Biology Exam #2 (chapters 4, 5, 6)

nucleus

(1) An atom's central core, containing protons and neutrons. (2) The chromosome-containing organelle of a eukaryotic cell. (3) A cluster of neurons.

Microfilaments

A cable composed of actin proteins in the cytoplasm of almost every eukaryotic cell, making up part of the cytoskeleton and acting alone or with myosin to cause cell contraction; also known as an actin filament.

aquaporin

A channel protein in the plasma membrane of a plant, animal, or microorganism cell that specifically facilitates osmosis, the diffusion of water across the membrane.

Ribosome

A complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm; consists of a large and a small subunit. In eukaryotic cells, each subunit is assembled in the nucleolus

Intermediate filaments

A component of the cytoskeleton that includes filaments intermediate in size between microtubules and microfilaments.

saturated

A fatty acid in which all carbons in the hydrocarbon tail are connected by single bonds, thus maximizing the number of hydrogen atoms that are attached to the carbon skeleton.

Chlorophyll

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

channel protein

A hollow or pore-containing protein that spans a cell membrane and acts as a conduit for small molecules, such as charged particles (ions

microtubules

A hollow rod composed of tubulin proteins that make up part of the cytoskeleton in all eukaryotic cells and is found in cilia and flagella

Phospholipid

A lipid made up of glycerol joined to two fatty acids and a phosphate group. The hydrocarbon chains of the fatty acids act as nonpolar, hydrophobic tails, while the rest of the molecule acts as a polar, hydrophilic head. Phospholipids form bilayers that function as biological membranes.

Flagella

A long cellular appendage specialized for locomotion. Like motile cilia, eukaryotic flagella have a core with nine outer doublet microtubules and two inner single microtubules ensheathed in an extension of the plasma membrane. Prokaryotic flagella have a different structure.

entropy

A measure of disorder, or randomness

Cell

A membrane bound structure that is the basic unit of life

Lysosome

A membrane-enclosed sac of hydrolytic enzymes found in the cytoplasm of animal cells and some protists.

central vacuole

A membranous sac in a mature plant cell with diverse roles in reproduction, growth, and development.

Anabolic

A metabolic pathway that consumes energy to synthesize a complex molecule from simpler compounds.

catabolic

A metabolic pathway that releases energy by breaking down complex molecules to simpler compounds.

feedback inhibition

A method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.

Cytoskeleton

A network of microtubules, microfilaments, and intermediate filaments that branch throughout the cytoplasm and serve a variety of mechanical, transport, and signaling functions.

Endergonic

A nonspontaneous chemical reaction, in which free energy is absorbed from the surroundings.

Plasmolysis

A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment.

endosymbiont theory

A process in which a unicellular organism (the "host") engulfs another cell, which lives within the host cell and ultimately becomes an organelle in the host cell; also refers to the hypothesis that mitochondria and plastids were formerly small prokaryotes that began living within larger cells.

Cell Wall

A protective layer external to the plasma membrane in the cells of plants, prokaryotes, fungi, and some protists. Polysaccharides such as cellulose (in plants and some protists), chitin (in fungi), and peptidoglycan (in bacteria) are an important structural component of cell walls.

peripheral membrane protein

A protein loosely bound to the surface of a membrane or to part of an integral protein and not embedded in the lipid bilayer.

Motor Protein

A protein that interacts with cytoskeletal elements and other cell components, producing movement of the whole cell or parts of the cell.

Carrier Protein

A protein that transports specific substance through intracellular compartments, into the extracellular fluid, or across the cell membrane

nonspontaneous

A reaction which cannot occur without the input of work from an external source. ΔG > 0

nucleolus

A specialized structure in the nucleus, consisting of chromatin regions containing ribosomal RNA genes along with ribosomal proteins imported from the cytoplasmic site of rRNA synthesis and ribosomal subunit assembly

exergonic

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

cholesterol

A steroid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids, such as hormones.

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.

Prokaryotic cell

A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles.

eukaryotic cell

A type of cell with a membrane-enclosed nucleus and membrane-enclosed organelles. Organisms with eukaryotic cells (protists, plants, fungi, and animals) are called eukaryotes.

Phagocytosis

A type of endocytosis in which large particulate substances are taken up by a cell. It is carried out by some protists and by certain immune cells of animals

Pinocytosis

A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes.

Desmosome

A type of intercellular junction in animal cells that functions as a rivet.

Tight Junction

A type of intercellular junction in animal cells that prevents the leakage of material between cells.

Gap junction

A type of intercellular junction in animals that allows the passage of materials between cells

flaccid

Limp. Lacking in stiffness or firmness, as in a plant cell in surroundings where there is no tendency for water to enter the cell.

Allosteric Site

Pertaining to or involving a change in the shape and activity of a protein, usually an enzyme, when it binds with a molecule on a region other than its active site

Isotonic

Referring to a solution that, when surrounding a cell, has no effect on the passage of water into or out of the cell.

Hypertonic

Referring to a solution that, when surrounding a cell, will cause the cell to lose water.

hypotonic

Referring to a solution that, when surrounding a cell, will cause the cell to take up water.

Kinetic Energy

The energy associated with the relative motion of objects. Moving matter can perform work by imparting motion to other matter.

potential energy

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

Plasma Membrane

The membrane at the boundary of every cell that acts as a selective barrier, regulating the cell's chemical composition.

rRNA

The most abundant type of RNA, which together with proteins makes up ribosomes.

active transport

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

receptor-mediated endocytosis

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.

Gibb's free energy

The portion of a biological system's energy that can perform work when temperature and pressure are uniform throughout the system. (The change in free energy of a system is calculated by the equation ΔG = ΔH - TΔS

1st law of thermodynamics

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

2nd law of thermodynamics

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

active site

The specific portion of an enzyme that binds the substrate by means of multiple weak interactions and that forms the pocket in which catalysis occurs.

Glycolsylation

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

simple diffusion

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

facilitated diffusion

The spontaneous passage of molecules or ions across a biological membrane with the assistance of specific transmembrane transport proteins.

extracellular matrix

The substance in which animal cells are embedded, consisting of protein and polysaccharides synthesized and secreted by cells.

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.

Integral membrane protein

Typically a transmembrane protein with hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane and with hydrophilic regions in contact with the aqueous solution on either side of the membrane (or lining the channel in the case of a channel protein).

bilayer

a film two molecules thick (formed, e.g., by lipids), in which each molecule is arranged with its hydrophobic end directed inward toward the opposite side of the film and its hydrophilic end directed outward.

inhibitor

a molecule, which binds to enzymes and decreases their activity. Since blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance, many drugs are enzyme inhibitors

spontaneous

a process that can occur without an input of energy

Nuclear Pore

a protein-lined channel in the nuclear envelope that regulates the transportation of molecules between the nucleus and the cytoplasm

equilibrium

a state in which opposing forces or influences are balanced

Semipermeable

allowing certain substances to pass through it but not others, esp. allowing the passage of a solvent but not of certain solutes

transmembrane

existing or occurring across a cell membrane.

Allosteric regulation

feedback control

Autophagy

is the basic catabolic mechanism that involves cell degradation of unnecessary or dysfunctional cellular components through the actions of lysosomes

enzyme

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

cell lysis

refers to the breaking down of a cell, often by viral, enzymic, or osmotic mechanisms that compromise its integrity

Magnification

the action or process of magnifying something or being magnified

transition state

the state corresponding to the highest potential energy along this reaction coordinate. At this point, assuming a perfectly irreversible reaction, colliding reactant molecules always go on to form products

Microscopy

the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye

Adenosine Triphosphate (ATP)

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.

peroxisome

An organelle containing enzymes that transfer hydrogen (H2) from various substrates to oxygen (O2), producing and then degrading hydrogen peroxide (H2O2).

Chloroplasts

An organelle found in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water.

Golgi Apparatus

An organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum and synthesize some products, notably noncellulose carbohydrates.

Mitochondria

An organelle in eukaryotic cells that serves as the site of cellular respiration.

Coenzyme

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

Cofactor

Any nonprotein molecule or ion that is required for the proper functioning of an enzyme. Cofactors can be permanently bound to the active site or may bind loosely with the substrate during catalysis.

endocytosis

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

Nuclear Envelope

The double membrane in a eukaryotic cell that encloses the nucleus, separating it from the cytoplasm.

Cilia

Hair-like projections on the cell surface used for locamotion or the movement of fluid over a cell.

amphipathic

Having both a hydrophilic region and a hydrophobic region.

induced fit

Induced 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.

turgid

Swollen or distended, as in plant cells. (A walled cell becomes turgid if it has a greater solute concentration than its surroundings, resulting in entry of water.)

Rough ER

That portion of the endoplasmic reticulum studded with ribosomes.

smooth ER

That portion of the endoplasmic reticulum that is free of ribosomes

activation energy

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

Energy

The capacity to cause change, especially to do work (to move matter against an opposing force).

exocytosis

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

Cotransport

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

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.

passive transport

The diffusion of a substance across a biological membrane with no expenditure of energy.

Osmosis

The diffusion of water across a selectively permeable membrane

Cell fractionation

The disruption of a cell and separation of its parts by centrifugation