Enzyme Action. Intermediate 2 Biology Unit 1: Living Cells

Transcription

1 Enzyme Action Intermediate 2 Biology Unit 1: Living Cells

2 Learning Objectives Describe 2 ways in which chemical reactions can be speeded up. Name the products of the breakdown of hydrogen peroxide. State the general effect of a catalyst on the speed of a chemical reaction. Say what effect a reaction has on the catalyst. Say what effect a catalyst has on the energy input needed to start a reaction.

3 Effect of heat on breakdown of hydrogen peroxide Hydrogen peroxide breaks down into water and oxygen Read through the experiment in your textbook Conclusions The breakdown of hydrogen peroxide is promoted by heat energy The rate of breakdown increases as the temperature increases

4 The effect of manganese dioxide on hydrogen peroxide Make a copy of this diagram, and draw a diagram of what happens when this is demonstrated by the teacher. Which gas is given off? How can you test for this gas? The chemical symbol for hydrogen peroxide is H 2 O 2 what else is produced?

5 Results of manganese dioxide and hydrogen peroxide Oxygen gas and water are the products of this reaction. Manganese dioxide remains chemically unaltered by this reaction.

6 Catalysts A chemical which speeds up the rate of a reaction and yet remains unaltered is called a catalyst. Catalysts lower the energy input (activation energy) required for a chemical reaction to proceed. Activation energy graph Uncatalysed reaction Catalysed reaction

7 Learning Objectives Give the general term for biological catalysts. Give the word equation for the reaction catalysed by the enzyme catalase. State where enzymes are found.

8 Enzymes Enzymes speed up the chemical reactions that take place in our cells (biological catalysts). Enzymes are proteins and occur naturally in living cells Catalase is an enzyme which catalyses the breakdown of hydrogen peroxide

9 The effect of catalase on hydrogen peroxide Explain the results of this experiment

10 Importance of enzymes Enzymes allow biochemical reactions to proceed at relatively low temperatures Without enzymes, biochemical reactions would proceed so slowly that life would cease to exist.

11 Pupil Activity Complete the testing your knowledge section on First edition pg 43/44 Second edition - pg

12 Learning Objectives Name the type of chemical of which enzymes are composed. Describe a test for protein. State the meaning of specific as applied to enzymes. Define the term substrate as applied to enzymes. Describe the active site of an enzyme. Explain the term complementary as applied to active sites. Explain the specific nature of an enzyme in terms of its active site.

13 Specificity Active site Where the substrate attaches to the enzyme Is a specific shape determined by its chemical structure resulting from bonding between amino acids

14 Lock and Key Theory Each enzyme is specific to one substance - its substrate The shape of the substrate molecule and the active site are complementary The enzyme and the substrate combine to form an enzyme-substrate complex The products then leave the active site leaving the enzyme unaltered

15 Enzyme Reactions Breakdown (degradation) reactions where one molecule breaks down into smaller molecules Starch maltose

16 Enzyme Reactions Building up (synthesis) reactions where molecules join together to make a larger molecules Glucose-1-phosphate starch

17 Learning Objectives Define the term breakdown reaction. State the reason for the breakdown of starch by animals. Name the substrate and product of the enzyme amylase. Describe a test for starch. Describe a test for maltose sugar. Explain the need for a control in an investigation.

18 Effect of amylase on starch Make a copy the diagram showing the action of amylase on starch (pg 45 Ed.1) What does tube A show? What is tube B for?

19 Control A control is a copy of the experiment All factors are kept exactly the same The factor being investigated is changed When comparing results Any difference found must be due to one factor In enzyme experiments the control tube is usually water, or boiled enzyme solution

20 Learning Objectives Define the term synthesis reaction. Name the substrate and product of the enzyme phosphorylase. Explain in terms of diffusion why plants store starch instead of glucose. Describe a phosphorylase experiment and its controls.

21 Effect of phosphorylase on glucose-1- phosphate Make a labelled drawing of the diagram on pg47 (ed.1) Make conclusions from this experiment.

22 Synthesis of starch Starch is synthesised from glucose. A starch molecule contains hundreds of glucose molecules. The enzyme phosphorylase can be used to speed up the synthesis of starch.

23 Learning Objectives Describe the effect of increasing temperature on enzyme-catalysed reactions. Draw and interpret a line graph showing the effect of temperature on enzyme activity. Define the term optimum temperature. State the optimum temperature for enzyme reactions in the human body. Describe the effect of high temperature on protein structure. Define the term denatured

24 Factors affecting enzyme activity To function efficiently enzymes require Suitable temperature Suitable ph Adequate supply of substrate

25 The effects of temperature on enzyme activity

26 The effects of temperature on enzyme activity Very low temperature Enzymes inactive Low temperatures Enzyme and substrate molecules move slowly Few enzyme-substrate collisions Low enzyme activity

27 The effects of temperature on enzyme activity Increasing temperature Enzyme and substrate molecules move faster More frequent enzyme substrate collisions More enzyme-substrate complexes (ESC) form Increasing rate of reaction

28 The effects of temperature on enzyme activity Optimum temperature Temperature at which the reaction works best Usually 40 o C Above this temperature Atoms vibrate within the enzyme molecule This breaks the chemical bonds that hold the amino acids together Enzyme molecule breaks apart changing the shape of the active site The enzyme becomes denatured this is irreversible

29 Planning and designing an investigation into the effect of temperature on the activity of lipase Read through the information provided in your textbooks (pg 53 1 st edition) Complete the what to do section by using the guidance to design an investigation

30 Learning Objectives Describe the ph scale. State the ph levels of the mouth, stomach and small intestine. Define the term optimum ph. Interpret data to identify the optimum ph for an enzyme. State the optimum ph for pepsin. State the optimum ph for trypsin. Describe the colour change of Clinistix when exposed to glucose. Name the substrate and products of the enzyme invertase.

31 The effects of ph on enzyme activity

32 The effects of ph on enzyme activity ph refers to the concentration of hydrogen ions in a solution More hydrogen ions, lower ph, more acidic One of the chemical bonds that hold enzymes in their specific 3D shape are hydrogen bonds If an enzyme is exposed to an unsuitable ph, these hydrogen bonds break and the enzyme becomes denatured. All enzymes have an optimum ph at which they work best.