Enzymes and Energy Carriers Higher Level Chapter 10

Enzymes and Energy Carriers Higher Level Chapter 10

Aidhm • Explain the active site theory to examine enzyme function & specificity. • Explain the term optimum activity with reference to temperature. • Explain the nature of heat denaturation

The Active Site • The Active site is the part of the enzyme that combines with the substrate to form an enzyme-substrate complex

Enzyme and Substrate • Enzymes work because they have the correct shape to fit the substrate • They have a complex 3 dimensional shape to fit the substrate • When enzymes and their substrates meet and come together they form an Enzyme/Substrate complex 4

Enzymes Reactions are reversible • In the following example the enzyme can break molecule X into Y+Z but it can also combine Y+Z to form X X Y+Z • Like a key can open or close a lock enzymes can make reactions go in either direction 5

Lock-and-key theory assumes the active site of an enzyme is rigid in its shape How ever crystallographic studies indicate proteins are flexible.

The Bean Bag Theory! • The induced fit model can be compared to the way a bean bag will adapt to fit snugly around our body shape when we sit in it

Induced Fit Model 1. Substrate binds to enzyme, forming enzyme-substrate complex 2. Substrate causes active site to change shape slightly 3. Substrate is altered 4. Product released and active site returns to original shape. Animation: http: //www. edcodigital. ie/edcodigital-viewer/? bookid=ASC 5351 S

The Induced-fit hypothesis suggests the active site is flexible and only assumes its catalytic conformation after the substrate molecules bind to the site. When the product leaves the enzyme the active site reverts to its inactive state.

Lets revise types of metabolic reactions In anabolic reactions enzymes bring the substrate molecules together. In catabolic reactions the enzyme active site affects the bonds in substrates so they are easier to break

Complete in your copy • What is meant by a substrate? • What is the unit formed when an enzyme combines with its substrate called? • Give an example of an anabolic reaction • Give an example of a catabolic reaction • Can enzyme reactions be reversed? 11

Mechanism of Enzyme action (Induced fit model) 1. The substrate combines with the active site of the enzyme Active Site Enzyme Substrate

2. The active site is induced or caused to change shape slightly Enzyme Active Site Substrate

3. The substrate and enzyme form an enzyme substrate complex • The bonds in the substrate are altered so that the substrate changes into the products Enzyme Substrate complex Substrate changed to products which are released

4. The products leave the active site. The active site returns to its original shape and is ready for a new substrate molecule Products Active Site Enzyme New Substrate

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Optimum Conditions • Optimum: p. H or temperature at which enzyme works best • Optimum temperature refers to the temperature at which the enzyme will work best • Optimum p. H refers to the p. H at which the enzyme will work best and so on • What do you think body enzyme’s optimum temperature is?

Activation energy • The minimum energy needed by particles for a reaction to happen Reactants • How can we make the reaction more likely to happen? Increase the temperature: Molecules have more energy, move faster, more collisions occur. But above 40 degrees the enzymes become denatured. Products

Denaturation If the temperature and p. H changes sufficiently beyond an enzyme’s optimum, the shape of the enzyme irreversibly changes. This affects the shape of the active site and means that the enzyme will no longer work. When this happens the enzyme is denatured. Denatured: Loss of enzyme function due to change in shape caused by heat or p. H Temperature above 40° C = denatured heat p. H normal denatured

Complete in your copy • Can you describe how enzymes and their substrates fit together? • What is this model of enzyme action called? • Can the enzyme work on more substrate once the products have been formed? • What is meant by Optimum? • What do you think the optimum temperature is for most body enzymes is?

Syllabus Can you? . . . • Explain the active site theory to examine enzyme function & specificity. • Explain the term optimum activity with reference to temperature. • Explain the nature of heat denaturation

Sentences Arrange yourselves to spell out the sentence correctly. (End of Part 1 of lesson).

Role of ATP and NAD Energy Carriers

What’s The Question? Work in groups of 3 You have 4 minutes If these are the answers then what’s the question 1. Induced Fit Theory 2. Above 40° C 3. Enzyme Substrate Complex 4. Because they have the correct shape to fit the substrate Clock

Aidhm • Explain the role of ATP and describe how it is formed from ADP + P • Explain the role of NADP+ in trapping and transferring electrons and hydrogen ions in cell activities

Energy Carriers • ATP , NADP+ and NAD+ play a vital role in trapping and transferring energy in cellular activities

ADP: Adenosine Diphosphate • Found in cells of all organisms • Low energy molecule (like an empty delivery van)

ATP: Adenosine Triphosphate Phosphorylation: when phosphate is added to a molecule ADP + energy + P ATP + water • Extra phosphate bound • Rich in energy and stores this energy carrying it around in the cell (like a delivery van full of cargo)

Where ATP is used • Photosynthesis: Used to make glucose • Respiration: Glucose breaks down to make ATP

ADP and ATP • Most cells release energy from ATP 10 million times every second! This energy is used for cellular reactions

1. 2. 3. 4. Learning Check What do ADP and ATP stand for? What base is found in ATP and ADP? What sugar is found in ATP and ADP? Which is a higher energy molecule?

H+: This is another name for a proton

NADP+: Nicotinamide Adenine Dinucleotide Phosphate NADP+ + 2 electrons + H+ NADP+ is a low energy molecule involved in photosynthesis NADP+ can combine with 2 high energy electrons and a proton to form NADPH is a very high energy molecule

O. I. L. R. I. G. • Oxidation is loss of electrons • Reduction is gain of electrons

NADP+: Nicotinamide Adenine Dinucleotide Phosphate NADP+ + 2 electrons + H+ NADPH energy NADP+ is a low energy molecule involved in photosynthesis NADP+ can combine with 2 high energy electrons and a proton to form NADPH NADP+ is reduced to NADPH is used to form glucose in photosynthesis NADPH is a very high energy molecule

NAD+ and NADH NAD+ reduced NADH Releases energy and electrons NAD+ is used in respiration like NADP+. It is a low energy carrier NADH is like NADPH. It is a high energy carrier

Summary of Energy Carriers Photosynthesis uses the molecules with a P Process Low Energy Molecule High Energy Molecule Photosynthesis ADP, NADP+ ATP, NADPH Respiration ADP, NAD+ ATP, NADH

Sentences Starter: Arrange yourselves to spell out the sentence correctly.

Learning Check • Is NADP+ used in photosynthesis or respiration? • What combines with NAD+ and NADP+ to form NADH and NADPH? • What do NADH and NADPH provide for reactions in cells? • How do they provide these things?

Syllabus Can You? . . . . • Explain the role of ATP and describe how it is formed from ADP + P • Explain the role of NADP+ in trapping and transferring electrons and hydrogen ions in cell activities

4. 5 (b) To investigate the effect of heat denaturation on catalase activity

Before you start get or make a copy of this Table of results Foam present or absent Boiled Un-Boiled enzyme

Step 1 Coffee filter paper is faster than normal filter paper. Filtering it removes cell debris Put 5 g of chopped and filtered (using coffee filter paper) celery into two boiling tubes in water baths at 100°C and 20°C for 10 minutes. Remove and cool.

Step 2 Add 20 ml of buffer p. H 9 to two graduated cylinders.

Step 3 Add one drop of washing up liquid to each graduated cylinder.

Step 4 Add the 5 g of boiled celery to one cylinder and label ‘A’. Add the 5 g of un-boiled celery to the other cylinder and label ‘B’.

Step 5 Add 2 ml of hydrogen peroxide to two new boiling tubes. Place both tubes in the water bath at 25 °C

Step 6 Stand cylinders and boiling tubes into the water bath until the desired temperature is reached.

Step 7 Add the hydrogen peroxide from each boiling tube to the corresponding graduated cylinder.

Expected result: Note the presence or absence of foam in each graduated cylinder.

Table of results Foam present or absent Boiled Un-Boiled enzyme

Overall reaction

Enzyme Blockbusters 12 11 18 6 15 9 1 24 2 5 25 16 13 23 22 21 3 17 4 10 14 7 19 8 20

5 -5 -1 Deluxe! Now reduce that to 5 key words… Write 5 sentences summarising today’s topic… And finally to one word….

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