2.5.1- The Structure Of Cell Membranes Flashcards
Define what a glycolipid is.
A lipid molecule with a chain of carbohydrate molecules attached to it, on the outside of a membrane.
Define what a glycoprotein is.
A protein molecule with a chain of carbohydrate molecules attached, positioned on the outside of a membrane.
The cell surface membrane is called the…
Plasma membrane.
What is permeability?
The ability to let substances pass through.
Explain how some very small molecules can pass through the plasma membrane.
They can diffuse through the membrane in between its structural molecules.
What are the four options for matter that want to pass through a cell membrane?
- diffusing through the bilayer
- protein channels
- protein carriers
- dissolve in the lipid layer and pass through
As the phospholipid bilayer does not allow all substances through, it is referred to as what?
A partially permeable/ selectively permeable membrane.
What determines the permeability of the cell membrane first and foremost?
The component molecules of the membrane.
List seven functions of the plasma membrane at the surface of cells?
- Regulates transport of material in and out of cell
- Can contain enzymes involved in metabolic pathways
- may release chemicals for chemical signalling
- may have receptors for cell signalling
- separates cells components and external environment
- has antigens
- can be the site of chemical reactions
Give a simple definition of the fluid mosaic model
The theory of cell membrane structure with proteins embedded in a sea of phospholipids.
explain why the membranes at the surface of the celebs have antigens.
So the organisms immune system can recognise the cell as being ‘self’ and not attack it
In some organelles, _________ _________ occur on the membranes
Metabolic processes
Explain why a lot of the organelles present in eukaryotic cells have membranes.
So the organelle contents is separate from the cytoplasm and that each organelle is a discrete entity and able to perform its function.
Discuss two reasons as to why mitochondria have folded inner membranes called cristae.
They give a large surface area for some of the reactions of aerobic respiration.
And localise some of the enzymes needed for respiration to occur.
Identify two functions of the inner membrane of chloroplasts (thylakoids).
House chlorophyll
Some of the reactions of photosynthesis occur here
Explain the functions of the plasma membrane of epithelial cells that line the small intestine.
There are digestive enzymes that catalyse some of the final stages of the breakdown of certain sugars on the membrane.
The fluid mosaic model (proposed 1972 by Singer and Nicholson) is a model that allows…
The passage of molecules through the membrane.
The fluid mosaic model explains how cell membranes could me more what?
Dynamic and interact more with the cells environment.
Explain how the FM model describes the fluidity of the membrane.
It suggests the lipid molecules can change places with each other and some of the proteins in the model can move.
What are the three types of protein that can be found spanning the membrane?
Protein channels
Protein carriers
Other proteins that can be attached to the carrier proteins
Describe what three functions the proteins that are attached to the carrier proteins sometimes can have.
Can act as enzymes, antigens or receptor sites for complementary shaped signalling chemicals, e.g. Hormones
Eukaryotic cell membranes contain ________
Cholesterol
What are the three main functions of cholesterol in membranes?
Control membrane fluidity
Maintain mechanical stability
Resist the effects of temperature changes on membrane structure
How thick is the total thickness of the cell membrane?
5-10 nanometers
