Author Box
Articles Categories
All Categories
Articles Resources

Biology Review: Proteins and Enzymes

March 12, 2012 | Comments: 0 | Views: 188


Proteins are long chains of amino acids joined by peptide bonds that fold up into complex three-dimensional structures.

The functions of proteins are so diverse and important that almost every function of every living organism depends on proteins.

This helps explain why evolutionary biologists tend to believe that protein synthesis preceded the evolution of the first cells.

In cells, proteins account for about half of the dry mass.

Proteins are used in facilitating chemical processes, structural support, transport, communication, movement, and defense against harmful substances.

As enzymes, proteins catalyze chemical reactions and are essentially the engines of life.

Proteins are extraordinarily diverse in both function and structure. Form indeed follows function as proteins have very complex three-dimensional structures that determine which substrates it affects and what it does.

They are made up of amino acid chains held together by peptide chains. Thus, they are made up of polypeptide chains.

Each polypeptide chain has an amino end (N-terminus) and a carboxyl end (C-terminus). Jutting out from the polypeptide backbone are side groups that are important in forming the structure of the protein.

Peptide Bonds

These are covalent bonds formed by dehydration synthesis between the carboxyl group of one molecule and the amino group of the other molecule.

As with all bonds made by dehydration synthesis, a water molecule is produced.


Enzymes are macromolecules that are most often proteins but can also be RNA enzymes.

The main functions of enzymes are to speed up the rate of chemical reactions and lower the activation energy needed for those reactions to happen. In doing so, the enzyme is not consumed in the process but can be reused over and over again.

Although spontaneous chemical reactions can take place without enzymes, their speed may be far too slow to allow life to function. A process that may take years might only take seconds with the help of an enzyme.

Activation Energy Barrier

When chemical reactions happen, bonds are always broken and made.

In order to get to the point where bonds can be broken and the chemical reaction started, energy must first be invested.

This requirement is usually met by absorbing heat from the surrounding environment. When absorbed, the reactants reach their energy summit called the transition state, where they are unstable and their bonds can be broken.

However, without the help of enzymes, the amount of energy needed to start the reactions may only happen sporadically and thus slow down the rate at which cycles of the reactions happen.

How Enzymes Lower This Requirement

Proteins catalyze reactions by lowering the energy investment needed so that the reactions can take place even at room temperature.

Since proteins are specific to certain substrates and can be turned on and off, this allows cells to exactly control their metabolism.

This is better than simply heating up the organism because that might kill off the cells and it speeds up all reactions indiscriminately.

Enzymes bind the substrate they are matched for in their active site and work to orientate the substrate correctly, stabilize the transition state, stress the substrates, and help directly in the reaction.

All of these actions lower the activation energy needed for the reaction to happen.

Enzymes work extremely fast: A single enzyme usually works through a thousand substrate molecules per second, with some enzymes being much faster.

Since enzymes are unharmed and unaltered through each cycle, a small number of enzymes can greatly catalyze chemical reactions.

For more high school AP Biology review:

AP biology

For more about proteins and enzymes:

Proteins and enzymes

Source: EzineArticles
Was this Helpful ?

Rate this Article

Article Tags:





Organic Chemistry




High School Biology


Activation Energy

For gaining entrance in coveted fields in a reputed University, the entrance examinations are the gateway. The purpose of these entrance examinations is to test the potential of a candidate and how

By: Sarkariexam l Reference & Education > Science l December 23, 2012 lViews: 521

Competition is increasing at an alarming level in every sphere. The students have to focus completely on their studies to ensure that they get admission in the line of their choice. What more, the

By: Sarkariexam l Reference & Education > Continuing Education l December 14, 2012 lViews: 1443

'How hard is a PhD'? Many PhD holders have been asked this question millions of times, but there is never any definite answer. We look at those who walk around proudly with a 'Doctor' title with

By: onlineedublog l Reference & Education > Continuing Education l November 11, 2012 lViews: 284

In this fast paced world which is sadly recession struck, it is indeed a good idea to work while acquiring further education. A master’s degree is obviously better than a bachelor’s in almost

By: onlineedublog l Reference & Education > Online Education l November 04, 2012 lViews: 262

An Online Degree Program in Finance is gaining popularity as it helps students to develop a lucrative career. It helps in a competitive business world. This has resulted in more number of students

By: Matthew l Reference & Education > Online Education l October 31, 2012 lViews: 288

Supporting justice is one of the reasons many people get into a career in the legal field. All-inclusive Online Associate’s Degree in Legal Studies assists many in the beginning stage of employment

By: Richard l Reference & Education > Online Education l October 26, 2012 lViews: 222

It seems that we have been able to decipher the DNA of a woolly mammoth which has been extinct for over 25,000 years or some say 12,000, while others 40,000. Whatever the time frame, that's pretty

By: Lance Winslowl Reference & Education > Biologyl June 14, 2012 lViews: 219

Well, the human brain is an incredible organic device. It is amazing what it can do on very little energy. Your laptop at home may use as much as 9 Amps, and if you were to convert that to calories

By: Lance Winslowl Reference & Education > Biologyl June 14, 2012 lViews: 245

The other day, there was a very interesting medical video about how the human brain grows and forms, how the cells divide, and how it becomes what it is, capable of doing the miraculous things it

By: Lance Winslowl Reference & Education > Biologyl June 06, 2012 lViews: 194

What are some of the Most Common Operations that Gynecologists Perform? There are several types of procedures and surgeries that a gynecologist can perform to correct and treat disorders pertaining

By: Cesar Martinl Reference & Education > Biologyl June 05, 2012 lViews: 219

Sea hares are marine species which greatly resembles with that of a sea slug. This species usually crawls and swims across a coral reef. When attacked or disturbed, they squirt a copious protective

By: Clariss A.l Reference & Education > Biologyl May 27, 2012 lViews: 205

Read this article if you want to learn techniques to find study resources that "click" best with you. The premise is that not all study resources are created equal and by finding ones that resonate

By: Michael Anatomyl Reference & Education > Biologyl May 23, 2012 lViews: 191

This article is about the process of gene expression. It would be particularly helpful for high school AP Biology students who want to brush up on this very important concept.

By: Luke T Liul Reference & Education > Biologyl March 11, 2012 lViews: 151

The common understanding is that the Industrial Revolution resulted in an explosion of innovation and economic growth. However, the truth is more muted and protracted. Economic growth was slow in the

By: Luke T Liul Reference & Education > Online Educationl February 28, 2012 lViews: 154

Discuss this Article

comments powered by Disqus