bio chapters 5-7
Terms
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- A property of biological membranes that allows some substances to cross more easily than others.
- selective permeability
- An increase or decrease in the density of a chemical substance in an area. Cells often maintain concentration gradients of ions across their membranes. When a gradient exists, the ions or other chemical substances involved tend to move from where they are more concentrated to where they are less concentrated
- concentration gradient
- The loss of electrons from a substance involved in a redox reaction
- oxidation
- In comparing two solutions, referring to the one with a greater solute concentration
- hypertonic
- A plant that uses the Calvin cycle for the initial steps that incorporate CO2 into organic material, forming a three-carbon compound as the first stable intermediate
- C3 plant
- Having the same solute concentration as another solution
- isotonic
- An organic molecule serving as a cofactor. Most vitamins function as coenzymes in important metabolic reactions
- coenzyme
- In comparing two solutions, the one with a lower solute concentration
- hypotonic
- The steps in photosynthesis that occur on the thylakoid membranes of the chloroplast and that convert solar energy to the chemical energy of ATP and NADPH, evolving oxygen in the process.
- light reactions
- spontaneous chemical reaction in which there is a net release of free energy
- exergonic reaction
- The diffusion of water across a selectively permeable membrane
- osmosis
- Organisms that make organic food molecules from CO2, H2O, and other inorganic raw materials: a plant, alga, or autotrophic bacterium
- producers
- A molecule that conveys electrons; one of several membrane proteins in electron transport chains in cells. they shuttle electrons during the redox reactions that release energy used to make ATP
- electron carrier
- 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.
- endocytosis
- The ground tissue of a leaf, sandwiched between the upper and lower epidermis and specialized for photosynthesis.
- mesophyll
- A substance that reduces the activity of an enzyme by entering the active site in place of the substrate whose structure it mimics
- competitive inhibitor
- The chlorophyll a molecule and the primary electron acceptor in a photosystem; they trigger the light reactions of photosynthesis. The chlorophyll donates an electron, excited by light energy, to the primary electron acceptor, which passes an electron to an electron transport chain
- reaction center
- The spontaneous tendency of a substance to move down its concentration gradient from a more concentrated to a less concentrated area
- diffusion
- An enzyme that pairs with NAD+ to shuttle electrons in redox reactions
- dehydrogenase
- A protein that binds selectively to a specific molecule (such as an intercellular mediator or antigen) and initiates a biological response.
- receptor
- A mechanism linking a mechanical or chemical stimulus to a cellular response
- signal transduction
- A chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules to carbon dioxide; occurs within the mitochondrion; the second major stage in cellular respiration
- Krebs cycle
- The addition of electrons to a substance involved in a redox reaction
- reduction
- plant that prefaces the Calvin cycle with reactions that incorporate CO2 into four-carbon compounds, the end product of which supplies CO2 for the Calvin cycle.
- C4 plant
- The transfer of a phosphate group to a molecule
- phosphorylation
- The cellular secretion of macromolecules by the fusion of vesicles with the plasma membrane
- exocytosis
- A flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy
- thylakoid
- Nicotinamide adenine dinucleotide, a coenzyme present in all cells that helps enzymes transfer electrons during the redox reactions of metabolism.
- NAD+
- The movement of specific molecules into a cell by the inward budding of membranous vesicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances
- receptor-mediated endocytosis
- A nonspontaneous chemical reaction in which free energy is absorbed from the surroundings
- endergonic reaction
- An energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP. Most ATP synthesis in cells occurs by ________
- chemiosmosis
- The conversion of pyruvate to carbon dioxide and ethyl alcohol
- alcoholic fermentation
- A cluster of several membrane proteins found in the mitochondrial crista (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. __________ provide a port through which hydrogen ions diffuse into the matrix of a mitrochondrion
- ATP synthase
- The splitting of glucose into pyruvate. this is the one metabolic pathway that occurs in all living cells, serving as the starting point for fermentation or aerobic respiration
- glycolysis
- An organism that obtains organic food molecules without eating other organisms or substances derived from other organisms.
- autotroph
- The process of generating ATP from ADP and phosphate by means of a proton-motive force generated by the thylakoid membrane of the chloroplast during the light reactions of photosynthesis
- photophosphorylation
- Solar energy, or radiation, which travels in space as rhythmic waves and also behaves as discrete packets of energy called photons
- electromagnetic energy
- An organism that makes ATP by aerobic respiration if oxygen is present but that switches to fermentation under anaerobic conditions.
- facultative anaerobe
- 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.
- active transport
- A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes
- pinocytosis
- The second of two major stages in photosynthesis (following the light reactions), involving atmospheric CO2 fixation and reduction of the fixed carbon into carbohydrate
- Calvin cycle
- The control of water balance in organisms living in hypertonic, hypotonic, or terrestrial environments
- osmoregulation
- sequence of electron carrier molecules (membrane proteins) that shuttle electrons during the redox reactions that release energy used to make ATP
- electron transport chain
- The conversion of pyruvate to lactate with no release of carbon dioxide
- lactic acid fermentation
- microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange
- stomata
- The formation of ATP by directly transferring a phosphate group to ADP from an intermediate substrate in catabolism
- substrate-level phosphorylation
- A chemical reaction involving the transfer of one or more electrons from one reactant to another
- redox reaction
- A stacked portion of the thylakoid membrane in the chloroplast. Grana function in the light reactions of photosynthesis.
- granum
- The incorporation of carbon from CO2 into an organic compound by an autotrophic organism (a plant, another photosynthetic organism, or a chemoautotrophic bacterium).
- carbon fixation
- The specific portion of an enzyme that attaches to the substrate by means of weak chemical bonds
- active site
- The spontaneous passage of molecules and ions, bound to specific carrier proteins, across a biological membrane down their concentration gradients
- facilitated diffusion
- An organism that cannot survive in an atmosphere of oxygen. Other substances, such as sulfate or nitrate, are the terminal electron acceptors in the electron transport chains that generate their ATP
- strict anaerobe
- A plant that uses crassulacean acid metabolism, an adaptation for photosynthesis in arid conditions, first discovered in the family Crassulaceae. Carbon dioxide entering open stomata during the night is converted into organic acids, which release CO2 for the Calvin cycle during the day, when stomata are closed
- CAM plant
- The diffusion of a substance across a biological membrane
- passive transport
- An adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed. This energy is used to drive endergonic reactions in cells.
- ATP
- A substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing its conformation so that it no longer binds to the substrate
- noncompetitive inhibitor
- The most prevalent and efficient catabolic pathway for the production of ATP, in which oxygen is consumed as a reactant along with the organic fuel
- cellular respiration
- The entry compound for the Krebs cycle in cellular respiration; formed from a fragment of pyruvate attached to a coenzyme
- acetyl CoA
- Energy stored in the chemical bonds of molecules; a form of potential energy.
- chemical energy
- Any nonprotein molecule or ion that is required for the proper functioning of an enzyme. _________ can be permanently bound to the active site or may bind loosely with the substrate during catalysis.
- cofactor
- A primary mechanism of homeostasis, whereby a change in a physiological variable that is being monitored triggers a response that counteracts the initial fluctuation
- negative feedback
- The compounds that form between the initial reactant, glucose, and the final product, pyruvic acid.
- intermediates
- 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.
- photosystem