1. Definition
1.1. Biological catalysts
1.1.1. Break down substrates-> digestion-> catabolic
1.1.2. Build up substances-> anabolic (synthesis)
1.1.3. Globular proteins
1.1.3.1. Shape decides their active site and function (e.g. Tertiary structure etc)
1.1.4. Definition: Catalysts speed/ slow reactions by lowering activation energy but not used up or changed
2. Properties
2.1. pH sensitive
2.2. Temperature sensitive
2.2.1. Denatured at high temperature
2.2.1.1. breakage of bonds that hold enzyme in its 3D shape
2.2.1.1.1. Bonds easily disrupted at higher temperature by excessive molecular motion
2.3. Water soluble
2.4. 3D conformation
2.4.1. Due to interactions between amino group (s), carboxyl group(s) and R group(s) via intramolecular H–bonds, hydrophobic interactions, ionic interactions or disulphide bonds.
2.5. Does not alter properties of end products of reaction
2.6. Highly specific
2.6.1. Catalyse only certain chemical reactions
2.7. Highly efficient in small amounts
2.7.1. approx. 1000 reactions in 1 sec
2.8. Optimum temperature for human enzymes: 37 Degree celsius
2.9. Protease optimum pH level: Low (about 2 to 4 pH) Amylase optimum pH level: high (alkaline,approx 7 to 10 pH level)
3. Different hypothesis
3.1. Lock and key diagram (exact fit)
3.1.1. Part 1: Substrates not broken down yet: Enzyme-substrate complex
3.1.2. Part 2: Active site: Small pocket/groove on surface of enzyme molecule. Specific shape of active site complementary to its substrate. End of reaction: Active site+ Product
3.2. "Induced Fit"
3.2.1. Active site flexible physically; does not initially exist in shape complementary to substrate.
3.2.1.1. Enzymes close up and enfold substrate when suitable substrates bind to binding residues of active sites
3.2.2. Diagram
4. Factors affecting Enzyme Action
4.1. Definition of enzyme action
4.1.1. Lowering activation energy of reactions they catalyse-> Increases speed of reaction
4.1.1.1. Activation energy required to initiate a chemical reaction in which two substances react.
4.1.1.1.1. Destabilizes existing chemical bonds
4.1.2. Process
4.1.2.1. Step 1: Formation of enzyme-substrate complex
4.1.2.1.1. Both shape and charge of active site allow substrates to enter in proper orientations to be in precise collision.
4.1.2.1.2. Enzyme temporarily form bonds with substrates forming enzyme-substrate complex.
4.2. Temperature
4.2.1. Process
4.2.1.1. At near or below freezing point, enzymes inactivated.
4.2.1.1.1. When temperature increases, rate of enzyme-catalysed reaction increases.
4.2.2. Diagram
4.3. Substrate concentration
4.3.1. Process
4.3.1.1. Many enzyme molecules have active sites unoccupied, and limited substrate molecules determines reaction rate.
4.3.1.1.1. Increase in substrate concentration-> More active sites used, higher chances of successful collisions between substrates and enzymes
4.3.2. Diagram
4.4. Enzyme concentration
4.4.1. Similar diagram to substrate concentration
4.4.2. Process
4.4.2.1. When enzyme concentration increases, rate of reaction increases proportionally to increase in enzyme concentration-> More active sites available for substrates to react in
4.4.2.1.1. When substrate concentration limited, point reached when increasing enzyme concentration no longer has effect as there are many more empty active sites than substrates
4.5. pH-> varying optimum pH level for each substrate
5. Enzyme Inhibition
5.1. Competitive inhibitor
5.1.1. Active site is blocked by competitive inhibitor
5.1.1.1. Competitive inhibitor must be similar to actual substrate molecule
5.1.1.1.1. Inhibitor effect can be countered by increasing substrate concentration
5.2. Non-competitive inhibitor
5.2.1. Binding of blocker to enzyme away from active site
5.2.1.1. May also cause a shape change in the whole enzyme molecule including the active site
5.2.1.1.1. Substrate can no longer bind
5.2.1.2. Allosteric Inhibitors/Activators
5.2.1.2.1. Changes efficiency of enzyme
6. Industrial uses of enzymes
6.1. Protease enzymes
6.1.1. Active ingredient in washing powder
6.1.2. Usable at high pH and temperature up to 60 Degree celsius
6.1.3. Main function: stain removal
6.1.4. Does not lose their activity around potentially inhibiting chemicals in detergent
6.2. Rennet
6.2.1. Mixture of several enzymes
6.2.2. Used to curdle milk and separate milk into curds and whey
6.2.3. Important in digestion of milk in mammals
6.2.4. Used to make cheese
6.3. Pectinase
6.3.1. Degrade pectins which are polysaccharides in plant cell walls
6.3.2. Pectins broken down into galacturonic
6.3.2.1. Pectin: Gelling agent in fruits, undesirable in fruit juices-> plays a part in soft rot of fruits
6.3.2.2. Reducing pectin in juices makes juice sweeter and prevents spoil/decay
6.3.3. Galaturonic acid is broken down into sugars
6.4. immobilising enzymes
6.4.1. Enzymes anchored to solid support
6.4.2. Attached to inert, insoluble materials
6.4.3. Advantages: Easier to separate enzymes and products. Enzymes more stable and can be manipulated easily. Enzyme can be reused. no purification of product needed.
6.4.4. Example: Removing lactose content of milk