Insulin
It occurs when feeding is restarted after prolonged starvation, because insulin drives these ions into cells.
Insulin
- Structure and Function: Insulin is a peptide hormone composed of 51 amino acids, consisting of two chains linked by disulfide bonds, with a molecular weight of approximately 5,800 Dalton. It primarily regulates glucose homeostasis and has d
- Muscle Tissue: Insulin facilitates glucose uptake for immediate use during exercise or storage as glycogen. Importantly, exercising muscles can uptake glucose independently of insulin.
- Liver: Insulin promotes glucose uptake and storage as glycogen. It inhibits glycogen phosphorylase (which breaks down glycogen) while activating glycogen synthase (which promotes glycogen formation). Additionally, insulin suppresses glucose
- Adipose Tissue: Insulin enhances glucose uptake and its conversion to glycerol for fat production. It inhibits the breakdown of triglycerides and stimulates fatty acid uptake, promoting triglyceride synthesis.
- Lack of Insulin: In the absence of insulin, free fatty acids accumulate in the bloodstream as the breakdown of triglycerides is not inhibited. The liver metabolizes these fatty acids, leading to increased production of phospholipids and cho
Read this in LECTURE 6: Pancreatic and Adrenal Hormones
Insulin
- Insulin is a peptide hormone composed of 51 amino acids arranged in two chains linked by disulfide bonds. It has a molecular weight of approximately 5,800 Daltons. Insulin regulates glucose, lipid, and protein metabolism, exhibiting various
- Insulin release is stimulated by an increase in blood glucose levels, amino acids, and gastrointestinal hormones.
- It is inhibited by norepinephrine and epinephrine, while cholinergic stimulation (such as through the vagus nerve) stimulates its release.
- Insulin is primarily produced by the beta cells of the pancreas.
- B. Physiological Actions of Insulin
Read this in LECTURE 6: Pancreatic and Adrenal Hormones
What our notes say
- It occurs when feeding is restarted after prolonged starvation, because insulin drives these ions into cells. (General Surgery CAT 2 (MBSG 4600): 4 October 2021)
- The rise in insulin concentration after a meal is reduced in type 1 but not in type 2 diabetes (Internal Medicine 4th Year Endocrinology CAT: 30 MCQs)
- Insulin: fixed-rate IV soluble insulin at 0.1 units/kg/hour, started after the first fluid bolus and after checking that potassium is above 3.3. (Internal Medicine (MBIM 4100) main exam, Paper One: 3 July 2019)
- Insulin requirement is likely to increase with onset of puberty (Paediatrics Year 6 MBChB end of semester CAT: clinical case MCQs, 29 of 30 quest)
- All children develop diabetes mellitus and need insulin by 5 years of age (Paediatrics end of 2nd semester exam (MBPE 4300): 5 October 2021, 50 MCQs)
- It lowers hepatic glucose output and raises insulin sensitivity (AMPK). (Clinical Pharmacology I (MBPL 4400) main exam: 25 January 2023)
Study material on Insulin
- LECTURE 6: Pancreatic and Adrenal Hormones
- Endocrine and Metabolic Pathology MCQs: Practice Questions
- Endocrine and Metabolic Pathology MCQs for Medical Students
- Integrated Tissue Metabolism -LAQs and SAQs
- Pancreatic Disorders: A Comprehensive Review
- Diabetic ketoacidosis and hyperglycaemic emergencies
- Internal Medicine 4th Year Endocrinology CAT: 30 MCQs
- Ovarian & Colorectal Cancer: Risks, Pathogenesis, Staging
- Chemical Pathology MCQs: Clinical Chemistry, Endocrine & Renal
- Basic Pharmacology - Study Guide
- Medical Physiology GIT MCQs
- Medical Physiology Ii
- Clinical Endocrinology Cases: Pituitary Tumour, PCOS, Type 1 Diabetes, and HHS
- cat makeup — Past Paper Questions & Answers
- Endocrine and Metabolic Pathology MCQs
- Medical Physiology Mid-Semester Exam — November 2019 (Past Paper)
Practice questions on Insulin
The pancreas synthesizes insulin but unable to secrete.
- Type 2 diabetes mellitus
- Type 1 diabetes mellitus
- Maturity-onset diabetes of the young (MODY)
- Gestational diabetes mellitus
Answer: A. Type 2 diabetes mellitus is characterized by insulin resistance and a relative deficiency of insulin secretion. While the pancreas may still synthesize insulin, the ability to secrete adequate amounts in response to glucose levels is impaired.
The pancreas synthesizes insulin but is unable to secrete.
- This describes type 1 diabetes mellitus.
- This describes type 2 diabetes mellitus.
- This describes a condition called 'brittle diabetes'.
- This describes a rare form of diabetes caused by pancreatic duct obstruction.
Answer: D. Type 1 diabetes is characterized by autoimmune destruction of beta cells, leading to absolute insulin deficiency (synthesis and secretion are impaired). Type 2 diabetes involves insulin resistance and often impaired insulin secretion. 'Brittle diabetes' refers to wide fluctuations in blood glucose. Pancreatic duct obstruction can impair secretion, but the phrasing suggests synthesis is intact while secretion is block
The pancreas synthesizes insulin but unable to secrete.
- Type 1 diabetes mellitus
- Type 2 diabetes mellitus
- Gestational diabetes mellitus
- Maturity-onset diabetes of the young (MODY)
Answer: D. Certain subtypes of MODY, particularly those related to transcription factor defects (e.g., MODY3 - HNF1A), can involve impaired insulin secretion despite normal or near-normal insulin synthesis. Type 1 diabetes is characterized by autoimmune destruction of beta cells, leading to absolute insulin deficiency. Type 2 diabetes involves insulin resistance and often impaired secretion.
The pancreas synthesizes insulin but is unable to secrete.
- Type 1 Diabetes Mellitus
- Type 2 Diabetes Mellitus
- Pancreatic cancer
- Insulinoma
Answer: B. Type 2 Diabetes Mellitus is characterized by insulin resistance and a progressive decline in beta-cell function, leading to impaired insulin secretion, even though the pancreas may still be synthesizing insulin. In Type 1 Diabetes, there is autoimmune destruction of beta cells, leading to absolute insulin deficiency. Pancreatic cancer can affect insulin production/secretion. Insulinoma is a tumor that secretes excess
The pancreas synthesizes insulin but unable to secrete.
- Type 1 diabetes mellitus
- Type 2 diabetes mellitus
- Maturity-onset diabetes of the young (MODY)
- Gestational diabetes
Answer: C. Maturity-Onset Diabetes of the Young (MODY) is a group of monogenic forms of diabetes mellitus. Certain subtypes of MODY are characterized by defects in insulin secretion with relatively preserved insulin synthesis. In contrast, Type 1 diabetes involves autoimmune destruction of beta cells, leading to little to no insulin synthesis. Type 2 diabetes involves insulin resistance and impaired insulin secretion, but typic
Insulin is a protein that is produced by certain pancreatic cells and secreted into the bloodstream. (This is true.). Which of the following choices best describes the route of insulin from its production to its exit from the cell?
- rough ER, Golgi apparatus, smooth ER, cell membrane
- Golgi apparatus, rough ER, Smooth ER
- rough ER, lysosomes, transport vesicles, cell membrane
- rough ER, transport vesicles, Golgi apparatus, transport vesicles, cell membrane
- rough ER, transport vesicles, cell membrane ✅ Answer: D
Answer: A. Secreted proteins like insulin are synthesized in the rough ER, transported via vesicles to the Golgi for processing, then packaged into vesicles for exocytosis at the cell membrane.