Cell Membrane Structure, Function, and Transport Mechanisms

What is the Fluid Mosaic Model?

A phospholipid bilayer with proteins embedded or associated, forming a flexible and dynamic membrane.

What happens to membrane fluidity when temperature decreases?

Membrane fluidity decreases.

How do organisms adapt membranes in cold conditions?

They increase unsaturated fatty acids and shorter fatty acid tails.

What are the three types of membrane proteins?

Integral, Peripheral, and Anchored proteins.

What are integral proteins?

Proteins that span the lipid bilayer.

What are peripheral proteins?

Proteins attached to the surface of the membrane.

What are anchored proteins?

Proteins covalently attached to fatty acids in the bilayer.

How are membranes dynamic?

They constantly form, transform, fuse, and break down, as seen in the endomembrane system.

What is cell adhesion?

The process by which cells attach to each other using proteins and carbohydrates.

What is homotypic binding?

Binding between identical cell types.

What is heterotypic binding?

Binding between different cell types.

What are tight junctions?

Structures that seal cells together, preventing movement of substances between them.

What are desmosomes?

Structures that anchor cells together for mechanical strength.

What are gap junctions?

Channels that allow direct communication between neighboring cells.

What are integrins?

Proteins that mediate attachment of cells to the extracellular matrix.

What is selective permeability?

Property of membranes that allows some substances to pass but not others.

What is passive transport?

Movement of substances across membranes without energy input, driven by concentration gradients.

What is diffusion?

Net movement of particles from high concentration to low concentration.

What factors affect diffusion rate?

Size and mass of molecules, temperature, solution density, concentration gradient, surface area, and distance.

What types of molecules can freely diffuse through membranes?

Small, uncharged molecules.

What types of molecules cannot freely diffuse through membranes?

Ions and large polar molecules.

What is osmosis?

Diffusion of water across a selectively permeable membrane.

What happens in an isotonic solution?

There is no net movement of water, and the cell maintains its shape.

What happens in a hypotonic solution?

Water enters the cell, causing it to swell.

What happens in a hypertonic solution?

Water leaves the cell, causing it to shrink.

What is facilitated diffusion?

Passive transport of molecules using channel or carrier proteins.

What are channel proteins?

Integral proteins that form hydrophilic tunnels across the membrane.

What are carrier proteins?

Proteins that bind substances and transport them across the membrane.

What are ion channels?

Channel proteins with hydrophilic pores, often gated by signals such as ligands or voltage.

What are aquaporins?

Protein channels that increase water permeability across membranes.

What is active transport?

Transport of substances against concentration or electrical gradients using energy, usually ATP.

What is primary active transport?

Direct use of ATP to transport substances.

What is secondary active transport?

Uses energy from ion concentration gradients created by primary active transport.

What is a symporter?

A transport protein that moves two substances in the same direction.

What is an antiporter?

A transport protein that moves two substances in opposite directions.

What are macromolecules?

Large molecules such as proteins, polysaccharides, and nucleic acids.

How do cells transport macromolecules across membranes?

Using vesicles in processes like endocytosis and exocytosis.

What is endocytosis?

Cellular uptake of substances by vesicle formation.

What is phagocytosis?

Endocytosis of large particles or entire cells.

What is pinocytosis?

Endocytosis of fluids and small dissolved substances.

What is receptor-mediated endocytosis?

Highly specific uptake of macromolecules via receptor proteins.

What is exocytosis?

Release of substances from a cell when vesicles fuse with the plasma membrane.