2.2 Transport across cell membranes Flashcards
What are the main components of a membrane?
Lipids, proteins and carbohydrates
What is the cell membrane mainly made up of?
Phospholipids
What are the components of a phospholipid?
- a polar hydrophilic phosphate head
- two non-polar hydrophobic fatty acid tails
- glycerol
Why is the structure of the cell membrane know as the ‘fluid mosaic model’?
Molecules are able to move and there are proteins embedded within the phospholipids
What is a phospholipid?
A lipid with a phosphate group attached
What role do phospholipids play in the cell membrane?
They form a barrier against water soluble substances and allow lipid soluble substances to pass through
What are intrinsic proteins?
Proteins that span the entire width of the cell membrane
What role do intrinsic proteins play in the cell membrane?
Allow water soluble molecules to pass through
What are extrinsic proteins?
Proteins on a single layer of the cell membrane
What role do extrinsic proteins play in the cell membrane?
They act as receptors
What are glycoproteins?
Glycogen bonded to a protein
What role do glycoproteins play in the cell membrane?
They act as antigens
What is cholesterol?
A lipid within the membrane
What role does cholesterol play in the cell membrane?
It regulates the fluidity of the cell membrane to maintain rigidity and structure
What is water potential?
The likelihood of water molecules diffusing into or out of a cell or solution
How is water potential affected by an increase in solutes?
Adding solutes decreases the water potential
What is the water potential of pure water?
0 kPa
Is facilitated diffusion an active or passive process?
Passive
What types of molecules diffuse through channel and carrier proteins?
Large, polar or charged molecules
What are channel proteins?
Pores in the membrane for charged particle to pass through. Each channel is specific to a particular particle.
What are carrier protein?
Proteins that allow large molecules to diffuse through the membrane. Each carrier protein is specific to a different molecule.
What is facilitated diffusion?
Diffusion of large or polar molecules through the membrane via channel or carrier proteins in the phospholipid bilayer.
What is a co-transporter?
A type of carrier protein that binds to two molecules at the same time
What is a symport protein?
Protein that transports both substances in the same direction
What is an antiport protein?
Protein that transports the two substances in opposite directions
Name three factors that affect the rate of active transport
- rate of respiration / ATP production
- number of carrier proteins on membrane
- speed of carrier proteins
How does a sodium-potassium pump build a concentration gradient?
Each time the carrier protein pumps, an extra positive ion is released, making the outside more positive than the inside
