2 triose phosphates (3 carbon)

these are then converted to 2 pyruvates (by losing phosphates) generating 4 ATP and 2NADPH + H+

27
Q

glycolysis in stages
Stage 1: glucose is ____ and _____

Stage 2: __ interconvertible ___-carbon molecules are formed - each triose loses ___ phosphate groups

Stage 3: generation of ___

A

Stage 1: glucose is trapped and destabilised

Stage 2: two interconvertible three-carbon molecules are formed. each triose loses 2 phosphate groups

Stage 3: generation of ATP

28
Q

there are two major cellular needs in glycolysis

production of ___

provision of ___ ____ s for _____ reactions

A

production of ATP

provision of building blocks for synthetic reactions

29
Q

there are ___ control points in glycolysis - caused by ____ catalysing ____ reactions

A

3, enzymes, irreversible

30
Q

which enzyme controls substrate entry ?

A

hexokinase

31
Q

which enzyme controls rate of flow?

A

phosphofructokinase

32
Q

which enzyme controls product exit?

A

pyruvate kinase

33
Q

hexokinase converts

___ + ATP —–> ___-__-____ + ADP + _+

A

glucose + ATP —–> glucose 6-phosphate + ADP + H+

34
Q

phosphofructokinase converts

____ - __-_____ + ATP —> ____ - __-_____ + ADP + H+

A

fructose 6-phosphate + ATP —> fructose 1,6-bisphosphate + ADP + H+

35
Q

pyruvate kinase converts

_______e + ADP + H+ —-> _____ + ATP

A

phosphoenolpyruvate + ADP + H+ —-> pyruvate + ATP

36
Q

Phosphofructokinase: Key enzyme controlling rate of substrate movement along glycolytic pathway

what two things will activate the enzyme and increase glycolysis if energy is needed?

A

AMP and fructose 2,1 - bisphosphate

37
Q

what things will inhibit the enzyme phosphofructokinase in the rate controlling step? 3

A

ATP, citrate, H+

38
Q

what is the effect of ATP on phosphofructokinase

A

Will slow glycolysis if energy abundant

39
Q

what is the effect of citrate on phosphofructokinase

A

TCA cycle intermediate. Slows

downstream pyruvate entry to TCA cycle if energy is abundant

40
Q

what is the effect of H+ on phosphofructokinase

A

Slows glycolysis if too much lactic acid is being produced

41
Q

Why is AMP and not ADP the positive regulator for phosphofructokinase?

A

if ATP is rapidly used up …
ATP → ADP + Pi
… adenylate kinase can salvage some of the energy in ADP
2 ADP → ATP + AMP

42
Q

what is the fate of the 2 NADH and 2H+ generated by the whole cycle (note 1 NADH and H+ from each triose) ?

A

electron transport chain and ATP synthesis

43
Q

what happens if mitochondrial metabolism is inhibited by lack of oxygen?

A

instead of pyruvate being converted to acetyl co a using the NAD+

it is converted to lactate using NADH+ and H+ from previous step

44
Q

what is the warburg effect?

A

Cancer cells produce energy by high rate of glucose

metabolism to lactate (anaerobic glycolysis)

45
Q

cancer cells have a ___ Km hexokinase

A

low

46
Q

what are the advantages of quick anaerobic glycolysis for cancer cells?

A
  • Rapid energy production
  • Supports other pathways for
    nucleotide synthesis (needed for growth)
  • Supports rapid cell growth (proliferation)
47
Q

what are the disdvantages of quick anaerobic glycolysis for cancer cells?

A
  • Produces H+ and lactate as end products
  • Very inefficient ATP synthesis
  • High glucose consumption demand
    Cancer patients lose weight
48
Q

what are the three ways of treating cancer by targeting glycolysis? they are either competitive inhibitors or block conversion of lactic acid to pyruvate

A

2-Deoxy-glucose
3-Bromopyruvate
Dichloroacetate

Principles: biochemistry (7 decks)

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