The Catabolism of Glucose

Question 1

the aim of glucose metabolism is the generate ___

Answer 1

ATP

Question 2

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

Answer 2

biosynthetic

Question 3

which cell types require glucose as an energy source?5

Answer 3

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

Question 4

why can diabetes cause eye damage

Answer 4

diabetes can result in the retina being starved of glucose

Question 5

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

Answer 5

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

Question 6

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

Answer 6

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

Question 7

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

Answer 7

D isoform

Question 8

describe lactose disaccharides

Answer 8

galactose beta 1,4- glucose

Question 9

describe maltose disaccharides

Answer 9

glucose alpha 1,4- glucose

Question 10

describe sucrose disaccharides

Answer 10

glucose alpha 1,2 - fructose

Question 11

describe cellobiose disaccharides

Answer 11

glucose beta 1,4- glucose §

Question 12

____ is the storage form of glucose

Answer 12

glycogen

Question 13

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

Answer 13

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

Question 14

glucose is converted to pyruvate by _____ through ____ ___

Answer 14

oxidation through aerobic glycolysis

Question 15

glucose is converted to lactate by _____ through ____ ___

Answer 15

fermentation by anaerobic glycolysis

Question 16

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

Answer 16

oxidation through the pentose phosphate pathway

Question 17

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

Answer 17

pyruvate, acetyl co a

Question 18

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

Answer 18

NADH and FADH2

Question 19

what are the two mechanisms of glucose transport into cells

Answer 19

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

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

Question 20

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 \_\_\_\_

Answer 20

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

Question 21

the GLUt transporters in the brain have a ___ Km

Answer 21

low - can utilise glucose at very low concs

Question 22

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

Answer 22

high - so they can control glucose

they are insulin dependent

Question 23

the GLUT 4 transporters in muscle and adipose are ____ dependent

Answer 23

insulin

Question 24

the GLUT 5 transporters in the gut transport _____

Answer 24

fructose

Question 25

glycolysis - overall numbers glucose + __ADP + __ Pi + __NAD+ --------> _ pyruvate + _ ATP +_ H2O + _ NADH + _ H+

Answer 25

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

Question 26

what are the two important intermediates between glucose and pyruvate?

Answer 26

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+

Question 27

glycolysis in stages Stage 1: glucose is ____ and _____ Stage 2: __ interconvertible ___-carbon molecules are formed - each triose loses ___ phosphate groups Stage 3: generation of ___

Answer 27

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

Question 28

there are two major cellular needs in glycolysis production of ___ provision of ___ ____ s for _____ reactions

Answer 28

production of ATP | provision of building blocks for synthetic reactions

Question 29

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

Answer 29

3, enzymes, irreversible

Question 30

which enzyme controls substrate entry ?

Answer 30

hexokinase

Question 31

which enzyme controls rate of flow?

Answer 31

phosphofructokinase

Question 32

which enzyme controls product exit?

Answer 32

pyruvate kinase

Question 33

hexokinase converts | ___ + ATP -----> ___-__-____ + ADP + _+

Answer 33

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

Question 34

phosphofructokinase converts ____ - __-_____ + ATP ---> ____ - __-_____ + ADP + H+

Answer 34

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

Question 35

pyruvate kinase converts _______e + ADP + H+ ----> _____ + ATP

Answer 35

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

Question 36

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?

Answer 36

AMP and fructose 2,1 - bisphosphate

Question 37

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

Answer 37

ATP, citrate, H+

Question 38

what is the effect of ATP on phosphofructokinase

Answer 38

Will slow glycolysis if energy abundant

Question 39

what is the effect of citrate on phosphofructokinase

Answer 39

TCA cycle intermediate. Slows | downstream pyruvate entry to TCA cycle if energy is abundant

Question 40

what is the effect of H+ on phosphofructokinase

Answer 40

Slows glycolysis if too much lactic acid is being produced

Question 41

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

Answer 41

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

Question 42

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

Answer 42

electron transport chain and ATP synthesis

Question 43

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

Answer 43

instead of pyruvate being converted to acetyl co a using the NAD+ it is converted to lactate using NADH+ and H+ from previous step

Question 44

what is the warburg effect?

Answer 44

Cancer cells produce energy by high rate of glucose | metabolism to lactate (anaerobic glycolysis)

Question 45

cancer cells have a ___ Km hexokinase

Answer 45

low

Question 46

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

Answer 46

- Rapid energy production - Supports other pathways for nucleotide synthesis (needed for growth) - Supports rapid cell growth (proliferation)

Question 47

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

Answer 47

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

Question 48

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

Answer 48

2-Deoxy-glucose 3-Bromopyruvate Dichloroacetate