Ch.3 energy, chemical reaction and cellular respiration

Describe the three classifications of chemical reactions.

1. changes in the chemical structure. 2. changes in the chemical energy 3. whether the reaction is irreversible or reversible. Decomposition reaction - the initial large molecule is digested or broken down into smaller structures. ex- Hydrolysis of sucrose into glucose and fructose (AB --> A+B) All of the decomp rxn in the body are collectively catabolism/catabolic rxn Synthesis rxn occurs when 2 or more atoms, ions, or molecules are combined to form a larger chemical structure as existing bonds are broken and new bonds are formed. ex- dehydration synthesis rxn (A+B-->AB) anabolism/anabolic rxn is the collective term for all synthesis rxns in the body. Exchange rxn in which atoms, molecules, ions, or electrons are exchanged between two chemical structures. An exchange rxn has both decomp and synthesis components and is the most prevalent type of rxn in the human body. (AB+C-->A+BC) Creatine phosphate + adenosine diphosphate (ADP) --> Creatine + ATP

Describe the generalized reversible reaction for release of energy from ATP and explain the role of ATP in the cell.

ATP- adenosine triphosphate. The main energy source for cells, the only "currency" a cell recognizes. Anytimea phosphate group breaks off, energy is released which is used to power different activities of the cell.(contraction, Na/K pump, etc) ATP becomes ADP. If another phosphate group breaks off, more energy isreleased, ADP becomes AMP and so forth. ATP is constantly used and constantly formed.

Distinguish between catabolism and anabolism.

Catabolism - breakdown of complex molecules into simple molecules Anabolism - formation of large, complex molecules from simple molecules.

Explain the effect of temperature on enzymes.

Enzymes function best at optimal temperature- 37C (98.6F). Temperature increases lead to increased enzymatic activity (fever- enhanced ability to fight infectious agents). Temperatures greater than 104f weaken the bonds in an enzyme altering its shape. The protein denatures and permanently loses function.

Describe how pH changes affect enzymes.

Enzymes function best at their optimal pH- 6-8. Increased or decreased H+ (change in pH) in the environment affect amount that binds to the enzyme. A change in the amount of H+ ions attached to the enzyme disrupts the electrostatic interactions that hold the enzyme protein in its shape. Protein shape determines function. Too much disruption could result in denaturation.

With respect to glycolysis, the Krebs (citric acid or TCA) cycle, and the electron transport chain: compare and contrast energy input, efficiency of energy production, oxygen use, by-products and cellular location

Glycolysis occurs within cytosol, doesn't use oxygen & uses 10 enzymes. Glucose is converted to 2 pyruvate molecules, producing 2 net ATP and 2 NADH per glucose. The Citric acid cycle occurs within the mitochondria, is a metabolic pathway that breaks down acetyl CoA with 2 CO2 and CoA released. 1 ATP, 3 NADH and 1 FADH2 are produced per acetyl CoA. The Electron transport system occurs in the cristae membrane of the mitochondrion. requires H+ pumps, electron carriers, and enzyme ATP synthase. H2O is formed from NADH and FADH2 and O2. A H+ gradient is formed and H+ flows down. Energy is harnessed by ATP synthase to produce ATP thru oxidative phosphorylation.

Distinguish between reactants and products.

Reactants are the substances that are present prior to the start of the chemical reaction; they are usually written on the left side of the equation. Products are substances that are formed from the reactants by the subsequent chemical reaction; generally written on the right side.

Define how enzyme and substrate concentration affect reaction rates.

The rate of a chemical rxn may be accelerated by either an increase in enzyme concentration or an increase in substrate concentration. increase in substrate concentration increases the rate of rxn only up to the point of saturation of the enzyme.

Explain the steps by which an enzyme catalyzes a reaction.

To catalyze a reaction, an enzyme will grab on (bind) to one or more reactant molecules. These molecules are the enzyme's substrates. In some reactions, one substrate is broken down into multiple products. In others, two substrates come together to create one larger molecule or to swap pieces. 1. the substrate enters the active site of the enzyme and the enzyme temporarily binds with the substrate to form an enzyme-substrate complex 2. entry of the substrate into the active site induces the conformation (structure) of the enzyme to change slightly, resulting in an even closer fit between substrate and enzyme. this response is referred to as the induced fit model of enzyme function. the interaction is analogous to giving someone a hug 3. stress on chemical bonds in the substrate molecule is caused by the change in enzyme shape. consequently, this stress lowers Ea (activation energy) and the bonds in the substrates are more easily broken, permitting new chemical bonds to be formed. 4. the newly formed molecule, now called the product, is released from the enzyme. the enzyme is then free to repeat the process again with other substrates.

Describe the general function of enzymes.

enzymes are proteins that catalyzes a chemical rxn by lowering the activation energy. they function to accelerate normal physiologic activities. Catalyst are substances that accelerate or promote chemical rxns They allow chemical reactions to occur at normal body temperature fast enough to sustain life.They reduce the activation energy needed to start a chemical reaction.

Discuss the exchange that takes place in an oxidation-reduction reaction.

exchange rxn involving transfer of electrons from one chemical to another; also called redox rxn oxidation occurs when a chemical loses an electron reduction occurs when a chemical gains an electron LEO says GER LEO - Loses Electrons is Oxidized GER - Gains Electrons is Reduced

Explain what occurs in a chemical reaction.

occurs when chemical bonds in an existing molecular structure are broken and new ones formed to produce a different structure. metabolism is the collective term for all biochemical reactions in living organisms.

Explain ATP cycling.

the continuous formation and breakdown of ATP. 1. ATP formation from ADP and free phosphate(Pi), which is an energy requiring (endergonic) rxn, and 2. ATP splitting into ADP and free phosphate (Pi), which is an energy releasing (exergonic) rxn