Micro Chapter 5

There are three basic mechanisms an organism may use to generate ATP

substrate level phosphorylation, oxidative phosphorylation, photophosphorylation

Active Site

The active site is the binding site for the enzyme's substrate.

Enzyme-substrate complex

*When an enzyme and substrate combine, the substrate is transformed into the product, and the enzyme is recovered.

Activation energy

Activation energy is the energy required for a chemical reaction to occur.

Substrate

Enzymes are specific for substrate molecules. This is all shape driven, so anything that alters the shape of the active site will affect enzyme activity.

Electron Transport Chain

a series of molecules in a membrane that pick up electrons from carrier molecules like NADH and FADH2, pass the electrons sequentially to one another in a series of oxidation-reduction reactions, and use the energy released from the electrons to pump protons across the membrane in which they are embeded

Describe Substrate-level phosphorylation

an enzyme transfers a phosphate group from a donor molecule (the substrate) to ADP to form ATP

Chemiosmosis

the energy of the protons moving through the channel energizes the ATP synthase and drives phosphorylation of ADP to make ATP

What is ATP?

"Adenosine triphosphate, a molecule that contains three phosphates held together by high energy bonds. When the third phosphate is cleaved, leaving adenosine diphosphate (ADP), energy is released to drive anabolic reactions. Energy is required to add a third phosphate to ADP to form ATP; the energy comes from catabolic reactions and is stored in the newly formed bond." Or, my shorthand: "The rechargeable battery of the cell".

Define ribozyme.

enzymatic RNA molecules that cut and splice RNA in eukaryotic cells.

The sum of all chemical reactions within a living organism is known as ________.

metabolism

Describe feedback inhibition

occurs when the end product of a metabolic pathway inhibits an enzyme's activity near the start of the pathway.

Differentiate between competitive and noncompetitive inhibition

Competitive Inhibitors - compete with the normal substrate for the active site of the enzyme. Noncompetitive Inhibitors - act on other parts of the apoenzyme or on the cofactor and decrease the enzyme's ability to combine with the normal substrate.

Define enzyme inhibition

Competitive inhibitors compete with the normal substrate for the active site of the enzyme. Noncompetitive inhibitors act on other parts of the apoenzyme or on the cofactor and decrease the enzyme's ability to combine with the normal substrate.

Describe the chemical nature of enzymes

Enzymes are generally globular proteins with characteristic three- dimensional shapes.

Enzyme

Enzymes are proteins, produced by living cells; they catalyze chemical reactions by lowering the activation energy. Enzymes are generally globular proteins with characteristic three- dimensional shapes.

Describe Oxidative phosphorylation

High energy electrons are obtained by oxidation of organic compounds, passed down an electron transport chain to a final electron acceptor, and the energy released during electron movement down the electron transport chain is harnessed to make ATP by chemiosmosis

Describe Photophosphorylation

Low energy electrons are raised to a higher energy level by light, passed down an electron transport chain to a final electron acceptor, and the energy released during electron movement down the electron transport chain is harnessed to make ATP by chemiosmosis

Explain how enzymes function.

*When an enzyme and substrate combine, the substrate is transformed into the product, and the enzyme is recovered.

Describe the efficiency of enzymes

*can operate at relatively low temperatures *are subject to various cellular controls.

Photosynthesis

ATP is generated by photophosphorylation. Cyclic reactions produce ATP. The electrons come from chlorophyll, pass down an electron transport chain, and return to chlorophyll. Non-cyclic reactions produce ATP and NADPH. The electrons come from chlorophyll, travel down an electron transport chain, and are passed to NADP to form NADPH. Chlorophyll is then reduced by H2O or some other oxidizable compound like H2S to replace the lost electrons.

Enzyme components

*Most enzymes are holoenzymes, consisting of a protein portion (apoenzymes) and a nonprotein portion (cofactor). *The cofactor can be a metal ion (iron, copper, magnesium, manganese, zinc, calcium, or cobalt) or a complex organic molecule known as a coenzyme (NAD+, NADP+, FMN, FAD, or coenzyme A).

Fermentation

ATP is generated by oxidation of organic molecules and the final electron acceptor is an organic molecule. The electrons produced by oxidation are not used to make ATP. ATP production is accomplished by substrate-level phosphorylation.

Anabolism vs. Catabolism

Anabolism refers to chemical reactions in which simpler substances are combined to form more complex molecules. Anabolic reactions usually require energy and build new molecules and/or store energy. Catabolism refers to chemical reactions that result in the breakdown of more complex organic molecules into simpler substances. These reactions usually release energy that is used to drive chemical reactions. *The energy of catabolic reactions is used to drive anabolic reactions. *The energy for chemical reactions is stored in ATP

Cellular Respiration: Aerobic & Anaerobic

Cellular respiration - ATP is generated by oxidation of organic molecules, the passage of electrons down an electron transport chain, and chemiosmosis. The final electron acceptor is almost always inorganic. Aerobic - the final electron acceptor is O2. Anaerobic - the final electron acceptor is some inorganic molecule other than O2.

Metabolic Pathway

Metabolic pathways are a series of chemical reactions in which the product of one reaction is the substrate for the next reaction. The chemical reactions are catalyzed by enzymes, so the metabolic pathways present in an organism depend on the enzymes present in the organism. The enzymes present in an organism depend on the genes present in the organism.

Define and describe oxidation-reduction reactions

Oxidation is the removal of one or more electrons from a substrate. Protons (H+) are often removed with the electrons. Reduction of a substrate refers to its gain of one or more electrons. Each time a substance is oxidized, another is simultaneously reduced. NAD+ is the oxidized form; NADH is the reduced form. Glucose is a reduced molecule; energy is released during a cell's oxidation of glucose.

List the four factors that influence enzymatic activity

Temperature - At high temperatures, enzymes undergo denaturation and lose their catalytic properties; at low temperatures, the reaction rate decreases. pH -The pH at which enzymatic activity is maximal is known as the optimum pH. Competitive Inhibitors - compete with the normal substrate for the active site of the enzyme. Noncompetitive Inhibitors - act on other parts of the apoenzyme or on the cofactor and decrease the enzyme's ability to combine with the normal substrate.

Describe what determines which metabolic pathways are present in a particular organism

The chemical reactions are catalyzed by enzymes, so the metabolic pathways present in an organism depend on the enzymes present in the organism. The enzymes present in an organism depend on the genes present in the organism. So: Genes determine enzymes, enzymes determine metabolic pathways

6 classes of enzymes?

The six classes of enzymes are defined on the basis of the types of reactions they catalyze. *Oxidoreductase - catalyzes redox reactions *Transferase - catalyzes transfer of functional groups *Hydrolase - splits chemical bonds by addition of water *Lyase - splits chemical bonds without using water (not a hydrolysis reaction) *Isomerase - rearranges atoms within a molecule *Ligase - forms a chemical bond between two atoms

Metabolism Anabolism Catabolism

The sum of all chemical reactions within a living organism is known as metabolism. Anabolism refers to chemical reactions in which simpler substances are combined to form more complex molecules. Anabolic reactions usually require energy and build new molecules and/or store energy. Catabolism refers to chemical reactions that result in the breakdown of more complex organic molecules into simpler substances. These reactions usually release energy that is used to drive chemical reactions. *The energy of catabolic reactions is used to drive anabolic reactions. *The energy for chemical reactions is stored in ATP