L20: Glycolysis

Question 1

glycolysis involves a sequence of rxns that metabolizes?

Answer 1

1 molecule of glucose into:
2 molecules of pyruvate
2 ATP

Question 2

is aerobic or anaerobic processes more efficient?

Answer 2

complete oxidation is more energy efficient than anaerobic glycolysis

Question 3

what processes only use glucose for fuel?

Answer 3

in the brain under non-starvation conditions

only fuel that RBCs can use

Question 4

sources of glucose in the diet

Answer 4

disaccharides – especially sucrose and lactose
starch
glycogen

Question 5

glucose uptake

Answer 5

occurs via protein transporters called glucose transporters or GLUTs

Question 6

GLUT1

Answer 6

ubiquitous but expressed highly in brain and RBCs

high affinity

Question 7

GLUT2

Answer 7

main transporter in liver

low affinity

Question 8

GLUT3

Answer 8

main transporter in neurons

high affinity

Question 9

GLUT4

Answer 9

present in skeletal muscle, heart, adipose tissue

insulin dependent

Question 10

which GLUT is the only one dependent upon insulin?

Answer 10

glut4

Question 11

relate Km and affinity of GLUTs for glucose

Answer 11

low Km = high affinity
inverse relationship

glut1 and 3 have highest affinity
glut4 is moderate but regulated
glut3 is lowest

Question 12

where does glycolysis occur in the body?

Answer 12

cytoplasm of eukaryotic cells

Question 13

glycolysis is broken down into 2 stages

Answer 13

1. trapping of glucose and its cleavage into 2 interconvertible 3-C molecules
2. generation of atp

Question 14

how does the first stage of glycolysis begin?

Answer 14

phosphorylation of glucose by hexokinase

Question 15

how does the first stage of glycolysis end?

Answer 15

isomerization of dihydroxyacetone phosphate to glyceraldehyde 3-phosphate

Question 16

stage 1, step 1

Answer 16

glucose is phosphorylated to
glucose-6-pi
atp consumed

enzymes: hexokinase and glucokinase

Question 17

stage 1, step 2

Answer 17

G6P isomerized to fructose-6-pi

enzyme: phosphoglucoisomerase

Question 18

stage 1, step 3

Answer 18

F6P phosphorylated to
fructose-1,6-biphosphate
atp consumed

enzyme: phosphofructokinase
* *rate limiting enzyme of glycolysis

Question 19

what is the rate limiting step of glycolysis?

Answer 19

stage 1, step 3

enzyme phosphofructokinase

Question 20

stage 1, step 4

Answer 20

F1,6BP broken into:
glyceraldehyde-3-pi and
dihydroxyacetone phosphate

enzyme aldose

Question 21

stage 1, step 5

Answer 21

DHAP isomerized to G3P

enzyme: triose pi isomerase

Question 22

GAP

Answer 22

glucose-3-pi or G3P

Question 23

second stage of glycolysis

Answer 23

nrg harnessed in GAP used to form ATP

Question 24

stage 2 steps

Answer 24

1. GAPDH step
2. phosphoglycerate kinase/mutase step
3. enolase/pyruvate kinase step

Question 25

GAPDH step

Answer 25

oxidative phosphorylation of gap forming: 1,3-BPG reduce NAD+ to NADH

Question 26

1,3-BPG

Answer 26

has a high phosphoryl-transfer potential

Question 27

NADH

Answer 27

contains a pair of 'high energy' electrons e- sent to ETC plays role in oxidative phosphorylation

Question 28

phosphoglycerate kinase/mutase step

Answer 28

kinase converts 1,3-BPG to 3-PG ADP is phosphorylated mutase moves pi from 3rd to 2nd position 2-PG **remember happens 2x = 2 atp

Question 29

enolase/pyruvate kinase step

Answer 29

dehydration of 2-pg by enolase --forms PEP pyruvate kinase transfers phosphoryl group from PEP to ADP - --forming ATP * *irreversible step * *2x

Question 30

PEP

Answer 30

an enol w/ high phosphoryl-transfer potential = unstable is converted from unstable enol to pyruvate ---a stable ketone

Question 31

fates of pyruvate

Answer 31

1. reduced to lactate w/ regeneration of NAD+ | 2. oxidized aerobically

Question 32

entry points of fructose

Answer 32

sucrose is a disaccharide of glucose and fructose

Question 33

entry points of galactose

Answer 33

lactose is a disaccharide of glucose and galactose

Question 34

fructose and galactose are converted into ?

Answer 34

glycolytic intermediates fructose is quickly turned to fat in times of high nrg

Question 35

galactose metabolism ends in ?

Answer 35

glucose-6-pi

Question 36

major regulatory enzymes

Answer 36

hexokinase phosphofructokinase pyruvate kinase

Question 37

goal of glycolysis

Answer 37

in muscles to generate ATP during activity ATP levels regulate glycolysis

Question 38

glycolysis of liver

Answer 38

to maintain blood glucose levels provide building blocks for other pathways in response to biochemical diversity and need

Question 39

phosphofructokinase

Answer 39

activated by F-2,6-BP | inhibited by citrate

Question 40

glucokinase

Answer 40

no hexokinase in liver cells glucokinase is not inhibited by glucose-6-pi glucose permanently trapped

Question 41

pyruvate kinase is regulated by ?

Answer 41

allosteric effectors and covalent modification

Question 42

what is the main glucose transporter in the liver?

Answer 42

glut2

Question 43

what enzyme is the most important regulator of glycolysis?

Answer 43

phosphofructokinase

Question 44

which of the following is not an intermediate in the glycolytic pathway? 1. 2-phosphoglycerate 2. fructose 1,6-BP 3. glucose-1-phosphate 4. glyceraldehyde 3-phosphate 5. phosphoenolpyruvate

Answer 44

glucose 1 phosphate

Question 45

high fructose consumption is linked to ?

Answer 45

fatty liver insulin insensitivity obesity type 2 diabetes

Question 46

actions of fructokinase and triose kinase bypass ?

Answer 46

the most important regulatory step in glycolysis phosphofructokinase-catalyzed rxn in regards to how fructose is processed by the liver

Question 47

fructose derivatives in the liver

Answer 47

GAP an DHAP are processed by glycolysis to pyruvate and acetyl CoA in unregulated fashion excess acetyl CoA converted to fatty acids transported to adipose tissues resulting in obesity and fatty liver

Question 48

lactose intolerance

Answer 48

inability to metabolize lactose due to deficiency in enzyme lactase

Question 49

lactase

Answer 49

enzyme that breaks down lactose to glucose and galactose

Question 50

galactosemia

Answer 50

disruption of galactose metabolism inherited deficiency in galactose-1-phosphate uridyl transferase activity

Question 51

what is the treatment for galactosemia

Answer 51

removal of galactose and lactose from diet

Question 52

cataracts

Answer 52

clouding of the eye lens non-active transferase in lens aldose reductase causes accumulating galactose to be reduced to galactitol

Question 53

Warburg effect

Answer 53

aerobic glycolysis | tumor cells can metabolize glucose to lactate even in presence of oxygen