Glycolysis (Glucose Metabolism)

Question 1

state what it is meant by the key term - metabolism

Answer 1

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

Question 2

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

Answer 2

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

Question 3

state the names of the two types of metabolic pathways

Answer 3

1. catabolic pathways

2. anabolic pathways

Question 4

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

Answer 4

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

Question 5

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

Answer 5

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

Question 6

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

Answer 6

1. cytosol
2. matrix of the mitochondria
3. cristae of the mitochondria

Question 7

state what it is meant by the key term - glycolysis

Answer 7

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

Question 8

how much glucose does the brain approximately use per day ?

Answer 8

approx. 190 grams

Question 9

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

Answer 9

approx. 160 grams

Question 10

what are the two general steps of glycolysis termed ?

Answer 10

1. energy requiring steps (first 5)

2. energy releasing steps (second 5)

Question 11

1) what is the first step of glycolysis termed ?

2) what is the reaction ?

Answer 11

1. phosphorylation of glucose

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

Question 12

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

Answer 12

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)

Question 13

1) what is the second step of glycolysis termed ?

2) what is the reaction ?

Answer 13

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

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

Question 14

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

Answer 14

1. doesn’t require an energy investment

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

Question 15

1) what is the third step of glycolysis termed ?

2) what is the reaction ?

Answer 15

1. phosphorylation of fructose-6-phosphate

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

Question 16

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

Answer 16

1. PFK is the rate limiting enzyme during glycolysis

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

Question 17

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

Answer 17

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

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

Question 18

1) what is step 4 of glycolysis termed ?

2) what is the reaction ?

Answer 18

1. cleavage of fructose 1,6 bisphosphate

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

Question 19

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

Answer 19

1. GAP and DHAP are isomers

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

Question 20

1) what is step 5 of glycolysis termed ?

2) what is the reaction ?

Answer 20

1. isomerisation of DHAP to GAP

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

Question 21

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

Answer 21

1. it is a rapid, and reversible, reaction

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

Question 22

1) what is stage 6 in glycolysis termed ?

2) what is the reaction ?

Answer 22

1. conversion of GAP to 1,3-diphosphoglycerate

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

Question 23

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

Answer 23

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

Question 24

1) what is step 7 of glycolysis termed ?

2) what is the reaction ?

Answer 24

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

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

Question 25

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

Answer 25

1. 'substrate level phosphorylation' is taking place | 2. 2 x ATP re-synthesised as there is two branches going on simultaneously

Question 26

1) what is step 8 of glycolysis termed ? | 2) what is the reaction ?

Answer 26

1. conversion of 3, phosphoglycerate to 2, phosphoglycerate 3, phosphoglycerate ------phosphoglycerate mutase---------> 2, phosphoglycerate

Question 27

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

Answer 27

1. mutase = moves the functional group | 2. the phosphoryl group is being moved from the 3rd carbon molecule to the second carbon molecule

Question 28

1) what is step 9 of glycolysis termed ? | 2) what is the reaction ?

Answer 28

1. conversion of 2, phosphoglycerate to phosphoenolpyruvate 2, phosphoglycerate -------enolase-------> phosphoenolpyruvate + H2O

Question 29

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

Answer 29

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

Question 30

1) what is step 10 of glycolysis termed ? | 2) what is the reaction ?

Answer 30

1. conversion of phosphoenolpyruvate to pyruvate phosphoenolpyruvate + ADP -------pyruvate kinase-------> pyruvate + ATP

Question 31

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

Answer 31

1. 'substrate level phosphorylation' takes place 2. an irreversible step 3. a net gain of 2ATP from glycolysis

Question 32

state the 4 factors which control flux through glucose metabolism

Answer 32

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

Question 33

what is the uptake of glucose into cells regulated by ?

Answer 33

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

Question 34

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

Answer 34

1. RBC's | 2. controls basal glucose uptake

Question 35

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

Answer 35

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

Question 36

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

Answer 36

1. Muscle cells, Adipocytes | 2. removes excess glucose from the blood; regulated by insulin

Question 37

state 2 introductory facts about 'enzyme concentration'

Answer 37

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

Question 38

explain how insulin effects 'enzyme concentration'

Answer 38

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

Question 39

explain how glucagon effects 'enzyme concentration' (3 points)

Answer 39

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

Question 40

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

Answer 40

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)

Question 41

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

Answer 41

1. hexokinase 2. PFK 3. pyruvate kinase

Question 42

explain allosteric regulation of hexokinase

Answer 42

1. hexokinase is inhibited by glucose-6-phosphate and is termed: allosteric product inhibition glucose + ATP ------hexokinase--------glucose-6-phosphate + ADP 2. glucose-6-phosphate effects the enzyme that catalysed its formation

Question 43

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

Answer 43

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

Question 44

where is glucokinase active and inactive ?

Answer 44

1. >5mM - glucokinase active (localised in the cytosol) | 2. <5mM - glucokinase inactive (localised in the nucleus)

Question 45

what is PFK inhibited by ? (allosteric regulation)

Answer 45

ATP and Citrate (from the Kreb's cycle)

Question 46

what is PFK activated by ? (allosteric regulation)

Answer 46

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

Question 47

PFK is a bifunctional enzyme...

Answer 47

1. PFK2 | 2. fructose 2,6 bisphosphatase

Question 48

in liver cells, what is PFK primarily regulated by ?

Answer 48

in liver cells, PFK is primarily regulated by sugar levels

Question 49

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

Answer 49

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

Question 50

how is pyruvate kinase allosterically regulated ?

Answer 50

1. pyruvate kinase is regulated by a feedforward mechanism by fructose 1,6 bisphosphate phosphoenolpyruvate ------pyruvate kinase-----> pyruvate 2. fructose 1,6 bisphosphate activates pyruvate kinase action 3. ATP and Acetyl CoA inhibits pyruvate kinase action

Question 51

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

Answer 51

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

Question 52

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

Answer 52

fructose 1,6 bisphosphate ----fructose 1,6 bisphosphatase -----> fructose-6-phosphate + Pi 1. citrate activates 2. AMP and Fructose 2,6 bisphosphate inhibit

Question 53

explain covalent modification of pyruvate kinase (5 points)

Answer 53

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