Unit 3 AOS 2 Key Terms Flashcards
Define activation energy
The energy required to initiate a reaction
Define active site
The place of an enzyme molecule where substrate molecules attach
Define adenosine diphosphate (ADP)
A low-energy compound made of adenine and ribose with two phosphate groups attached; it is converted to ATP for energy storage when it gains a phosphate group
Define adenosine triphosphate (ATP)
A high-energy compound made of adenine and ribose with a chain of three phosphate groups attached; it releases energy for cellular reactions when its last phosphate group is removed and it is converted to ADP
Define aerobic cellular respiration
A metabolic reaction that requires oxygen to produce energy for the cell
Define allosteric site
A binding site on a protein (usually an enzyme), that is not part of the active site; binding of a specific molecule at this site results in a change in activity of the protein
Define anabolic reaction
A reaction in which atoms and small molecules are joined together to make larger molecules
Define anaerobic cellular respiration
Cellular respiration in the absence of oxygen
Define ATP synthase
An enzyme that provides energy for the cell through synthesis of ATP
Define biochemical pathway
A series if chemical reactions, each controlled by an enzyme, that brings about the step-by-step conversion of an initial substrate molecule to a final product
Define catabolic reaction
A reaction in which larger molecules are broken down into smaller molecules
Define catalyst
A substance that increases the rate of a reaction without itself undergoing any permanent chemical change
Define cellular metabolism
The sum of metabolic reactions in a cell
Define cellular respiration
A process occurring in all living cells where large molecules are broken down to release energy
Define chlorophyll
The green pigment in plant chloroplasts; it absorbs light energy, making it available for photosynthesis
Define chloroplast
A membrane-bound organelle containing chlorophyll and found in the cytoplasm of plants and algae; its main function is photosynthesis and storage of carbohydrates
Define coenzyme
A small molecule that assists enzyme activity by carrying groups of atoms to or from the reaction
Define cofactor
A molecule that assists enzyme activity by helping the enzyme to fold properly or to facilitate the reaction
Define competitive inhibitor
A substance that competes with a substrate for an enzyme’s active site and thereby reduces the enzyme’s activity
Define electron transport chain
The process involving the stepwise transport of electrons to a final electron acceptor, such as oxygen (in aerobic cellular respiration); ultimately, it creates an electrochemical gradient across membranes to drive the addition of phosphate to ADP to yield ATP
Define endergonic reaction
A chemical reaction that requires the input of energy for it to proceed
Define endothermic reaction
A reaction that absorbs energy from its surroundings
Define exergonic reaction
A spontaneous reaction that releases energy
Define exothermic reaction
A chemical reaction that releases energy, usually in the form of heat or light
Define FADH₂
The loaded form of flavin adenine dinucleotide, a coenzyme that acts in both cellular respiration and photosynthesis
Define feedback inhibition
A control mechanism used by cells in which an enzyme’s activity is stopped or reduced by the product
Define glycogen
An energy-storage polysaccharide in animals that is made of many connected glucose molecules
Define glycolysis
An energy-yielding process occurring in the cytosol of cells in which glucose is partially broken down to pyruvate in enzyme reactions that do not require oxygen; this first stage of cellular respiration produces 2 ATP molecules
Define induced-fit model
A model of enzyme action that explains that the shape of an enzyme’s active site undergoes specific changes, induced by the substrate, to achieve a high degree of specificity with the substrate
Define lactic acid
A product of anaerobic cellular respiration in animals
Define loaded
Carry protons, electrons or chemical groups that are needed for anabolic reactions to occur
lock-and-key model
A model of enzyme action that suggests that the shape if a substrate molecule is an exact fit to the shape of an enzyme’s active site
Define NAD⁺
The unloaded form of nicotinamide adenine dinucleotide phosphate, a coenzyme that has a rile in cellular respiration
Define NADH
The loaded form of nicotinamide adenine dinucleotide, a coenzyme that has a role in cellular respiration
Define NADP⁺
The unloaded form of nicotinamide adenine dinucleotide phosphate, a coenzyme that has a role in photosynthesis
Define NADPH
The loaded form of nicotinamide adenine dinucleotide phosphate, a coenzyme that has a role in photosynthesis
Define non-competitive inhibitor
A molecule that binds to an enzyme at a site other than the active site; this changes the shape of the enzyme so that the substrate can no longer bind to the active site
Define optimum pH
the pH at which an enzyme works fastest
Define optimum temperature
The temperature at which an enzyme works fastest
Define photosynthesis
The anabolic reaction in which light energy is captured by chlorophyll molecules and used to split water molecules, releasing oxygen and hydrogen atoms, which are joined to carbon dioxide to form glucose
Define reactant
The imputs of a chemical reaction that are required to form products or outputs
Define substrate
A substance on which an enzyme acts; a reactant for an enzyme-controlled reaction
Define unloaded
Can accept protons, electrons or chemical groups that are released from catabolic reactions
Define acetyl CoA
A molecule used to convey carbon atoms to the Krebs cycle
Define aerobe
An organism that requires oxygen to survive and reproduce
Define alcoholic fermentation
A form of anaerobic respiration (no oxygen present); glucose is converted to ethanol, a type alcohol
Define anaerobe
An organism that does not require oxygen to survive and reproduce
Define autotroph
An organism that makes its own food from inorganic substances, using light (through photosynthesis) or chemical energy (through chemosynthesis); includes green plants, algae and certain bacteria
Define biofuel
A fuel that has used biomass as its original source
Define biomass
The total dry weight of an organic material
Define C₃ plant
A plant that directly uses CO₂ as an imput for photosynthesis
Define Calvin-Benson cycle
A biochemical pathway in which sugar molecules are produced using carbon dioxide
Define CAM (crassulacean acid metabolism)
A plant that shuts its stomata during the day and fixes carbon during the night when its stomata are open; an adaptation to hot dry environments
Define carbon fixation
The conversion of atmospheric carbon dioxide into carbohydrates in the stroma of chloroplasts in eukaryotic cells
Define chemoautotroph
An organism that makes its own food from inorganic substances, using chemicals as the primary energy food source
Define christae
The folding of the inner mitochondrial membrane into the matrix, thus increasing the total surface area of the inner memebrane
Define cytochrome
A family of membrane-bound proteins that carry out electron transport; located in the mitochondrial inner membrane and in the chloroplast thylakoid membrane
Define grana
The stack of thylakoid membranes in a chloroplast that contain chlorophyll
Define heterotroph
An organism that cannot make its own organic compounds from simple inorganic compounds; it depends on other organisms for nutrients and energy requirements
Define Krebs cycle
A biochemical pathway that requires oxygen and takes place in the mitochondria as part of cellular respiration; acetyl CoA, the product of glycolysis, is broken down to produce carbon dioxide, water and energy in the form of ATP
Define lactic acid fermentation
A form of anaerobic respiration (no oxygen present) that occurs in animal cells and some anaerobic bacteria; glucose is converted to lactic acid
Define light-dependent stage
The fist stage of photosynthesis; it requires light energy that is absorbed by chlorophyll to split water molecules to produce oxygen, hydrogen ions and ATP
Define light-independent stage
The second stage of photosynthesis; through a series of reactions, carbon dioxide, hydrogen ions and ATP produce carbohydrate
Define limiting factor
The factor that limits the rate of reactions
Define matrix
A gel-like fluid in mitochondria, where the Krebs cycle (citric acid cycle) of cellular respiration takes place
Define mitochondrion
An organelle within the cytoplasm that is the site of aerobic cellular respiration, which releases energy for the cell
Define photoautotroph
An organism that makes its own food from inorganic substances, using light as its primary energy source
Define photorespiration
The process in which plants take up oxygen and release carbon dioxide
Define pigment
A molecule that absorbs certain wavelengths of light and reflects all others
Define pyruvate
A three-carbon moleucle that is the end product of glycolysis
Define stroma
The jelly-like, semifluid interior of a chloroplast
Define thylakoid membrane
The interconnected, folded membrane within a chloroplast
