Carbohydrates metabolism Flashcards
What are glycogenoses?
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
Mention 5 glycogen storage diseases
- Von-Gierke’s diseases (glucose-6-phosphatase deficiency)
- Pompe’s disease (deficiency of α-1,4-glucosidase)
- Cori’s disease (absence of glycogen debranching enzyme)
- Anderson’s disease (presence of abnormally long & unbranched glycogen structures)
- 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)
Explain type 1 glycogen storage disease (GSD)
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
Can you talk about the methods for Treatment of Von-Gierke’s disease?
- Drug-induced inhibition of hepatic glucose uptake
- Intra-gastric feeding overnight
- Surgical transposition of the portal vein to supply the systemic circulation directly
- Liver Transplant
Explain type 2 G.S.D
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
Explain type 3 G.S.D
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
Explain type IV GSD
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.
Explain type V GSD
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.
Glycolysis is also known as?
Embden-Meyerhof pathway
What is Glycolysis?
Glycolysis is the sequence of enzyme catalysed reactions that break down glucose to pyruvate.
List the 10 substrates in glycolysis
- Glucose
- Glucose-6-phosphate
- Fructose-6-phosphate
- Fructose-1,6-bisphosphate
Followed by splitting into 2 compound’s - DHAP (Dihydroxacetone) & GAP (Glyceraldehyde-3-phosphate)
- G.A.P proceeds to become 1,3 bisphosphoglycerate
- 3-phosphoglycerate
- 2-phosphoglycerate
- Phosphoenol pyruvate
- Pyruvate
Define Glycogenesis?
Glycogenesis is the process by which glucose molecules are polymerised and stored as glycogen in the liver and muscle cells.
List the components of the pyruvate dehydrogenase complex
- Pyruvate dehydrogenase (E1)
- Dihydrolipoamide acetyl transferase (E2)
- Dihydrolipoamide dehydrogenase (E3)
Why is fluoride used clinically as an anti coagulant when blood is collected for glucose determination?
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
List the importance of glycolysis
- Energy production
- Glucose metabolism
- Regulation of cellular processes
- Synthesis of metabolic intermediates
What are the catabolic fates of pyruvate?
- Aerobic respiration
- Anaerobic respiration(includes lactic fermentation and alcoholic fermentation)
- Glycogenesis
- Fatty acid synthesis
- Amino acid synthesis
Where does absorption of carbohydrates take place?
Duodenum and proximal jejenum
Glucose in the blood is absorbed by?
- Facilitated, and
- Active transport systems
What are the anabolic fates of glucose?
- Glycogenesis
- Lipogenesis
- Gluconeogenesis
- Pentose Phosphate Pathway
Between lactating and non-lactating women, in whom would PPP be more active and why?
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.
In the mouth, ptyalin(salivary amylase) acts on?
1-4 glycosidic bonds linkages
What is peristalsis and it’s relevance in metabolism of carbohydrates?
Peristalsis is the contraction and relaxation of the oesophagus to push food down to the stomach
What is substrate level phosphorylation?
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.
What is Oxidative phosphorylation?
Oxidative phosphorylation is an indirect methods of ATP synthesis that occurs in the inner mitochondrial membrane
Discuss the biochemical implications that may occur is insulin is not released to the bloodstream?
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
What is hyperglycemia?
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.
What is Ketogenesis?
Ketogenesis is the synthesis of ketone bodies from fatty acids which could lead to high blood ketone levels, metabolic acidosis and electrolyte imbalance.
How does insulin affect electrolyte imbalance?
Insulin deficiency leads to electrolyte imbalance, particularly potassium ions. This can result in conditions such as hyperkalemia which can be life-threatening.
Differentiate between hypoglycemia and hyperglycemia?
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.
What is the role of NADH & FADH2 in biologic oxidation
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
