Cell Membrane, Cell Communication, and Multicellularity Flashcards

Vocabulary flashcards covering cell membrane structure, membrane transport mechanisms, cell signaling, and multicellularity evolution based on Bio 103 Lecture 5.

Fluid mosaic model

A structural model of biological membranes depicting a phospholipid bilayer in which a variety of proteins float.

Peripheral membrane proteins

Membrane proteins that lack exposed hydrophobic groups and do not penetrate the lipid bilayer.

Integral membrane proteins

Membrane proteins containing hydrophobic and hydrophilic regions that are partially embedded in or extend across the lipid bilayer.

Transmembrane proteins

Integral membrane proteins that extend all the way through the phospholipid bilayer, with distinct functions on the inner and outer sides.

Freeze-fracturing

A technique that reveals proteins embedded in the phospholipid bilayers of cellular membranes.

Glycolipid

A molecule formed by a carbohydrate covalently attached to a lipid, located on the outer surface of membranes.

Glycoprotein

A molecule formed by a carbohydrate covalently attached to a protein, serving in cell recognition and binding.

Passive transport

The movement of substances across a membrane without requiring outside energy input, driven by a concentration gradient.

Concentration gradient

The difference in concentration of a substance between one side of a membrane and the other.

Diffusion

The net movement of particles from regions of greater concentration to regions of lesser concentration until equilibrium is reached.

Simple diffusion

The unassisted passive transport of small, water, or lipid-soluble molecules directly across the lipid bilayer.

Osmosis

The diffusion of water molecules across a membrane from a region of higher water concentration to a region of lower water concentration.

Hypertonic solution

A solution that has a higher solute concentration compared to another solution.

Isotonic solution

A solution that has equal solute concentration compared to another solution.

Hypotonic solution

A solution that has a lower solute concentration compared to another solution.

Turgor pressure

Internal pressure built up inside plant cells with rigid cell walls as water enters, preventing further net water entry.

Channel proteins

Integral membrane proteins that form hydrophilic pores or channels through the lipid bilayer.

Carrier proteins

Membrane proteins that bind specific polar substances and undergo shape changes to speed their diffusion across the bilayer.

Aquaporins

Special water channel proteins that facilitate the rapid movement of water across a biological membrane.

Active transport

The movement of substances across a membrane against a concentration or electrical gradient, requiring metabolic energy such as ATP.

Uniporter

A transport protein that moves one single substance in one direction across a membrane.

Symporter

A transport protein that moves two different substances in the same direction across a membrane.

Antiporter

A transport protein that moves two different substances in opposite directions across a membrane.

Primary active transport

Active transport that directly requires the hydrolysis of ATP to move substances across a membrane.

Secondary active transport

Active transport driven by an ion concentration gradient previously established by primary active transport.

Sodium–potassium ($Na^+ - K^+$) pump

An integral membrane glycoprotein and antiporter found in animal cells that carries out primary active transport.

Endocytosis

A cellular process that brings molecules and cells into a eukaryotic cell through plasma membrane invagination and vesicle formation.

Phagocytosis

A form of endocytosis in which large molecules, foreign particles, or entire cells are engulfed into a food vacuole or phagosome.

Pinocytosis

A form of endocytosis in which small vesicles form to bring fluids or dissolved substances into the cell.

Receptor-mediated endocytosis

A highly specific form of endocytosis that relies on membrane receptor proteins in coated pits (lined with clathrin) to bind target substances.

Exocytosis

The process by which material packaged inside membrane vesicles is expelled from a cell.

Signal transduction pathway

The sequence of molecular events leading to a cell's specific response to an external chemical or physical signal.

Autocrine signals

Chemical signals that act directly on the same cell that produced and secreted them.

Juxtacrine signals

Chemical signals that affect only adjacent cells in direct contact.

Paracrine signals

Chemical signals that diffuse through extracellular fluid to affect nearby target cells.

Hormones

Chemical signals that travel through the circulatory system to affect distant target cells in large multicellular organisms.

G protein-linked receptors

Plasma membrane receptors that alter shape upon ligand binding to bind a mobile G protein containing three subunits.

Protein kinase receptors

Plasma membrane receptors that undergo shape changes upon signal binding to catalyze the phosphorylation of themselves or other proteins.

Protein kinase cascade

A signal transduction pathway in which one protein kinase phosphorylates and activates the next kinase in sequence, amplifying the signal at each step.

Second messengers

Small non-protein molecules, such as cAMP, that distribute and amplify signals within the cell during signal transduction.

Cyclic AMP (cAMP)

A common second messenger produced from ATP by the enzyme adenylyl cyclase upon receptor activation.

Volvocine line

A group of aquatic green algae (Chlorophyta) ranging from single-celled Chlamydomonas to colonial Volvox that illustrates the evolution of multicellularity.