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Bsc Sports Biochemistry (year 1) > Glycolysis (Glucose Metabolism) > Flashcards

Glycolysis (Glucose Metabolism) Flashcards

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1
Q

state what it is meant by the key term - metabolism

A

metabolism is the total of all of an organisms life-sustaining chemical reactions

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2
Q

state what it is meant by the key term - metabolic pathway

A

a metabolic pathway is a series of steps found in biochemical reactions that help to convert molecules/substrates into different, more readily usable materials

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3
Q

state the names of the two types of metabolic pathways

A
  1. catabolic pathways

2. anabolic pathways

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4
Q

state what it is meant by the key term - catabolic pathways

A

a catabolic pathway is where a large molecule is broken down into it’s smaller molecules, and where energy is released

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5
Q

state what it is meant by the key term - anabolic pathways

A

an anabolic pathway is where small molecules are assembled into larger ones, and energy is required to do so

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6
Q

where is the location of: 1) glycolysis, 2) kreb’s cycle, and 3) the electron transport chain

A
  1. cytosol
  2. matrix of the mitochondria
  3. cristae of the mitochondria
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7
Q

state what it is meant by the key term - glycolysis

A

glycolysis is a series of reactions that extracts energy from glucose by splitting it into two 3 carbon molecules called pyruvate

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8
Q

how much glucose does the brain approximately use per day ?

A

approx. 190 grams

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9
Q

how much glucose does the body (excluding the brain) approximately use per day ?

A

approx. 160 grams

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10
Q

what are the two general steps of glycolysis termed ?

A
  1. energy requiring steps (first 5)

2. energy releasing steps (second 5)

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11
Q

1) what is the first step of glycolysis termed ?

2) what is the reaction ?

A
  1. phosphorylation of glucose

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

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12
Q

state 2 expansionary facts about the ‘phosphorylation of glucose’ step (1st) of glycolysis

A
  1. produces a more relative molecule
  2. as glucose-6-phosphate contains an ionised phosphate group, it becomes impermeable to the cell membrane (trapped inside the cell)
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13
Q

1) what is the second step of glycolysis termed ?

2) what is the reaction ?

A
  1. conversion of glucose-6-phosphate to fructose-6-phosphate

glucose-6-phosphate ——glucose phosphate isomerase ——> fructose-6-phosphate

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14
Q

state 2 expansionary facts about the ‘conversion of glucose-6-phosphate to fructose-6-phosphate’ step (2) of glycolysis

A
  1. doesn’t require an energy investment

2. isomerase: catalyses the rearrangement of an isomer (same chemical formula, different chemical structure)

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15
Q

1) what is the third step of glycolysis termed ?

2) what is the reaction ?

A
  1. phosphorylation of fructose-6-phosphate

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

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16
Q

state 2 expansionary facts (relative to step 3 in glycolysis) about the PFK enzyme

A
  1. PFK is the rate limiting enzyme during glycolysis

2. there is a lot of PFK is fast twitch muscle fibres

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17
Q

state 2 expansionary facts about the ‘phosphorylation of fructose-6-phosphate’ step (3) of glycolysis

A
  1. prevents the re-formation of glucose-6-phosphate

2. 2nd phosphate allows 1 phosphate in each triose in step 4

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18
Q

1) what is step 4 of glycolysis termed ?

2) what is the reaction ?

A
  1. cleavage of fructose 1,6 bisphosphate

fructose 1,6 bisphosphate ——– aldolase —–> glyceraldehyde-3-phosphate (GAP) + dihydroxyacetone phosphate (DHAP)

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19
Q

state 2 expansionary facts about the ‘cleavage of fructose 1,6 bisphosphate’ step (4) in glycolysis

A
  1. GAP and DHAP are isomers

2. only GAP is able to continue down the glycolysis pathway

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20
Q

1) what is step 5 of glycolysis termed ?

2) what is the reaction ?

A
  1. isomerisation of DHAP to GAP

dihydroxyacetone phosphate (DHAP) ———-triose phosphate isomerase) ——> glyceraldehyde-3-phosphate (GAP)

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21
Q

state 2 expansionary facts about the ‘isomerisation of DHAP to GAP’ step (5) in glycolysis

A
  1. it is a rapid, and reversible, reaction

2. the reaction enables us to use both molecules in glycolysis

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22
Q

1) what is stage 6 in glycolysis termed ?

2) what is the reaction ?

A
  1. conversion of GAP to 1,3-diphosphoglycerate

glyceraldehyde-3-phosphate + NAD+ ——-glyceraldehyde-3-phosphate dehydrogenase ——-> 1,3-diphsphoglycerate + NADH

23
Q

state 3 expansionary facts about the ‘conversion of GAP to 1,3-diphosphoglycerate’ step (6) in glycolysis

A
  1. GAP is oxidised and NAD+ it reduced to form NADH
  2. if low-mod intensity exercise, NADH used in aerobic metabolism
  3. if mod-high intensity exercise, pyruvate is reduced using NADH to form lactate
24
Q

1) what is step 7 of glycolysis termed ?

2) what is the reaction ?

A
  1. conversion of 1,3-diphosphoglycerate to 3, phosphoglycerate

1,3-diphosphoglycerate + ADP ——–phosphoglycerate kinase——> 3, phosphoglycerate + ATP

25
Q

state 2 expansionary facts to the ‘conversion of 1,3-diphosphoglycerate to 3, phosphoglycerate’ step (7) of glycolysis

A
  1. ‘substrate level phosphorylation’ is taking place

2. 2 x ATP re-synthesised as there is two branches going on simultaneously

26
Q

1) what is step 8 of glycolysis termed ?

2) what is the reaction ?

A
  1. conversion of 3, phosphoglycerate to 2, phosphoglycerate

3, phosphoglycerate ——phosphoglycerate mutase———> 2, phosphoglycerate

27
Q

state 2 expansionary facts about the ‘conversion of 3, phosphoglycerate to 2, phosphoglycerate’ step (8) of glycolysis

A
  1. mutase = moves the functional group

2. the phosphoryl group is being moved from the 3rd carbon molecule to the second carbon molecule

28
Q

1) what is step 9 of glycolysis termed ?

2) what is the reaction ?

A
  1. conversion of 2, phosphoglycerate to phosphoenolpyruvate

2, phosphoglycerate ——-enolase——-> phosphoenolpyruvate + H2O

29
Q

state 3 expansionary facts about the ‘conversion of 2, phosphoglycerate to phosphoenolpyruvate’ step (9) of glycolysis

A
  1. a water molecule is removed from 2, phosphoglycerate
  2. usually, an enzyme which removes water = dehydrolase
  3. this enzyme is called the old, established name as it produces a substituted enol
30
Q

1) what is step 10 of glycolysis termed ?

2) what is the reaction ?

A
  1. conversion of phosphoenolpyruvate to pyruvate

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

31
Q

state 3 expansionary facts about the ‘conversion of phosphoenolpyruvate to pyruvate’ step (10) in glycolysis

A
  1. ‘substrate level phosphorylation’ takes place
  2. an irreversible step
  3. a net gain of 2ATP from glycolysis
32
Q

state the 4 factors which control flux through glucose metabolism

A
  1. substrate availability
  2. enzyme concentration
  3. allosteric regulation
  4. covalent modification of enzymes
33
Q

what is the uptake of glucose into cells regulated by ?

A

the uptake of cells is regulated by the GLUT family of transporter proteins

34
Q

what is the location, and function, of GLUT 1 transporters ?

A
  1. RBC’s

2. controls basal glucose uptake

35
Q

what is the location, and function, of GLUT 2 transporters ?

A
  1. Liver cells, Pancreatic Beta cells

2. uptake of glucose at a rate proportional to the amount of glucose present; removes excess glucose from the blood

36
Q

what is the location, and function, of GLUT 4 transporters ?

A
  1. Muscle cells, Adipocytes

2. removes excess glucose from the blood; regulated by insulin

37
Q

state 2 introductory facts about ‘enzyme concentration’

A
  1. the rate limiting enzymes of glucose metabolism catalyse the irreversible reactions
  2. the concentration of key rate limiting enzymes are regulated by the hormones insulin and glucagon
38
Q

explain how insulin effects ‘enzyme concentration’

A

up-regulates the regulation of glucose enzymes: hexokinase, PFK and pyruvate kinase

39
Q

explain how glucagon effects ‘enzyme concentration’ (3 points)

A
  1. down-regulates the expression of glycolytic enzymes and up-regulates the expression of gluconeogenic enzymes
  2. glucose-6-phosphatase and phosphoenolpyruvate carboxykinase
  3. glucagon also stimulates glycogenolysis
40
Q

state what it is meant by the key term - allosteric regulation

A

allosteric regulation is the inhibition or activation of an enzyme by a small regulatory molecule that interacts at a site (allosteric site) other than the active site (at which catalytic activity occurs)

41
Q

which 3 glycolytic enzymes do you need to know that get effected by allosteric regulation ?

A
  1. hexokinase
  2. PFK
  3. pyruvate kinase
42
Q

explain allosteric regulation of hexokinase

A
  1. hexokinase is inhibited by glucose-6-phosphate and is termed: allosteric product inhibition

glucose + ATP ——hexokinase——–glucose-6-phosphate + ADP

  1. glucose-6-phosphate effects the enzyme that catalysed its formation
43
Q

state the 4 locations of the 4 hexokinases you need to know

A

hexokinase 1: brain
hexokinase 2: muscle and adipocytes
hexokinase 3: kidney
hexokinase 4: liver (glucokinase)

44
Q

where is glucokinase active and inactive ?

A
  1. > 5mM - glucokinase active (localised in the cytosol)

2. <5mM - glucokinase inactive (localised in the nucleus)

45
Q

what is PFK inhibited by ? (allosteric regulation)

A

ATP and Citrate (from the Kreb’s cycle)

46
Q

what is PFK activated by ? (allosteric regulation)

A

AMP (from the liver) and fructose-6-bisphosphate

47
Q

PFK is a bifunctional enzyme…

A
  1. PFK2

2. fructose 2,6 bisphosphatase

48
Q

in liver cells, what is PFK primarily regulated by ?

A

in liver cells, PFK is primarily regulated by sugar levels

49
Q

in skeletal muscle cells, what is PFK primarily regulated by ?

A

in skeletal muscle cells, PFK is primarily regulated by ATP and AMP levels (ADP + ADP –>

50
Q

how is pyruvate kinase allosterically regulated ?

A
  1. pyruvate kinase is regulated by a feedforward mechanism by fructose 1,6 bisphosphate

phosphoenolpyruvate ——pyruvate kinase—–> pyruvate

  1. fructose 1,6 bisphosphate activates pyruvate kinase action
  2. ATP and Acetyl CoA inhibits pyruvate kinase action
51
Q

what 4 gluconeogenic enzymes do you need to know get effected by allosteric regulation ?

A
  1. glucose-6-phosphatase
  2. fructose 1,6 bisphosphate
  3. phosphoenolpyruvate carboxylase
  4. pyruvate carboxylase
52
Q

explain how fructose 1,6 bisphosphatase is allosterically regulated in gluconeogenesis

A

fructose 1,6 bisphosphate —-fructose 1,6 bisphosphatase —–> fructose-6-phosphate + Pi

  1. citrate activates
  2. AMP and Fructose 2,6 bisphosphate inhibit
53
Q

explain covalent modification of pyruvate kinase (5 points)

A
  1. low blood glucose inhibits H2O –> P, and activates ATP –> ADP
  2. increases phosphorylated pyruvate kinase (less activated)
  3. more of that, increases dephosphorylation to dephosphorylated pyruvate kinase (more active)
  4. more of that, more phosphorylated is produced …
  5. negative feedback

Bsc Sports Biochemistry (year 1) (12 decks)

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