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biochemistry block 2 > Glycolysis > Flashcards

Glycolysis Flashcards

1
Q

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

A

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

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2
Q

Location of glycolysis?

Aerobic glycolysis can happen in cells that have ___

A

Cytoplasm

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

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3
Q

Anaerobic glycolysis would happen in tissues where __

Name 4 places in the body that relies on anaerobic glycolysis

A

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)

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4
Q

First 5 steps in glycolysis vs the steps afterwards?

A

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

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5
Q

Glycolysis overview:

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

A

Splitting one glucose molecule into 2 glyceraldehyde-3-phosphates

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6
Q

ATP is generated in what two steps?

Which of these is reversible?

A

ATP is generated in steps 7 and 10

7 is reversible, 10 is not

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7
Q

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

A

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)

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8
Q

NADH is generated in which step?

Why is NADH important?

A

6

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

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9
Q

Which steps require ATP

A

Steps 1 and 3

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10
Q

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?
A
  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
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11
Q

Functions of hexokinase and glucokinase

A

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

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12
Q

Hexokinase:

  1. Provides energy when glucose concentration is high or low?
  2. __ Km; __ Vmax
  3. Inhibited by?
A
  1. Low (fasting state)
  2. Low Km (high affinity for glucose); low Vmax
  3. Glucose-6-phosphate
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13
Q

Glucokinase:

  1. Location
  2. __ Km; __ Vmax
  3. Induced by?
  4. Provides energy when glucose concentration is high or low?
A
  1. Liver and islet cells of pancreas
  2. High Km; high Vmax
  3. Insulin
  4. High
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14
Q

Key feature about glucokinase?

~what GLUT transporter transports to liver and pancreas?

A

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

~GLUT2

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15
Q

Broad path of how glucokinase works

A

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

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16
Q
  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?
A
  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
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17
Q

Step 3: irreversible

  1. ____ is converted to ____ by ?
  2. What is significant about this step
  3. What is significant about PFK1?
A
  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
18
Q

Function of Aldolase A and B

A

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)

19
Q

What are incretins

A

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)

20
Q

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

A

Calcium

21
Q

Function of glyceraldehyde 3 phosphate dehydrogenase? (G3P dehydrogenase)

What does this step require?

A

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

Requires inorganic phosphate (Pi) to attach to carboxyl group

22
Q

Clinical relevance of arsenic poisioning?

A

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

23
Q
  1. What increases O2 delivery (ie at high altitudes)?
  2. How does it do this?
  3. What is the function of 1,3-biphosphoglycerate
A
  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
24
Q
  1. What enzyme is inhibited by fluoride?

2. Explain

A
  1. Enolase
  2. Bacteria can form lactic acid from food which turns teeth yellow. Fluoride prevents glycolysis that forms the lactic acid
25
Q
  1. What catalyzes the second substrate level phosphorylation step in glucose?
  2. What happens?
A
  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)
26
Q

Metabolic fate of pyruvate:

  1. Aerobic conditions?
  2. Anaerobic?
A
  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
27
Q

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

A

It will increase

28
Q

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

A

Hexokinase, glucokinase, PFK1, and pyruvate kinase

29
Q

What does PFK2 do?

A

Controls PFK1 of glycolysis in the liver - covalent modification

30
Q

Clinical correlations for glucokinase:

  1. It is induced by?
  2. Type 1 diabetes?
  3. Hyperinsulinemia and hypoglycemia?
  4. Gestational diabetes (MODY)?
A
  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)
31
Q

PFK1 is only activated if __ is present

Positive allosteric effector?

Negative allosteric effector?

A

Fructose 2,6 bisphosphate (even if citrate levels are high)

High fructose 2,6 bisphosphate (liver), high ADP (liver) / High AMP (muscle)

Citrate (liver)

32
Q

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

A

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

33
Q

High glucagon (cAMP) inactivates?

Effect of this?

A

PFK2 (because high glucagon means fructose 2,6 bisphosphate decreases in liver cells)

Effect is glycolysis will decrease and gluconeogenesis will increase

34
Q
  1. Hormonal control of glycolysis in well fed state

2. Fasting state

A
  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
35
Q
  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?
A
  1. Glycolysis
  2. RBCs that depend solely on anaerobic glycolysis
  3. 2,3 BPG levels
  4. Hemolytic anemia (due to lysis of RBCs)
36
Q
  1. What is lactic acidosis?
  2. What is it the result of?
  3. May be seen associated with?
A
  1. Accumulation of lactic acid in blood
  2. Failure of delivery of oxygen to tissues - dependent on anaerobic glycolysis
  3. Severe MI, uncontrolled hemorrhage
37
Q

What is a fluoride bulb?

A

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

38
Q

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

A

2 ATP and 1 NADH

39
Q

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

A

Zero

40
Q

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

A

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

biochemistry block 2 (12 decks)

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