E3 Module 9

Question 1

Distinguish between the chemical structures of glucose and fructose

Answer 1

both simple sugars with 6 carbons
glucose, 6-membered ring, has an aldehyde group, fructose, 5-membered ring, has a ketone group

Question 2

Simple sugars are metabolites that feed into the ____________ pathway, such as _________ sugars like glucose and __________ sugars like fructose

Answer 2

glycolytic
aldose
ketose

Question 3

define the difference between aldose and ketose sugars; provide examples

Question 4

Demonstrate the cyclization of linear glucose to cyclic glucopyranose.

Question 5

Explain the significance of Benedict’s test

Answer 5

test uses an alkaline solution of copper as a mild oxidizing agent to detect the presence of reducing. The reduction of Cu2+ to Cu+ changes the color from blue to red because of a copper oxide precipitate.

*reduction of sugar turns it red

Question 6

lactose
sucrose
trehalose

Answer 6

Question 7

Differentiate between reducing and non-reducing sugars

Question 8

demonstrate the difference between α-1,4 and β-1,4 linkages

Question 9

List the 10 enzymes of glycolysis

Answer 9

1. hexokinase
2. phosphoglucoisomerase
3. phosphofructokinase-1
4. aldolase
5. triose phosphate isomerase
6. glyceraldehyde-3-phosphate dehydrogenase
7. phosphoglycerate kinase
8. phosphoglycerate mutase
9. enolase
10. pyruvate kinase

Question 10

What is the overall net reaction of glycolysis?

Answer 10

Glucose + 2NAD+ + 2ADP + 2Pi ——–> 2 pyruvate + 2NADH + 2H+ +. 2ATP + 2H20

Question 11

distinguish between the ATP investment and ATP earnings stages

Question 12

Define substrate level phosphorylation

Question 13

describe the two enzymatic reactions in glycolysis that result in ATP synthesis

Question 14

Explain how the conversion of phosphofructokinase-1 between the T and R state is allosterically controlled by ATP, ADP and AMP

Question 15

List three ways in which substrate availability and enzyme activity levels control flux through the glycolytic pathway

Question 16

Compare and contrast Hexokinase I and glucokinase (hexokinase IV)

Answer 16

hexokinase I
-high affinity for substrate (low Km ~0.1mM)
-expressed in all tissues, not specific
-phosphorylates a variety of hexose sugars
-inhibited by the product of the rxn, glucose-6-P

Glucokinase
-low affinity for substrate (1000x higher Km ~10mM)
-highly specific for glucose
-expressed primarily in liver and pancreatic cells
-not inhibited by glucose-6-P

Question 17

List the cell signaling steps of going from glucose to insulin signaling (in pancreatic beta cells) using glucokinase (glucose sensor)

Answer 17

1. Stimulation of glucokinase enzyme levels
2. Increased ATP synthesis
3. ATP inhibits K+ channel
4. Membrane depolarization
5. Activation of voltage-gated Ca2+ channel
6. Ca2+ stimulates insulin vesicles to fuse with plasma membrane
7. Insulin signaling

Question 18

Explain why glucokinase is a molecular sensor and the molecular basis for lactose intolerance and for fructose intolerance

Question 19

List the potential metabolic fates of pyruvate and explain why, under anaerobic conditions, pyruvate must be metabolized to either lactate or ethanol

Answer 19

1) anaerobic - production of lactate
2) anaerobic - production of CO2 + ethanol
3) aerobic - production of CO2 + H20

Question 20

What does glycolysis accomplish for the cell?

Answer 20

-generates 2 ATP which is critical under anaerobic conditions (no O2)
-generates pyruvate, a precursor to acetyl CoA, lactate, and ethanol (in yeast)

Question 21

What are the key regulated enzymes in glycolysis?

Answer 21

Hexokinase, Phosphofructokinase-1, pyruvate kinase

Question 22

What are examples of glycolysis in everyday biochemistry?

Answer 22

-sole source of ATP under anaerobic conditions which can occur in animal muscle tissue during intense exercise
-Fermentation, used to make alcoholic beverages when yeast cells are provided with glucose without oxygen

Question 23

Draw out the structures for Stage 1: Investment of glycolysis

Answer 23

Question 24

Draw out the structures for Stage 2: ATP earnings

Answer 24

Question 25

what is metabolic flux and what does it depend on?

Answer 25

the rate at which metabolites go through a pathway

depends on substrate concentration

*NOT equilibrium

Question 26

For the rxn Glucose-6-P —-> Fructose-6-P (deltaG^degree’ = +1.7kJ/mol)

What is the effect on deltaG if [Glucose-6P] increases 100 fold to 8.3 mM in the cell (up from 83uM) i.e., what is the new value for delta G?

Answer 26