38 Questions
What is the effect of insulin on potassium and phosphate transport into cells?
It increases their transport
What is the primary stimulus for glucagon secretion?
Hypoglycaemia
At what plasma glucose concentration does significant glycosuria usually occur?
10 mmol/L
What is the role of TPP in the tricarboxylic acid cycle?
It is a cofactor for a-Ketoglutarate dehydrogenase
What is the effect of insulin on gene expression?
It regulates the expression of certain genes
What is the effect of glucagon on glycogenolysis?
It enhances glycogenolysis
What is the effect of insulin on glucose transport into cells?
It increases glucose transport into cells
What is the structure of glucagon?
A single-chain polypeptide
What is the function of glucose-6-phosphatase in the liver?
To release glucose and maintain extracellular fasting concentrations
What is the source of fatty acids that are converted to ketones in the liver during fasting?
Adipose tissue
Which hormone stimulates hepatic glycogenolysis in response to low plasma glucose concentration?
Glucagon
What is the fate of the carbon chains of some amino acids in the liver during fasting?
They are converted into ketones
What is the primary function of the liver in maintaining glucose homeostasis during fasting?
To release glucose into the bloodstream
Which tissues can use ketones as an energy source during fasting?
Brain and other tissues
What is the response of the pancreas to a fall in plasma glucose concentration?
It releases glucagon
What is the role of catecholamines in the liver during fasting?
They stimulate hepatic glycogenolysis
What is the primary treatment for a patient with suspected diabetes mellitus?
Careful intravenous rehydration, insulin, and heparin
Why is it necessary to contact the laboratory before performing an oral glucose tolerance test?
To confirm the local details of the test procedure
What is the minimum duration of fasting required before an oral glucose tolerance test?
10 hours
What is the purpose of withdrawing a venous blood sample during an oral glucose tolerance test?
To measure plasma glucose levels
What is the primary purpose of monitoring glycated haemoglobin in diabetes mellitus?
To assess the mean plasma glucose concentration during the preceding 6–8 weeks
What is the consequence of measuring glucose concentration in whole blood instead of plasma?
The results will be approximately 1.0 mmol/L lower
What is the unit of measurement for glycated haemoglobin?
Mmol/mol
What is the significance of a high glycated haemoglobin value?
Poor glycaemic control
Why is it important to exclude other potential causes of hyperglycaemia before diagnosing diabetes mellitus?
To ensure accurate diagnosis and treatment
What is the primary indication for performing an oral glucose tolerance test?
All of the above
What is the primary purpose of screening tests for glycosuria?
To detect urinary glucose using enzyme-based diagnostic strips
What is the purpose of allowing the patient to drink water during an oral glucose tolerance test?
To prevent dehydration
What is the conversion equation between DCCT-HbA1c and IFCC units?
IFCC-HbA1c (mmol/mol) = [DCCT-HbA1c (%) – 2.15] ¥ 10.929
What is the significance of urinary albumin excretion?
Both A and B
What is the normal range for urinary albumin excretion in males?
Less than 3.5 g/mol
What can slow the progression of microalbuminuria?
Both A and B
What happens to the rate of glycogen synthesis in liver cells in response to systemic hyperglycaemia?
It increases due to the stimulatory effect of insulin
What is the primary function of the liver in maintaining a fasting supply of glucose to vulnerable tissues such as the brain?
To store some of the excess glucose as glycogen
Which of the following amino acids is classified as glycogenic and ketogenic?
Isoleucine
What is the eventual fate of fatty acids synthesized from excess glucose in the liver?
They are transported to adipose tissue for storage
What is the source of glucose that passes through the liver during fasting?
Glycogen stored in the liver
What is the effect of insulin on the liver during fasting?
It has no effect on glycogen metabolism
Study Notes
Insulin and Glucagon
- Insulin directly increases the transport of amino acids, potassium, and phosphate into cells, especially muscle cells.
- Insulin regulates growth and development, and the expression of certain genes in the long term.
Glucagon
- Glucagon is a single-chain polypeptide synthesized by the α-cells of the pancreatic islets.
- Glucagon's secretion is stimulated by hypoglycemia (low blood sugar).
- Glucagon enhances hepatic glycogenolysis (glycogen breakdown) and gluconeogenesis.
Glucose Metabolism
- Little glucose is lost unchanged from the body during normal metabolism.
- The liver contains the enzyme glucose-6-phosphatase, which releases glucose and helps maintain extracellular fasting concentrations.
- Hepatic glycogenolysis is stimulated by glucagon and catecholamines (such as adrenaline or noradrenaline).
Fasting and Glucose Concentration
- During fasting, the liver converts fatty acids to ketones, which can be used by other tissues as an energy source.
- The carbon chains of some amino acids can also be converted to ketones.
- Ketones can be used by the brain as an energy source when plasma glucose concentrations are low.
Glycogen Synthesis and Storage
- The liver cells can store excess glucose as glycogen.
- The rate of glycogen synthesis (glycogenesis) from glucose-6-phosphate (G6P) may be increased by insulin.
- The liver can convert excess glucose to fatty acids, which are stored in adipose tissue.
Monitoring of Diabetes Mellitus
- Glycosuria can be defined as a concentration of urinary glucose detectable using relatively insensitive screening tests.
- Glycated haemoglobin (HbA1c) is used to assess the mean plasma glucose concentration over the preceding 6-8 weeks.
- HbA1c is expressed in mmol/mol units.
Investigation of Suspected Diabetes Mellitus
- A diagnosis can be established from either fasting or random blood glucose determinations.
- In equivocal cases, an oral glucose tolerance test (OGTT) may be required.
- The OGTT procedure involves a 10-16 hour fast, and a venous sample is withdrawn for plasma glucose estimation.
This quiz covers the functions of insulin and glucagon, including their roles in regulating blood sugar levels, cellular transport, and gene expression.
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