Cori Cycle

The Cori Cycle operates during exercise, when aerobic metabolism in muscle cannot keep up with energy needs.

For a brief burst of ATP utilization, muscle cells utilize ~P stored as phosphocreatine. For more extended exercise, ATP is mainly provided by Glycolysis.

Lactate, produced from pyruvate, passes via the blood to the liver where it is converted to glucose. The glucose may travel back to the muscle to fuel Glycolysis.

The Cori Cycle costs 6 P in liver for every 2P made available in muscle. The net cost is 4 P Although costly in terms of "high energy" bonds, the Cori Cycle allows the organism to accommodate to large fluctuations in energy needs of skeletal muscle between rest and exercise.

COPPER

The normal serum level of copper is 25 to 50 mg/dl.

Functions of copper

(a) Copper is necessary for iron absorption and incorporation of iron into hemoglobin.

(b) It is very essential for tyrosinase activity

(c) It is the co-factor for vitamin C requiring hydroxylation

(d) Copper increases the level of high density lipo protein and protects the heart.

Wilson’s disease

In case of Wilson’s disease ceruloplasmin level in blood is drastically reduced.

Wilson’s disease leads to

(i) Accumulation of copper in liver leads to hepatocellular degeneration and cirrhosis

(ii) Deposition of copper in brain basal ganglia leads to leticular degeneration

(iii) Copper deposits as green pigmented ring around cornea and the condition is called as Kayser-Kleischer ring

Over accumulation of copper can be treated by consumption of diet containg low copper and injection of D-penicillamine, which excretes copper through urine.

Menke’s kidney hair syndrome

 It is X-linked defect. In this condition copper is absorbed by GI tract, but cannot be transported to blood. The defect in transport of copper to blood is due to absence of an intracellular copper binding ATPase.

Vitamin B6: Pyridoxine, Pyridoxal, Pyridoxamine

Aids  in protein metabolism and red blood cell formation. It is also involved in the body’s production of chemicals such as insulin and hemoglobin.

Vitamin B6 Deficiency Deficiency symptoms include skin disorders, dermatitis, cracks at corners of mouth, anemia, kidney stones, and nausea. A vitamin B6 deficiency in infants can cause mental confusion.

By rearranging the above equation we arrive at the Henderson-Hasselbalch equation:

pH = pK_a + log[A^-]/[HA]

It should be obvious now that the pH of a solution of any acid (for which the equilibrium constant is known, and there are numerous tables with this information) can be calculated knowing the concentration of the acid, HA, and its conjugate base [A^-].

At the point of the dissociation where the concentration of the conjugate base [A^-] = to that of the acid [HA]:

pH = pK_a + log[1]

The log of 1 = 0. Thus, at the mid-point of a titration of a weak acid:

pK_a = pH

In other words, the term pK_a is that pH at which an equivalent distribution of acid and conjugate base (or base and conjugate acid) exists in solution.

- There are two important phospholipids, Phosphatidylcholine and Phosphatidylserine found the cell membrane without which cell cannot function normally.

- Phospholipids are also important for optimal brain health as they found the cell membrane of brain cells also which help them to communicate and influence the receptors function. That is the reason food stuff which is rich in phospholipids like soy, eggs and the brain tissue of animals are good for healthy and smart brain.

- Phospholipids are the main component of cell membrane or plasma membrane. The bilayer of phospholipid molecules determine the transition of minerals, nutrients, and drugs in and out of the cell and affect various functions of them.

- As phospholipids are main component of all cell membrane, they influence a number of organs and tissues, such as the heart, blood cells and the immune system. As we grown up the amount of phospholipids decreases and reaches to decline.

- Phospholipids present in cell membrane provide cell permeability and flexibility with various substances as well its ability to move fluently. The arrangement of phospholipid molecules in lipid bilayer prevent amino acids, carbohydrates, nucleic acids, and proteins from moving across the membrane by diffusion. The lipid bi-layer is usually help to prevent adjacent molecules from sticking to each other.

- The selectivity of cell membrane form certain substances are due to the presence of hydrophobic and hydrophilic part molecules and their arrangement in bilayer. This bilayer is also maintained the normal pH of cell to keeps it functioning properly.

- Phospholipids are also useful in the treatment of memory problem associated with chronic substances as they improve the ability of organism to adapt the chronic stress.

General structure of amino acids

• All organisms use same 20 amino acids.
• Variation in order of amino acids in polypeptides allow limitless variation.
• All amino acids made up of a chiral carbon attached to 4 different groups      

 - hydrogen
 - amino group
 - carboxyl
 - R group: varies between different amino acids

• Two stereoisomers (mirror images of one another) can exist for each amino acid. Such stereoisomers are called enantiomers. All amino acids found in proteins are in the L configuration.
• Amino acids are zwitterions at physiological pH 7.4. ( i.e. dipolar ions). Some side chains can also be ionized

Structures of the 20 common amino acids

• Side chains of the 20 amino acids vary. Properties of side chains greatly influence overall conformation of protein. E.g. hydrophobic side chains in water-soluble proteins fold into interior of protein
• Some side chains are nonpolar (hydrophobic), others are polar or ionizable at physiological pH (hydrophilic).
• Side chains fall into several chemical classes: aliphatic, aromatic, sulfur-containing, alcohols, bases, acids, and amides. Also catagorized as to hydrophobic vs hydrophilic.
• Must know 3-letter code for each amino acid.

Aliphatic R Groups

• Glycine: least complex structure. Not chiral. Side chain small enough to fit into niches too small for other amino acids.
• Alanine, Valine, Leucine, Isoleucine
  • no reactive functional groups      
  • highly hydrophobic: play important role in maintaining 3-D structures of proteins because of their tendency to cluster away from water
• Proline has cyclic side chain called a pyrolidine ring. Restricts geometry of polypeptides, sometimes introducing abrupt changes in direction of polypeptide chain.

Aromatic R Groups

• Phenylalanine, Tyrosine, Tryptophan
  • Phe has benzene ring therefore hydrophobic.  
  • Tyr and Trp have side chains with polar groups, therefore less hydrophobic than Phe.
  • Absorb UV  280 nm. Therefore used to estimate concentration of proteins.

Sulfur-containing R Groups

• Methionine and Cysteine)
  • Met is hydrophobic. Sulfur atom is nucleophilic.
  • Cys somewhat hydrophobic. Highly reactive. Form disulfide bridges and may stabilize 3-D structure of proteins by cross-linking Cys residues in peptide chains.

Side Chains with Alcohol Groups

• Serine and Threonine
  • have uncharged polar side chains. Alcohol groups give hydrophilic character.
  • weakly ionizable.

Basic R Groups

• Histidine, Lysine, and Arginine.
  • have hydrophilic side chains that are nitrogenous bases and positively charged at physiological pH.
  • Arg is most basic a.a., and contribute positive charges to proteins.

Acidic R Groups and their Amide derivatives

• Aspartate, Glutamate
  • are dicarboxylic acids, ionizable at physiological pH. Confer a negative charge on proteins.
• Asparagine, Glutamine
  • amides of Asp and Glu rspectively
  • highly polar and often found on surface of proteins
  • polar amide groups can form H-bonds with atoms in other amino acids with polar side chains.