Chapter 2:Enzymes

Higher Human Unit 1: Cell Function and Inheritance Chapter 2:Enzymes Mrs Smith

Learning Intentions • To revise purpose of enzymes • To revise how enzymes work • To examine factor affecting rate of enzyme-catalysed reactions Mrs Smith

A catalyst is a substance that: Speeds up the rate of a chemical reaction but remains unchanged at the end of the reaction. Enzymes are biological catalysts (made of protein) that are present in all living cells. They speed up the rate of biochemical reactions at relatively low temperatures. Without enzymes important biological processes like respiration and photosynthesis would proceed too slowly to maintain life. Biological Catalyst Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. amylase Structure • Globular proteins • One or more polypeptide chains • Function determined by structure • Reaction occurs at active site • Specific for one reaction due to shape of active site – “lock and key” hypothesis Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Function • Biological catalysts - increase reaction rates • Approx 40,000 different types in human cells • Intracellular (inside cell) e.g. catalase • Extra-cellular (outside cell) e.g. pepsin • Needed for respiration, photosynthesis, digestion, motors, membrane pumps, receptors Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. How many chemical reactions happen in our body? Since we have about 200 trillion cells and each one performs millions of chemical reactions, the total number of chemical reactions in the human body is about 400 billion per second every second of your life. That's 4 times the amount of stars in our galaxy which is a mere 100 billion Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Reaction Mechanism Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Specific Enzymes • Enzymes are SPECIFIC = This means that each enzyme can only react with one set of substrate molecules. • For example amylase cannot act on glucose and potato phosphorylase cannot act on starch. Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Lock and Key Theory • The shape of a molecule of enzyme exactly matches the shape of a molecule of its substrate like a key which fits exactly into a lock. This allows the two molecules to combine briefly at a point called the active site, which brings about the reaction. • We call this the “LOCK & KEY” theory. Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Model enzymes Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Model Enzymes – Synthesis reaction. Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Specific Enzymes –Degradation Reaction Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Factors Affecting Enzyme Activity Enzymes are sensitive to the following: • pH • Temperature • Enzyme concentration • Substrate concentration Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. pH Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Optimum pH • Enzymes have an optimum pH at which they catalyse reactions best. • Most enzymes function at a pH of 5-9 with an optimum pH of 7 (neutral). • There are exceptions to this rule: • Pepsin secreted by stomach’s gastric glands optimum pH is 2.5 (very acidic) • Catalase found in living cells optimum pH is 9 (very alkaline) Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Denaturing Enzymes are denatured (destroyed and inactive) at extremes of PH: Too many H+ ions or OH+ ions will alter the shape of the enzymes active site so it can no longer fit with its substrate and catalyse a reaction. Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Optimum pH Catalase Increasing rate of reaction Pepsin Amylase Optimum pH 1 2 3 4 5 6 7 8 9 10 11 12 pH Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Temperature Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Optimum temperature • At low temperatures enzyme activity will be very slow. • At warmer temperatures the enzyme activity will increase • The temperature at which the enzyme works best at is called its “optimum temperature”. • The optimum temperature for most animal enzymes is 37°C. Some plant enzymes have an optimum temperature around 20°C. Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Denaturing • Enzymes are denatured (destroyed and inactive) at high temperatures (usually above 420C: • Increasing the temperature beyond an enzymes optimum will destroy the shape of its active site so it can no longer fit with its substrate and catalyse a reaction. Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Enzyme Concentration Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Enzyme Concentration • Increasing concentrations increases activity. • Enzyme activity can be decreased in the presence of INHIBITORS (molecules which will join preferentially to the enzyme). Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Inhibition • Substrate can’t fit into active site of enzyme • Reaction rate lowered • 2 types: • Competitive • Non-competitive Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Competitive Inhibition • Competitive inhibitors block the active site of the enzyme molecule. This type of inhibition is reversible. Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Non-competitive Inhibition • Non-competitive inhibitors attach to some other part of the enzyme and in doing so alter the shape of the active site indirectly. • This is irreversible inhibition. Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Outcome 3 • Assessed practical • “Effect of enzyme concentration on enzyme action” • Submit write-up by:- Mon 28th June Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Substrate Concentration Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Activation of Enzymes • Many enzymes require the presence of other substrates to make them work. • These ACTIVATORS can be mineral ions, vitamins or other enzymes. • Cofactors (coenzymes) required • metal ions – iron (Fe2+), magnesium (Mg2+), copper (Cu2+) • organic molecules e.g. haem, NAD, coenzyme A Mrs Smith

Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. Inborn errors of metabolism • Metabolism – all the chemical reactions that occur in an organism • Error in gene coding for enzyme results in blockage in pathway • May result in health problems Mrs Smith

Phenylketonuria • Occurs when enzyme required to breakdown the amino acid phenylalanine present in the diet into tyrosine. • The excess phenylalanine is broken down into toxic substances which can lead to brain damage and poor mental development in children. Mrs Smith

Chapter 2:Enzymes