Think about… 4.1 Metabolism 4.2 Properties and actions of enzymes

Think about… 4.1 Metabolism 4.2 Properties and actions of enzymes 4.3 Factors affecting the rate of enzymatic reactions 4.4 Applications of enzymes Recall ‘Think about…’ Summary concept map

Stonewashed jeans Want old, worn-out jeans? I can help you!

Stonewashed jeans Wash jeans with stones. • Stones break some cellulose fibres & remove the blue dye.

enzyme Stonewashed jeans Now we can use enzymes to break down the fibres more quickly!

What are enzymes enzyme 1

What are the importance of enzymes to organisms enzyme 2

What are the advantages of using enzymes in the making of stonewashed jeans enzyme 3

4.1 Metabolism • different chemical reactions take place in living cells respiration Important for protein synthesis keeping alive! lipid synthesis

4.1 Metabolism • different chemical reactions take place in living cells sum of the chemical reactions that take place in an organism =metabolism(新陳代謝)

4.1 Metabolism Metabolism Anabolism (合成代謝) Catabolism (分解代謝)

4.1 Metabolism 1 Catabolism complex molecule simple molecules energy • breaking-down reactions • release of energy

4.1 Metabolism 1 Catabolism • example: respiration carbon dioxide water + glucose energy

4.1 Metabolism Metabolism Anabolism (合成代謝) Catabolism (分解代謝)

4.1 Metabolism 2 Anabolism simple molecules complex molecule energy • building-up reactions • requires energy

4.1 Metabolism 2 Anabolism • example: condensation of glucose starch energy glucose

4.1 Metabolism What are catabolism, anabolism and metabolism? Catabolism all breaking-down reactions in an organism all building-up reactions in an organism Anabolism Metabolism all chemical reactions in an organism

4.2 Properties and actions of enzymes What is the role of enzymes in metabolism?

4.2 Properties and actions of enzymes  product (生成物) reacting molecules energy barrier (能障)

4.2 Properties and actions of enzymes energy product (生成物) reacting molecules Energy supplied to overcome the energy barrier energy barrier (能障)

4.2 Properties and actions of enzymes • analogy: pushing a rock up a hill reacting molecule product

4.2 Properties and actions of enzymes energy barrier • analogy: pushing a rock up a hill reacting molecule product • the reaction does not startdue to the presence of energy barrier

4.2 Properties and actions of enzymes • analogy: pushing a rock up a hill maximum energy energy • when energy is supplied … reaction starts

4.2 Properties and actions of enzymes How can the energy barrier be overcome in our body?

4.2 Properties and actions of enzymes By increasing the temperature? smaller energy barrier • energy level raised • energy barrier is easier to overcome

4.2 Properties and actions of enzymes Not possible because high temperature kill the body cells! By increasing the temperature? smaller energy barrier • energy level raised • energy barrier is easier to overcome

4.2 Properties and actions of enzymes lower energy barrier • rate of chemical reactions is speeded up by enzymes (酶)

4.2 Properties and actions of enzymes energy • rate of chemical reactions is speeded up by enzymes (酶)

4.2 Properties and actions of enzymes 4.1 Demonstration of the breaking-down action of enzymes 1Prepare liver extract. a Grind fresh liver with cold distilled water. fresh pig liver cold distilled water

4.2 Properties and actions of enzymes 4.1 b Filter the ground tissue with filter paper. filter paper liver extract

4.2 Properties and actions of enzymes 4.1 c Dilute the liver extract by 50% with cold distilled water. distilled water liver extract

4.2 Properties and actions of enzymes 4.1 2 Set up 3 test tubes A to C. Observe for the release of gas and the gas given off with a glowing splint. hydrogen peroxide+ liver extract hydrogen peroxide+ distilled water distilled water + liver extract A B C

4.2 Properties and actions of enzymes 4.1 Results and discussion • A gas is released from tube A. The gas is oxygen becauseit re-lights a glowing splint. • No oxygen is released from the control set-ups (tubes B and C).

4.2 Properties and actions of enzymes 4.1 Results and discussion • Fresh liver tissues can break down hydrogen peroxide possibly due to the presence of catalase in the liver tissue. • Catalase speeds up the breakdown of hydrogen peroxide.

4.2 Properties and actions of enzymes How do enzymes work? • each enzyme has an active site of a specific (專一的) shape active site(活性部位) enzyme

4.2 Properties and actions of enzymes How do enzymes work? • active site can combine with substrate(受質) molecule(s) substrate shapes fit together! enzyme

4.2 Properties and actions of enzymes How do enzymes work? • active site can combine with substrate(受質) molecule(s) enzyme-substrate complex (酶受質複合物) substrate enzyme • complex breaks down to give product(s)

4.2 Properties and actions of enzymes How do enzymes work? • in catabolic reactions: substrate enzyme- substrate complex enzyme

4.2 Properties and actions of enzymes How do enzymes work? • in catabolic reactions: products enzyme- substrate complex enzyme unchanged and can be reused

4.2 Properties and actions of enzymes How do enzymes work? • in anabolic reactions: substrates enzyme- substrate complex enzyme

4.2 Properties and actions of enzymes How do enzymes work? • in anabolic reactions: product enzyme- substrate complex enzyme unchanged and can be reused

4.2 Properties and actions of enzymes Properties of enzymes 1) Biological catalysts • act as catalysts (催化劑) in organisms speed up metabolic reactions

4.2 Properties and actions of enzymes Properties of enzymes 2) Reusable • enzyme returns to its original form after reaction after reaction before reaction same!

4.2 Properties and actions of enzymes Properties of enzymes 3) Required in small amount large amount of products produced reusable reusable reusable

4.2 Properties and actions of enzymes Properties of enzymes 4) Proteins • enzymes are denatured (變性) at high temperatures and extreme pH

4.2 Properties and actions of enzymes different shape! Properties of enzymes 5) Specific action

4.2 Properties and actions of enzymes Properties of enzymes 5) Specific action • each enzyme combines with a specific substrate • each enzyme catalyses only one type of reaction

4.2 Properties and actions of enzymes Properties of enzymes 5) Specific action • can be explained by lock-and-key hypothesis (鎖鑰假說)

4.2 Properties and actions of enzymes Lock-and-key hypothesis specific shape • fit only a particular lock

4.2 Properties and actions of enzymes Lock-and-key hypothesis active sites of specific shape • fit only a particular substrate

Think about… 4.1 Metabolism 4.2 Properties and actions of enzymes