5.1-5.2 plasma membranes Flashcards
(24 cards)
what are intrinsic proteins?
proteins that are embedded through both layers of the cell surface membrane.
what are examples of extrinsic proteins?
channel proteins and carrier proteins
describe the role of a channel protein
channel protein is a water-filled pore that provides a hydrophilic channel for facilitated diffusion of polar molecules and ions
how are intrinsic proteins held in the plasma membrane?
the hydrophobic R groups on their amino acids interact with the hydrophobic core
how does a carrier protein work?
the shape of the protein changes ( the side that is open swaps) to allow the active transport of molecules through
what is an extrinsic protein?
a protein that is embedded in one side of the bilayer but can move between the two sides.
how are extrinsic proteins held in the plasma membrane?
the hydrophilic R groups on there amino acids interact with the polar heads
example of an extrinsic protein
glycoprotein
describe the structure of a glycoprotein
carbohydrate chains attached to the protein by cell adhesion
what is the role of glycoproteins
they have receptor cells that monitor chemical signals (e.g for neurotransmitters or peptide hormones)
what is a glycolipid?
a carbohydrate chain attached to a lipid
what is the role of a glycolipid?
they form cell markers/antigens for cell to cell recognition
what are the 4 main components of a cell surface membrane?
-phospholipids
-cholesterol
-glycoproteins and glycolipids
-transport proteins
what is the role of cholesterol in the cell membrane?
-Regulates the fluidity of the membrane so that is it’s too rigid in low temperatures by stopping the fatty acids from becoming too close to one another and crystallising
- increase the stability of the membrane to prevent it from becoming too fluid at high temperatures
Describe and explain the structure of a cell surface membrane?
forms a phospholipid bilayer:
-2 hydrophobic, non-polar fatty acid tails ( prevent polar molecules from passing through so amino acids and water can’t leak out)
-hydrophillic polar phosphate head
Explain the concept of the fluid mosaic model
Fluid- the membrane is flexible due to the movement of the proteins and phospholipids
Mosaic - scattered pattern of proteins in the bilayer look mosaic
Why is the fluid-mosaic model useful?
Helps to explain:
-cell signalling
-cell to cell interactions
-movement between cells and their surroundings
What is compartmentalisation in membranes?
The separation of areas of organelle with the intracellular membrane, isolating each area from its external environment
It allows the cells to maintain a chemical gradient for the exchange of material
What factors affect the structure of the cell membrane?
Temperature and solvents
How does temperature effect the cell membrane?
-Phospholipids in membranes are constantly moving so when the temperature increases so does the kinetic energy of the phospholipids which causes the membrane to become more fluid until it loses its structure and eventually breaks down.
-proteins within the membrane denature at high temperatures
-increasing temperature increases the permeability of the membrane
What is the effect of solvents on the membrane?
Organic solvents dissolve membranes and break down cells
What is an example of solvents effecting membranes?
-Alcohol in anti-septic wipes dissolve the membranes of bacteria, killing them.
-pure or strong alcohols can kill body cells by dissolving the membranes as the non-polar molecules slot between phospholipids distrupting the membrane
What is the effect of distrupting a cell membrane
The membrane becomes more fluid and more permeable
How could you test the effect of temperature of permeability of a membrane
Using a beetroot and a colorimeter
