Define proteins as enzymes, Biology

Assignment Help:

Define Proteins as Enzymes?

From conception to death, living cells use oxygen and metabolize fuel. Cells synthesize new products, degrade others, and generally are in a state of metabolic flux. For these processes to occur, catalysts are needed to enhance each of the many thousands of reactions occulring in the cell. These catalysts called 'enzyrnes' are proteins. Enzymes make up the largest and the most specialized class of proteins. Each enzyme is unique and catalyzes a specific kind of reaction. In the cell, enzymes are found in cellular compartments (cytoplasm, nucleus, mitochondria, etc.), as well as, the membranes within and around the cell wall. The location of an enzyme is one of its characteristics and dictates, in part, its role in metabolism. Many enzymes are complex proteins; they consist of a protein component and a prosthetic group. The protein part is called apoenzyme and the prosthetic group, 'coenzyme' as illustrated in Figure

1788_Proteins as enzymes 1.png

Figure: Holoenzyme

Enzymes consist of specific sequences of amino acids. The catalytic function of an enzyme is intimately related to its amino acid sequence. Enzymes must possess a shape that will complement the reactive molecular shape of the substrate in the same way as a key fits into a lock. This is commonly referred to as 'lock and key mechanism'. This shape is a function of the enzyme protein's primary, secondary, tertiary and quaternary structure. In the same way, substrates should also have specific shapes in order to be catalyzed by their respective enzymes.

39_Proteins as enzymes 2.png

This is the reason why only D-sugars or L-amino acids can be metabolized by mammalian cells. These stereoisomers conform to the shape required by the enzyme which serves as its catalyst. While enzymes show absolute specificity, the specificity generally applies to the entire molecule. If however the substrate is large and complex, the structural requirements are less stringent in that only that part of the substrate involved in the enzyme-substrate complex should have the appropriate molecular arrangement. The portion of the substrate not involved in the reaction need not be the appropriate conformation. Some enzymes are specific for only one substrate; others may catalyze several related reactions. While some are specific for a particular substrate, others are specific for certain bonds. This is called 'group specificity'. For example, glycosidases act on glycosides, pepsin and trypsin act on peptide bonds and esterases act on ester linkages. Within this group, certain enzymes exhibit greater specificity. Chymotrypsin preferentially acts on peptide bonds in which the carboxyl group is a part of the aromatic amino acids (phenylalanine, tyrosine or tryptophan). Enzymes such as carboxypeptidase catalyzk the hydrolysis of the carboxy-terminal or amino-terminal amino acid of a polypeptide chain. This bond specificity, rather than molecular specificity, is useful to the animal in that it reduces the number of enzymes needed within the organism. Incidentally, the above enzymes are very useful to the protein chemist in his 1 her determination of the amino acid sequence of a given protein. Cells synthesize enzymes in much the same fashion as they synthesize other proteins; yet enzymes are relatively short lived. Cells must continually synthesize their enzymes if they are to survive. So, we have looked at the functions of proteins as enzymes. Proteins also function as carriers in the body.


Related Discussions:- Define proteins as enzymes

State the success which signifies optimum health, Success which signifies O...

Success which signifies Optimum Health The features or clinical conditions which are representative of this group are: i) No pain or tenderness in the implant upon function.

Useful products that can be obtained by genetic engineering, Name three use...

Name three useful products that can be obtained by genetic engineering. Useful products of genetic engineering are:- A) chymosin, B) Alpha-anti-trypsin, C) hepatitis

How sugar is used in icings, How sugar is used in Icings? Sugars provid...

How sugar is used in Icings? Sugars provide sweetness, flavor, bulk and structure to icings and frostings. In addition to sweetness and flavor, icings also function as a barrie

Etiological factor of lactose intolerance, Q. Etiological factor of lactose...

Q. Etiological factor of lactose intolerance? These diseases are referred to as idiopathic (cause unknown) and though the possible mechanism suggested includes genetic factors,

Dealcoholism, DEALCOHOLISM - Treatment of alcoholism or withdrawal s...

DEALCOHOLISM - Treatment of alcoholism or withdrawal symptoms of alcohol is known as dealcoholism. Recovery from alcohol dependence is greatly aided by sociobehavioural c

Determination of erythrocyte transketolase (etk) activity, Determination of...

Determination of Erythrocyte Transketolase (ETK) Activity? The enzyme transketolase requires TPP for its activity, for the metabolism of pentose phosphate sugars as described u

Light microscopy, LIGHT MICROSCOPY (LM) A study of the structure of organ...

LIGHT MICROSCOPY (LM) A study of the structure of organisms is an essential requirement of biology. However, unaided human eye cannot see objects smaller than 0.1 mrn(100 p) in d

Determine about the adequacy of children''s food, Determine the Adequacy of...

Determine the Adequacy of children's food? Adequacy of children's food and nutrient intake depends on: Sibling company Peer pressure Model set by parents and

Study of phylems, iwant to know all about phylem protozoa?

iwant to know all about phylem protozoa?

Compare & contrast replication, Compare and contrast replication, transcrip...

Compare and contrast replication, transcription, and translation based on the following criteria.   Criteria Replication Transcription

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd