Bio Exam 3 Study Guide

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Energy

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The capacity to do work by moving matter against an opposing force.

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Entropy

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A quantitative measure of disorder or randomness, symbolized by S.

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Chemical energy

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energy stored in the bonds of chemicalcompounds (atoms and molecules). It is released in a chemicalreaction, often producing heat as a by product (exothermic reaction). Batteries, biomass, petroleum, natural gas, and coal are examples of stored chemical energy.

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calorie

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The amount of heat energy required to raise the temperature of 1 g of water 1°C; the amount of heat energy that 1 g of water releases when it cools by 1°C. The Calorie (with a capital C), usually used to indicate the energy content of food, is a kilocalorie.

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Metabolism

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The totality of an organism's chemical processes, consisting of catabolic and anabolic pathways.

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Enzymes

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A class of proteins serving as catalysts, chemical agents that change the rate of a reaction without being consumed by the reaction.

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Activation energy

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The energy that must be possessed by atoms or molecules in order to react.

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Substrates

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The substance on which an enzyme works. (2) The foundation to which an organism is attached.

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Active site

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The specific portion of an enzyme that attaches to the substrate by means of weak chemical bonds.

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Induced fit

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The change in shape of the active site of an enzyme so that it binds more snugly to the substrate, induced by entry of the substrate.

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Enzyme inhibitors

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A method of metabolic control in which the end-product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.

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Feedback regulation

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Control mechanisms whereby an increase or decrease in the level of a particular factor inhibits or stimulates the production, utilization, or release of that factor; important in the regulation of enzyme and hormone levels, ion concentrations, temperature, and many other factors.

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Passive transport

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The diffusion of a substance across a biological membrane.

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Active transport

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The movement of a substance across a biological membrane against its concentration or electrochemical gradient, with the help of energy input and specific transport proteins.

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Diffusion

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The spontaneous tendency of a substance to move down its concentration gradient from a more concentrated to a less concentrated area.

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Selectively permeable

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A property of biological membranes that allows some substances to cross more easily than others.

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Facilitated Diffusion

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The spontaneous passage of molecules and ions, bound to specific carrier proteins, across a biological membrane down their concentration gradients.

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Osmosis

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The diffusion of water across a selectively permeable membrane.

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Solute

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A substance that is dissolved in a solution.

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Hypertonic

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A solution with a greater solute concentration than another, a hypotonic solution.

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Hypotonic

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A solution with a lesser solute concentration than another, a hypertonic solution.

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Isotonic

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Solutions of equal solute concentration.

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Osmoregulation

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Adaptations to control the water balance in organisms living in hypertonic, hypotonic, or terrestrial environments.

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Endocytosis

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The cellular uptake of macromolecules and particulate substances by localized regions of the plasma membrane that surround the substance and pinch off to form an intracellular vesicle.

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Exocytosis

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The cellular secretion of macromolecules by the fusion of vesicles with the plasma membrane.

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Phagocytosis

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A type of endocytosis involving large, particulate substances.

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Autotroph

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An organism that obtains organic food molecules without eating other organisms. Autotrophs use energy from the sun or from the oxidation of inorganic substances to make organic molecules from inorganic ones.

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Heterotroph

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An organism that obtains organic food molecules by eating other organisms or their by-products.

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Producer

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An autotrophic organism, usually a photosynthesizer, that contributes to the net primary productivity of a community.

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Consumer

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A heterotroph that derives its energy from living or freshly killed organisms or parts thereof. Primary consumers are herbivores; higher-level consumers are carnivores.

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Aerobic

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Containing oxygen; referring to an organism, environment, or cellular process that requires oxygen.

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Redox reactions

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A chemical reaction involving the transfer of one or more electrons from one reactant to another; also called oxidation-reduction reaction.

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Oxidation

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The loss of electrons from a substance involved in a redox reaction.

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Reduction

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The gaining of electrons by a substance involved in a redox reaction.

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Glycolysis

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The splitting of glucose into pyruvate. Glycolysis is the one metabolic pathway that occurs in all living cells, serving as the starting point for fermentation or aerobic respiration.

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Cristae

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An infolding of the inner membrane of a mitochondrion that houses the electron transport chain and the enzyme catalyzing the synthesis of ATP.

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Matrix

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The nonliving component of connective tissue, consisting of a web of fibers embedded in homogeneous ground substance that may be liquid, jellylike, or solid.

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Anaerobic

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Lacking oxygen; referring to an organism, environment, or cellular process that lacks oxygen and may be poisoned by it.

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Acetyl CoA

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The entry compound for the Krebs cycle in cellular respiration; formed from a fragment of pyruvate attached to a coenzyme.

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Electron transport chain

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A sequence of electron-carrier molecules (membrane proteins) that shuttle electrons during the redox reactions that release energy used to make ATP.

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ATP synthase

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A cluster of several membrane proteins found in the mitochondrial cristae (and bacterial plasma membrane) that function in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen-ion concentration gradient to make ATP. ATP synthases provide a port through which hydrogen ions diffuse into the matrix of a mitrochondrion.

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Fermentation

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A catabolic process that makes a limited amount of ATP from glucose without an electron transport chain and that produces a characteristic end-product, such as ethyl alcohol or lactic acid.

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Photosynthesis

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The conversion of light energy to chemical energy that is stored in glucose or other organic compounds; occurs in plants, algae, and certain prokaryotes.

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Autotrophs

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An organism that obtains organic food molecules without eating other organisms. Autotrophs use energy from the sun or from the oxidation of inorganic substances to make organic molecules from inorganic ones.

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Photoautotrophs

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An organism that harnesses light energy to drive the synthesis of organic compounds from carbon dioxide.

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chloroplasts

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An organelle found only in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water.

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Chlorophyll

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A green pigment located within the chloroplasts of plants; chlorophyll a can participate directly in the light reactions, which convert solar energy to chemical energy.

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Stomata/stoma

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The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.

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Carbonfixation

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The incorporation of carbon from CO2 into an organic compound by an autotrophic organism (a plant, another photosynthetic organism, or a chemoautotrophic bacterium).

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Electromagnetic spectrum

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The entire spectrum of radiation; ranges in wavelength from less than a nanometer to more than a kilometer.

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Wavelength

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The distance between crests of waves, such as those of the electromagnetic spectrum.

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Photon

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A quantum, or discrete amount, of light energy.

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Photosystem

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The light-harvesting unit in photosynthesis, located on the thylakoid membrane of the chloroplast and consisting of the antenna complex, the reaction-center chlorophyll a, and the primary electron acceptor. There are two types of photosystems, I and II; they absorb light best at different wavelengths.

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Electron transport chain

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A sequence of electron-carrier molecules (membrane proteins) that shuttle electrons during the redox reactions that release energy used to make ATP.