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

Are the phloem and the xylem made of living cells, Are the phloem and the x...

Are the phloem and the xylem made of living cells? The cells of phloem are living cells and the cells that constitute the xylem ducts are dead cells killed by the lignin deposi

Define impediments and recommendations to infuse biology, Define Impediment...

Define Impediments and Recommendations to Infuse Biology? As has been illustrated in this report, there are compelling instances demonstrating the value of and needs for concer

Urine examination of the diabetes patient, Q. Urine Examination of the diab...

Q. Urine Examination of the diabetes Patient? Generally when blood testing facilities are not available, urine is tested for the presence of sugar. A urine sample shows presenc

How all the exercises are active exercises, How All these exercises are act...

How All these exercises are active exercises All these exercises are active exercises that is active exercises are those type of physical activities carried out by the individ

Explain the urinary system in human body, Explain the Urinary System in hum...

Explain the Urinary System in human body? The urinary system removes the waste materials produced as a result of all the metabolic process required to sustain life. The process

What is st depression with long diastolic filling, Q. What is ST Depression...

Q. What is ST Depression with Long Diastolic Filling? For the person with a slow heart rate and a long period of a diastole after a premature ventricular contraction, the next

Diagram, #questioi want clarius diagramn..

#questioi want clarius diagramn..

Define unsafe water and sanitation - public nutrition, Define Unsafe Water ...

Define Unsafe Water and sanitation - public nutrition? Safe water and sanitation may seem tenuous in their link to food security but their impact is unquestionable. With 19% US

Inheritence, What is inheritence and what is the relation between mendel an...

What is inheritence and what is the relation between mendel and darwin?

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