Membrane Structure and Transport

These flashcards cover key concepts related to membrane structure, transport mechanisms, and the role of various molecules and proteins in cell membranes, as discussed in the chapter.

What is the basic structure of the cell membrane?

The cell membrane is primarily composed of a phospholipid bilayer.

What are phospholipids?

Amphipathic molecules that contain a hydrophobic region facing in and a hydrophilic region facing out.

Describe the fluid-mosaic model of the membrane.

The membrane is considered a mosaic of lipid, protein, and carbohydrate molecules, resembling a fluid due to the movement of lipids and proteins relative to each other.

What role does cholesterol play in membranes?

Cholesterol stabilizes membranes and affects their fluidity depending on temperature.

What is passive transport?

Movement of substances across a membrane without the need for energy, occurring down a concentration gradient.

What are the different types of active transport?

Active transport can involve uniporters, symporters, and antiporters, all requiring energy to move substances against their gradient.

Define osmosis.

Osmosis is the movement of water across a membrane from an area of higher water concentration to an area of lower water concentration.

What is the difference between isotonic, hypertonic, and hypotonic solutions?

Isotonic solutions have equal concentrations of solute inside and outside the cell; hypertonic solutions have higher solute concentration outside; hypotonic solutions have lower solute concentration outside.

What are transport proteins?

Transmembrane proteins that facilitate the movement of ions and hydrophilic molecules across membranes.

What are the forms of endocytosis?

Three types of endocytosis are receptor-mediated endocytosis, pinocytosis (cell drinking), and phagocytosis (cell eating).

Describe the function of the sodium-potassium pump.

The sodium-potassium pump actively transports 3 Na+ ions out of the cell and 2 K+ ions into the cell against their gradients.

What is the purpose of contractile vacuoles in freshwater protists?

Contractile vacuoles expel excess water to prevent osmotic lysis in a hypotonic environment.

What is turgor pressure?

Turgor pressure is the pressure exerted by the fluid in the vacuole against the cell wall, helping to maintain plant cell shape and size.

What distinguishes channels from transporters in membrane transport?

Channels form open passageways for direct diffusion, while transporters undergo conformational changes to move solutes across the membrane.

What happens during exocytosis?

Material inside the cell is packaged into vesicles and released into the extracellular space.

What is the role of flippase in membrane fluidity?

Flippase is an enzyme that transports lipids between the two leaflets of the phospholipid bilayer and requires ATP.