AP Biology - Cellular Energetic Vocabulary

autotrophs

organisms that are able to produce their own food.

chemiosmosis

the movement of hydrogen ions through a membrane during cellular respiration.

fractionation

a process in which a mixture is split up into a number of smaller quantities.

photosynthesis

the process of converting light energy to chemical energy; in the process, carbon dioxide and water are converted into oxygen and sugars.

pigment

a substance that absorbs light.

wavelength

the distance between two repeating points in a wave.

chemical work

the pushing of endergonic reactions that would not occur spontaneously, such as the synthesis of polymers from monomers

transport work

the pumping of substances across membranes against the direction of spontaneous movement

mehcanical work

the beating of cilia, the contraction of muscle cells, and the movement of chromosomes during cellular respiration

energy coupling

the use of an exergonic process to drive an endergonic one

phosphorylated intermediate

a molecule (often a reactant) with a phosphate group covalently bound to it, make it more reactive (less stable) than the unphosphorylated molecule

fermentation

a partial degradation of sugars or other organic fuel that occurs without the use of oxygen and produces ethanol (alcohol) or lactic acid.

aerobic respiration

a catabolic pathway for orgnaic molecules, using oxygen as the final electron acceptor in an ETC and producing ATP

cellular respiration

the catabolic pathways of both anaerobic and aerobic respiration which breaks down organic molecules and use an ETC for the production of ATP. This process includes glycolysis, the Krebs cycle, and oxidative phosphorylation.

oxidation

the loss of electrons from a substance in a redox reaction

reduction

the addition of electrons to a substance in a redox reaction

reducing agent

the electron donor in a redox reaction

oxidizing agent

the electron acceptor in a redox reaction

NAD plus

the oxidized form of nicotinamide adenine dinucleotide, a coenzyme that accepts electrons, becoming NADH. NADH temporarily stores electrons during cellular respiration.

NADH

the reduced form of nicotinamide adenine dinucleotide that temporarily stores electrons during cellular respiration. NADH acts as an electron acceptor during the ETC.

electron transport chain (ETC)

a sequence of electron carrier molecules that shuttle electrons down a series of redox reactions that release energy to make ATP.

glycolysis

occurs in the cytosol, begins the degradation process by breaking down glucose into two molecules of a compound called pyruvate. is the starting point for fermentation and cellular respiration.

citric acid cycle (or Krebs cycle)

oxidizes acetyl-CoA (from pyruvate) into carbon dioxide. occurs within the mitochondria in eukaryotic cells and in the cytosol of prokaryotes and is the second major stage in cellular respiration.

oxidative phosphorylation

the production of ATP using energy from the redox reactions of an electron transport chain and is the third major stage of cellular respiration.

substrate-level phosphorylation

the enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism.

ATP synthase

the enzyme that makes ATP from ADP and inorganic phosphate (Pi). ___ _________ are found in the inner mitochondrial membrane of eukaryotic cells and the plasma membrane of prokaryotes.

proton-motive force

the potential energy stored in the form of a proton electrochemical gradient, generated by the pumping of hydrogen ions across a biological membrane during chemiosmosis.

photoautotrophs

organisms that use light as a source of energy to synthesize organic substances.

heterotrophs

unable to make their own food; they live on compounds produced by other organisms.

decomposers

consume the remains of other organisms and organic litter such as feces and fallen leaves.

endosymbiotic theory

the original chloroplast was a photosynthetic prokaryote that lived inside an ancestor of eukaryotic cells.

mesophyll

the tissue in the interior of the leaf. specilaized for photosynthesis, in C3 and CAM plants, mesophyll cells are located between the upper and lower epidermis; in C4 plants, the are located between the bundle-sheath cells and the epidermis.

stomata

CO₂ enters the leaf and O₂ exits via microscopic pores called…

chlorophyll

a green pigment that gives leaves their color. ___________ participates directly in the light reactions, which convert solar energy into chemical energy.

light reactions

the photo part of photosynthesis. the first of two stages of photosynthesis, these _________ occur in the thylakoid membrane of the chloroplasts or on membranes of certain prokaryotes, convert solar energy into the chemical energy of ATP and NADPH, releasing oxygen in the process.

the Calvin cycle

the synthesis part of photosynthesis. the second of two major stages of photosynthesis, involving fixation of atmospheric carbon dioxide and reduction of the fixed carbon into carbohydrates.

NADPH

the reduced form of nicotinamide adenine dinucleotide phosphate; temporarily stores energized electrons produced during the light reactions. NADPH acts as a “reducing power” that can be passed along to an electron acceptor, reducing it.

photophosphorylation

the process of generating ATP from ADP and phosphate by means of chemiosmosis, using a proton-motive force generated across the thylakoid membrane of the chloroplast or the membrane of certain prokaryotes during the light reactions of photosynthesis.

carbon fixation

the initial corporation of carbon into organic compounds by autotrophic organisms

electromagnetic spectrum

the entire spectrum of electromagnetic radiation, ranging in wavelength from less than a nanometer to more than a kilometer.

visible light

the portion of the electromagnetic spectrum that can be detected as various colors by the human eye, ranging in wavelength form about 380nm to about 740 nm.

photons

a quantum or discrete quantity, of light energy that behaves as if it were a particle.

spectrophotometer

an instrument that measures the proportions of light of different wavelengths absorbed and transmitted by a pigment solution.

absorption spectrum

the range of a pigment’s ability to absorb various wavelengths of light; also a graph plotting a pigment’s light absorption versus wavelength.

chlorophyll a

the key light-capturing pigment that participates directly in the light reactions.

chlorophyll b

an accessory photosynthetic pigment that transfers energy to chlorophyll a

action spectrum

a graph that profiles the relative effectiveness of different wavelengths of radiation in driving a particular process.

carotenoids

hydrocarbons that are various shades of yellow and orange because they absorb violet and blue-green light. an accessory pigment, either yellow or orange, in the chloroplasts of plants and in some prokaryotes. by absorbing wavelengths of light that chlorophyll cannot, ___________ broaden the spectrum of colors that can drive photosynthesis.

photosystem

is composed of a reaction-center complex surrounded by several light-harvesting complexes. there are two types, I and II; they absorb light best at different wavelengths.

reaction-center complex

a complex of proteins associated with a special pair of chlorophyll a molecules and a primary electron acceptor. located centrally in a photosystem, this ______ triggers the light reactions of photosynthesis. excited by light energy, the pair of chlorophylls donates an electron to the primary electron acceptor, which passes an electron to an ETC.

light-harvesting complex

a complex of proteins associated with pigment molecules (including chlorphyll a, chlorophyll b, and carotenoids) that captures light energy and transfers it to reaction-center pigments in a photosystem.

primary-electron acceptor

a molecule capable of accepting electrons and becoming reduced. in the thylakoid membrane of a chloroplast or in the membrane of some prokaryotes, a specialized molecule that shares the reaction-center complex with a pair of chlorophyll a molecules and that accepts an electron from them.

photosystem II

(PSII) one of two light capturing units in a chloroplast’s thylakoid membrane or in the membrane of some prokaryotes; it has two molecules of P680 chlorophyll a at its reaction center.

photosystem I

(PSI) a light capturing unit in a chloroplast’s thylakoid membrane or in the membrane of some prokaryotes; it has two molecules of P700 chlorophyll a at its reaction center.

linear electron flow

a route of electron flow during the light reactions of photosynthesis that involves both photosystems (I and II) and produces ATP, NADPH, and oxygen. the net electron flow is from water to NADP plus.

G3P (glyceraldehyde 3-phosphate)

a three-carbon carbohydrate that is the direct product of the Calvin cycle; it is also an intermediate in glycolysis.

rubisco (RuBP)

ribulose biphosphate (RuBP) carboxylase-oxygenase, the enzyme that normally catalyzes the first step of the Calvin cycle (the addition of carbon dioxide to RuBP). when excess oxygen is present or carbon dioxide levels are low, rubisco can bind oxygen, resulting in photorespiration.

acetyl CoA

Acetyl coenzyme A; the entry compound for the citric acid cycle in cellular respiration, formed from a two-carbon fragment of pyruvate attached to a coenzyme.

alcoholic fermentation

glycolysis followed by the reduction of pyruvate to ethyl alcohol, regenerating NAD-plus and releasing carbon dioxide.

obligate anaerobes

an organism that carries out only fermentation or anaerobic respiration. such organism cannot use oxygen and inf fact may be poisoned by it.

facultative anaerobes

an organism that makes ATP by aerobic respiration if oxygen is present but that switches to anaerobic respiration or fermentation of oxygen is not present.

beta oxidation

a metabolic sequence that breaks down fatty acids to two-carbon fragments that enter the citric acid cycle as acetyl-CoA.