plasma membrane Flashcards
(38 cards)
what is the main function of the plasma membrane?
To control the entry and exit of substances between the cell’s internal and external environments.
Describe the fluid mosaic model of the plasma membrane.
A model describing the membrane as a flexible phospholipid bilayer with embedded and moving proteins.
What is the phospholipid bilayer and how are phospholipids arranged within it?
Two layers of phospholipids with hydrophilic (water-loving) heads facing outwards and hydrophobic (water-fearing) tails facing inwards, creating a barrier to water-soluble substances.
What contributes to the fluidity of the plasma membrane?
The phospholipid bilayer’s ability to stretch, contract, break, and reform, along with cholesterol.
What is the role of proteins in the plasma membrane?
They are embedded within the bilayer and perform various functions like transport, signaling, and anchorage.
What does it mean for the plasma membrane to be selectively permeable?
It allows some substances to cross while preventing others from crossing.
Describe the structure of a phospholipid molecule.
It has a hydrophilic head (phosphate group) facing outward and two hydrophobic tails (fatty acid chains) facing inward.
What are integral proteins?
Proteins embedded within the phospholipid bilayer, often spanning the entire membrane (trans-membrane proteins).
What are peripheral proteins?
Proteins attached to the membrane surface, either by binding to lipids or integral proteins.
What is the function of transport proteins?
To facilitate the movement of substances across the membrane.
What are channel proteins?
Transport proteins that form water-filled pores for specific substances (usually small and charged) to diffuse through.
What are carrier proteins?
Transport proteins that bind to specific molecules and change shape to move them across the membrane.
What is the function of receptor proteins?
To bind to signaling molecules and initiate a cellular response.
What is the function of cell identity proteins (glycoproteins, antigens)?
To mark the cell as “self” and distinguish it from foreign cells.
What is the role of cholesterol in the plasma membrane?
To maintain membrane fluidity across different temperatures.
cholesterol maintains space between the fatty acid tails, preventing them from binding strongly together under cold conditions.
Where are carbohydrates located in the plasma membrane and what is their function?
On the external surface, attached to lipids (glycolipids) or proteins (glycoproteins), involved in cell recognition.
What are the main functions of the plasma membrane?
- Active and selective boundary
- Cell identity
- Receives external signals
- Transports materials
Define hydrophilic and hydrophobic.
Hydrophilic = water-loving (polar), hydrophobic = water-fearing (nonpolar).
What is the difference between passive and active transport?
Passive transport does not require energy (moves down concentration gradient), active transport requires energy (moves against concentration gradient).
Describe simple diffusion.
Movement of solutes across the phospholipid bilayer from high to low concentration, without the help of membrane proteins.
Describe facilitated diffusion.
Movement of solutes from high to low concentration with the help of channel or carrier proteins.
What is osmosis?
The net movement of water across a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration.
What is bulk transport and when is it used?
Bulk transport is the movement of large particles or large quantities of substances across the plasma membrane using vesicles. It is used for molecules that are too large to pass through transport proteins. There are two main types: endocytosis (into the cell) and exocytosis (out of the cell).
what is trans-membrane proteins
Trans-membrane proteins are a type of integral protein that spans the entire width of the plasma membrane, with parts of the protein exposed on both sides of the membrane.
