1 Enzymes

2 What is Metabolism? sum total chemical activities cells The sum total of the chemical activities of all cells.

3 Two Types of Metabolism Anabolic Pathways Anabolic Pathways Catabolic Pathways Catabolic Pathways

4 Anabolic Pathway Metabolic reactions, consume energy(endergonic), build Metabolic reactions, which consume energy (endergonic), to build complicated molecules from simpler compounds. Photosynthesis Photosynthesis 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 SUN lightenergy (glucose)

5 Catabolic Pathway Metabolic reactions release energy (exergonic)breaking down Metabolic reactions which release energy (exergonic) by breaking down complex molecules in simpler compounds Cellular Respiration Cellular Respiration C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + ATP (glucose) energy

6 Cellular Energy - ATP

7 ATP Components: Components: 1. adenine: nitrogenous base 2. ribose: five carbon sugar 3.phosphate group: chain of 3 ribose adenine PPP phosphate group

8 How does ATP work ? enzymes energy-rich glucose Organisms use enzymes to break down energy-rich glucose to release its potential energy adenosine triphosphate(ATP) This energy is trapped and stored in the form of adenosine triphosphate(ATP)

9 How Much ATP Do Cells Use? each cell 10,000,000 molecules of ATP per second It is estimated that each cell will generate and consume approximately 10,000,000 molecules of ATP per second

Enzymes What are they? Why do we need them? Name some examples ?

Enzymes Globular proteins that catalyse chemical reactions in living organisms Properties Specific Increase rate of the reaction Unchanged at the end of the reaction Need them Reactions too slow to maintain life Can’t increase temperatures/pressure in cells (fatal)

Enzymes Are Proteins The enzyme binds to the substrates by its active site The active site is a pocket formed by the folding of the protein where the substrates bind.

Active site The active site involves a small number of key residues that actually bind the substrates The rest of the protein structure is needed to maintain these residues in position

The Fit Between Enzyme and Substrate is Critical and Precise Hexokinase, an enzyme (blue), binding its substrate, glucose (yellow).

The active site of an enzyme is where substrate is bound. Many Enzymes Work by Altering the Shape of Their Substrates

Enzyme Deficiency and Health Most genetic disorders are due to a deficiency in enzyme function. This archival photo shows three children with the enzyme deficiency that causes phenylketonuria.

An Example Sucrose + H 2 O Glucose + Fructose Substrates Products How do enzymes work?

For a reaction to occur the sucrose and water would have to collide with enough energy to break and form bonds This is the activation energy

Sucrose + H 2 OGlucose + Fructose + + Substrates Products

Energy Progress of reaction Substrates Products High energy intermediate Activation energy

The minimum amount of energy needed to start the reaction, leading to the formation of a high energy intermediate = The Activation energy

Energy Progress of reaction Substrates Products High energy intermediate Activation energy Enzymes reduce the height of the energy barrier

23 Enzyme Function

Lock and Key However certain substances can bind to the enzyme at sites other than the active site and modify its activity (inhibitors/coenzymes) Idea that the enzyme is flexible

25 Cofactors and Coenzymes Inorganic substances (zinc, iron) vitamins enzymatic activity Inorganic substances (zinc, iron) and vitamins (respectively) are sometimes need for proper enzymatic activity. Example : Example : Iron hemoglobin oxygen Iron must be present in the quaternary structure of hemoglobin in order for it to pick up oxygen.

Induced Fit

Enzyme reactions enzyme + substrateenzyme-substrate complex E +SES enzyme-substrate complexenzyme + product ESE +P

Enzyme activity How fast an enzyme is working is called Rate of Reaction Rate of Reaction = Amount of substrate changed (or amount product formed) in a given period of time.

Optimum Condition Enzymes function best or are most active in specific conditions known as optimum conditions.

Enzyme activity Four Variables Temperature pH Enzyme Concentration Substrate Concentration

Rate of Reaction Temperature o C - denatures o C Increase in Activity <5 o C - inactive

Effect of heat on enzyme activty If you heat the protein above its optimal temperature bonds break meaning the protein loses it secondary and tertiary structure Denaturing the protein

Effect of heat on enzyme activty Denaturing the protein ACTIVE SITE CHANGES SHAPE SO SUBSTRATE NO LONGER FITS Even if temperature lowered – enzyme can’t regain its correct shape

Rate of Reaction pH Narrow pH optima WHY?

Rate of Reaction pH Narrow pH optima Disrupt Ionic bonds - Structure Effect charged residues at active site

Rate of Reaction Enzyme Concentration Activity increases as enzyme concentration increases

Rate of Reaction Substrate Concentration Active sites full- maximum turnover Activity increases until all enzymes are “busy” and can process no more substrate

Properties of enzymes Made of protein. Speed up reactions. Are specific. Not used up during the reaction. Require optimum conditions at which they work best. At high temperature they become denatured