Enzymes Sections 5.1-5.9 in Concepts and Connections We couldn’t live with out them!..... And we die if they get messed up!

Chemical Reactions Before we talk about enzymes…. We need to discuss chemical reactions. A chemical reaction: Involves rearrangement of atoms/bonds Reactants are changed into products Reactants are on the left Products are on the right Ex. A + B  C + D reactants products

Chemical Reactions There are four types of reactions: Synthesis Decomposition Single Replacement Double Replacement

Practice: Identify reactants and products

Practice: Identify reactants, products and type of reaction

Practice: Identify reactants, products and type of reaction

Many molecules contain energy Energy (E) is the capacity to do work. Chemical energy is the potential energy of molecules. This is the most important type of energy for living organisms During photosynthesis sun E is stored as chemical E This energy is used by organisms during cellular respiration. Endergonic - chemical reaction that requires energy input Ex. photosynthesis Exergonic – chemical reaction that releases energy Ex. Cellular respiration

Exergonic vs. Endergonic Ex. Lighting gasoline Ex. Dissolving salt in water

The cell uses ATP as energy currency Adenosine triphosphate (ATP) is the cell’s supply of energy. ATP is like money in a checking account Available right away wherever needed. But only limited supply ATP is a nucleotide

What is an enzyme? Known as a biological catalyst Catalyst is something that speeds up a chemical reaction Enzymes speed up reactions in living cells by lowering energy barriers So reactions happen faster, and with less ATP

Enzymes LOWER Activation Energy ACTIVATION ENERGY (EA) - the energy required for a reaction to begin Energy Uncatalysed reaction Catalysed reaction Reactants Products Progress of reaction

Imagine Jumping Beans (pg76)

Or building a snowman… on a hillside

Enzymes Most essential reactions of metabolism occur quickly and precisely for the cell to survive. The cell could die before it gets enough jumping beans or snowballs (cellular products) Without enzymes, many metabolic reactions would occur too slowly to sustain life

Properties of Enzymes They are made of PROTEIN Reusable - they are not changed by the reactions they speed up They are specific - means that only one particular enzyme will work with one particular substrate

Shape is Essential! Like all proteins, enzymes have a unique 3-dimensial shape. (globular) The shape determines which chemical reaction the enzyme catalyzes. Each enzyme can only perform a few types of reactions ….. So there are thousands of enzymes in a cell!

Enzymes are specific! Substrate – the substance that the enzyme works on e.g. Amylase the substrate is starch Product – the substance that is made by the reaction e.g. Breakdown of starch by Amylase the product is Maltose Active site – the part of the enzyme that actually binds the substrate. The shape of this pocket/groove determines what substrates an enzyme acts upon.

Enzymes are specific! Each enzyme only catalyzes one, or a specific few types of reactions. Enzymes are named using the suffix –ase Examples: Lipase – hydrolyzes (breaks down) lipids Protease – hydrolyzes proteins (proteolysis) Amylase – hydrolyzes starch Sucrase – hydrolyzes sucrose into fructose and glucose Catalase – decomposition of H202 into water and O2 ATP synthase – synthesizes ATP

CATALASE Found in animal and plant cells Needed to speed up the breakdown of HYDROGEN PEROXIDE Breaks it down to OXYGEN and WATER The word equation for this looks like this HYDROGEN PEROXIDE OXYGEN AND WATER HPCOW CATALASE

CATALASE

Sucrase Found in small intestine Break down enzyme Breaks SUCROSE down to GLUCOSE AND FRUCTOSE Word equation looks like this SUCROSE GLUCOSE + FRUCTOSE SUCRASE SSGF

Sucrase

Amylase Found in saliva and in the pancreas Break down enzyme Breaks STARCH down to MALTOSE Word equation looks like this STARCH MALTOSE AMYLASE SAM

Amylase

Potato Phosphorylase Synthesis enzyme (puts together) Builds Glucose-1-Phosphate molecules into Starch The formation of starch is tested using iodine solution Starch Glucose-1-Phosphate Phosphorylase G1PPS

Potato Phosphorylase

More about Specific This means amylase will only breakdown starch Catalase will only breakdown hydrogen peroxide Amylase will NOT breakdown hydrogen peroxide Catalase will NOT breakdown starch

Lock and Key All enzymes have a special shaped area that fits onto their substrate This area is called the ACTIVE SITE This Active site will fit onto the substrate while the reaction takes place Because it fits like a lock and key we call this the lock and key mechanism

enzyme substrate complex Model of Lock and Key substrate products enzyme substrate complex active site enzyme enzyme – unchanged

Inducted Fit hypothesis active site is empty 2. Sucrose enters…. “Induced fit” – enzyme changes shape and facilitates reaction 3. Substrate is converted to products glucose and fructose 4. The enzyme releases products and is unchanged Sucrase, pg 77