EnzymesBiochemistry Unit

Workbook: pg. 61

Textbook: pg. 69

Animation: What is an Enzyme?

http://www.sumanasinc.com/webcontent/animations/content/enzymes/enzymes.html

What is an Enzyme? Enzymes are biological catalysts that increase

the speed of biochemical reactions within cells. Enzymes are globular proteins that are NOT

consumed during reactions. This means they are readily available to catalyze the same reaction over and over again.

Enzymes speed up chemical reactions by lowering the activation energy needed for the reaction to proceed. Without the presence of enzymes, biochemical reactions within the cells would not occur fast enough to sustain life.

Activation Energy EXERGONIC

REACTION: products have a

lower energy than the reactants

products have less free energy than that of the reactants and energy is given off from the system.

Activation Energy ENDERGONIC

REACTION : Products have a

higher energy than the reactants

The system requires energy

These reactions cannot occur spontaneously, energy is required to be invested in the products.

What is an Enzyme? The shape of an enzyme is so specific that only

one type of substrate (reactant) is capable of properly binding to the enzyme. If the shape of the enzyme should change or become altered, the enzyme will be inactive and the chemical reaction will not be catalyzed.

Most enzymes end with “ase”. So if you are struggling with the name of an enzyme and you know the name of the substrate, just change the ending to “ase”. So lactase is the enzyme involved with converting lactose into glucose and galactose. Amylose is the substrate for the enzyme amylase.

The Effects of pH

http://lgfl.skoool.co.uk/content/keystage3/biology/pc/learningsteps/PAELC/launch.html

Digital Experiment: http://lgfl.skoool.co.uk/content/keystage3/biology/pc/learningsteps/DIELC/launch.html Textbook: pg.

72

The Effects of Temperature http://lgfl.skoool.co.uk/content/keyst

age3/biology/pc/learningsteps/TAELC/launch.html

Textbook: pg. 72

How do they work?

http://www.lpscience.fatcow.com/jwanamaker/animations/Enzyme%20activity.html

The Active Site In an enzyme catalyzed

reaction, the substrate binds to a location called the active site.

A substrate-enzyme complex forms when the substrate binds to the enzyme.

The active site involves a small number of key residues that actually bind to the substrates

The rest of the protein structure is needed to maintain these residues in position

Induced Fit Model (vs. lock and key) Initially the active site is

not a direct fit for the substrate. As the substrate begins to

interact with the amino acid side chains of the enzyme, the enzyme modifies its shape to better accommodate the substrate.

This slight change in the shape of the enzyme allows the enzyme to catalyze the reaction. Workbook : pg.

61

Enzyme Helpers Some enzymes require co-factors or co-enzymes to

help them function properly. Co-factors are inorganic, non protein molecules that include zinc, iron, and copper. These metal ions can either bind to the active site or to the substrate to facilitate the formation of the enzyme-substrate complex.

Some of the most important coenzymes include nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+) which are involved in the process of cellular respiration and photosynthesis, respectively. These two molecules carry electrons during both reactions.

Enzyme Inhibitors There is an array of substances that

can inhibit and deactivate enzyme activity by: either: altering the active site or by mimicking the structure of a particular

substrate.

There are two types of inhibition: competitive and noncompetitive.

Workbook : pg. 61

Textbook: pg. 73

Competitive Inhibitors

Compete with the substrate for the enzyme's active site. Enter the enzyme's active site and prevent the normal

substrate from binding.

Noncompetitive Inhibitors

Attaches to a binding site on an enzyme other than the active site.

http://bcs.whfreeman.com/thelifewire/content/chp06/0602001.html

Feedback Cellular Respiration (text pg. 113) – negative feedback Oxytosin and birth (text pg.336) – positive feedback

http://www.northland.cc.mn.us/biology/Biology1111/animations/enzyme.html

Textbook: pg. 74

Allosteric Regulation Cells need to regulate and control chemical reactions

in order to coordinate cellular activities. control enzyme activity by:▪ altering the production of a particular enzyme ▪ preventing an enzyme from functioning.

Some enzymes contain allosteric sites which are receptor sites that are located far from the active site. Allosteric activator: keeps the active site of an enzyme

available to its substrate. Allosteric inhibitor: is a substance that binds to the

allosteric site and induces an inactive form of an enzyme so that the substrate cannot bind.

Workbook : pg. 63

Allosteric Regulation: Activation vs. Repression

http://www.stolaf.edu/people/giannini/flashanimat/enzymes/allosteric.swf

Degradation Reactions

Synthesis Reactions

Intro to Metabolism: 58-68 #1-10Enzymes: 69-77 #1-8

Your Homework: