Cell Membranes Flashcards
(37 cards)
Name the current model of the membrane.
Fluid mosaic.
Why is the cell membrane described as fluid?
The membrane moves as a result of individual phospholipid molecules that move relative to each other, therefore it is flexible.
Why is the membrane described like a mosaic?
Due to the components such as proteins embedded in it, it makes it look like a mosaic.
Name 3 ways substances can cross the cell membrane.
Diffusion
Osmosis
Active transport
Describe the structure of a phospholipid.
Name the bonds in a phospholipid.
Polar phosphate head attached to a glycerol which is bonded to 2 non polar fatty acids. The bond is called an ester bond.
How do phospholipids act in the presence of water?
The polar phosphate head is hydrophillic so it attracts to water.
The non polar fatty acid tails is hydrophobic so it repels water.
Describe how the cell membrane is arranged.
Arranged into a phospholipid bilayer where hydrophilic heads point outwards and hydrophobic tails point inwards.
Why can water diffuse through the cell membrane despite being polar?
It is very small.
Why is oxygen and carbon dioxide able to diffuse through the cell membrane?
They are small and uncharged.
Describe the solubility of phospholipids in water.
Phosphate head is soluble.
Fatty acid tails are insoluble.
How do phospholipids arrange when mixed/shaken in water?
They form micelles which are small lipid droplets where the hydrophilic heads point outwards and hydrophobic tails point inwards.
What is an intrinsic protein?
A protein embedded in the membrane.
What is an extrinsic protein?
A protein that is found on the inner or outer surface of the cell membrane.
What is a carrier protein?
A protein that spans across the membrane. The molecule binds to the protein which changes shape to push it across the membrane.
Active transport relies on which protein?
Carrier proteins.
Why do carrier proteins require ATP?
The ATP is needed to change the shape of the carrier protein.
Name 2 molecules that use carrier proteins.
Glucose
Amino acids.
What are channel proteins?
Proteins that span the whole membrane that create ‘channels’ for water soluble ions to move across.
What are channel proteins filled with?
Water.
Why are channel proteins selective to specific ions?
Due to their highly complex tertiary structure.
Facilitated diffusion relies on which 2 types of protein?
Carrier proteins
Channel proteins
How can channel proteins control how much of substance diffuses at a time?
The ends of the channel can open and close.
What do ions do to the channel protein before they can diffuse across the membrane?
They bind to the end of the channel protein.
