First Five Define and give an example of: – Carbohydrate – Lipid – Protein – Nucleic Acid

Enzymes

Major Characteristics of Enzymes Enzymes are special proteins present in the cytoplasm of all cells They help speed up the chemical reactions in cells There are hundreds of different kinds of enzymes, but each enzyme only speeds up one reaction.

Enzymes For example, glucose and fructose might join up slowly to form sucrose glucose- -fructose With the right enzyme present, the reaction happens faster glucose--fructose

Enzyme Action Enzymes are large proteins – like all proteins, each enzyme molecule has a certain shape – the shape determines which reaction the enzyme can speed up In speeding up the reaction, the enzyme combines temporarily with a substrate – substrate: any substance an enzyme acts on

enzyme substrate A substrate B The substrate molecules fit the shape of the enzyme

STAGE 1

two substrates combine temporarily with enzyme the enzyme joins the two substrates together STAGE 2

new compound released by enzyme enzyme unchanged and ready for next reaction STAGE 3

Different Types of Enzyme Reactions Enzymes can – join substrates together – break a substrate apart

A ‘breaking-down’ reaction the shape of the substrate molecule fits the enzyme shape this is called the active site of the enzyme STAGE 1

substrate combines temporarily with enzyme enzyme will break molecule here STAGE 2 A ‘breaking-down’ reaction

substrate splits and separates from enzyme STAGE 3

Final break-down products end-products enzyme ready for next reaction STAGE 3

Properties of Enzymes 1.Enzymes can act on only one type of substrate 2.Enzymes always produce the same end- products. 3.Enzymes are not used up in the reaction. – They return to their original state after the reaction.

Enzymes can act on only one type of substrate this substratecannot combine with this enzyme this substrate cannot combine with this enzyme

Properties of Enzymes 4.Enzymes – like any protein – are denatured by heat or some chemicals. – Denaturing changes the shape of a protein – For an enzyme, this means that it can no longer combine with the substrate. 5.Each enzyme works best at a particular temperature and pH (acidity or alkalinity) – These are referred to as the optimal temperature and optimal pH

Because enzymes are proteins, they are denatured by heat or some chemicals enzyme denatured by heat denatured enzyme cannot combine with substrate enzyme + substrate

1 glucose molecules E 1. A glucose molecule combines with the active site on the enzyme phosphorylase ENZYME ACTION

E 2 A region of the active site is still available

part of starch molecule E 3 One end of a growing starch molecule combines with the glucose molecule at the active site

E 4 The growing starch molecule breaks free from the enzyme phosphorylase which is now free to repeat the reaction

Enzyme action EE E 2 E 3 E 4 part of starch molecule 1 glucose molecules E 1

Enzymes Reading Read the text individually Mark the text as you read: Answer the summary questions in your journal. – Put all answers into your own words. Finish as homework. Due Tuesday