Biological Membranes and Transport 3

Flashcards covering key vocabulary related to biological membranes and various types of membrane transport, including passive, active, and vesicular transport, based on the provided lecture notes.

Phospholipid bilayer

The fundamental structure of biological membranes, composed of two layers of phospholipids.

Transmembrane protein

A protein that spans across the entire biological membrane.

Peripheral membrane protein

A protein associated with the surface of the biological membrane.

Oligosaccharide (carbohydrate)

A carbohydrate component found on the surface of cell membranes, often attached to proteins or lipids.

Cholesterol

A lipid component found in biological membranes, contributing to membrane fluidity and stability.

Glycoprotein

A protein with an oligosaccharide (carbohydrate) chain attached, found in biological membranes.

Integral membrane protein

A protein permanently embedded within the biological membrane, including transmembrane proteins.

Fluid-mosaic model

The model describing the structure of biological membranes as a fluid bilayer of phospholipids with embedded and associated proteins.

Membrane Transport

The movement of substances across a biological membrane.

Passive Transport

A type of membrane transport that does not require cellular energy, moving substances down their concentration gradient.

Simple Diffusion

A form of passive transport where substances move directly across the phospholipid bilayer down their concentration gradient.

Facilitated Diffusion

A form of passive transport where substances move across the membrane down their concentration gradient with the help of membrane proteins.

Osmosis

The passive transport of water across a selectively permeable membrane.

Active Transport

A type of membrane transport that requires cellular energy (usually ATP) to move substances, often against their concentration gradient.

Vesicular (Bulk) Transport

A type of membrane transport that involves the movement of substances into or out of the cell using vesicles.

Diffusion

The net movement of particles from an area of higher concentration to an area of lower concentration.

Solute

The substance dissolved in a solvent to form a solution.

Solvent

The substance in which a solute is dissolved.

Steepness of gradient

A factor affecting the rate of diffusion; a steeper concentration gradient increases the rate of movement.

Channel protein

A type of transmembrane protein that forms a hydrophilic pore through the membrane, allowing specific polar substances to diffuse across.

Gated channel

A channel protein whose pore can open or close in response to a stimulus, such as the binding of a ligand.

Ligand

A molecule that binds specifically to another molecule, often a receptor or protein, to initiate a cellular response.

Carrier protein

A transmembrane protein that binds to a specific solute molecule and changes shape to transport it across the membrane.

GLUT1

A carrier protein for glucose found in metabolizing body cells, facilitating glucose transport into cells.

GLUT2

A carrier protein for glucose found in liver cells, facilitating glucose transport, especially when blood glucose is high, for storage as glycogen.

Glycogen

A storage carbohydrate, formed from glucose hydrolysis in liver cells.

Selectively permeable membrane

A membrane that allows certain molecules or ions to pass through it while restricting others.

Hypotonic solution

A solution with a lower solute concentration (and higher water concentration) compared to the inside of a cell, causing water to move into the cell.

Isotonic solution

A solution with the same solute concentration as the inside of a cell, resulting in no net water movement.

Hypertonic solution

A solution with a higher solute concentration (and lower water concentration) compared to the inside of a cell, causing water to move out of the cell.

Aquaporin

A channel protein embedded in the cell membrane that specifically facilitates the rapid movement of water molecules across the membrane.

ATP (Adenosine Triphosphate)

The main energy currency of the cell, composed of adenine, ribose, and three phosphate groups.

Hydrolysis (of ATP)

The chemical process of breaking down ATP into ADP and an inorganic phosphate group, releasing energy.

ADP (Adenosine Diphosphate)

The molecule produced when ATP loses one phosphate group through hydrolysis, representing a lower energy state.

Sodium/Potassium (Na+/K+) Pump

A type of active transport protein that pumps three sodium ions out of the cell and two potassium ions into the cell, against their concentration gradients, using ATP.

Vesicle

A small, membrane-bound sac within a cell involved in the transport and storage of substances during vesicular transport.

Endocytosis

A process of cellular ingestion by which the plasma membrane folds inward to engulf substances, forming a vesicle.

Exocytosis

A process of cellular secretion by which a vesicle fuses with the plasma membrane, releasing its contents to the outside of the cell.

Phagocytosis

A type of endocytosis where the cell engulfs large particles or 'food' by extending pseudopodia, forming a food vacuole (cell eating).

Pinocytosis

A type of endocytosis where the cell takes in extracellular fluid and its dissolved solutes by forming small vesicles (cell drinking).

Receptor-mediated endocytosis

A highly specific type of endocytosis where specific ligands bind to receptors on the cell surface, triggering the formation of coated vesicles to internalize the ligands.

LDL (Low-density lipoprotein)

A lipoprotein particle that transports cholesterol in the blood, often referred to as 'bad' cholesterol.

LDL receptor

A cell surface protein that binds to LDL particles, initiating their uptake into the cell via receptor-mediated endocytosis.

Familial Hypercholesterolemia

A genetic disorder characterized by defects in ApoB-100 or LDL receptors, leading to high levels of LDL cholesterol in the blood.

Apo B-100 (protein)

A protein component of LDL particles, essential for their binding to LDL receptors.