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Enzymes by Mind Map: Enzymes
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Biological catalysts

Break down substrates-> digestion-> catabolic

Build up substances-> anabolic (synthesis)

Globular proteins, Shape decides their active site and function (e.g. Tertiary structure etc)

Definition: Catalysts speed/ slow reactions by lowering activation energy but not used up or changed


pH sensitive

Temperature sensitive

Denatured at high temperature, breakage of bonds that hold enzyme in its 3D shape, Bonds easily disrupted at higher temperature by excessive molecular motion, Hydrogen bonds especially sensitive to temperature changes

Water soluble

3D conformation

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.

Does not alter properties of end products of reaction

Highly specific

Catalyse only certain chemical reactions

Highly efficient in small amounts

approx. 1000 reactions in 1 sec

Optimum temperature for human enzymes: 37 Degree celsius

Protease optimum pH level: Low (about 2 to 4 pH) Amylase optimum pH level: high (alkaline,approx 7 to 10 pH level)

Different hypothesis

Lock and key diagram (exact fit)

Part 1: Substrates not broken down yet: Enzyme-substrate complex

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

"Induced Fit"

Active site flexible physically; does not initially exist in shape complementary to substrate., Enzymes close up and enfold substrate when suitable substrates bind to binding residues of active sites


Factors affecting Enzyme Action

Definition of enzyme action

Lowering activation energy of reactions they catalyse-> Increases speed of reaction, Activation energy required to initiate a chemical reaction in which two substances react., Destabilizes existing chemical bonds, Acts as a barrier to reaction

Process, Step 1: Formation of enzyme-substrate complex, Both shape and charge of active site allow substrates to enter in proper orientations to be in precise collision., Step 2:Catalysis/Lowering of activation energy, Interactions between enzyme and substrate molecules; straining chemical bonds within substrates-> Lowering of activation energy, Step 3:Product formation and regeneration of enzyme, When reaction between substrates finished, product no longer fit into active site and is expelled., Temporary changes in shape, charge and bonding pattern within enzyme revert to original, and enzyme ready to accept another substrate., Enzyme temporarily form bonds with substrates forming enzyme-substrate complex.


Process, At near or below freezing point, enzymes inactivated., When temperature increases, rate of enzyme-catalysed reaction increases., Greater amount of heat energy, greater amount of kinetic energy-> more successful collisions, However, temperature above optimum temperature will cause enzyme to denature (refer to 'temperature sensitive'), Shape of active site changed and substrate no longer fits into it, enzyme no longer effective in catalysing reactions


Substrate concentration

Process, Many enzyme molecules have active sites unoccupied, and limited substrate molecules determines reaction rate., Increase in substrate concentration-> More active sites used, higher chances of successful collisions between substrates and enzymes, Eventually, substrate concentration will no longer affect enzyme reaction-> Rate of reaction becomes constant. Excess substrate molecules queuing for vacant active sites


Enzyme concentration

Similar diagram to substrate concentration

Process, When enzyme concentration increases, rate of reaction increases proportionally to increase in enzyme concentration-> More active sites available for substrates to react in, When substrate concentration limited, point reached when increasing enzyme concentration no longer has effect as there are many more empty active sites than substrates

pH-> varying optimum pH level for each substrate

Enzyme Inhibition

Competitive inhibitor

Active site is blocked by competitive inhibitor, Competitive inhibitor must be similar to actual substrate molecule, Inhibitor effect can be countered by increasing substrate concentration

Non-competitive inhibitor

Binding of blocker to enzyme away from active site, May also cause a shape change in the whole enzyme molecule including the active site, Substrate can no longer bind, Allosteric Inhibitors/Activators, Changes efficiency of enzyme, They attach to allosteric site away from active site and causes change in conformation of active site-> Substrate can no longer bind with enzyme

Industrial uses of enzymes

Protease enzymes

Active ingredient in washing powder

Usable at high pH and temperature up to 60 Degree celsius

Main function: stain removal

Does not lose their activity around potentially inhibiting chemicals in detergent


Mixture of several enzymes

Used to curdle milk and separate milk into curds and whey

Important in digestion of milk in mammals

Used to make cheese


Degrade pectins which are polysaccharides in plant cell walls

Pectins broken down into galacturonic, Pectin: Gelling agent in fruits, undesirable in fruit juices-> plays a part in soft rot of fruits, Reducing pectin in juices makes juice sweeter and prevents spoil/decay

Galaturonic acid is broken down into sugars

immobilising enzymes

Enzymes anchored to solid support

Attached to inert, insoluble materials

Advantages: Easier to separate enzymes and products. Enzymes more stable and can be manipulated easily. Enzyme can be reused. no purification of product needed.

Example: Removing lactose content of milk