solid phase - A protein has a constant solubility regardless of the amount of substance present in the?

salting effect - Low concentration of neutral salts increases the solubility of proteins

salting out effect - high concentrations causes precipitation of proteins

isoelectric point - Proteins are most soluble at a pH above or below their?

Organic acids - are more effective than the mineral acids in liberating the amino group from its amides

ALKALIS: NaOH, KOH and Ba(OH)2 - cause very rapid and complete hydrolysis but they bring about decomposition, especially the deamination of certain amino acids.

Pepsin - hydrolyzes proteins to proteoses, peptones and polypeptides only.

Trypsin and ereptic enzymes - hydrolyze proteins into aminoacids but the process is slow and incomplete.

Precipitation of protein molecules - refers to the settling of insoluble, solid particles of these substances in a solution. Proteins are precipitated by the following agents:

free amino groups - Proteins react with acids because of their?

alkaloidal reagents - The acids which precipitate the proteins are called ______ because they precipitate many of the alkaloids.

proteinates - The metals unite with the carboxyl group, thus forming?

Dilute or aqueous solutions - What alcohol reduces the solubility of the proteins due to an increase in the electrical forces between charged particles in solutions?

denaturation - When proteins are heated, they undergo slight intermolecular rearrangement, giving rise to changes in the chemical, physical and biological properties.

COAGULATION – is the clumping of the dispersed chains of denatured proteins into a solid mass that is hard to dissolve.

FLOCCULATION – the denatured protein is rendered soluble at its isoelectric point but can be redissolved by adjustment of the pH.

Denaturation - is the alteration of a protein structure through some form of external stress in such a way that it will no longer be able to carry out its cellular function.

In quaternary structure denaturation - protein sub-units are dissociated and/or the spatial arrangement of protein subunits is disrupted.

Covalent interactions - interactions between amino acid side chains (such as disulfide bridges between cysteine groups)

Non-covalent dipole-dipole interactions – interactions between polar amino acid side chains (and the surrounding solvent)

Van der Waals (induced dipole) interactions – interactions  between non-polar amino acid side chains.

secondary structure denaturation - proteins lose all regular repeating patterns such as alpha-helixes and betapleated sheets, and adopt a random coil configuration.

Primary structure – this substances such as the sequence of amino acids held together by covalent peptide bonds, is not disrupted by denaturation.

50   0C - Most proteins become denatured when heated above?.

globulins present in the lens - Clouding of the lens of the eye in old-age cataract is probably due to denaturating of the?. Light - Change of fibrinogen to fibrin in blood clotting may be partly due to?

agitation, trituration, surface action and high pressure - Most globular proteins are denatured by mechanical methods or forces like?

gastric juice - Digestion of proteins begins in the stomach by the secretion of?

HYDROCHLORIC ACID – acid secreted by the parietal cells

HYDROCHLORIC ACID - used to kill some bacteria and to denature proteins, making them more susceptible to subsequent hydrolysis by proteases.

PEPSIN – an acid stable endopeptidase secreted by the serous cells as an inactive zymogen, pepsinogen, that is activated by HCl or autocatalytically by other pepsin molecules.

serous cells – pepsin is secreted by?

Pepsin - breaks down and releases peptides and a few free amino acids from dietary proteins.

TRYPSIN – secreted as trypsinogen then activated by enteropeptidase, an enzyme synthesized by the intestinal mucosal cells otherwise known as enterokinase. It hydrolyzes the polypeptide chain from the carboxyl end of arginine and lysine. Trypsin also plays as the common activator of all pancreatic zymogens.

TRYPSIN – secreted as trypsinogen

Enteropeptidase - an enzyme synthesized by the intestinal mucosal cells otherwise known as enterokinase.

Enteropeptidase - otherwise known as enterokinase

TRYPSIN - It hydrolyzes the polypeptide chain from the carboxyl end of arginine and lysine

CHYMOTRYPSIN – secreted as chymotrypsinogen and is activated by trypsin molecules.

CHYMOTRYPSIN - It hydrolyzes the polypeptide chain from the carboxyl end of tryptophan, tyrosine, phenylalanine, methionine and leucine.

ELASTASE – secreted as proelastase and is activated by trypsin molecules.

ELASTASE - It hydrolyzes the polypeptide chain from the carboxyl end of alanine, glycine and serine.

CARBOXYPEPTIDASE A – secreted as procarboxypeptidase A and is activated by trypsin molecules.

CARBOXYPEPTIDASE A - It hydrolyzes the polypeptide chain from the carboxyl end of alanine, isoleucine, leucine and valine.

CARBOXYPEPTIDASE B – secreted as procarboxypeptidase B and is activated by trypsin molecules.

CARBOXYPEPTIDASE B - It hydrolyzes the polypeptide chain from the carboxyl end of arginine and lysine, similar to trypsin.

aminopeptidase - The luminal surface of the small intestines contains?

Aminopeptidase - an exopeptidase that repeatedly cleaves the N-terminal residue from oligopeptides to produce free amino acids and smaller peptides.

portal circulation - These amino acids are absorbed mainly in the small intestines through the?

active transport - Amino acids enter the cells by? 30 to 50 minutes -The absorption of amino acids is very rapid so that the maximum concentration in the blood is attained ______after eating.

4 8 mg per 100 ml -  the amino acid nitrogen level is kept more or less constant between _________of blood plasma.

NITROGEN BALANCE OR EQUILIBRIUM – occurs when protein intake is equal or about the same as the protein breakdown.

NITROGEN BALANCE OR EQUILIBRIUM – This condition is typified by young adults whose protein intake is just enough to replace the daily amount of protein used.

POSITIVE NITROGEN BALANCE – implies a net gain of protein in the body.

POSITIVE NITROGEN BALANCE – This is found whenever new tissues are being synthesized as in growth stage, convalescence and pregnancy. In here, protein intake exceeds protein output.

NEGATIVE NITROGEN BALANCE – implies greater protein utilization than protein intake, causing loss of protein from the body. This state is found in:

KWASHIORKOR disease – type of malnutrition usually in children due to the inadequate intake of protein

MARASMUS - a gradual wasting away of the body, generally associated with severe malnutrition or inadequate absorption of protein and occurring mainly in young children

TISSUE PROTEINS - including enzymes and hormones. The amino acids pass into systemic blood to the different organs and are used as building blocks for the synthesis of tissue proteins.

PLASMA PROTEINS - like plasma albumin, globulin, and fibrinogen where the liver is the primary site for their biosynthesis

LABILE PROTEINS - that is important for the optimal structure and function of some important organs like liver, intestines and kidneys

The alpha-amino groups from amino acids - are the precursors in the biosynthesis of purine and pyrimidine bases of the nucleotides, porphyrins, creatine, neurotransmitters and other nitrogenous compounds

DECARBOXYLATION – refers to the removal of the carboxyl group of the amino acid for the formation of a physiologic active amine by the aid of a decarboxylase enzyme.

decarboxylase enzyme - DECARBOXYLATION refers to the removal of the carboxyl group of the amino acid for the formation of a physiologic active amine by the aid of?

TRANSAMINATION – refers to the removal of the amino group that begins with the transfer of this amino group to an amino group acceptor, usually alpha-ketoglutarate that eventually turns into glutamate.

TRANSAMINATION - This reaction is catalyzed by a transaminase.

alpha – keto acid or a carbon skeleton - After transamination, the amino acid turns into an?

alpha – keto acid or a carbon skeleton - It turns into acetyl-coA, pyruvate or other intermediates and is oxidized to produce biochemical energy (ATP) via the Kreb’s cycle with the release of carbon dioxide and water.

alpha – keto acid or a carbon skeleton - It is converted into a carbohydrate or fat molecule

alpha – keto acid or a carbon skeleton - It is reaminated to form amino acids

OXIDATIVE DEAMINATION – once the amino groups have all been collected in the form of glutamate, this substance undergoes oxidative deamination to reform alpha-ketoglutarate and release ammonia.

ammonia - It is utilized for the synthesis of non-protein nitrogenous compounds

ammonia - It enters the ornithine cycle for the formation of urea

ammonia - It is detoxified for the synthesis of glutamine

Ketogenic amino acids - are amino acids whose catabolism yields either acetoacetate or one of its precursors, acetyl CoA or acetoacetyl CoA. Leucine and lysine are the only exclusively ketogenic amino acids found in proteins.

B. GLUCOGENIC AMINO ACIDS

Glucogenic amino acids - are amino acids whose catabolism yields pyruvate or one of the intermediates of the citric acid cycle.

Glucogenic amino acids - These intermediates are substrates for gluconeogenesis and therefore can give rise to the net formation of glycogen in liver and muscle.

PHENYLKETONURIA / PHENYLPYRUVIC OLIGOPHRENIA – due to the absence of the enzyme phenylalanine hydroxylase which converts phenylalanine to tyrosine.

PHENYLKETONURIA / PHENYLPYRUVIC OLIGOPHRENIA - Phenylalanine is instead converted into phenylpyruvic acid which impairs normal development of child’s brain leading to mental retardation.

phenylalanine hydroxylase - converts phenylalanine to tyrosine

TYROSINOSIS – due to the absence of hydroxyphenylpyruvic acid oxidase. I

TYROSINOSIS - In here, hydroxyphenylpyruvic acid is not oxidized into homogentesic acid.

ALKAPTONURIA – due to the absence of homogentisic acid oxygenase. Vitamin C (Ascorbic acid) is needed for the activity of the enzyme.

ALKAPTONURIA - When the urine containing homogentesic acid is exposed to the atmosphere, it turns black due to oxidation.

ochronosis - abnormal pigmentation of cartilages, fibrous tissues and tendons

homogentisic acid oxygenase - an iron containing enzyme which catalyzes the oxidation of homogentisic acid to fumarate and acetate

ALBINISM – due to the absence of the enzyme tyrosinase. which converts tyrosine into DOPA (L-3,4dihydroxyphenylalanine) convertible to melanin.

Tyrosinase - converts tyrosine into DOPA (L-3,4dihydroxyphenylalanine) convertible to melanin.