Mod2

Question 1

Glycolysis occurs in the

Answer 1

Cytosol

Question 2

Net ATP produced in glycolysis

Answer 2

2 (2 used in first stage, 4 made in second (2each made by both three carbons molecules))

Question 3

Glucose transporters

Answer 3

• GLUT 1: all mammalian tissues (basal glucose uptake)
• GLUT 2: liver and pancreatic B cells (regulation of insulin in pancreas, removes excess glucose from blood in liver)
• GLUT 3: all mammalian tissues (basal glucose uptake)
• GLUT 4: muscle and fat cells
• GLUT 5: small intestine (fructose transporter)

Question 4

Kinase

Answer 4

phosphorylate biomolecules using ATP as the phosphate donor

Question 5

Isomerization rxn

Answer 5

No atoms lost —> only a rearrangement of the atoms occurs

Question 6

Bisphosphate means 2 separate monophosphoryl groups are present

Answer 6

Diphosphate means two phosphoryl groups are present and are connected by an anhydride linkage

Question 7

Dehydrogenases

Answer 7

Enzymes that catalyze redox reactions

Question 8

Mutases

Answer 8

Isomerases that reposition phosphate groups in a molecule

Question 9

Net rxn for glycolysis

Answer 9

Glucose + 2 Pi + 2 ADP + 2 NAD+ —> 2 pyruvate + 2 ATP + 2 NADH + 2 H+ + 2 H2O

-22kj/mol

Question 10

Metabolism of pyruvate (diff metabolic fates)

Answer 10

Need to regenerate NAD+ consumed by glyceraldehyde-3-P dehydrogenase

• ethanol (first converted to acetaldehyde by pyruvate decarboxylase —> acetaldehyde reduced to ethanol by alcohol dehydrogenase) —> no net redox —> fermentation
• lactate (pyruvate reduced to lactate by lactate dehydrogenase) - as lactate builds up in muscle during anaerobic conditions, fatigue sets in cuz ph goes down and inhibits pfk (so glucose can’t be metabolized for energy)
• acetyl CoA (NAD+ noT regenerated, but more is consumed for the CA cycle)

Question 11

Fructose

Answer 11

• Component of sucrose (table sugar) and also in corn syrup (sweetener)

Question 12

Galactose

Answer 12

Component of lactose (milk sugar)

Question 13

Galactose entry into glycolysis

Answer 13

Converted to G6P and enters

1. Phosphorylation of galactose
2. Transfer of galactose to an activated carrier (UDP)
3. Rearrangement of one hydroxyl group on galactose to form glucose by epimerase (isomerase that repositions hydroxyl groups)
4. Glucose-1-P converted to G6P by phosphoglucomutase

Question 14

Lactose intolerance

Answer 14

• 75% of world population
• deficiency in lactase in small intestine, which breaks down lactose into glucose and galactose

Question 15

Fructose entry into glycolysis

Answer 15

Metabolized in liver:

1. Fructose phosphorylated to F1P by fructokinase in liver
2. F1P split into two 3-carbon sugars, dihydroxyacetone phosphate and glyceraldegyde by a F1P aldolase
3. Glyceraldehyde phosphorylated to glyceraldehyde 3 phosphate by triose kinase

Question 16

Excessive fructose consumption leading to obesity, fatty liver and type 2 diabetes

Answer 16

Bypasses PFK main regulatory point, causing uncontrolled flow of metabolites through glycolysis —> excessive amounts of pyruvate, converted to acetyl CoA, converted to fatty acids —> fatty liver (lighter and causes cirrhosis and liver failure)

Question 17

Glycolysis roles

Answer 17

• degrade glucose to generate ATP
• provide building blocks for biosynthetic processes (such as formation of glycogen, fatty acids, amino acids)

Question 18

Glycolysis regulation enzymes

Answer 18

Hexokinase, PFK, pyruvate kinase

Question 19

Why is hexokinase not the major point of control when it’s the first step in glycolysis

Answer 19

Phosphorylation of glucose to G6P is not the first committed step for this pathway —> G6P can enter other pathways like the PPP and glycogen synthesis

Question 20

Alcoholic fermentation

Answer 20

A metabolic pathway that generates ethanol from pyruvate through decarboxylation and reduction

Question 21

Feedback inhibition

Answer 21

The inhibition of an early step in a pathway by the product of a later step

Question 22

Feedforward stimulation

Answer 22

Activation of a later step in a pathway by the product of an earlier step

Question 23

Glycolysis

Answer 23

A 10 reaction pathway by which glucose is metabolized to 2 molecules of pyruvate with the generation of 2 molecules of ATP and 2 molecules of NADH

Question 24

Substrate level phosphorylation

Answer 24

Direct transfer of a phosphoryl group in a biomolecule to ADP to generate ATP

Question 25

Liver glycolysis PFK inhibitor and activator

Answer 25

• Inhibited by Citrate
• Activated by Fructose-2,6-bisphosphate

Question 26

Glucokinase

Answer 26

Isoform of hexokinase in liver with lower affinity for glucose

• not inhibited by G6P

Question 27

Muscle glycolysis PFK regulation

Answer 27

• Inhibitor: ATP and low pH
• activator: AMP

Question 28

Muscle glycolysis hexokinase inhibitor

Answer 28

G6P

Question 29

Muscle glycolysis pyruvate kinase inhibitor and activator

Answer 29

• Inhibitor: ATP
• activator: Fructose-1,6-bisphosphate

Question 30

Fructose 1,6-bisphosphatase

Answer 30

• Activator: citrate
• Inhibitors: AMP, F-2,6-BP