Enzymes Chapter 3b Copyright © McGraw-Hill Companies Permission required for reproduction or display

Outline Energy Flow in Living Things Laws of Thermodynamics Free Energy Activation Energy

Energy Flow in Living Things Energy - Capacity to perform work. Kinetic Energy - Energy of motion. Potential Energy - Stored energy due to an object’s relative position. Thermodynamics - Study of energy. Kilocalorie (1,000 calories) Calorie - Heat required to raise temperature of one gram of water one degree Celsius.

Energy Flow in Living Things Oxidation-Reduction During a chemical reaction, the energy stored in chemical bonds may transfer to new bonds. Oxidation - Atom or molecule loses an electron. Reduction - Atom or molecule gains an electron. Always take place together.

Laws of Thermodynamics First Law - Energy is neither created nor destroyed; it can only change from one form to another. Total amount of energy in the universe remains constant. During energy conversion, some energy dissipates into the environment as heat. Energy flows one-way from the sun through the environment.

Laws of Thermodynamics Second Law - Entropy in the universe is continuously increasing. Entropy increases continuously.

Free Energy Free Energy of a molecule is the amount of energy actually available to break and subsequently form other chemical bonds. the energy available to do work.

Endergonic Reaction - Requires energy input. Free Energy Endergonic Reaction - Requires energy input. Exergonic Reaction - Occurs spontaneously and releases excess free energy. Copyright © McGraw-Hill Companies Permission required for reproduction or display

Activation Energy Activation Energy is the energy required to destabilize existing chemical bonds and initiate a chemical reaction. Most reactions require energy to get started Catalysis - Process of lowering necessary activation energy.

Activation Energy and Catalysis Copyright © McGraw-Hill Companies Permission required for reproduction or display

Enzymes Enzymes carry out most catalysis in living organisms. Unique three-dimensional shape of an enzyme enables it to stabilize a temporary association between substrates. Lowers activation energy necessary for new bonds to form. (stop here for now!)

Enzymes (continued from last week) How Enzymes Work Most enzymes are globular proteins with one or more active sites for substrates to bind. Substrate binding induces enzyme to adjust its shaped for an induced fit.

Enzyme Catalytic Cycle Copyright © McGraw-Hill Companies Permission required for reproduction or display

Enzymes Enzyme Forms Multienzyme Complexes Enzymes catalyzing different steps of a sequence are loosely associated with one another. Increase catalytic efficiency. Not all Biological Catalysts are Proteins.

Factors Affecting Enzyme Activity Temperature Rate increase with temperature up to temperature optimum. pH Changing concentration of hydrogen ions shifts the balance between positively and negatively charged amino acid residues. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Factors Affecting Enzyme Activity Inhibitors and Activators Inhibitors - Decrease enzyme activity. Competitive - Compete with substrate for same binding site. Noncompetitive - Bind to enzyme in other location, altering shape. Allosteric Site Activators - Bind to allosteric sites and keep enzymes in active configurations. Increase enzyme activity. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Raven - Johnson - Biology: 6th Ed Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Factors Affecting Enzyme Activity Enzyme Cofactors - Enzyme function assisted by additional chemical components. Coenzyme - Nonprotein organic molecule serves as cofactor. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Adenosine triphosphate (energy currency) Composed of: ATP Adenosine triphosphate (energy currency) Composed of: Five-carbon sugar (ribose) Adenine Triphosphate group Energy Storage Phosphate groups are highly negatively charged. Unstable bonds easily broken. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Cells use ATP to drive endergonic reactions. Instability makes ATP ideal for short-term energy source, but a poor candidate for long-term energy storage. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Anabolism - Expend energy to make chemical bonds. Biochemical Pathways Metabolism - Total of all chemical reactions carried out by an organism. Anabolism - Expend energy to make chemical bonds. Catabolism - Harvest energy when chemical bonds are broken. Biochemical Pathways - Products of one reaction becomes substrate for the next. Regulated by feedback inhibition. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Biochemical Pathways Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Evolution of Metabolism Degradation Glycolysis Anaerobic Photosynthesis Nitrogen Fixation Oxygen-Forming Photosynthesis Aerobic Photosynthesis Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Energy Flow in Living Things Laws of Thermodynamics Free Energy Review Energy Flow in Living Things Laws of Thermodynamics Free Energy Activation Energy Enzymes Factors Affecting Enzyme Activity ATP Biochemical Pathways Evolution of Metabolism Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies