6) Discuss protein digestion and absorption 7) Explain the mechanism of insulin

ID: 3483121 • Letter: 6

Question

6) Discuss protein digestion and absorption
7) Explain the mechanism of insulin release
8) Discuss the functional consequences of insulin release during absorptive state
9) Explain the functional consequences of glucagon release during post-absorptive state
10) Compare & contrast between spermatogenesis and oogenesis 6) Discuss protein digestion and absorption
7) Explain the mechanism of insulin release
8) Discuss the functional consequences of insulin release during absorptive state
9) Explain the functional consequences of glucagon release during post-absorptive state
10) Compare & contrast between spermatogenesis and oogenesis 6) Discuss protein digestion and absorption
7) Explain the mechanism of insulin release
8) Discuss the functional consequences of insulin release during absorptive state
9) Explain the functional consequences of glucagon release during post-absorptive state
10) Compare & contrast between spermatogenesis and oogenesis

Explanation / Answer

6. Protein digestion and Absorption:

Protein Digestion: Protein digestion starts in the stomach (saliva do not have any proteolytic enzyme) where pepsin in the gastric juice converts proteins into proteoses, peptones and large polypeptide chains. Most of the protein digestion occurs in small intestine by the action of Pancreatic juice and succus entericus. Pancreatic juice contains Trypsin and Chymotrypsin which converts proteoses, petones into dipeptides, tripeptides and polypeptides. The carboxypeptidases A and B convert the dipeptides, tripeptides and polypeptides into aminoacids

Succus entericus contains dipeptidases, tripeptidases and amino peptidases. Dipeptidases convert dipeptides into amino acids, tripeptides convert tripeptides into amino acids and amino peptidases convert large polypeptides into amino acids

Thus, the final end products of protein digestion are amino acids which are absorbbed from intestine

Protein absorption: Proteins are absorbed in the form of amino acids form small intestine. Levo form of amino acids are absorbed by sodium cotransport and dextro amino acids are absorbed by facilitated diffusion. The absorption rate is high in duodenum, jejunum and slow in ileum

7. Insulin is a polypeptide hormone(2chains linked by disulphide bridges A chain- 21 amino acids B chain 30 amino acids) secreted from Beta cells of Islets of langerhans of pancreas and helps in regulation of blood glucose level.

Mechanism of Insulin release: Under resting conditions approximately 1 unit of Insulin is secreted per hour by human pancreas. But after food consumption more insulin has to be released(Increased blood levels of glucose serve as stimulus for insulin release) and the mechanism involves:

The Beta cells have a glucose sensing mechanism through Glucose transporter called as GLUT2. When GLUT2 is activated it results in partial depolarisation of the beta cells and increases intracellular Calcium ions(Ca2+) that leads to exocytotic release of Insulin.

Apart from glucose, Amino acids, fatty acids and ketone bodies also result in insulin release. Glucose inhibits the ATP sensitive Potassium channels which result in depolarisation of membrane followed by Calcium mediated Insulin release. The chemical signals called Incretins(Gut glucagon, secretin, Gastric inhibitory polypeptide, vasoactive intestinal peptide, pancreozymin-cholecystokinin) cause anticipatory release of Insulin

Number of hormones like growth hormone, corticosteroids, thryoxine also regulate the insulin release

Adrenergic Beta stimulation also results in increased insulin release by stimulation of adenylyl cyclase in the Beta cells. Parasympathetic system through Muscarininc receptors increase Insulin release by IP3-DAG(Inositol triphosphate-Diacyl Glycerol) pathway

8. Functional consequences of Insulin release during absorptive state include hypoglycemia, glycogenesis, inhibition of glycogenolysis and gluconeogenesis(production of glucose from non carbohydrate sources), synthesis of fatty acids and triglycerides due to the following functions of Insulin:

1. Insulin increases the transport and uptake of glucose by increasing the GLUT4(Glucose transporters).

2. Insulin increases the utilisation of glucose and helps in immediate oxidation of glucose in the cell.

3. It increases the production of glycogen that is stored in muscle and liver when glycogen is excessively stored, insulin converts glucose to fatty acids

4. It prevents the breakdown of glycogen

5. It promotes the synthesis of proteins and fat

(OVERALL BLOOD GLUCOSE IS REDUCED WITH INSULIN)

9. Functional consequences of Glucagon release during post-absorptive state include (opposite role of Insulin) like Hyperglycemia, Glycogenolysis, lipolysis, ketogenesis, gluconeogenesis leading OVERALL RISE IN BLOOD GLUCOSE LEVELS. The actions of glucagon involves:

1. Blood glucose levels are increased due to increased glycogenolysis that breaks down glycogen to glucose

2. Promotes gluconeogenesis where glucose is synthesised from non carbohydrate sources like proteins

3. Promotes lipolysis and ketogenic actions which also increase the blood glucose levels.

10. Spermatogenesis and Oogenesis:

1. Spermatogenesis is the process in which spermatazoa are formed from primitive spermatogenic cells in the testes

2. For the formation of sperm from a primitive germ cell, it takes 74 days. But millions of sperms are produced

3. The essential nutrients for spermatogenesis are provided by the Sertoli cells

4. Spermatogenesis can occur many times

5. Spermatogenesis occurs in four stages i. Proliferation stage ii. Stage of growth iii. Maturation stage iv. Transformation stage

5. Hormone involved is Testosterone

1. Oogenesis involves the formation of ovum from primary oocyte in the ovaries

2. Oogenesis results in production of only one ovum

3. The development of ovum occurs in the fluid filled structure called graffian follicle in the ovary

4. Oogenesis occurs only once in the month

5. It has 3 stages i. Multiplication phase ii. Growth phase and iii, Maturation phase

5. Hormones involved are Oestrogen and Progesterone

Spermatogenesis Oogenesis