Structure & Function of Plasma Membranes

This collection of flashcards covers essential concepts about the structure and function of plasma membranes, including their components, transport mechanisms, and the principles of membrane fluidity.

What does the fluid mosaic model describe about the plasma membrane?

It describes the plasma membrane as a fluid structure with a mosaic of various proteins embedded in it.

What are the main components of the plasma membrane?

Phospholipids, cholesterol, integral proteins, and peripheral proteins.

Why are membranes asymmetrical?

The inner surface differs from the outer surface, meaning the interior and exterior environments of the cell are not identical.

What are the functions of the plasma membrane?

It defines cell borders, manages material exchange, receives signals, and adheres to neighboring cells.

What is selective permeability in the context of plasma membranes?

It refers to the ability of the plasma membrane to allow some substances to pass through more easily than others.

How does temperature affect membrane fluidity?

Cold temperatures restrict movement, causing phospholipids to be closer together, while warm temperatures create gaps and increase fluidity.

What role does cholesterol play in membrane fluidity?

Cholesterol maintains fluidity by creating space between phospholipids, affecting their movement.

What is the difference between integral proteins and peripheral proteins?

Integral proteins are embedded in the bilayer and span across it, while peripheral proteins are located on the surfaces of the membrane.

What are glycoproteins and glycolipids?

Glycoproteins are carbohydrates bound to proteins, while glycolipids are carbohydrates bound to lipids, both important for cell recognition.

What is the process of diffusion?

The tendency for molecules to spread evenly into available space, moving from areas of high concentration to low concentration.

What is osmosis?

The movement of water across a semipermeable membrane, determined by solute concentration.

What are the types of passive transport?

Diffusion, osmosis, and facilitated diffusion.

What is the sodium-potassium pump?

A primary active transport mechanism that moves 3 Na+ out of the cell and 2 K+ into the cell using ATP.

What is the electrochemical gradient?

The combined effect of concentration and electrical gradients across a membrane, crucial for cell function.

What types of molecules can easily pass through the plasma membrane?

Small, nonpolar molecules like O2 and CO2 can pass easily, while larger or charged molecules require assistance.

What is the role of carrier proteins in active transport?

Carrier proteins bind to specific molecules, change shape, and transport them across the membrane against their concentration gradient.

What distinguishes bulk transport from other forms of transport?

Bulk transport involves the import or export of large molecules or particles via vesicles, such as through endocytosis and exocytosis.

What are the three types of endocytosis?

Phagocytosis (cellular eating), pinocytosis (cellular drinking), and receptor-mediated endocytosis.

How do cells maintain water balance in hypotonic environments?

Plant cells become turgid and healthy due to water uptake, balanced by the cell wall's elastic pressure.

What is osmotic pressure?

The pressure required to stop the net movement of water across a semipermeable membrane.

What happens to cells in hypertonic solutions?

Cells lose water, causing shrinkage or crenation due to higher solute concentration outside the cell.

What is a major factor affecting diffusion rate?

Concentration gradient; the greater the difference in concentration, the faster the diffusion occurs.

What are aquaporins?

Specialized channel proteins that facilitate the rapid transport of water across cell membranes.

How do neurotransmitters use gated ion channels in muscle cells?

They bind to receptors and open channels, allowing ions to flow across the membrane and generate a cellular response.