Fluid Mosiac Model Flashcards
What does the cell membrane being partially permeable mean?
Small molecules can pass between the gaps in the phosolipds
What is a phospholipid made of?
A tail made up of 2 fatty acids with a phosphate group head attached to it
Is the phosphate head hydrophobic or hydrophillic and why?
Hydrophillic
The phosphate group heads are polar so they attract other polar molecules
Are the lipid tails hydrophobic or hydrophillic and why?
Hydrophobic
The lipid tails are non-polar so they repel polar molecules
How do the phospholipids molecules in cell membrane arrange themselves?
They automatically arrange themselves into a fluid bilayer
Why is the phospholipid bilayer fluid?
The phospholipid molecules are constantly moving
Describe the phospholipid bilayer structure
- The hydrophilic phosphate heads face out towards the water (either the aqueous tissue fluid/the aqueous cytoplasm) on either side of the membrane
- The hydrophobic lipid tails are on the inside, making the centre of the bilayer hydrophobic
What does the centre of the bilayer being hydrophobic mean?
Membrane doesn’t allow water-soluble, charged or polar substances e.g ions through it
Why do the phospholipids not form micelles in the membrane?
The 2 fatty acids in the tails are too bulky to fit in the micelle’s interior
Where are the proteins in the bilayer?
They are scattered throughout the bilayer (like tiles in a mosaic)
Why can some of the proteins move?
As the phospholipid bilayer is fluid
Define an “integral” protein
Protein that are fully embedded within the phospholipids, some even spanning both layers
Describe the structure of integral protein
- The regions at the end are polar hydrophillic amino acids
- The middle portion is made up of non-polar, hydrophobic amino acids
Define a “peripheral” protein
Proteins loosely attached on the outside surface of the cell membrane
What are the two types of protein?
- Integral
- Peripheral
What are the different kinds of proteins found in the cell membrane?
- Glycoproteins
- Channel proteins
- Carrier proteins
- Enzymes
What is a glycoprotein?
Proteins with a polysaccharide chain attached to them
What is the function of a glycoprotein?
To act as a receptor for hormones by producing specific shapes
What is the function of channel/carrier proteins?
Large molecules and ions can only pass through them
What are glycolipids?
Lipids with a polysaccaride chain attached
What is the function of a glycolipid?
To provide energy and be markers for cellular recognition
What is the function of cholesterol in the cell membrane?
To fit in between the phospholipids, making bonds with them and therefore make the membrane more rigid
How does the ratio of phosopholipds containing unsaturated fatty acids to those containing saturated fatty acids relate to the fluidity of the membrane?
The greater the ratio of phosopholipds containing unsaturated fatty acids to those containing saturated fatty acids, the more fluid the membrane
How do unsaturated phospholipds ensure membrane fluidity?
The kinks in the hydrocarbon tails of the unsaturated phospholipids prevent them packing too closely together