Campbell Biology, Exam II

hormones

in the multicellular organisms, one of many types of secreted chemicals that are formed in specialized cells, travel in body fluids, and act on specific target cells in other parts of the organism, changing the target cells’ functioning

signal reception

in cellular communication, the first step of a signaling pathways in which a signaling molecule is detected by a receptor molecule on or in the cell

signal transduction pathway

a series of steps linking a mechanical, chemical, or electrical stimulus to a specific cellular response

ligand

a molecule that binds specifically to another molecule, usually a larger one

protein kinase

an enzyme that transfers phosphate groups from ATP to a protein, thus phosphorylating the protein

phosphorylation cascade

a series of chemical reactions during cell signaling mediated by enzymes (kinases), in which each kinase in turn phosphorylates and activates another, ultimately leading to phosphorylation of many proteins

protein phosphatases

an enzyme that removes phosphate groups from (dephosphorylates) proteins, often functioning to reverse the effect of a protein kinase

second messengers

a molecule that relays messages in a cell from a receptor to a target where an action within the cell takes place

cyclic AMP

cyclic adenosine monophosphate, named because of its ring structure, is a common chemical signal that has a diversity of roles, including as a second messenger in many eukaryotic cells, and as a regulator of some bacterial operons

adenylyl cyclase

an enzyme that converts ATP to cyclic AMP in response to an extracellular signal

inositol trisphosphate

a second messenger that functions as an intermediate between certain signaling molecules and a subsequent second messenger, a calcium ion, causing a rise in cytoplasmic calcium ion concentration 

diacylglycerol

a second messenger produced by the cleavage of phospholipid PIP2 in the plasma membrane

scaffolding proteins

a type of large relay protein to which several other rely proteins are simultaneously attached, increasing the efficiency of signal transduction

apoptosis

a type of programmed cell death, which is brought about by activation of enzymes that break down many chemical components in the cell

photosynthesis

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

autotrophs

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

heterotrophs

an organism that obtains organic food molecules by eating other organisms or substances derived from them

mesophyll

leaf cells specialized for photosynthesis

stomata

a microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange between the environment and the interior of the plant

chlorophyll

a green pigment located in membranes within the chloroplasts of plants and algae and in the membranes of certain prokaryotes; participates directly in the light reactions, which convert solar energy to chemical energy

light reactions

the first two major stages in photosynthesis (preceding the calvin cycle); occur on the thylakoid membranes of the chloroplast or on membranes of certain prokaryotes and convert solar energy to the chemical energy of ATP and NADPH, releasing oxygen in the process

calvin cycle

the second of two major stages in photosynthesis (following the light reactions), involving fixation of atmospheric carbon dioxide and reduction of the fixed carbon into carbohydrate 

NADP plus

the oxidized form of nicotinamide adenine dinucleotide phosphate, an electron carrier that can accept electrons

NADPH

the reduced form of nicotinamide adenine dinucleotide phosphate; temporarily stores energized electrons produced during the light reactions; acts as “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 incorporation of carbon from carbon dioxide into an organic compound by an autotrophic organism (a plant, another photosynthetic organism, or a chemoautotrophic prokaryote)

wavelength

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

electromagnetic spectrum

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

visible light

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

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 of such a range

chlorophyll a

a photosynthetic pigment that participates directly in the light reactions, which convert solar energy to chemical energy

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

an accessory pigment, either yellow or orange, in the chloroplasts of plants and in some prokaryotes; broaden the spectrum of colors that can drive photosynthesis by absorbing wavelengths of light that chlorophyll cannot

photosystem

a light-capturing unit located in the thylakoid membrane of the chloroplast or in the membrane of some prokaryotes, consisting of a reaction-center complex surrounding numerous light-harvesting complexes; two types

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 and triggers the light reactions of photosynthesis

light-harvesting complex

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

primary electron acceptor

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 2

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 1

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 (1 and 2) and produces ATP, NADPH, and oxygen; the net electron flow is from water to NADP plus

cyclic electron flow

a route of electron flow during the light reactions of photosynthesis that involves only photosystem 1 and that produces ATP but not NADPH or oxygen

glyceraldehyde 3-phosphate

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

rubisco

ribulose biphosphate carboxylase-oxygenase, the enzyme that normally catalyzes the first step of the calvin cycle

C3 plants

a plant that uses the calvin cycle for the initial steps that incorporate carbon dioxide into organic material, forming a three-carbon compound as the first stable intermediate

photorespiration

a metabolic pathway that consumes oxygen and ATP, releases carbon dioxide, and decreases photosynthetic output; generally occurs on hot, dry, bright days, when the stomata close and the oxygen to carbon dioxide ratio in the leaf increases, favoring the binding of oxygen rather than carbon dioxide by rubisco

C4 plants

a plant in which the calvin cycle is preceded by reactions that incorporate carbon dioxide into a four-carbon compound, the end product of which supplies carbon dioxide for the calvin cycle

bundle-sheath cells

in C4 plants, a type of photosynthetic cell arranged into tightly packed sheaths around the veins of a leaf

PEP carboxylase

an enzyme that adds carbon dioxide to phosphoenolpyruvate to form ozyloacetate in mesophyll cells of C4 plants; acts prior to photosynthesis

crassulacean acid metabolism

an adaptation for photosynthesis in arid conditions; in this process, a plant takes up carbon dioxide and incorporates it into a variety of organic acids at night; during the day, carbon dioxide is released from organic acids for use in the calvin cycle

CAM plants

a plant that uses crassulacean acid metabolism, an adaptation for photosynthesis in arid conditions; in this process, carbon dioxide entering open stomata during the night is converted to organic acids, which release carbon dioxide for the calvin cycle during the day, when stomata are closed

fermentation

a catabolic process that makes a limited amount of ATP from glucose (or other organic molecules) without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid

aerobic respiration

a catabolic pathway for organic molecules, using oxygen as the final electron acceptor in an electron transport chain and ultimately producing ATP; the most efficient catabolic pathway and is carried out in most eukaryotic cells and many prokaryotic organisms

cellular respiration

the catabolic pathways of aerobic and anaerobic respiration, which break down organic molecules and use an electron transport chain for the production of ATP

redox reactions

a chemical reaction involving the complete or partial transfer of one or more electrons from one reactant to another

oxidation

the complete or partial loss of electrons from a substance involved in a redox reaction

reduction

the complete or partial addition of electrons to a substance involved in a redox reaction

reducing agent

the electron donor in a redox reaction

oxidizing agent

the electron acceptor in a redox reaction

NAH plus

the oxidized form of nicotinamide adenine dinucleotide, a coenzyme that can accept electrons, becoming NADH

NADH

the reduced form of nicotinadmide adenine dinucleotide that temporarily stores electrons during cellular respiration; acts as an electron donor to the electron transport chain

electron transport chain

a sequence of electron carrier molecules (membrane proteins) that shuttle electrons down a series of redox reactions that release energy used to make ATP

glycolysis

a series of reactions that ultimately spits glucose into pyruvate

citric acid cycle

a chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules begun in glycolysis by oxidizing acetyl CoA (derived from pyruvate) to carbon dioxide; occurs within the mitochondrion in eukaryotic cells and in the cytosol of prokaryotes 

oxidative phosphorylation

the production of ATP using energy derived from the redox reactions of an electron transport chain; 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

acetyl CoA

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

cytochromes

an iron-containing protein that is a component of electron transport chains in the mitochondria and chloroplasts of eukaryotic cells and the plasma membrane of prokaryotic cells

ATP synthase

a complex of several membrane proteins that functions in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion (proton) concentration gradient to make ATP

chemiosmosis

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

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

alcohol fermentation

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

lactic acid fermentation

glycolysis followed by the reduction of pyruvate to lactate, regenerating NAD plus with no release of carbon dioxide

obligate anaerobes

an organism that carries out only fermentation or anaerobic respiration

facultative anaerobes

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

beta oxidation

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

metabolism

anabolic or catabolic pathways, which manage the material and energy resources of the organism

metabolic pathways

a series of chemical reactions that either builds a complex molecule (anabolic pathway) or breaks down a complex molecule to simpler molecules (catabolic pathway)

catabolic pathways

a metabolic pathway that releases energy by breaking down complex molecules to simpler molecules

anabolic pathways

a metabolic pathway that consumes energy to synthesize a complex molecule from simpler molecules

bioenergetics

the overall flow and transformation of energy in an organism

kinetic energy

energy associated with the relative motion of objects

thermal energy

kinetic energy associated with the random movement of atoms or molecules

heat

thermal energy in transfer from one object to another

potential energy

an object not presently moving that possess energy

chemical energy

energy available in molecules for release in a chemical reaction; a form of potential energy 

thermodynamics

the study of energy transformations that occur in a collection of matter

first law of thermodynamics

the principle of the conservation of energy: energy can be transferred and transformed, but it cannot be created or destroyed

entropy

a measure of molecular disorder, or randomness

second law of thermodynamics

the principle stating that every energy transfer or transformation increases the entropy of the universe

spontaneous process

a process that occurs without an overall input of energy; a process that is energetically favorable

free energy

the portion of a biological system’s energy that can perform work when temperature and pressure are union throughout the system

exergonic reaction

a spontaneous chemical reaction in which there is a net release of free energy

endergonic reaction

a non-spontaneous chemical reaction in which free energy is absorbed from the surroundings

energy coupling

in cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction

ATP

an adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed

phosphorylated intermediate

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

activation energy

the amount of energy that reactants must absorb before a chemical reaction will start