Chapter 2:Enzymes Higher Human Unit 1: Cell Function and Inheritance 7/7/20161Mrs Smith

Learning Intentions To revise purpose of enzymes To revise how enzymes work To examine factor affecting rate of enzyme- catalysed reactions 7/7/20162Mrs 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. 7/7/20163Mrs Smith Biological Catalyst

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 amylase 7/7/20164Mrs 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 7/7/20165Mrs Smith Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.

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 How many chemical reactions happen in our body? 7/7/20166Mrs Smith Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.

Reaction Mechanism 7/7/20167Mrs Smith Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.

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. Specific Enzymes Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. 7/7/20168Mrs Smith

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. Lock and Key Theory Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. 7/7/20169Mrs Smith

Model enzymes Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. 7/7/201610Mrs Smith

Model Enzymes – Synthesis reaction. Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. 7/7/201611Mrs Smith

Specific Enzymes –Degradation Reaction Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. 7/7/201612Mrs Smith

Factors Affecting Enzyme Activity Enzymes are sensitive to the following: pH Temperature Enzyme concentration Substrate concentration 7/7/201613Mrs Smith Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.

pH 7/7/201614Mrs 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) Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. 7/7/201615Mrs Smith

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. Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. 7/7/201616Mrs Smith

Optimum pH Increasing rate of reaction pH Pepsin Optimum pH Amylase Catalase Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. 7/7/201617Mrs Smith

Temperature 7/7/201618Mrs 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. Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. 7/7/201619Mrs Smith

Denaturing Enzymes are denatured (destroyed and inactive) at high temperatures (usually above 42 0 C: 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. Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions. 7/7/201620Mrs Smith

Enzyme Concentration 7/7/201621Mrs Smith Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.

Enzyme Concentration 7/7/201622Mrs Smith Increasing concentrations increases activity. Enzyme activity can be decreased in the presence of INHIBITORS (molecules which will join preferentially to the enzyme). 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 7/7/201623Mrs Smith Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.

Competitive Inhibition 7/7/201624Mrs Smith Competitive inhibitors block the active site of the enzyme molecule. This type of inhibition is reversible. Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.

Non-competitive Inhibition 7/7/201625Mrs Smith 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. 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 28 th June 7/7/201626Mrs Smith Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.

Substrate Concentration 7/7/201627Mrs 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 (Fe 2+ ), magnesium (Mg 2+ ), copper (Cu 2+ ) –organic molecules e.g. haem, NAD, coenzyme A 7/7/201628Mrs 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 7/7/201629Mrs Smith Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.

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. 7/7/2016Mrs Smith30