BSC1010 Exam 2:

Cell (plasma) membrane

The boundary of every cell on Earth, made of a lipid bilayer with proteins and carbohydrates.

Oligosaccharide

A chain of around 6-10 sugars long

Peripheral membrane protein

A protein found on the inner or outer surface of a cell membrane.

Integral membrane protein

A protein embedded, or integrated, into a cell membrane.

Transmembrane protein

A type of integral membrane protein that spans the lipid bilayer of a cell membrane.

Kinetic energy

The energy of Motion

Diffusion

Movement of ions or molecules from an area of higher concentration to an area of lower concentration

Entropy

The tendency of systems to reach a state of higher disorder or randomness

Osmosis

Movement of water across a membrane, from an area of higher concentration (low solute concentration) to an area of lower concentration (higher solute concentration)

Concentration gradient

A difference in a substance’s concentration in space—usually across a cell membrane

Potential energy

The energy of position

Facilitated diffusion

Diffusion of substances across cell membranes through integral membrane proteins

Passive transport

Movement of ions or molecules that does not require an input of energy; occurs down a gradient and is spontaneous because it increases entropy

Active Transport

Movement of ions or molecules that requires an input of energy; occurs against a gradient and is nonspontaneous because it decreases entropy

Channel protein

An integral membrane protein that forms a tunnel for a specific ion to diffuse across a membrane

Carrier protein

An integral membrane protein that facilitates diffusion of a specific molecule across a membrane by changing shape once the molecule binds to it

Pump

An integral membrane protein that transports specific ions or molecules against their concentration gradient across a membrane; uses energy input

Hormone

A molecule that acts as a long-distance signal between cells in the same multicellular individual.

Ligand

Any molecule that binds to a receptor and triggers a response. Includes both long-distance and short-distance cell-to-cell signals as well as intracellular signals.

Signal transduction

A change in the form of a signal, for example from a hormone that binds to a receptor on the surface of a cell to a second messenger or phosphorylation cascade inside the cell.

Kinase

An enzyme that catalyzes the addition of a phosphate group from ATP to a recipient molecule.

Phosphorylation cascade

A chain reaction that amplifies the signal from a chemical messenger. It occurs when each kinase in a signaling network phosphorylates multiple target proteins, which each then go on to phosphorylate multiple target proteins, and so on.

Second messenger

An ion or small molecule that is released in response to a chemical messenger binding to a cell-surface receptor and acts as an intracellular signal

Cell

The smallest thing that can function as an independent organism; also the building block of larger organisms.

Chromosome

A DNA molecule — circular or linear, depending on the species — usually associated with specific proteins that bind to the DNA.

Ribosome

A molecular machine consisting of RNA and proteins that is the site of protein synthesis.

Organelle

Any membrane-bound compartment inside a cell.

Cytoskeleton

Rod-like proteins inside cells that function in structural support, transport of materials, and movement in some species.

Cell wall

A stiff structure outside the cell membrane composed of carbohydrates and other molecules.

Flagellum

A long, flexible structure that extends from the cell and whips or rotates to propel the cell through water.

Nucleus

An organelle unique to eukaryotes enclosed by a double membrane and containing the cell’s chromosomes.

Mitochondrion

An organelle found in all eukaryotes that functions in “burning” sugars to provide energy for the cell.

Eukaryote

A lineage of species with cells that contain a nucleus and mitochondria.

Prokaryote

A species in the lineages Archaea and Bacteria, with cells that lack a nucleus.

Vacuole

An organelle that stores key molecules; very prominent in most plant cells.

Chloroplast

An organelle that contains the molecular machinery required for photosynthesis.

Cell wall

A stiff structure outside of many types of cells, usually made primarily of carbohydrates.

Endoplasmic reticulum (ER)

A eukaryotic organelle that forms a branching network of narrow tubes and flattened sacs. The place where proteins, membrane lipids, and other molecules are synthesized and/or processed. Can have ribosomes associated with it (rough ER) or not (smooth ER).

Golgi

An organelle comprised of stacked, flattened sacs, where proteins and other molecules are processed and packaged for shipment to specific destinations.

Actin filaments

Small-diameter cytoskeletal fibers made of subunits of the protein actin.

Intermediate filaments

Cytoskeletal fibers whose size is intermediate between those of actin filaments and microtubules and can be made from a variety of protein subunits.

Microtubules

Large-diameter, hollow cytoskeletal elements made of pairs of the proteins α-tubulin and β-tubulin.

Endomembrane system

A collection of machines, cytoskeletal components, and organelles that together produce, process, and transport proteins and lipids destined for organelles, the cell membrane, or outside the cell.

Signal sequence

A series of amino acids at the start of a protein that allows that protein to enter the endomembrane system.

Motor protein

A protein that functions in cell movement through shape changes caused by phosphorylation or dephosphorylation.

Phosphorylation

The addition of a phosphate group (PO₄^3-) to a protein or other molecule. In most cases, the phosphate group comes from ATP. Dephosphorylation is the reverse process.