Cell Membranes - Bio CH7

30 flashcards covering key concepts about cell membranes, including structure, function, transport mechanisms, and various types of transport.

What are the main components of cellular membranes?

Lipids and proteins, with carbohydrates also being important.

What is the structure of phospholipids in a membrane?

They form a bilayer with hydrophobic tails inside and hydrophilic heads exposed to water.

What model describes the structure of cellular membranes?

The fluid mosaic model.

What happens to membrane fluidity as temperatures cool?

Membranes switch from a fluid state to a solid state.

How do unsaturated fatty acids affect membrane fluidity?

Membranes rich in unsaturated fatty acids are more fluid than those rich in saturated fatty acids.

What role does cholesterol play in membrane fluidity?

Cholesterol restrains movement at warm temperatures and maintains fluidity at cool temperatures.

What happens to cells in hypertonic solutions?

Cells will lose water, shrivel, and likely die.

What is the process of osmosis?

The diffusion of free water across a selectively permeable membrane.

How do hydrophobic molecules pass through the lipid bilayer?

They dissolve in the lipid bilayer and pass through rapidly by diffusion.

What type of transport proteins assist hydrophilic substances in crossing membranes?

Channel proteins and carrier proteins.

How do channel proteins function?

They provide corridors that allow specific molecules or ions to cross the membrane.

What is facilitated diffusion?

The passive movement of molecules across the plasma membrane aided by transport proteins.

How do carrier proteins accomplish transport?

They bind to molecules and change shape to shuttle them across the membrane.

What is passive transport?

Diffusion of a substance across a membrane with no energy investment on the part of the cell.

What drives the process of diffusion?

The concentration gradient of the substance.

What is tonicity?

The ability of a surrounding solution to cause a cell to gain or lose water.

What is an isotonic solution?

A solution with the same solute concentration as that inside the cell.

What is a hypertonic solution?

A solution with a greater solute concentration than that inside the cell.

What is a hypotonic solution?

A solution with a lower solute concentration than that inside the cell.

What type of environment do paramecium live in, and how do they cope with it?

They live in a hypotonic environment and have a contractile vacuole to pump out excess water.

What is the role of gated channels?

They open or close in response to stimuli to regulate ion transport.

What is active transport?

The movement of solutes against their concentration gradients, requiring energy.

What is the sodium-potassium pump?

An electrogenic pump that actively transports Na+ out and K+ into the cell using ATP.

What is cotransport?

When active transport of a solute indirectly drives the transport of another substance.

What types of transport occur via bulk transport?

Exocytosis and endocytosis.

What occurs during exocytosis?

Transport vesicles fuse with the membrane and release contents outside the cell.

What is phagocytosis?

Cellular eating, where a cell engulfs a particle by extending pseudopodia.

What is pinocytosis?

Cellular drinking, where extracellular fluid is gulped into tiny vesicles.

What defines receptor-mediated endocytosis?

Vesicle formation triggered by solute binding to receptors.

How are emptied receptors recycled after endocytosis?

They are recycled to the plasma membrane by the same vesicle.