Chapters 7-12 Biology Vocabulary Flashcards

Comprehensive vocabulary flashcards covering key terms and definitions from Chapters 7 through 12 of the biological science lecture notes.

Selective permeability

A property of biological membranes that allows them to regulate the passage of substances across them.

Fluid mosaic model

The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids.

Diffusion

The spontaneous movement of a substance down its concentration or electrochemical gradient, from a region where it is more concentrated to a region where it is less concentrated.

Concentration gradient

A region along which the density of a chemical substance increases or decreases.

Osmosis

The diffusion of free water across a selectively permeable membrane.

Facilitated diffusion

The passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific transmembrane transport proteins, requiring no energy expenditure.

Ion channel

A transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient.

Gated channel

A transmembrane protein channel that opens or closes in response to a particular stimulus.

Active transport

The movement of a substance across a cell membrane against its concentration or electrochemical gradient, mediated by specific transport proteins and requiring an expenditure of energy.

Sodium-potassium pump

A transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into the cell.

Membrane potential

The difference in electrical charge (voltage) across a cell's plasma membrane due to the differential distribution of ions.

Electrochemical gradient

The diffusion gradient of an ion, which is affected by both the concentration difference of an ion across a membrane (a chemical force) and the ion's tendency to move relative to the membrane potential (an electrical force).

Proton pump

An active transport protein in a cell membrane that uses ATP to transport hydrogen ions out of a cell against their concentration gradient, generating a membrane potential in the process.

Cotransport

The coupling of the 'downhill' diffusion of one substance to the 'uphill' transport of another against its own concentration gradient.

Exocytosis

The cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane.

Endocytosis

Cellular uptake of biological molecules and particulate matter via formation of vesicles from the plasma membrane.

Ligand

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

Metabolism

The totality of an organism's chemical reactions, consisting of catabolic and anabolic pathways, which manage the material and energy resources of the organism.

Metabolic pathway

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.

Potential energy

The energy that matter possesses as a result of its location or spatial arrangement (structure).

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. See first law of thermodynamics; second law of thermodynamics.

First law of thermodynamics

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

Entropy

A measure of disorder, or randomness.

Second law of thermodynamics

The principle stating that every energy transfer or transformation increases the entropy of the universe. Usable forms of energy are at least partly converted to heat.

Free energy

The portion of a biological system's energy that can perform work when temperature and pressure are uniform throughout the system.

Energy coupling

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

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.

Enzyme

A macromolecule serving as a catalyst, a chemical agent that increases the rate of a reaction without being consumed by the reaction.

Activation energy

The amount of energy that reactants must absorb before a chemical reaction will start; also called free energy of activation.

Substrate

The reactant on which an enzyme works.

Enzyme substrate complex

A temporary complex formed when an enzyme binds to its substrate molecule(s).

Active site

The specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis occurs.

Induced fit

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

Cofactors

Any nonprotein molecule or ion that is required for the proper functioning of an enzyme.

Coenzyme

An organic molecule serving as a cofactor. Most vitamins function as coenzymes in metabolic reactions.

Allosteric regulation

The binding of a regulatory molecule to a protein at one site that affects the function of the protein at a different site.

Cooperativity

A kind of allosteric regulation whereby a shape change in one subunit of a protein caused by substrate binding is transmitted to all the other subunits, facilitating binding of additional substrate molecules to those subunits.

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 ($O_2$) as the final electron acceptor in an electron transport chain and ultimately producing ATP.

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; short for reduction-oxidation reaction.

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.

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 splits glucose into pyruvate. Glycolysis occurs in almost all living cells, serving as the starting point for fermentation or cellular respiration.

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; together with pyruvate oxidation, the second major stage in cellular respiration.

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.

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. ATP synthases are found in the inner mitochondrial membranes of eukaryotic cells and in the plasma membranes of prokaryotes.

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. Under aerobic conditions, most ATP synthesis in cells occurs by chemiosmosis.

Proton motive force

The potential energy stored in the form of a proton electrochemical gradient, generated by the pumping of hydrogen ions ($H^+$) across a biological membrane during chemiosmosis.

Alcohol fermentation

Glycolysis followed by the reduction of pyruvate to ethyl alcohol, regenerating $NAD^+$ and releasing carbon dioxide.

Lactic acid fermentation

Glycolysis followed by the reduction of pyruvate to lactate, regenerating $NAD^+$ with no release of carbon dioxide.

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.

autotroph

An organism that obtains organic food molecules without eating other organisms or substances derived from other organisms.

heterotroph

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

stoma

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.

thylakoids

A flattened, membranous sac inside a chloroplast.

chlorophyll

A green pigment located in membranes within the chloroplasts of plants and algae and in the membranes of certain prokaryotes.

light reactions

The first of two major stages in photosynthesis (preceding the Calvin cycle).

calvin cycle

The second of two major stages in photosynthesis (following the light reactions), involving fixation of atmospheric $CO_2$ and reduction of the fixed carbon into carbohydrate.

NADP+

Nicotinamide adenine dinucleotide phosphate, an electron acceptor that, as NADPH, temporarily stores energized electrons produced during the light reactions.

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 $CO_2$ 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.

visible light

That portion of the electromagnetic spectrum that can be detected as various colors by the human eye, ranging in wavelength from about $380\,nm$ to about $750\,nm$.

photon

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.

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 surrounded by numerous light-harvesting complexes.

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.

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.

rubisco

Ribulose bisphosphate (RuBP) carboxylase, the enzyme that catalyzes the first step of the Calvin cycle (the addition of $CO_2$ to RuBP).

C3 plants

A plant that uses the Calvin cycle for the initial steps that incorporate $CO_2$ 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.

C4 plant

A plant in which the Calvin cycle is preceded by reactions that incorporate $CO_2$ into a four-carbon compound, the end product of which supplies $CO_2$ for the Calvin cycle.

Signal transduction pathway

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

Local regulators

A secreted molecule that influences cells near where it is secreted.

Hormone

In 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 body, changing the target cells' functioning.

G protein-coupled receptor (GPCR)

A signal receptor protein in the plasma membrane that responds to the binding of a signaling molecule by activating a G protein.

G protein

A GTP-binding protein that relays signals from a plasma membrane signal receptor, known as a G protein-coupled receptor, to other signal transduction proteins inside the cell.

Receptor tyrosine kinases

A receptor protein spanning the plasma membrane, the cytoplasmic (intracellular) part of which can catalyze the transfer of a phosphate group from ATP to a tyrosine on another protein.

Ligand gated ion channel

A transmembrane protein containing a pore that opens or closes as it changes shape in response to a signaling molecule (ligand), allowing or blocking the flow of specific ions; also called an ionotropic receptor.

Protein kinase

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

Protein phosphatase

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

Second messenger

A small, nonprotein, water-soluble molecule or ion, such as a calcium ion ($Ca^{2+}$) or cyclic AMP, that relays a signal to a cell's interior in response to a signaling molecule bound by a signal receptor protein.

Cyclic AMP or cAMP

Cyclic adenosine monophosphate, a ring-shaped molecule made from ATP that is a common intracellular signaling molecule (second messenger) in eukaryotic cells.

Adenylyl cyclase

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

Apoptosis

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

Cell division

The reproduction of cells.

Cell cycle

An ordered sequence of events in the life of a cell, from its origin in the division of a parent cell until its own division into two.

Genome

The genetic material of an organism or virus; the complete complement of an organism's or virus's genes along with its noncoding nucleic acid sequences.

Chromosome

A cellular structure carrying genetic material, found in the nucleus of eukaryotic cells.

Chromatin

The complex of DNA and proteins that makes up eukaryotic chromosomes.

Sister chromatids

Two copies of a duplicated chromosome attached to each other by proteins at the centromere and, sometimes, along the arms.

Mitosis

A process of nuclear division in eukaryotic cells conventionally divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase.

Mitotic phase

The phase of the cell cycle that includes mitosis and cytokinesis.