Chemical Reactions & Enzymes

There are two types of organisms 1. Autotrophs – organisms that can make their own food. Most use sunlight as an energy source. Examples: plants, bacteria, algae 2. Heterotrophs – organisms that take in food from other sources. They break down food to produce energy. Examples: animals, fungi Chemistry in Biology Basic Cellular Reactions Food Sources

Either way, food must be taken into the cell and used to provide energy. A variety of reactions (physical and chemical) take place on the cellular level in order for this to happen. Metabolism – the total of all the reactions that take place in the cell. Chemistry in Biology Basic Cellular Reactions Food Sources

Anabolic Reaction – reactions that take simple substances and join them to form more complex substances. Endergonic Reaction = Require energy Build new molecules & stores energy Synthesis Reaction = Dehydration Reaction, or loss of H 2 O Example: Protein Synthesis, Carbohydrate Production, Anabolic Steroids  promote cell growth Chemistry in Biology Basic Cellular Reactions Two Types of Reactions

Catabolic Reaction – reactions that take complex substances and break them down to their more basic substances. Exergonic Reaction = Releases/Produces energy Breaks down molecules and gives off energy Hydrolysis Reaction = Condensation Reaction or gains water, takes up H 2 O Example: Digestion, Cellular Respiration Chemistry in Biology Basic Cellular Reactions Two Types of Reactions

Energy – the ability to do work Chemical reactions need energy to take place. Energy is used to break and form bonds. There are 2 types of energy: 1. Potential Energy: stored energy Example: wood, ball at top of hill 2. Kinetic Energy: energy in motion Example: burning wood, ball rolling Chemistry in Biology Energy of Reactions Chemical Reactions

Energy is stored in the bonds of molecules. When bonds are broken, energy is released. When new molecules are created, energy is stored in the bonds formed. Chemistry in Biology Energy of Reactions Chemical Reactions

Activation Energy: the minimum amount of energy required to start a chemical reaction. Chemistry in Biology Energy of Reactions Chemical Reactions

Chemical reactions are controlled by substances called catalysts. A catalyst is a substance that lowers the activation energy needed to start a chemical reaction. Chemistry in Biology Enzymes Chemical Reactions It does not increase how much product is made and it does not get used up in the reaction. One type of catalyst are special proteins called Enzymes.

Lower activation energy in a reaction to reduce damage of cells Substances that are acted upon by enzymes are called substrates. Enzyme named after the substrate it bonds to, name ends in –ase, Protase  Protein Maltase  Maltose Ribonuclease  RNA (Ribonucleic Acid) Chemistry in Biology Enzymes Chemical Reactions

Co-enzyme – small molecules that will work with an enzyme to control a reaction. These are not needed in all reactions. Chemistry in Biology Enzymes Chemical Reactions

Enzymes are very specific in shape and structure. A special region on the enzyme where the substrate attaches is called the active site Lock and Key Model: the active site is VERY specific, only a certain substrate will attach to the active site. Once the substrate binds to the enzyme, this molecule is called the Enzyme Substrate Complex Chemistry in Biology Model of an Enzyme Chemical Reactions

Purpose of the Enzyme Substrate Complex (ESC) is to lower the activation energy of the reaction allowing it to speed up. Once the substrate “key” bonds to the enzyme it will split into its various products. The enzyme is free to take on another substrate Chemistry in Biology Model of an Enzyme Chemical Reactions

Chemistry in Biology Model of an Enzyme Chemical Reactions  The reactants that bind to the enzyme are called substrates.  The specific location where a substrate binds on an enzyme is called the active site.

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Induced Fit: the substrate binds to an enzyme, the active site changes shape slightly so it embraces the substrate Chemistry in Biology Induced Fit Model Chemical Reactions

Four factors effect enzyme activity: 1. Temperature Enzymes are heat specific Low temperatures will lower the rate of the reaction Molecules move slower, lessen collisions Heat will increase the rate of the reaction, up to a certain point At 50°C (122°F)enzymes will become denatured Denaturation: the change in the shape of the enzyme destroying the active site Chemistry in Biology Factors Effecting Enzyme Activity Chemical Reactions

Temperature 37° temperature reaction rate What’s happening here?! Chemistry in Biology Factors Effecting Enzyme Activity Chemical Reactions

Four factors effecting enzyme activity: 2. pH Enzymes are pH specific Some enzymes work best at low pH (acidic) Some enzymes work best at high pH (basic) Some enzymes work best at neutral pH Denaturation of the enzyme will occur if the pH is changed. Chemistry in Biology Factors Effecting Enzyme Activity Chemical Reactions

pH 7 reaction rate stomach pepsin intestines trypsin What’s happening here?! Chemistry in Biology Factors Effecting Enzyme Activity Chemical Reactions

Four factors effecting enzyme activity: 3. Concentration of the substrate As substrate concentration increases, so will enzyme activity, up to a certain point. Then it will level out because the enzyme-substrate only occurs when the enzyme’s active site is free. Chemistry in Biology Factors Effecting Enzyme Activity Chemical Reactions

Four factors effecting enzyme activity 4. Chemicals in the environment Chemicals that interfere with the enzyme-substrate complex are called inhibitors. Chemistry in Biology Factors Effecting Enzyme Activity Chemical Reactions

Recall: The main source of energy for living things is glucose. When glucose is broken down by the cell energy is given off in the form of ATP (adenosine triphosphate). Chemistry in Biology Chemical Reactions in the Human Body Chemical Reactions

Cellular Respiration – the process in which glucose is broken down in the cell and the energy is used to make ATP. There are 2 types: Aerobic: respiration which requires oxygen Anaerobic: respiration which does not use oxygen Reaction Equation C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + ATP Chemistry in Biology Chemical Reactions in the Human Body Chemical Reactions

Cellular Respiration consists of 3 main reactions: 1. Glycolysis 2. Citric Acid Cycle; AKA: Krebs Cycle 3. Electron Transport Chain Chemistry in Biology Chemical Reactions in the Human Body Chemical Reactions

Glycolysis: anaerobic reaction that occurs in the cytoplasm of the cell. Citric Acid Cycle: aerobic step that occurs in the mitochondria of the cell. Electron Transport Chain: aerobic step that occurs in the mitochondria. One cycle of Cellular Respiration produces a total of 36 ATP. Chemistry in Biology Chemical Reactions in the Human Body Chemical Reactions