ENZYMES What do enzymes look like and what

ENZYMES

What do enzymes look like and what are they made from? • Enzymes are made from proteins folded into specific shapes Diagram of an enzyme in action Protein structure of an enzyme

What do enzymes do? • Speed up biochemical reactions (reactions that occur in organisms)give examples e. g. photosynthesis. Therefore we call them “catalysts”. • These reactions may be: 1. Anabolic- when enzymes are used to build/ make new molecules 2. Catabolic- when enzymes are used to break apart molecules. • They don’t facilitate new reactions, these reactions happen naturally in the organism, however they speed them up because if the reactions were to occur naturally, they would be too slow and the organism could die. • They are reusable/ recyclable in chemical reactions

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How do enzymes work? - Activation energy Enzymes make reactions speed up because they lower the activation energy needed for the reaction to occur. But what is activation energy?

Activation Energy • Activation energy is the minimum energy that is needed to make a reaction happen. • Enzymes work by providing an alternate pathway for the reaction which has a lower activation energy.

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How do enzymes work? - The Collision Theory For an enzyme to catalyse a reaction, two things must happen. 1. The enzyme and substrate must combine with sufficient force 2. The enzyme and substrate must combine at the correct angle

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How do enzymes work? - Specificity Enzymes are specific: • Enzymes are only able to catalyse specific reactions in specific environments. • They have a specifically shaped active site which fits the substrate it reacts with and won’t react with other substrates. This is important because… There are two models for how enzymes work…

Model 1: Lock and Key Model 1. Each enzyme has a unique active site which has a specific shape 2. A specific substrate fits the enzyme (like a key fits a lock), forming the enzyme/substrate complex. 3. The chemical reaction occurs 4. The products of the reaction are released 5. The enzyme is unchanged and can participate in more reactions

Model 2: Induced Fit Model 1. Before binding, the substrate does not completely fit the active site of the enzyme 2. The substrate binds to the enzyme and the enzyme will mould slightly to fit the shape of the specific substrate. 3. The enzyme-substrate complex is formed and the reaction occurs 4. Product/s are released 5. The enzyme returns to its original shape

Which model is most correct? The induced fit model is thought to be most accurate because: 1. Enzymes are not rigid like a lock 2. Enzyme can change shape easily due to the weak hydrogen bonds present in their secondary protein structures.

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Types of enzymes Enzyme names generally end with –ase Example: What do these enzymes do? 1. Lipase 2. Protease 3. Carbohydrase Although some enzymes that have been known longer don’t end in “ase” e. g. pepsin and trypsin (enzymes located in the digestive tract which break down proteins for digestion).

Why do organisms need enzymes? • To breakdown molecules/ substances i. e. for digestion and absorption of nutrients from food in animals. • To make new molecules/ substances i. e. proteins from amino acids. • To carry out essential metabolic processes within the organism e. g. respiration and photosynthesis. These life processes require a number of enzymes to catalyse the reactions to increase the efficiency of each process.

FACTORS AFFECTING ENZYMES (AND THEIR RATE OF REACTION!)

Temperature- Scipad page 75

p. H- Scipad page 77

Surface Area- Scipad page 79 • SA: V ratio

Concentration of substrate/ enzyme

Co-factors and inhibitors