Carbohydrates metabolism

Question 1

What are glycogenoses?

Answer 1

Glycogenoses can be defined as a metabolic disorder characterized by the the inability to metabolize glycogen properly.
It refers to inborn or inherited disorders of glycogen metabolism in the liver or skeletal muscle

Question 2

Mention 5 glycogen storage diseases

Answer 2

1. Von-Gierke’s diseases (glucose-6-phosphatase deficiency)
2. Pompe’s disease (deficiency of α-1,4-glucosidase)
3. Cori’s disease (absence of glycogen debranching enzyme)
4. Anderson’s disease (presence of abnormally long & unbranched glycogen structures)
5. McArdle disease (defect in glycogen phosphorylase activity in the muscle)

Here’s a simple acronym to remember:
Vice President Came Around-on Monday (the first alphabets represent each disease)

Question 3

Explain type 1 glycogen storage disease (GSD)

Answer 3

Type 1 G.S.D also known as Von Gierke’s disease results from a genetic defect in glucose-6-phosphatase. This enzyme deficiency causes excess intracellular glucose-6-phosphate which leads to accumulation of large amounts of glycogen in the liver and kidneys.
Symptoms are;
1. Hepatomegaly(enlarged liver) due to accumulation of glycogen
2. Hypoglycemia: because glucose cannot be formed from break down of stored glycogen

Question 4

Can you talk about the methods for Treatment of Von-Gierke’s disease?

Answer 4

1. Drug-induced inhibition of hepatic glucose uptake
2. Intra-gastric feeding overnight
3. Surgical transposition of the portal vein to supply the systemic circulation directly
4. Liver Transplant

Question 5

Explain type 2 G.S.D

Answer 5

Type 2 G.S.D is also known as Pompe’s disease. Here there is a deficiency in lysosomal α-1,4-glucosidase, which is responsible for the hydrolysis of maltose, linear Oligosaccharides, and outer branches of glycogen.
This causes accumulation of glycogen in lysosomes of all body organs.
Symptoms
1. There is massive increase in the amount of normal glycogen in tissues causing death by cardio-respiratory failure usually before the age of 2.
It is the most devastating of all G.S.Ds

Question 6

Explain type 3 G.S.D

Answer 6

Type 3 GSD is also known as Cori’s disease. It is caused by the absence of glycogen debranching enzyme.
Symptoms are the same as von-gierke’s disease
1. Hepatomegaly
2. Hypoglycemia

Question 7

Explain type IV GSD

Answer 7

Also known as Anderson disease. It is one of the most fatal G.S.D’s . here glycogen in the liver is present in normal amount but the structures are abnormally long and unbranched. This reduces it’s solubility
Symptoms
1. Hepatomegaly
2. Splenomegaly
3. Liver failure
4. Spleen failure
It usually results in death before the age of 4.

Question 8

Explain type V GSD

Answer 8

Type V is also known as McArdle’s disease. It is caused by an inherited defect in glycogen phosphorylase activity but confined to the muscle.
Symptoms
Because glycogen metabolism in the muscle isn’t essential to life, victim develops normally but experiences painful muscle cramps and progressive weakness during strenuous exercise.

Question 9

Glycolysis is also known as?

Answer 9

Embden-Meyerhof pathway

Question 10

What is Glycolysis?

Answer 10

Glycolysis is the sequence of enzyme catalysed reactions that break down glucose to pyruvate.

Question 11

List the 10 substrates in glycolysis

Answer 11

1. Glucose
2. Glucose-6-phosphate
3. Fructose-6-phosphate
4. Fructose-1,6-bisphosphate
   Followed by splitting into 2 compound’s
5. DHAP (Dihydroxacetone) & GAP (Glyceraldehyde-3-phosphate)
6. G.A.P proceeds to become 1,3 bisphosphoglycerate
7. 3-phosphoglycerate
8. 2-phosphoglycerate
9. Phosphoenol pyruvate
10. Pyruvate

Question 12

Define Glycogenesis?

Answer 12

Glycogenesis is the process by which glucose molecules are polymerised and stored as glycogen in the liver and muscle cells.

Question 13

List the components of the pyruvate dehydrogenase complex

Answer 13

1. Pyruvate dehydrogenase (E1)
2. Dihydrolipoamide acetyl transferase (E2)
3. Dihydrolipoamide dehydrogenase (E3)

Question 14

Why is fluoride used clinically as an anti coagulant when blood is collected for glucose determination?

Answer 14

Fluoride is used as an anti coagulant because it inhibits enzymatic activity. It inhibits the enzyme enolase, in the glycolytic pathway, which prevents the further break down in the blood sample.
This preserves the glucose concentration as at the time of collection

Question 15

List the importance of glycolysis

Answer 15

1. Energy production
2. Glucose metabolism
3. Regulation of cellular processes
4. Synthesis of metabolic intermediates

Question 16

What are the catabolic fates of pyruvate?

Answer 16

1. Aerobic respiration
2. Anaerobic respiration(includes lactic fermentation and alcoholic fermentation)
3. Glycogenesis
4. Fatty acid synthesis
5. Amino acid synthesis

Question 17

Where does absorption of carbohydrates take place?

Answer 17

Duodenum and proximal jejenum

Question 18

Glucose in the blood is absorbed by?

Answer 18

1. Facilitated, and
2. Active transport systems

Question 19

What are the anabolic fates of glucose?

Answer 19

1. Glycogenesis
2. Lipogenesis
3. Gluconeogenesis
4. Pentose Phosphate Pathway

Question 20

Between lactating and non-lactating women, in whom would PPP be more active and why?

Answer 20

The Pentose phosphate pathway would be more active in lacerating women because in PPP, NADPH is released which is important for the synthesis of fatty acids and cholesterol needed for milk production.

Question 21

In the mouth, ptyalin(salivary amylase) acts on?

Answer 21

1-4 glycosidic bonds linkages

Question 22

What is peristalsis and it’s relevance in metabolism of carbohydrates?

Answer 22

Peristalsis is the contraction and relaxation of the oesophagus to push food down to the stomach

Question 23

What is substrate level phosphorylation?

Answer 23

Is a direct method of ATP synthesis that that occurs in glycolysis and TCA.
What happens is, a phosphate group is transferred from a high energy substrate molecule directly to ADP forming ATP.

Question 24

What is Oxidative phosphorylation?

Answer 24

Oxidative phosphorylation is an indirect methods of ATP synthesis that occurs in the inner mitochondrial membrane

Question 25

Discuss the biochemical implications that may occur is insulin is not released to the bloodstream?

Answer 25

If insulin is not released into the bloodstream or there is insufficient insulin production, several biochemical implications occur such as:
1. Hyperglycemia
2. Increased lipolysis
3. Protein breakdown
4. Ketogenesis
5. Impaired glycogen synthesis
6. Electrolyte imbalance
7. Increased glycogen level

Question 26

What is hyperglycemia?

Answer 26

Without insulin, glucose uptake is impaired leading to elevated blood glucose levels known as hyperglycemia. This could lead to glycation of proteins, oxidative stress and damage of organs overtime.

Question 27

What is Ketogenesis?

Answer 27

Ketogenesis is the synthesis of ketone bodies from fatty acids which could lead to high blood ketone levels, metabolic acidosis and electrolyte imbalance.

Question 28

How does insulin affect electrolyte imbalance?

Answer 28

Insulin deficiency leads to electrolyte imbalance, particularly potassium ions. This can result in conditions such as hyperkalemia which can be life-threatening.

Question 29

Differentiate between hypoglycemia and hyperglycemia?

Answer 29

They are 2 opposite conditions related to blood glucose levels.
Hyperglycemia refers to high blood glucose levels. It occurs due to inadequate insulin secretion or action
While, hypoglycemia refers to low blood glucose levels, typically below 70mg/DL. It occurs due to excessive insulin or oral antidiabetic medication dosage, delayed or skipped meals, increased physical activity or alcohol consumption.

Question 30

What is the role of NADH & FADH2 in biologic oxidation

Answer 30

NADH & FADH are coenzymes involved in the electron transport chain during cellular respiration. In the electron transport chain, NADH donates it’s electrons to the ETC where they are passed along a series of protein complexes that lead to production of ATP