OCR-B4-Lesson 2 enzymes and pH

IB4.2.2H Images

© Oxford University Press 2011

Learning outcomessummarise the role of enzymes in living organismsdescribe enzyme action in terms of active site shapedescribe the effect of pH on enzyme activity

Keywords- enzyme, pH, active site, enzyme action, catalyst, reactants, products, Lock and key model.

Enzymes and pH

IB4.2.2H Images

© Oxford University Press 2011

What do you know about enzymes?

Write a list

IB4.2.2H Images

© Oxford University Press 2011

In B2 we learned that:Enzymes are proteins that speed up chemical reactions, in the context that genes determine which proteins are made in cells.

Enzymes can be thought of as catalysts as well as agents that break large molecules into smaller ones

IB4.2.2H Images

© Oxford University Press 2011

What effect does catalase (in celery) have on hydrogen peroxide?Discuss the role of catalase in cells.

What is hydrogen peroxide?

H2O2

IB4.2.2H Images

© Oxford University Press 2011

Watch the demonstration of the reaction of catalase and hydrogen peroxide

Then carry out your investigationYou will consider the effect of different pH levelsEach group will carry put two (2) investigations and results will be added to the board

IB4.2.2H Images

© Oxford University Press 2011

As a class we carried out a practical, looking at the effect of enzymes on pH. We started with 3 buffer solutions of pH 4, pH 7 and pH 9. we used yeast as the catalase and added this to the hydrogen peroxide, collecting the oxygen produced.

IB4.2.2H Images

© Oxford University Press 2011

What can we conclude from out results

What happens?????????

What ‘reactants’ and ‘products’ in the context of this particular enzyme.

Catalase + hydrogen peroxide oxygen and water

IB4.2.2H Images

© Oxford University Press 2011

An enzyme

A computer graphic of an enzyme, its active site, and the product of a reaction

IB4.2.2H Images

© Oxford University Press 2011

How does the enzyme speed up the reaction? look at the first two screens of Animation IB4.2.4 Enzymes introducing the idea of the lock-and-key model.complete Activity AB4.2.2 Lock-and-key model using Textbook Section B and Animation IB4.2.4 Enzymes.

IB4.2.2H Images

© Oxford University Press 2011

Enzyme animations

IB4.2.2H Images

© Oxford University Press 2011

Your core body temperature is about 37°C, but a small variation either side of this is normal. a core temperature over 42°C or under 28°C usually results in death.

IB4.2.2H Images

© Oxford University Press 2011

Around 80% of the energy from your food is used for keeping warm

IB4.2.2H Images

© Oxford University Press 2011

Shrews have a large surface area for their volume. They lose heat to the environment over their whole body surface. To release enough energy to maintain their body temperature, they have to eat 75% of their body mass in food each day.