Cells: Cell membrane structure Flashcards
What is the fluid mosaic model
It is a model describing the structure of the plasma membrane as a mosaic of phospholipids, cholesterol protein and carbohydrates
The plasma membrane of a cell is semi-permeable, what does this mean
This means that the membrane only allows some materials through
What materials can pass through the plasma membrane
Small, non-polar molecules
State the function of a cell surface membrane
- Acts as a barrier between the cell and its environment
- They control which substances enter and leave the cell
- Cell signalling
Name the three ways in which substances move across the cell surface membrane
- Diffusion
- Active transport
- Osmosis
What does the fluid mosaic model explain
- Passive and active movement between cells and their surroundings
- Cell-to-cell interactions
- Cell signalling
What is the structure of a phospholipid bilayer
- Two layers of phospholipid monolayers - consisting of hydrophobic tails (fatty acid chains) and hydrophilic heads (phosphate group)
Which part of the phospholipid is polar
- Phosphate head
Which part of the phospholipid is non-polar
- Fatty acid tail
What forms when phospholipids are mixed/shaken with water
- Micelle
- Phospholipid bilayer
Name the features of a cell membrane
- Phospholipid bilayer
- Intrinsic proteins (protein channels, carrier proteins)
- Extrinsic proteins
- Glycoproteins
- Glycolipids
- Cholesterol
What are intrinsic proteins
Proteins that are fully embedded in the membrane from one side to the other
How are intrinsic proteins adapted to carry out their functions
- They have hydrophobic amino acids on the outside which interacts with the hydrophobic fatty acid ails in the phospholipid bilayer
What are extrinsic proteins
Proteins found on one side of the membrane proteins
Can extrinsic proteins attach to intrinsic proteins
Yes
State the role of extrinsic proteins
- Act as receptors for other molecules - allowing the cell to detect chemicals released from other cells so they can respond (e.g hormones)
- Structural role
What are glycoproteins
Proteins with a carbohydrate attached
State the functions of a glycoprotein
- They can allow cells to attach to each other to form tissue
- They can present antigens to T cells
- They can act as receptors for hormones
What are glycolipids
Lipids with carbohydrate attached (carbohydrate attached to the phosphate head of the phospholipid bilayer)
State the functions of a glyolipid
- They can acts as antigens
- They can be used when cells come in contact with each other - each recognising the glycolipid of another cell
State what carrier proteins are and how they work
A transport protein that carries ions or molecules across the plasma membrane by changing shape after binding to it
State what channel proteins are and how they work
A transport protein that acts like a pore in the plasma membrane letting small ions or water molecules through
What is cholesterol
A lipid that slots between the phospholipid tail
What is the function of cholesterol
- It binds to the hydrophobic tail of the phospholipid causing them to pack more closely together
- This restricts the movement of the phospholipid making the membrane more rigid
Why is cholesterol beneficial to the plasma membrane
It helps to maintain the shape of animal cells (which don’t have cell walls)
