EnzymesWelcome to a new topic!

Write down the enzyme names

That you hear about in the

presentation

EnzymesEnzymes are proteins that act

as biological catalystsThey lower the activation

energy of a specific chemical reaction

Catalysts – speed up the chemical reaction and are not changed by the reaction

Lowering the activation energy has a profound effect on how rapidly the reaction is completed

What are enzymes? Enzymes are typically

proteins

Enzymes are specific

Enzymes act as catalysts to speed up the rate of reaction of a biological process

Enzymes are not used up by the reaction they catalyse

Enzymes: Vocabulary Check

Catalyst: A substance that speeds up a chemical reaction without itself being changed

Enzyme: A biological catalyst that is usually a protein

Substrate: The reactant(s) upon which an enzyme has its action

Product: A substance that results from a chemical reaction

Enzymes change substrates into products

Enzymes have active site (s)

An intricate pocket or cleft – a 3-dimensional entity – structurally tailored to accept a particular substrate

Only fits its particular substrate

How do enzymes work?

Substrate specificity

Activation energy

Induced fit versus Lock and key mechanism

Another animated summary of how enzymes work

Enzymes Lower Activation Energy

What are the models used to describe enzyme

action?

What are the models used to describe enzyme

action?

Lock and key mechanism

Induced fit mechanism

The induced fit theoryThe substrate plays a role in determining the final shape of the enzyme and that the enzyme is has some flexibility.

This explains why certain compounds can bind to the enzyme but do not react because the enzyme has been distorted too much.

Other molecules may be too small to induce the proper alignment and therefore cannot react.

Only the proper substrate is capable of inducing the proper alignment of the active site

Induced fit in a moment....

Naming Enzymes (simplified classification)

Enzymes can be named according to the type of reaction that they catalyse

Carbohydrases

Lipases

Proteases

Enzymes can be named according to the substrate the interact with:

Maltase

Sucrase

Some enzymes just have individualised names:

Pepsin

Trypsin

Catalase

Key properties of enzymes

1. All enzymes are proteins

2. Enzymes are denatured (inactivated) by extreme temperatures

3. Enzymes work best at a particular temperature (which depends on the organism)

4. Enzymes work best at a particular pH (which depends on the organism)

5. Enzymes are catalysts (not degraded, ccan be used over and over again)

6. Enzymes are specific

Factors affecting Enzymes

1.Temperature

2.pH

3.Substrate concentration

4.Enzyme concentration

The best way to understand temperature, pH and substrate concentration effects is through paying with this game....

and here's another....

Factors which affect enzyme activity 1: Temperature

From: GCSE Bitesize:26.08.12

http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_pre_2011/homeostasis/importancerev4.shtml

The effect of temperature

For most human enzymes the optimum temperature is about 37°C

Many are a lot lower. For example, cold water fish can die at 30°C since many of their enzymes denature

Many plant enzymes have optimal temperature of 28 – 30 C

A few bacteria in hot springs have enzymes that can withstand very high temperatures up to 100°C

Most enzymes are fully denatured at 70°C

Factors which affect enzyme activity 2: pH

Optimum pH values

Enzyme

activity

Trypsin

Pepsin

pH1 3 5 7 9 11

The effect of pH The pH of a solution affects the shape of an

enzyme

At non-ideal pH values, the active site is distorted and the substrate molecules will no longer fit

Extreme pH levels will produce denaturation

Many enzymes have pH values which are NOT neutral (pH = 7): e.g. pepson, trypsin in the stomach and gut

DenaturationDenaturation is a change in the shape of an

enzyme which prevents it from fulfilling its function.

Enzymes (and other proteins) can be denatured by heat, pH changes, or certain chemicals

NB: Denaturation is not the same as ‘killing’ – proteins and enzymes are not living things, so can’t be killed!

What does ‘enzyme denaturation’ mean?

Factors which affect enzyme activity 3: Substrate and enzyme concentration

From: http://www.skinnersbiology.co.uk/enzyme.htmAugust 26th 2012

Substrate concentration: Enzymic reactions

Reaction velocity

Substrate concentration

Vmax

‘Celebrity’ biological enzymes

Metabolic Enzymes

ATP synthase

Enzymes in digestion

Amylase

Pepsin

Lactase

Metabolic enzyme: ATP synthase

‘one of the wnders of the molecular world’

ATP synthase is an enzyme, a molecular motor, an ion pump, and another molecular motor all wrapped together in one amazing nanoscale machine

ATP synthase in action

Amylase all about amylase...

Amylase digestion (II)

Pepsin All about pepsin

pepsin working in the stomach

Lactase Got lactase?

Lactase