Question

1. Identify examples of metabolic regulation and exactly what is regulated for each example. Your answer must include the 6 nutrient classes (20 points).

Answer 1

The six major class of nutrients include Carbohydrates, Fats, Proteins, Vitamins, Minerals and Water.

Carbohydrates : Molecules containing the basic structure as (CH2O)n.

These include Glucose, Fructose, Arabinose and so on.

Regulation of Glucose: Glucose levels in blood are regulated by mainly two pancreatic secretions Insulin and Glucagon. Where the insulin secreted by Beta-cells of pancreas induces the intake of blood glucose by the cells and proceed for glycolysis, the glucagon secreted by alpha cells of pancrease, induces the release glucose from glycogen stored in liver via glycogenolysis to increase the blood glucose level.

Molecule regulated: Blood glucose.

Fats: These are the fatty acids, (carboxylic acid) containing long aliphatic chains of carbon (either saturated or unsaturated). Examples: Palmitic acid, Linoleic acid and linolenic acid.

Metabolic regulation Regulation of palmitic acid: These are also used for obtaining energy, long chain fatty acids are carried by the carrier proteins to different cells requiring high energy. On entering cell, the enzyme fatty acid - CoA ligase catalyzes the formation of fatty acid adenylate fom fat and ATP which then reacts with Coenzyme A to give fatty -acyl CoA molecule. The synthesis of fatty acids are mainly regulated by the phosphorylation in mammals.

Molecule regulated : Acetyl CoA decarbylase

With the increase in plasma insulin levels dephosphorylation of the acetyl -CoA decarboxylase. Aetyl CoA is converted to Malonyl CoA and Carbohydrates converted to fats, Increase in plasma glucagon causes phosphorylationi of the enzyme leading to Beta oxidation of fatty acids producing ATP.

Proteins: Proteins are required for almost alll the processes inside the body. Having amino acids as their monomer units. Examples: Separase, Other ezyme proteins, Hormones (Adrenaline), Hemoglobin.

Regulation of Separase: Separase is a protein important for the metaphase anaphase transition in the M phase of cell cycle. These are regulated by Cyclin dependent kinases (another enzyme protein), that phosphorylate separase-securin comlplex thus activating them. After the anaphase transition these are dephosphorylated by phosphatase enzymes.

Molecule regulated: Separase.

Vitamins: Vitamins are the molecules which are essential for providing immunity and serve as key factors in many processes. And these are required in appropriate quantities, neither high nor low. Examples: Vitamin A, Vitamin B, Vitamin C, Vitamin K.

Regulation of Vitamin A: Vitamin A is chemically Beta-carotene, which are significant in the synthesis of rhodopsin (pigment protein) in the eye. Vitamin A is regulated by its conversion into retinoids by the action of dioxygenase enzyme, Thus, its level remains constant. In general it does not exceed in the concentration, whatever the high amounts we intake. People with defective lipoxygenase due to retinal endothelial apoptosis, should not intake highe Vitamin A quntities.

Molecule regulated: Beta-carotene.

Minerals: These are the metal ions responsible for the signal transmission and maintaining the electrode potentials of cells.

Some of minerals are Calcium, Iron, Sodium Potassium

Regulation of Iron inside cells: If a cell lacks Fe2+ Iron Response-element protein (Irp I) binds to the sequences of genes containing the Iron Response Elements of transferrin receptor That increase the iron concentration in cells. On the other hand if the Fe2+ concentrationn is too high inside the cells Iron Response element protein becomes inactive and does not bind to the Iron response elements of the genes.

Regulated molecule : Transferrin (glycoprotein).

Water: Water is an essential component of body, About 70% of our body is water. Regulated by the hypothalamus, which creates a sensation of thirst. The osmoreceptors present in the hypothalamus , a sensory receptor that determines any osmotic changes occuring and induces hypothalamus to secrete antidiuretic hormone causing a feeling of thirst.

Regulated moleule: ADH (Antidiuretic hormone).