What are Enzymes?

• Enzymes are special types of proteins

• They speed up chemical reactions in cells by acting as biological “catalysts”– Involved in breaking bonds in the reactants

and forming new bonds in the products of chemical reactions

– Example: Breakdown of starch into simple sugars

What do Enzymes do?

Enzymes play essential roles in:•regulating chemical pathways.•making material that cells need.•releasing energy.•transferring information.

How do Enzymes work?• Enzymes speed up reactions when a substrate

(molecule) binds to the enzyme’s active site (like a lock and key, or a puzzle piece).

• Enzymes can either break a substance down or link substances together through chemical reactions.

• Remember that Proteins do their jobs, because of their shape

Enzyme substrate complex• Is formed when the enzyme binds to the

reactant molecule.• When the reaction is complete, the enzyme

and the product molecule unbind and the enzyme is available for more reactions.

Hexokinase, an enzyme (blue), binding to its substrate, glucose (yellow).

(The fit between enzymes & substrate is critical & precise

EXAMPLE OF WHAT ENZYMES DO:Dehydration synthesis & also Hydrolysis

• Dehydration synthesis removes water to bond monomers to make polymers (builds up)

• Hydrolysis adds water in to a polymer to break it apart to form the monomers (breaks down)

• http://nhscience.lonestar.edu/biol/dehydrat/dehydrat.html

Enzymes are biological Catalysts• A substance that

speeds up the rate of a chemical reaction.

• They work by

lowering the reaction’s activation energy (which is the energy needed to get a reaction started.

Lowering activation energy with enzymes

Another Activation energy example

Metabolic pathways• The synthesis of biological molecules often requires

many enzyme-catalyzed steps.• The entire set of steps is a metabolic pathway.

Types of Enzymes

• Lipase – Breakdown of fats.

• Protease – breaks down proteins.

Types of Enzymes

• Amylase- Breaks down starch into sugar.

• Polymerase- position and link DNA nucleotides together.

Types of Enzymes• Helicase- unwinds DNA by breaking the

hydrogen bonds.

Factors affecting enzyme action1. Temperature

– Disrupts hydrogen bonds, alters protein shape (denature)

2. pH– hydrogen ion concentration disrupts bonds between

amino acids 3. Substrate Concentration

– Increased substrate concentration increases reaction rate until all enzymes are involved, then reactions level out

4. Enzyme Concentration– Increased enzyme concentration increases reaction rate

until all substrate is used up, then reactions decrease.

These can denature the proteins (enzymes).

Some Diseases caused by lack of or malfunctioning enzymes

• PKU - missing phenylalanine hydroxylase (breaks down an amino acid called phenylalanine).

• Tay-Sachs – lack of Hexosaminidase (breaks down fatty substances, called GM2 gangliosides, in cells of the brain).

• Lactose Intolerance – reduction in production of lactase (breaks down lactose, milk sugar).

• Maple Syrup Urine Disease – lacks an enzyme to breakdown three different amino acids.

Activity: toothpickase

• Follow the directions on your handout to simulate enzyme action and understand the terms involved and what factors affect enzyme action.

• Be able to identify and describe the following terms:– Enzyme– substrate– Enzyme-substrate complex– Activation energy– Dehydration synthesis– Hydrolysis– Metabolism– Catalyst

Take the name of the substrate the enzyme works on and add the suffix -ase

Example: Lactose Lactase

Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College

http://en.wikipedia.org/wiki/File:Lactase.jpg

Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College

http://en.wikipedia.org/wiki/File:Digestive_system_diagram_en.svg