Cell Membrane Flashcards

Flashcards based on lecture notes about cell membranes.

What is the main function of the cell membrane?

To separate the interior of the cell from the outside environment and to regulate the passage of molecules.

What does it mean for a cell membrane to be selectively permeable?

It allows easy diffusion of small, non-polar molecules and regulates the passage of larger, or charged molecules.

Describe the fluid-mosaic model of the cell membrane.

The membrane is a mosaic of lipid, protein, and carbohydrate molecules that can move relative to each other, exhibiting fluid-like properties.

What are the main components of the cell membrane?

Phospholipids, cholesterol, proteins (peripheral and integral), and carbohydrates (glycolipids and glycoproteins).

How do phospholipids arrange themselves in a cell membrane?

Into bilayers with polar groups facing the aqueous surroundings and lipophilic chains facing inward, away from the water.

What is the role of cholesterol in the cell membrane?

It helps regulate membrane fluidity and integrity, stabilizing the membrane at different temperatures.

What is the difference between peripheral and integral membrane proteins?

Peripheral membrane proteins adhere temporarily to the membrane, while integral proteins penetrate the lipid bilayer.

How are carbohydrates attached to the cell membrane and what are their functions?

Carbohydrates attach to lipids (glycolipids) and proteins (glycoproteins) via glycosylation, and they function in cell recognition and adhesion.

Describe the role of Membrane Carbohydrates.

They function in Cellular recognition and Cellular adhesion

What does cell recognition entail?

A,B,O blood typing.

What is the freeze-fracture technique and what did it prove?

A technique that captures membrane dynamics, proving that membranes are bilayers of lipids.

What are the six major functions of membrane proteins?

Transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, and attachment to the cytoskeleton and extracellular matrix.

Name the main types of transport across the cell membrane.

Passive transport (diffusion, osmosis, facilitated diffusion) and active transport (pumps, bulk transport).

Define passive transport.

Movement of molecules across the membrane without the cell expending any energy.

What is diffusion?

The movement of molecules from an area of high concentration to an area of lower concentration.

What factors affect the rate of diffusion?

Concentration gradient, temperature, type of diffusing molecule, and medium of diffusion.

Define osmosis.

The net movement of water from an area of high water potential to an area of lower water potential across a semi-permeable membrane.

Differentiate between hypertonic, hypotonic, and isotonic solutions.

Hypertonic has a higher solute concentration, hypotonic has a lower solute concentration, and isotonic has the same solute concentration on both sides of the cell.

How do cells with and without cell walls respond differently to hypotonic, hypertonic, and isotonic solutions?

Cells without cell walls may burst in hypotonic solutions or shrivel in hypertonic solutions; cells with cell walls become turgid in hypotonic solutions or undergo plasmolysis in hypertonic solutions.

Define facilitated diffusion.

The passive transport of molecules or ions across a plasma membrane via specific transmembrane integral proteins.

What is active transport?

The movement of substances across the membrane against their concentration gradient, requiring energy (ATP).

Describe the function of ion pumps.

Transmembrane proteins that use cellular energy (ATP) to pump ions across a plasma membrane against their concentration gradient.

What is the function of the sodium-potassium pump?

It transports 3 sodium ions out of the cell and 2 potassium ions in, against their concentration gradient.

Define bulk transport.

The process of moving large molecules or pathogens across the membrane using vesicles.

Differentiate between exocytosis and endocytosis.

Exocytosis is the process of vesicles fusing with the plasma membrane and releasing their contents outside the cell, while endocytosis is the process of capturing a substance from outside the cell by engulfing it with the cell membrane.

What are the types of endocytosis?

Receptor-mediated endocytosis, pinocytosis (cellular drinking), and phagocytosis (cellular eating).

Describe receptor-mediated endocytosis.

A selective process of importing materials into the cells where cells only take molecules that bind receptor proteins.