Chemical Reactions and Enzymes Enzymes - Introduction

What happens to the food we eat?

It breaks down into…. Carbohydrate s Proteins Lipid s Nucleic acids!

Let’s look at… Lactose What is lactose? –Lactose is a sugar found in dairy products

They lack an enzyme: LACTASE Vocab: Sugars end in “-ose” Enzymes end in “-ase” But…what is an enzyme? What do people who are lactose-intolerant lack?

Why do we study chemical reactions in biology? Chemistry isn’t just what life is made of, chemistry is also what life does Everything that happens in an organism is based on chemical reactions (growth, response to environment, etc.)

Chemical Reaction A process that changes reactants into products (the end substance in a the reaction). Slow Reactions vs. Fast Reactions

Chemical reactions  breaking bonds in reactants and forming bonds in products

CATABOLIC PATHWAY (CATABOLISM) Release of energy by the breakdown of complex molecules to simpler compounds EX: digestive enzymes break down food ANABOLIC PATHWAY (ANABOLISM) consumes energy to build complicated molecules from simpler ones EX: linking amino acids to form proteins w_combinations/ eng-NZ/chemical_reactions_involve_making_new_combinations_full_size_landscape.jpg

THERMODYNAMICS = the study of energy transformations CLOSED system (EX: liquid in a thermos) = isolated from its surroundings OPEN system energy + matter can be transferred between the system and its surroundings Organisms are open systems

Endergonic vs. Exergonic reactions exergonicendergonic - energy released - digestion - energy invested - synthesis -G-G  G = change in free energy = ability to do work +G+G

Reactions can occur without the help of catalysts, but not at the speed our body requires.

Energy Changes Some reactions release energy and some absorb energy Activation Energy: the energy required to start a reaction

Speeding up Reactions Slow reactions or reactions with high activation energies need a catalyst Catalyst = any substance that lowers the activation energy of a reaction to “speed it up” Enzymes are proteins which act like a catalyst to speed up reactions. (found in the body, plants, animals, food, etc.

Where are enzymes? Enzymes are found in all cells Mostly in the stomach and intestines Enzymes - Introduction

Enzymes Enzymes provide a site where reactants can be brought together to react. In an enzyme-catalyzed reaction, the reactants are called substrates (the starting substance – found in the same place you would find the enzymes – binds to the enzyme and is than made into a product). Each enzyme has a specific shape and a specific portion called the active site, where substrates bind.

The substrates must fit exactly into the active site. This is called the lock and key model. The active site changes shape slightly to hold the substrate – induced fit Once the reaction is complete, the enzyme releases the products of the reaction. Enzymes can join or break substrates into products.

Breaking 1 Substrate into 2 Products Enzymes can break or join substrates into products.

Joining 2 Substrates into 1 Product Roles of Enzymes: 1) regulating chemical pathways 2) making materials 3) releasing energy 4) transferring info

Each enzyme works best at a certain temperature and pH.

What keeps enzymes from doing their jobs? Temperature can affect an enzyme by changing its shape

Changes in pH can also change an enzyme’s shape

When an enzyme changes its shape it can’t do its job. We say it is denatured!

So, if changing the shape of the active site keeps the enzyme from working, what else might keep it from working?

COFACTORS = non-protein enzyme helpers EX: Zinc, iron, copper COENZYMES = organic enzyme helpers Ex: vitamins

COMPETITIVE inhibitor REVERSIBLE; Mimics substrate and competes with substrate for active site on enzyme ENZYME ANIMATION Enzyme Inhibitors

NONCOMPETITIVE inhibitors bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective ENZYME ANIMATION

Digestive enzymes names match the foods they help react Lactase helps break down lactose. Each enzyme is specially designed to react a certain molecule

Lactase is just one enzyme that breaks down lactose but there are many different enzymes at work in your body.

What happens if we don’t have them? Example: Lactose – Lactase We can’t convert it fast enough into glucose So it builds up.. Since our body can’t get rid of it.. We feel sick. (nauseous, throwing up)

More enzymes that break things down in your body… Sucrose = Glucose + Fructose Sucrose is table sugar!

AMYLASE: breaks down starch in your mouth and stomach LIPASE: breaks down fats PEPSIN: breaks down proteins

Every reaction in your body is helped by an enzyme. Enzymes are the “workers” of your body. Enzymes

Factors affecting enzyme function Enzyme concentration –as  enzyme =  reaction rate more enzymes = more frequently collide with substrate –reaction rate levels off substrate becomes limiting factor not all enzyme molecules can find substrate enzyme concentration reaction rate

Factors affecting enzyme function substrate concentration reaction rate Substrate concentration –as  substrate =  reaction rate more substrate = more frequently collide with enzyme –reaction rate levels off all enzymes have active site engaged enzyme is saturated maximum rate of reaction

TEMPERATURE & ENZYME ACTIVITY Each enzyme has an optimal temperature at which it can function (Usually near body temp)  Optimum T°  greatest number of molecular collisions  human enzymes = 35°- 40°C  body temp = 37°C  Heat: increase beyond optimum T°  denaturation = lose 3D shape (3° structure)  Cold: decrease T°  molecules move slower thermometers/001.htm

7 pH reaction rate pepsintrypsin What’s happening here?! pepsin trypsin