A handful of peanuts contains enough energy to boil a quart of water Energy: Potential & Kinetic Energy A handful of peanuts contains enough energy to boil a quart of water It takes about 10 million ATP molecules per second to power an active muscle cell

About 75% of the energy generated by a car’s engine is lost as heat You’d have to run about 14 miles to burn the calories from a pepperoni pizza

Thermodynamics: 1st Law of Thermodynamics: total amount of energy in universe is constant energy can not be created or destroyed energy is just converted from one form to another

Efficiency of chemical reactions is NOT 100% 2nd Law of Thermodynamics: The second law of thermodynamics states that energy cannot be changed from one form to another without a loss of usable energy. Efficiency of chemical reactions is NOT 100% some energy escapes in the form of heat not available to do work a product of all energy conversions pg 100

Cells and Energy

Conservation of Energy Energy is defined as the capacity to perform work Kinetic energy is the energy of motion Potential energy is stored energy see Fig 6.5

Chemical Energy Is a form of potential energy Is found in food, gasoline, and other fuels What drives our cellular metabolism work of cells is powered by potential energy in molecular bonds Fuel rich in chemical energy Heat Waste products poor in chemical Gasoline Oxygen Combustion Kinetic energy of movement Water (a) Energy conversion in a car

Chemical reactions either store or release energy: Energy is stored (endergonic) making a chemical bond form of potential energy ex: photosynthesis - storage of energy in sugar Energy is released (exergonic) initial energy require to start reaction breaking a chemical bond ex: cellular respiration – glycolysis

energy needed to get reaction started Activation Energy: energy needed to get reaction started kinetic energy converted to potential energy heat energy released conversion of potential energy to kinetic energy fig 6.5 biological reactions happen too slowly on their own without help

Enzymes biological catalysts speed up chemical reactions by lowering activation energy less energy needed to start reaction

How Enzymes Work: proteins or nucleic acids binding to specific molecule stressing bonds of molecules to make reactions MORE likely to occur enzymes LOWERS the activation energy of a reaction enzyme shape determines its activity fig 6.6

Degradation vs. Synthesis Enzyme complexes with a single substrate molecule Substrate is broken apart into two product molecules Synthesis: Enzyme complexes with two substrate molecules Substrates are joined together and released as single product molecule

How Enzymes Work: specificity space/binding sites specific to particular molecule e.g., sucrase breaks down sucrose! used over and over enzymes may temporarily transform, but unchanged by reaction optimal conditions e.g., temperature, pH Pepsin is an enzyme whose precursor form (pepsinogen) is released by the chief cells in the stomach and that degrades food proteins into peptides. Trypsin is produced in the pancreas as the inactive proenzyme trypsinogen. Trypsin cleaves peptide chains mainly at the carboxyl side of the amino acids lysine or arginine, except when either is followed by proline. It is used for numerous biotechnological processes fig 6.8 & 6.9

Biochemical Pathways: series of chemical reactions where the product of one reaction is the substrate (reactants) of the next reactions frequently embedded in a membrane where the enzyme assembly is held in close contact to facilitate chemical reactions

Begins with a particular reactant ( A ), Proceeds through several intermediates ( B – F ) , and Terminates with a particular end product ( G ) Each enzyme accelerates a specific reaction Each reaction in a metabolic pathway requires a unique and specific enzyme End product will not appear unless ALL enzymes present and functional E1 E2 E3 E4 E5 E6 A  B  C  D  E  F  G

The active site complexes with the substrates Causes active site to change shape Shape change forces substrates together, initiating bond Induced fit model

Regulation of enzymatic activity: enzyme activity may be repressed by the presence of a repressor molecule which changes the shape of the active site enzyme activity may be “activated” by the binding of an activator; changing the shape of the enzyme which then allows the substrate to fit the active site

product blocks production Enzyme Inhibitors Competitive inhibitor Can inhibit a metabolic reaction Bind to the active site, as substrate impostors Noncompetitive inhibitor Bind at a remote site, changing the enzyme’s shape (like repressor) In some cases, this is called feedback regulation product blocks production

Factors Affecting Enzyme Activity: Feedback Inhibition

Irreversible Inhibition Materials that irreversibly inhibit an enzyme are known as poisons Cyanides inhibit enzymes resulting in all ATP production Penicillin inhibits an enzyme unique to certain bacteria Heavy metals irreversibly bind with many enzymes Nerve gas irreversibly inhibits enzymes required by nervous system

Factors Affecting Enzyme Activity Cells can affect presence/absence of enzyme Cells can affect concentration of enzyme Cells can activate or deactivate enzyme Enzyme Cofactors Molecules required to activate enzyme Coenzymes are organic cofactors, like some vitamins Phosphorylation – some require addition of a phosphate

Which of the following statements regarding enzymes is FALSE? a. Enzymes are proteins that function as catalysts. b. Enzymes display specificity for certain molecules to which they attach. c. Enzyme function is dependent on the three-dimensional structure of the enzyme. d. Enzymes work optimally at the specific pHs and temperatures associated with the environment (e.g., stomach) in which they are produced. e. An enzyme be may be used many times over, but will eventually be worn down and replaced.

ATP - adenosine triphosphate ENERGY STORAGE MOLECULE! energy currency of body highly reactive: ADP + Pi + energy  ATP when bonds break -- energy released when bonds formed -- energy input is stored ATP molecules cycle over and over: Coupled reaction

Coupled Reactions Figure 6.4

Examples of work: muscle contractions breakdown of food make proteins - grow cilia moving particles out of airways cellular work = metabolism “Cellular Work” drives functioning of body needs energy to make energy need oxygen Active transport muscle contraction

Oxidative-Reduction oxidation oxygen has a strong pull on electrons oxidation is the process of oxygen (or another electron acceptor) pulling away an electron an oxidized molecule has LOST an electron reduction reduced atoms or molecule has GAINED an electron may gain more than just an electron (e.g., along with H+) energy is transferred along with the electron

Photosynthesis Respiration Water + Carbon Dioxide Glucose + Oxygen Glucose + Oxygen Water + Carbon Dioxide oxidation reduction oxidation reduction

Electron Transport Chain Membrane-bound carrier proteins found in mitochondria and chloroplasts Physically arranged in an ordered series Starts with high-energy electrons and low-energy ADP Pass electrons from one carrier to another Electron energy used to pump hydrogen ions (H+) to one side of membrane Establishes electrical gradient across membrane Electrical gradient used to make ATP from ADP – Chemiosmosis Ends with low-energy electrons and high-energy ATP

A Metaphor for the Electron Transport Chain

Chemiosmosis

Glucose molecules provide energy to power the swimming motion of sperm Glucose molecules provide energy to power the swimming motion of sperm. In this example, the sperm are changing ______. a. chemical energy into kinetic energy b. chemical energy into potential energy c. kinetic energy into potential energy d. kinetic energy into chemical energy

For the following reaction, energy is released when the reaction goes which direction? ADP + P  ATP right to the left left to the right “a” and “b” depends on the presence of enzymes depends on temperature

Cycle of Energy: Cellular Respiration & Photosynthesis fig 6.11 photosynthesis: conversion of light energy into chemical energy sunlight into glucose (carbohydrate) cellular respiration: conversion of potential energy w/in chemical bonds (w/in carbohydrate) into kinetic energy (cellular work)