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Biochemistry > Glycolysis > Flashcards

Glycolysis Flashcards

1
Q

What is the general scheme of absorption of carbohydrates in the digestive system?

A
  1. Mouth: alpha amylase-> breaks down to starch dextrins, maltose, isomaltose, lactose and sucrose.
  2. Stomach: low pH is not optmum for alpha amylase, hence, slows it down.
  3. Pancreatic alpha amylase: Continues to work on starch dextrins to give isomaltose, maltose, sucrose and lactose.
  4. Mucosal cell membrane bound enzymes: Maltase, Isomaltase, sucrase and lactase-> breakdown disaccharides to monosaccharides.
  5. Intestines: Absorption of monosaccharides-> sent to liver through portal circulation.
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2
Q

Arrange the rate of absorption of monosaccharides in the intestines in decreasing order.

A

Galactose> Glucose> Fructose

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3
Q

What kind of transport enables absorption of glucose and galactose in the endothelial cells in the intestine?

A

Secondary Active Transport

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4
Q

What are the fates of glucose?

A
  1. Glucose to pyruvate through Glycolysis
  2. Glucose to glycogen through Glycogenesis
  3. Glucose to ribose (nucleic acid synthesis) and NADPH (lipid synthesis) through Ribose Phosphate Pathway.
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5
Q

What is glycolysis?

A

Glycolysis is the breakdown of glucose into two pyruvate molecules under aerobic conditions and two lactate molecules under anaerobic conditions, aiming for ATP synthesis and the production of other intermediates.

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6
Q

What is the goal of glycolysis?

A
  1. Pathway for ATP synthesis
  2. Production of other intermediates
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7
Q

Where does glycolysis take place?

A

Cytoplasm of cells

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8
Q

What is the significance of glycolysis?

A
  1. It is the only pathway that takes place in all the cells of the body.
  2. It is the only source of energy in cells like RBCs and skeletal muscle cells.
  3. Anaerobic pathway of glycolysis is the source of energy in muscles cells that lack oxygen after strenuous exercise.
  4. Prelimnary step before complete oxidation of glucose.
  5. Carbon skeleton for the synthesis of non-essential amino acids and glycerol for lipid synthesis.
  6. Most reactions are reversible and can hence be used for gluconeogenesis.
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9
Q

What are the possible substrates of gluconeogenesis?

A
  1. Pyruvate
  2. Glucogenic amino acids
  3. Lactate
  4. Glycerol
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10
Q

What transmembrane proteins are used for the transport of gluscose from ECF to tissue cells?

A

Facilitative Glucose Transporters (GluT)

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11
Q

What kind of transport is used to transport glucose from ECF to tissue cells?

A

Facilitative diffusion

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12
Q

What is the target tissue and function of GluT-1?

A

Target tissue- Brain, Kidney, RBC
Function- Glucose intake

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13
Q

What is the target tissue and function of GluT-2?

A

Target tissue- Hepatocytic membrane
Function- Decrease blood glucose levels

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14
Q

What is the target tissue and function of GluT-3?

A

Target tissue- Brain, Kidney
Function- Glucose intake

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15
Q

What is the target tissue and function of GluT-4?

A

Target tissue- Heart, Skeletal Muscles, Adipose
Function- Insulin mediated glucose intake

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16
Q

What is the target tissue and function of GluT-5?

A

Target tissue- Small intestine, Kidney, Sperm
Function- Glucose Intake

17
Q

How does insulin help in regulating blood sugar levels?

A

Insulin helps in the translocation of GluT-4 and brings it to the surface of cells, for the transportation of glucose.

18
Q

Why do Type 2 Diabetes mellitus patients suffer from insulin resistance?

A

GluT-4 is reduced in Type 2 DM patients that causes insulin resistance in muscle and fat cells.

19
Q

True or False:
Glucose uptake is half the normal in muscle cells of Type 2 DM patients.

A

True

20
Q

How many phases does glycolysis have?

A

2 phases:
1. Energy Investment Phase
2. Energy Generative Phase

21
Q

When does the Energy Investment phase end and Energy Generation phase begin?

A

When dihydroxyacetone phosphate is converted to Glyceraldehyde-3-phosphate, by the action of Triosphosphate Isomerase.

22
Q

What regulates the formation of Glucose to G-6-P?

A

The enzyme hexokinase and glucokinase (in liver and pancreas):
Inhibited- G-6-P, Glucagon
Stimulated- Insulin

22
Q

In which step of glycolysis does oxidative phosphorylation take place?

A

Glyceraldehyde 3-phosphate is converted to 1,3-bisphosphoglycerate through Glyceraldehyde 3-phosphate dehydrogenase.
-CHO is oxidised to -COO and phosphate group is added.
NAD+ is reduced to NADH

22
Q

Which steps of glycolysis involve investment of ATP molecules?

A
  1. Glucose to G-6-P by Hexokinase
  2. Fructose-6-phosphate to Fructose-1,6-bisphosphate by Phosphofructo kinase
22
Q

What regulates the formation of Fructose-6-phosphate to Fructose-1,6-bisphosphate?

A

The enzyme phosphofructokinase is:
Inhibited- Citrate, ATP, H+, Glucagon
Stimulated- AMP, Fructose-2,6-bisphosphate, Insulin

23
Q

What is the significance of 2,3-biphosphoglycerate in RBCs?

A

2,3-BPG stabilise the T-form or the deoxy form of Hb by binding to the positively charged amino acids in the beta-chain, hence decreasing Oxygen affinity.
This shifts the O2 dissociation curve to the right.

24
Q

Which steps of the Glycolysis pathway generates ATP?

A
  1. 2,3-BPG to 3-Phosphoglycerate by Phosphoglycerate kinase (2 ATP)
  2. Phosphoenolpyruvate to pyruvate by pyruvate kinase (2 ATP)
25
Q

What regulates the formation of pyruvate from phosphoenol pyruvate?

A

The enzyme Pyruvate kinase is:
Inhibited by- Glucagon
Stimulated by- F-1,6-bisphosphate (in liver), Insulin

26
Q

What is the importance of phosphorylated intermediates in the Glycolytic pathway?

A
  1. Help trap Glucose in the cell.
  2. 2,3-bisphosphoglycerate and phosphoenolpyruvate give phosphate to convert ADP to ATP.
27
Q

How is glucose trapped in the cell?

A
  1. Phosphorylation of glucose to G-6-P changes its 3D shape making it recognisable to enzymes.
  2. Unrecognisable to Glucose transporters.
  3. Charges it so it cannot pass through the plasma membrane.
28
Q

Where does anaerobic glycolysis take place?

A
  1. RBCs
  2. In skeletal muscle tissue cells during strenuous exercise.
  3. Ischemic tissues (w/ blocked oxygen supply)
29
Q

How do NaF and Arsenate operate as inhiitors?

A

Arsenate- Prevents ATP formation
NaF- Inhibits Enolase

Biochemistry (6 decks)

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