Glycolysis

Question 1

Glycolysis can be either aerobic or anaerobic. What is the main difference in their products?

Answer 1

Both types of glycolysis the product is pyruvate. Anaerobic glycolysis takes it a step further and converts pyruvate to lactate

Question 2

Location of glycolysis?

Aerobic glycolysis can happen in cells that have ___

Answer 2

Cytoplasm

Mitochondria (paths that happen in mitochondria are the ones that make the most ATP)

Question 3

Anaerobic glycolysis would happen in tissues where __

Name 4 places in the body that relies on anaerobic glycolysis

Answer 3

Blood supply is very minimal or there is no oxygen

Medulla of kidney, RBCs, contracting skeletal muscle and cornea/lens of eyes (if these were vascularized, you would lose vision)

Question 4

First 5 steps in glycolysis vs the steps afterwards?

Answer 4

First 5 steps = investing phase (energy is utilized), steps after you start getting a profit (energy production)

Question 5

Glycolysis overview:

The first 5 steps of glycolysis are acting to do what?

Answer 5

Splitting one glucose molecule into 2 glyceraldehyde-3-phosphates

Question 6

ATP is generated in what two steps?

Which of these is reversible?

Answer 6

ATP is generated in steps 7 and 10

7 is reversible, 10 is not

Question 7

Each product that is generated in steps 6-10 are from?

Answer 7

Each of the glyceraldehyde-3-phosphates generated in steps 4 and 5. (So thats why everything is doubled, because there are 2 glyceraldehyde-3-phosphates)

Question 8

NADH is generated in which step?

Why is NADH important?

Answer 8

6

Its an electron carrier with the potential to make more ATPs through oxidative phosphorylation

Question 9

Which steps require ATP

Answer 9

Steps 1 and 3

Question 10

First step:

1. Glucose is converted to ____ by ___?
2. When this step starts, why does the product get trapped in the cell?
3. What has to happen to become not stuck?

Answer 10

1. Glucose-6-phosphate by hexokinase/glucokinase
2. Cells lack transport systems for phosphorylated glucose (GLUT transporters only work on glucose)
3. Glucose-6-phosphate has to be oxidized

Question 11

Functions of hexokinase and glucokinase

Answer 11

Phosphorylates glucose, and uptake of glucose by the tissue (GLUT)

Question 12

Hexokinase:

1. Provides energy when glucose concentration is high or low?
2. __ Km; __ Vmax
3. Inhibited by?

Answer 12

1. Low (fasting state)
2. Low Km (high affinity for glucose); low Vmax
3. Glucose-6-phosphate

Question 13

Glucokinase:

1. Location
2. __ Km; __ Vmax
3. Induced by?
4. Provides energy when glucose concentration is high or low?

Answer 13

1. Liver and islet cells of pancreas
2. High Km; high Vmax
3. Insulin
4. High

Question 14

Key feature about glucokinase?

~what GLUT transporter transports to liver and pancreas?

Answer 14

Acts as a glucose sensor to let pancreas know that insulin needs to be released

~GLUT2

Question 15

Broad path of how glucokinase works

Answer 15

Carb rich meal increased blood glucose, GLUT2 transports to pancreas and increases glucose concentration of beta cells, glucose gets phosphorylated to enter glycolysis and TCA. ATP builds up and is stored in channels by the beta cells

Question 16

1. What are the two channels where ATP is stored?
2. The amount of glucose entering beta cell is equal to?
3. Relationship between potassium channels and insulin?

Answer 16

1. Potassium channel and voltage dependent calcium channel
2. Amount of insulin being secreted from beta cells into the blood
3. If K channels close, you cannot secrete insulin

Question 17

Step 3: irreversible

1. ____ is converted to ____ by ?
2. What is significant about this step
3. What is significant about PFK1?

Answer 17

1. Fructose-6-phosphate to fructose 1,6 bisphosphate by PFK1
2. This is the rate limiting step (committed step)
3. It is the most regulated enzyme

Question 18

Function of Aldolase A and B

Answer 18

Aldolase A= cleaves fructose 1,6 bisphosphate to 2 triose sugars

Aldolase B= cleaves fructose-6-phosphate and is part of fructose metabolism (so not involved in glycolysis)

Question 19

What are incretins

Answer 19

Peptides in GI that are secreted when we eat. They act on beta cells and increase insulin secretion (thats how positively charged amino acids can increase insulin secretion; increase positive charge leads to depolarization)

Question 20

What is needed in order to get insulin out of its storage vesicle?

Answer 20

Calcium

Question 21

Function of glyceraldehyde 3 phosphate dehydrogenase? (G3P dehydrogenase)

What does this step require?

Answer 21

Catalyzes the only step where NADH is synthesized (step 6)

Requires inorganic phosphate (Pi) to attach to carboxyl group

Question 22

Clinical relevance of arsenic poisioning?

Answer 22

It competes with G3P dehydrogenase, thereby preventing net NADH and ATP production (takes all the energy out of glycolysis)

Question 23

1. What increases O2 delivery (ie at high altitudes)?
2. How does it do this?
3. What is the function of 1,3-biphosphoglycerate

Answer 23

1. 2,3-biphosphoglycerate
2. Favors unloading of O2 to tissues, High BPG shifts oxygen dissociation curve to the right
3. Intermediate of RBC responsible for accepting or releasing oxygen in the tissues

Question 24

1. What enzyme is inhibited by fluoride?

2. Explain

Answer 24

1. Enolase
2. Bacteria can form lactic acid from food which turns teeth yellow. Fluoride prevents glycolysis that forms the lactic acid

Question 25

1. What catalyzes the second substrate level phosphorylation step in glucose? 2. What happens?

Answer 25

1. Pyruvate kinase 2. Enzyme mediates the transfer of phophates from PEP to ADP forming two ATPs; PEP is converted to pyruvate (end product of aerobic glycolysis)

Question 26

Metabolic fate of pyruvate: 1. Aerobic conditions? 2. Anaerobic?

Answer 26

1. Can be converted to acetyl CoA and enter Krebs cycle; acetyl CoA is completely oxidized and generates ATP through oxidative phosphorylation in Krebs 2. Seen mainly in RBCs and contracting skeletal muscle; pyruvate is converted to lactate

Question 27

Ratio of NADH to NAD is high, what will happen to lactate?

Answer 27

It will increase

Question 28

So the enzymes that catalyze the irreversible and regulated steps of glycolysis are?

Answer 28

Hexokinase, glucokinase, PFK1, and pyruvate kinase

Question 29

What does PFK2 do?

Answer 29

Controls PFK1 of glycolysis in the liver - covalent modification

Question 30

Clinical correlations for glucokinase: 1. It is induced by? 2. Type 1 diabetes? 3. Hyperinsulinemia and hypoglycemia? 4. Gestational diabetes (MODY)?

Answer 30

1. Insulin (so if you dont have insulin, you cannot make glucokinase) 2. If you have a near complete deficiency in glucokinase 3. Decrease Km 4. Increase Km (decreased activity of glucokinase)

Question 31

PFK1 is only activated if __ is present Positive allosteric effector? Negative allosteric effector?

Answer 31

Fructose 2,6 bisphosphate (even if citrate levels are high) High fructose 2,6 bisphosphate (liver), high ADP (liver) / High AMP (muscle) Citrate (liver)

Question 32

Two inhibitors of PFK1 and why one of them is significant?

Answer 32

Citrate and ATP; citrate is the only example of a CAC intermediate regulating a glycolytic enzyme

Question 33

High glucagon (cAMP) inactivates? Effect of this?

Answer 33

PFK2 (because high glucagon means fructose 2,6 bisphosphate decreases in liver cells) Effect is glycolysis will decrease and gluconeogenesis will increase

Question 34

1. Hormonal control of glycolysis in well fed state | 2. Fasting state

Answer 34

1. Uptake of glucose by GLUT4 (skeletal muscle and adipose), utilization of glucose by oxidation, anabolic pathways 2. Decrease in utilization of glucose by oxidation by inactivation of the key glycolytic enzymes

Question 35

1. Pyruvate kinase deficiency will lead to decrease in rate of? 2. What does this mainly affect in the body? 3. Associated with a rise in? 4. Clinical presentation?

Answer 35

1. Glycolysis 2. RBCs that depend solely on anaerobic glycolysis 3. 2,3 BPG levels 4. Hemolytic anemia (due to lysis of RBCs)

Question 36

1. What is lactic acidosis? 2. What is it the result of? 3. May be seen associated with?

Answer 36

1. Accumulation of lactic acid in blood 2. Failure of delivery of oxygen to tissues - dependent on anaerobic glycolysis 3. Severe MI, uncontrolled hemorrhage

Question 37

What is a fluoride bulb?

Answer 37

Used for blood glucose estimation since fluoride blocks glycolysis, adding it to the blood inhibits glucose utilization in vitro - prevents false low values for blood glucose

Question 38

**Starting with glyceraldehyde-3-PO4 and synthesizing one molecule of pyruvate, the net yield of ATP and NADH would be?

Answer 38

2 ATP and 1 NADH

Question 39

If someone who does not exercise often is hiking 2500 meters above sea level, how many ATPs would be generated by his/her RBCs?

Answer 39

Zero

Question 40

Why is it bad to drink alcohol after running a marathon?

Answer 40

Running a marathon produces a lot of lactic acid and you will be dehydrated - this will result in lactic acidosis