Assignment Code: BBCCT-119/TMA/2023

Course Code: BBCCT-119

Assignment Name: Metabolism of Carbohydrates and Lipids

Year: 2023

Verification Status: Verified by Professor

Attempt all questions. The marks for each question are indicated against it.

Marks: 50

Part-(A)

Q1) Write about the following in brief:

(a) Paracrine signalling.

Ans) A molecule that is released from one cell and moves to nearby cells to interact with their receptors.

Examples:

1. When cytokines are released, they cause inflammation in the area.

2. At synapses, neurotransmitters are let out.

(b) Luteinizing hormone.

Ans) Luteinizing hormone makes a female ovulate by breaking the follicle and letting the egg out. The ovary's luteal cells (corpora lutea), which make progesterone, are made from the follicle's leftover cells. In male, luteinizing hormone makes the Leydig cells, which are also called interstitial cells, make androgens like testosterone.

(c) Myxoedema

Ans) Myxoedema is a type of hypothyroidism that can cause dry, flaky skin, hair loss, and swelling. Most of the time, oedema affects a large area. It happens when skin proteins, polysaccharides, and hyaluronic acid build up in the subcutaneous spaces. It is because of this swelling that the condition is called "myxoedema."

(d) Primary action of EGF

Ans) EGF is found in the fibroblast cells of the skin, which are responsible for cell growth, development, and healing. Its main job is to repair damaged skin. EGF finds and binds to a specific receptor on the skin's outer layer (epidermis). The receptors on these skin cells send a message and draw cells to that area so that the skin can heal quickly and evenly.

(e) Hypothalamus

Ans) The hypothalamus is located below the thalamus. It is a small part of the diencephalon. The anatomy of the hypothalamus shows that it starts at the level of the optic chiasm and the attached lamina terminalis and goes all the way to the coronal plane just behind the mammillary bodies. Through the median eminence and the infundibular stalk, the hypothalamus is linked to the pituitary gland in the middle. The portal vessels that carry hormones from the hypothalamus to the anterior lobe of the hypophysis are in the median eminence and the pituitary stalk. These things affect how the hypophyseal tropic hormones are made.

Q2) (a) What are cell surface receptors? Illustrate their general structure with the help of a suitable diagram.

Ans) Cell-surface receptors, also called membrane or transmembrane receptors, are parts of a cell's plasma membrane that bind to molecules outside the cell to send signals.

Q2) (b) Describe hypothalamic-pituitary axis and its biological importance.

Ans) The infundibulum or pituitary stalk connects the hypothalamus to the pituitary gland. Once, the pituitary was thought to be the master endocrine gland because it controlled many bodily functions. Now, however, the hypothalamus controls it, so it is no longer thought of as the master endocrine gland. Negative feedback loops and secretions from the hypothalamus control how much of the pituitary hormones are made. The pituitary gland, or hypophysis, is at the base of the brain in a depression of the sphenoid bone. It is made up of three parts, or lobes: the adenohypophysis, or anterior pituitary, the intermediate lobe, or pars intermedia, and the neurohypophysis, or the posterior pituitary, or pars nervosa.

Q3) (a) Explain any two diseases related to hypothalamus-pituitary axis.

Ans) Pituitary disorders include pituitary tumours, traumatic brain injuries, hypopituitarism, hyperpituitarism, and diabetes insipidus. Most pituitary tumours are not cancerous, but they can affect how the pituitary works. They can cause pressure on the pituitary, which can lead to headaches, trouble seeing, or other problems. Tumours could also make hormones make more of them or make them make less. Traumatic brain injury is when the brain is hurt by something outside of the body. It can cause problems with the pituitary gland. In fact, 20–50% of people with TBI have pituitary problems, the most common of which is GH deficiency.

Q3) (b) What are secondary sex characteristics in males and females and which hormones are involved in their development.

Ans) Secondary sex characteristics are things that develop during puberty that are only for one sex. The secretion of testosterone in males and estrogens in females is what causes these traits to develop. In males, these include increased hair growth, thickening of the skin, enlargement of the larynx and thickening of the vocal cords, thickening and strengthening of the bones' muscles, widening of the shoulders and narrowing of the waist, and enlargement of the penis and other external genitalia. Female secondary characteristics include a high-pitched voice, less body hair and more hair on the scalp, narrow shoulders, broad hips, converging thighs, and diverging arms, and fat build-up in the breasts and buttocks.

Q4) Describe biological effects of thyroid hormones.

Ans) The effects of T3 and T4 are identical in terms of quality. The primary result of thyroid hormones is an increase in baseline metabolic rate, which is accompanied by an increase in lipid synthesis, mobilisation, and breakdown as well as glucose metabolism. The stimulation of protein synthesis makes thyroid hormone necessary for healthy development. The correct development of the central nervous system, particularly the myelination of nerve fibres, depends on thyroid hormones as well.

Basal Metabolic Rate

With the notable exceptions of the brain, uterus, testes, and spleen, thyroid hormones raise practically every organ's basal metabolic rate and, therefore, oxygen consumption. It's interesting to note that thyroid hormones' impacts on metabolism do not affect the anterior pituitary gland or the thyroid gland. An increase in the quantity and size of mitochondria as well as an uptick in the activity of key metabolic enzymes are the main mechanisms causing this impact.

Actions of Thyroid Hormones on Protein and Bone

The thyroid hormones also have effects on protein and bone. The synthesis of many proteins is dependent upon the presence of thyroid hormones, hence thyroid hormone is essential for normal growth and development. In some animals these hormones control metamorphosis. A deficiency of the thyroid hormones may result in an impairment of normal growth; however, an excess has similar effects due to the stimulation of gluconeogenesis promoting protein catabolism.

Thyroid Hormones, Catecholamines, Cardiovascular and Central Nervous System

An enhanced expression of beta-adrenoceptors by adipocytes may help to explain how thyroid hormones potentiate the effects of catecholamines. There are impacts on the cardiovascular system in addition to the effects on glucose metabolism. Thyroid hormones boost cardiac output, sometimes the strength of the heart's contraction, and the pace at which blood flows through surface veins. It is likely that these effects are not primarily caused by an increase in the beta-adrenoceptors' sensitivity, but also in part by the tissues' higher metabolic needs and by the direct actions of thyroid hormones on cardiac muscle.

Q5) (a) How does testosterone produce its effects?

Ans) Testosterone is a sex hormone that helps the body do important things. Male's libido, bone mass, fat distribution, muscle mass and strength, and the production of red blood cells and sperm are thought to be controlled by testosterone. A small amount of testosterone in the blood is changed into oestradiol, which is a type of oestrogen. As males get older, they usually make less testosterone, which means they also make less oestradiol. So, some or all the changes that are often attributed to a lack of testosterone could be caused by the same drop in oestradiol.

Testosterone was first used as a clinical drug in 1937, but not much was known about how it worked at the time. Males whose bodies naturally make low levels of the hormone are now often given prescriptions for it.

Q5) (b) Write functions of growth hormone.

Ans)

Functions of Growth Hormone

1. It controls how much kids grow when they are young. When a child is young, the epiphyses are not yet fused to the long bones, and growth hormones allow bone matrix to build up at the ends of the long bones. This helps the long bones grow, which makes the child taller.

2. GH is a protein-building hormone that speeds up the metabolism, makes nitrogen and phosphorus balance out, and lowers the number of amino acids in the blood. Because the production of soluble collagen is sped up, the GI tract can take in more calcium and get rid of more 4-hydroxyproline.

3. It helps get free fatty acids out of adipose tissue, which is good for ketogenesis. It also stops many tissues, such as muscles, from taking in glucose. This is called an "anti-insulin action." These things can help you lose body fat and gain lean body mass.

Part-(B) Marks: 50

Q6) (a) How does calcitonin affect the calcium ion concentration in blood?

Ans) Calcitonin Decreases Blood Calcium Ion Concentration in two ways:

1. The immediate effect is to stop the osteoclasts from absorbing calcium and even stop the osteolytic effect of the osteolytic membrane from breaking down bone. This changes the balance in favour of calcium deposition in exchangeable calcium salts. This effect is especially important in young animals because calcium is quickly taken up and put down.

2. Lessen the number of new osteoclasts that are made. Since osteoclastic resorption of bone leads to osteoblastic activity, fewer osteoclasts mean fewer osteoblasts. So, over a long time, there is a net decrease in osteoclastic and osteoblastic activity, which has a slight effect on the concentration of calcium ions in plasma.

Q6) (b) What is osteoporosis and the causative factors?

Ans) Osteoporosis is not caused by a lack of bone calcification. Instead, it is caused by a decrease in the organic bone matrix. In osteoporosis, most of the osteoblastic activity in the bone is below normal, which slows down the rate at which bone osteoid is added to the bone. Osteoporosis is caused by various factors:

1. Because they do not move much, the bones do not get enough physical stress.

2. Malnutrition bad enough that you can't make a good protein matrix.

3. Lack of vitamin C, which is needed for all cells to release substances from inside of them and for osteoclasts to make the bone-like substance called osteoid.

4. Because oestrogen decreases the number and activity of osteoclasts, there is less of it in the body after menopause.

Q7) (a) Explain the structure and function of gastro- intestinal tract.

Ans) The GI tract comes from the endoderm, which is the middle layer of the three that make up an embryo. During foetal life, it is split into three parts: the foregut, which gets its blood supply from the coeliac trunk, the midgut, which gets its blood supply from the superior mesenteric artery, and the hindgut.

The Gastrointestinal tract and other glandular organs make up the Gastrointestinal system. The mouth, pharynx, oesophagus, stomach, small intestine, large intestine, and anus are all parts of the GI tract. Accessory glandular organs include the salivary glands, liver, gallbladder, and pancreas. From the oesophagus to the anus, the tissues of the GI tract are made up of the same four layers. These are mucosa, submucosa, muscularis and serosa.

Q7) (b) How do muscles differ from liver in terms of carbohydrate metabolism?

Ans) In Relation to Carbohydrate Metabolism, Muscle differs from the liver in three ways:

1. Myocytes do not have a place for glucagon to attach.

2. When there is a lot of cAMP, PKA does not phosphorylate the muscle isozyme of pyruvate kinase. This means that glycolysis does not stop.

3. In a "fight or flight" situation, epinephrine is released into the blood. When the concentration of cAMP goes up, PKA is turned on, and glycogen phosphorylase kinase is phosphorylated and turned on.

Q8) Write functions of pancreatic hormones.

Ans) The pancreas is a gland that is part of the digestive system. It is in the abdomen. It makes insulin and secretes fluid that helps break down food. Enzymes are digestive juices that the pancreas sends to the small intestine. It keeps breaking down food that has already left the stomach. The pancreas also makes the hormone insulin and sends it into the bloodstream. Insulin controls the amount of sugar or glucose in the body.

Problems with insulin control can cause secondary diabetes, and inflammation of the pancreas can cause pancreatitis. On the pancreas, both healthy and cancerous cells can grow. A healthy pancreas makes chemicals that help the body break down food. The exocrine tissues release a clear, watery, alkaline juice into the common bile duct and, eventually, the duodenum. This thing has several enzymes in it, which break food down into small molecules. The smaller molecules can then be taken in by the intestines. The Enzymes Include:

1. To break down proteins, trypsin and chymotrypsin are used.

2. Amylase is used to break down carbs.

3. Lipase breaks down fats into fatty acids and cholesterol.

Insulin and other hormones are released into the blood by the endocrine tissue. When the blood sugar level gets too high, beta cells in the pancreas release insulin. Insulin moves glucose from the blood into muscles and other tissues where it can be used as energy. Insulin also helps the liver take in glucose and store it as glycogen in case the body needs energy during times of stress or exercise. When the blood sugar level drops, alpha cells in the pancreas let out the hormone glucagon. The liver breaks down glycogen into glucose when glucagon is present. The glucose is then absorbed into the bloodstream, which brings the sugar levels back to normal.

Q9) (a) Explain the pathophysiology of following diseases:

(i) Addison’s disease

Ans) Addison's disease, which is caused by not making enough cortisol, is usually caused by atrophy of the adrenal cortex. This can happen when other parts of the cascade from the limbic system down do not work right. Steroids must be taken every day for the rest of the person's life. Addison's disease causes sodium loss, too much potassium in the blood, low blood pressure, low blood sugar, high levels of ACTH and MSH, and skin pigmentation from high levels of ACTH and/or MSH.

(ii) Osteoporosis

Ans) Osteoporosis is a classic example of a disease that has more than one cause. It is caused by a complex mix of genetic, internal, external, and lifestyle factors that interact with each other. Traditional pathophysiological models of postmenopausal osteoporosis often focused on endocrine mechanisms, such as oestrogen deficiency and secondary hyperparathyroidism in the elderly due to oestrogen deficiency, reduced dietary intake, and widespread vitamin D deficiency, as the main causes of the disease. In the last few years, though, it has become clear that the pathophysiological mechanisms that lead to osteoporosis are much more complicated than this.

Q9) (b) Expand the following terms and state their function:

(i) JAK

Ans) Cytokines are molecules that help keep immune responses in balance. One of the most interesting cytokine receptors is a protein that sticks together with a cytoplasmic tyrosine kinase called JAnus Kinase, or JAK for short.

(ii) STAT

Ans) The JAK-STAT signal pathway is a signal transduction pathway that is activated by cytokines and is involved in important biological processes like cell growth, differentiation, apoptosis, and immune regulation.

(iii) MAPK

Ans) Mitogen-activated protein kinases are protein Ser/Thr kinases that turn signals from outside the cell into a wide range of responses from the cell. MAPKs are one of the oldest signalling pathways, and they have been used in many ways throughout evolution.

(iv) PKB

Ans) Protein kinase B, also known as Akt, is a serine/threonine-specific protein kinase that is involved in many cellular processes that are important for cell survival, growth, proliferation, angiogenesis, migration, apoptosis, autophagy, and lipid and glycogen metabolism.

(v) EpoR

Ans) Erythropoietin and its receptor are important for erythroid progenitors to grow, change, and stay alive. Erythropoietin is a 165-amino-acid glycoprotein hormone that is made in the liver and kidneys of foetuses and adults in response to low oxygen levels to speed up the production of red blood cells. It is the main thing that controls erythropoiesis and helps erythroid progenitor cells live, grow, and change into mature cells.

Q10) Explain the role of second messengers in signal transduction.

Ans) Signal transduction, which is also called cell signalling, is the ability of a cell to change its behaviour in response to an interaction between a receptor and a ligand. The main message is sent by the ligand. When the molecule binds to the receptor, the target cell makes other molecules, called second messengers. The message is sent from one place to another by second messengers.

Hormones are made, go where they need to go, and attach to a receptor. Also, when the hormone binds to its receptor, an initial signal is sent, which leads to the final hormone action through a series of steps. For example, when you're stressed, your adrenal glands release epinephrine, which binds to receptors in your skeletal muscle. This breaks down glycogen and makes your body release glucose. Steps in the signal transduction process link the binding of epinephrine to a receptor to the breaking down of glycogen. There are two key mechanisms of signal transduction:

1. Transmission of signals by small molecules that diffuse through the cells, and

2. Transmission of signals by phosphorylation of proteins.

Second messengers are small molecules that can move around and are used to send messages. So, we can say that second messengers are small molecules that move quickly and send the first signals from cell-surface receptors to effector proteins. Second Messengers are categorized into four major classes:

1. Signalling cyclic nucleotides in the cytosol

2. Inside cell membranes, lipid messengers send and receive messages.

3. Ions that send signals inside and between different parts of a cell

There are gases and free radicals that can send signals to other parts of the cell and even to cells next to it.