Enzymes

Front

what are enxymes? + funciton

Back

1. enzymes are protein molecules which act as biological catalysts

2. 2: fyucntion is to gretyl icnrease the rate if a chemical reaction without themselves being changed at the end of the reaction

Front

need of nexyme?

Back

without enxymes, biochemical reactions would take place too slowly to sustain life. and increasing the temperature would increase speed of reaction but would be detrimental to cell

Front

what do enxymes enable and its limitation

Back

enzymes enable metabolic reactions to proceed rapidly BUT AT LOW TEMEPRATURES

AND enzymes are specific and will generally catalyse a single reaction .

enzymes serve to control reactions within each metabolic pathway.

Front

properties of enzymes?

Back

1. 1. most are globular proteins with active sites with a specific shape where reactions takes place

2. 2: they function as biological catalysts and hence have the same properties of catalysts, 1. are effective in small amounts, 2:. remain chemically unaltered at the end of the reaction they catalyse 3: they function by lowering activation energy required for reaction to occur

3: enzymes are extremely effective (10^3-10^8)

4: enzymes have a high degree of specificity, a enzyme either is specific to one type of substrate molecule or a group of substrate molecules with a similar shape. --> specificity is due to the conformation at enzyme's active site

5: enzymes activity can be affected by changes in ph. temp, subs and enzyme conc, and presence of inhibitors or activators ie rate of product formation can be controlled according to needs of cells

Front

modes of actions of enzyme

Back

1. 1. lock and key hypothesis

2. 1:active site of enzyme has a specific shape to which the substrate binds

3. 2: the substrate is imagined as a key, aand its shape is complementary to the shape of the enzyme's active site

4. 3: the shape of the substrate or substrates is complementary and fits exactly into the shape of enzyme's active site to form the enzyme substrate complex.

5. 4: once reaction is completed, products no longer fir into the active site and are released into surrounding medium, leaving active site free to receive new substrate molecule

   2: induced fit hypothesis

6. 1: some enzymes and their active sites were physically flexible structures

7. 2: shape of the substrate is still complementary to enzyme's active site shape but does not fit exactly

8. 3: binding of the substrate to the active site induces a small conformational change in the shape of enzyme which enables the enzyme to fit more snuggly into the active site when forming enzyme substrate complex and enables enzyme to perform its catalytic function more effectively

9. 4:once reaction is completed, products no longer fir into the active site and are released into surrounding medium, leaving active site free to receive new substrate molecule

Front

how do enzymes work at the moleuclar level

Back

1. 1. collision between substrate molecules and enzyme at the correct orientation causes the substrate to bind to the enzyme molecule at its active site, forming a short lived enzyme substrate complex. within the complex, chances of reactions occurring are greatly enhanced

2. 2: the reaction occurs

3. 3: once reaction has occurred, products are formed and released and the unchanged enzyme molecule is also released and is then available to catalyse another cycle of reaction

Front

general structure of enzymes

Back

1. 1. all enzymes have a complex globular shape and are relatively large molecules

2. 2: only active site comes into direct contact with the substrate

3. 3: a substrate binds to the active site of the enzyme, forming the enzyme substrate complex

4. 4: shape of active site is complementary to shape of substrate

Front

activation energy

Back

1. 1. defined as the energy required to make substances react

2. 2: it represents the energy barrier needed to overcome before a reaction can take place to form products

3. 3: the larger the activation energy, slower the reaction at any particular temperature

4. 4: if activation energy is lowered the rate of reaction would be increased

5. 5: enzymes are special biological catalysts which serve to reduce the activation energy required for a chemical reaction to start.

Front

effects if temperature on enzyme activity

Back

1. as temp increases, there is an increase in kinetic energy of enzyme and substrate molecules

2. 2: this results in an increase in the frequency of effective collisions between enzyme and substrate molecules. hence more enzyme substrate complexes are formed per unit time

3. this occurs until optimum temperature is reached

4. 3: if temperature increases beyond optimum temperature, rate of enzymatic reactions decreases rapidly because enzymes is denatured

5. 4: optimum temperature occurs when enzyme is functioning at maximum rate

6. (30-40 degrees celcius)

when ENZYME IS DENATURED:

1: since enzymes are proteins , excessive heat, disrupts the intramolecular bonds specifically hydrogen and hydrophobic bonds which stabilise the structures mainly tertiary and quaternary of the enzyme

2: this causes enzyme to unfold and the precise shape of active site is lost and enzyme is denatured

--> denaturation is IRREVERSIBLE

--> AT COLD TEMPERATURES NEAR OR BELOW FREEZING POINT --> enzyme is INACTIVE, enzyme activty is low due to lesser KE, but they regain CATALYTIC influence when higher temperatures are restored.

Front

effects of Ph on enzyme activity

Back

1: optimum pH is when the maximum rate of reaction occurs

2:at this pH the intramolecular bonds which maintain the protein structure of the enzyme are intact AND the conformation of active site is ideal for substrate binding

3: hence there will be highest frequency of effective collisions between enzymes and substrates, therefore greatest number of enzyme and substrate complexes formed per unit time.

4: when higher or lower pH than optimum pH, it would alter the bonds that help to maintain the conformation of the enzyme and therefore active site and substrate binding would be affected --> THIS IS USALLY REVERISBLE unless extreme pH changes causes severe alteration of conformation of enzyme which denatures the enzyme.