Gluconeogenesis

It is the process by which Glucose or glycogen is formed from non carbohydrate substances.

Gluconeogenesis occurs mainly in liver.

Gluconeogenesis inputs:  
The source of pyruvate and oxaloacetate for gluconeogenesis during fasting or carbohydrate starvation is mainly amino acid catabolism. Some amino acids are catabolized to pyruvate, oxaloacetate, Muscle proteins may break down to supply amino acids. These are transported to liver where they are deaminated and converted to gluconeogenesis inputs. 
Glycerol, derived from hydrolysis of triacylglycerols in fat cells, is also a significant input to gluconeogenesis

Glycolysis & Gluconeogenesis pathways are both spontaneous If both pathways were simultaneously active within a cell it would constitute a "futile cycle" that would waste energy

Glycolysis yields 2~P bonds of ATP.
Gluconeogenesis expends 6~P  bonds of ATP and GTP.
A futile cycle consisting of both pathways would waste 4 P.bonds per cycle.To prevent this waste, Glycolysis and Gluconeogenesis pathways are reciprocally regulated.

CLASSIFICATION OF ENZYMES

1. Oxidoreductases : Act on many chemical groupings to add or remove hydrogen atoms. e.g. Lactate dehydrogenase

2. Transferases Transfer functional groups between donor and acceptor molecules. Kinases are specialized transferases that regulate metabolism by transferring phosphate from ATP to other molecules. e.g. Aminotransferase.

3. Hydrolases Add water across a bond, hydrolyzing it. E.g. Acetyl choline esterase

4. Lyases Add water, ammonia or carbon dioxide across double bonds, or remove these elements to produce double bonds. e.g. Aldolase.

5. Isomerases Carry out many kinds of isomerization: L to D isomerizations, mutase reactions (shifts of chemical groups) and others. e.g. Triose phosphate isomerase

6. Ligases Catalyze reactions in which two chemical groups are joined (or ligated) with the use of energy from ATP. e.g. Acetyl CoA carboxylase

K_eq, K_w and pH

As H₂O is the medium of biological systems one must consider the role of this molecule in the dissociation of ions from biological molecules. Water is essentially a neutral molecule but will ionize to a small degree. This can be described by a simple equilibrium equation:

H₂O <-------> H⁺ + OH^-

This equilibrium can be calculated as for any reaction:

K_eq = [H⁺][OH^-]/[H₂O]

Since the concentration of H₂O is very high (55.5M) relative to that of the [H⁺] and [OH^-], consideration of it is generally removed from the equation by multiplying both sides by 55.5 yielding a new term, K_w:

K_w = [H⁺][OH^-]

This term is referred to as the ion product. In pure water, to which no acids or bases have been added:

K_w = 1 x 10^-14 M²

As K_w is constant, if one considers the case of pure water to which no acids or bases have been added:

[H⁺] = [OH^-] = 1 x 10^-7 M

This term can be reduced to reflect the hydrogen ion concentration of any solution. This is termed the pH, where:

pH = -log[H⁺]

FAT-SOLUBLE VITAMINS

The fat-soluble vitamins, A, D, E, and K, are stored in the body for long periods of time and generally pose a greater risk for toxicity when consumed in excess than water-soluble vitamins.

VITAMIN A: RETINOL

 Vitamin A, also called retinol, has many functions in the body. In addition to helping the eyes adjust to light changes, vitamin A plays an important role in bone growth, tooth development, reproduction, cell division, gene expression, and regulation of the immune system.

The skin, eyes, and mucous membranes of the mouth, nose, throat and lungs depend on vitamin A to remain moist. Vitamin A is also an important antioxidant that may play a role in the prevention of certain cancers.

One RAE equals 1 mcg of retinol or 12 mcg of beta-carotene. The Recommended Dietary Allowance (RDA) for vitamin A is 900 mcg/ day for adult males and 700 mcg/ day for adult females.

Vitamin A Deficiency

Vitamin A deficiency is rare, but the disease that results is known as xerophthalmia.

Other signs of possible vitamin A deficiency include decreased resistance to infections, faulty tooth development, and slower bone growth.

Vitamin A toxicity The Tolerable Upper Intake Level (UL) for adults is 3,000 mcg RAE.

VITAMIN D

Vitamin D plays a critical role in the body’s use of calcium and phosphorous. It works by increasing the amount of calcium absorbed from the small intestine, helping to form and maintain bones.

Vitamin D benefits the body by playing a role in immunity and controlling cell growth. Children especially need adequate amounts of vitamin D to develop strong bones and healthy teeth.

RDA  From 12 months to age fifty, the RDA is set at 15 mcg.

20 mcg of cholecalciferol equals 800 International Units (IU), which is the recommendation for maintenance of healthy bone for adults over fifty.

Vitamin D Deficiency

Symptoms of vitamin D deficiency in growing children include rickets (long, soft bowed legs) and flattening of the back of the skull. Vitamin D deficiency in adults may result in osteomalacia (muscle and bone weakness), and osteoporosis (loss of bone mass).

Vitamin D toxicity

The Tolerable Upper Intake Level (UL) for vitamin D is set at 100 mcg for people 9 years of age and older. High doses of vitamin D supplements coupled with large amounts of fortified foods may cause accumulations in the liver and produce signs of poisoning.

VITAMIN E: TOCOPHEROL

Vitamin E benefits the body by acting as an antioxidant, and protecting vitamins A and C, red blood cells, and essential fatty acids from destruction.

RDA  One milligram of alpha-tocopherol equals to 1.5 International Units (IU). RDA guidelines state that males and females over the age of 14 should receive 15 mcg of alpha-tocopherol per day.

Vitamin E Deficiency Vitamin E deficiency is rare. Cases of vitamin E deficiency usually only occur in premature infants and in those unable to absorb fats.

VITAMIN K

Vitamin K is naturally produced by the bacteria in the intestines, and plays an essential role in normal blood clotting, promoting bone health, and helping to produce proteins for blood, bones, and kidneys.

RDA

Males and females age 14 - 18: 75 mcg/day; Males and females age 19 and older: 90 mcg/day

Vitamin K Deficiency

Hemorrhage can occur due to sufficient amounts of vitamin K.

Vitamin K deficiency may appear in infants or in people who take anticoagulants, such as Coumadin (warfarin), or antibiotic drugs.

Newborn babies lack the intestinal bacteria to produce vitamin K and need a supplement for the first week.

The Hemoglobin Buffer Systems

These buffer systems are involved in buffering CO₂ inside erythrocytes. The buffering capacity of hemoglobin depends on its oxygenation and deoxygenation. Inside the erythrocytes, CO₂ combines with H₂O to form carbonic acid (H₂CO₃) under the action of carbonic anhydrase.

At the blood pH 7.4, H₂CO₃ dissociates into H⁺ and HCO₃ ⁻ and needs immediate buffering.

Function of Calcium

The major functions of calcium are

(a) Excitation and contraction of muscle fibres needs calcium. The active transport system utilizing calcium binding protein is called Calsequestrin. Calcium decreases neuromuscular irritability.
(b) Calcium is necessary for transmission of nerve impulse from presynaptic to postsynaptic region.
(c) Calcium is used as second messenger in system involving protein and inositol triphosphate.
(d) Secretion of insulin, parathyroid hormone, calcium etc, from the cells requires calcium.
(e) Calcium decrease the passage of serum through capillaries thus, calcium is clinically used  to reduce allergic exudates.
(f) Calcium is also required for coagulation factors such as prothrombin.
(g) Calcium prolongs systole.
(h) Bone and teeth contains bulk quantity of calcium.