Membrane strucutre Flashcards
What molecules make up the plasma membrane?
- Lipids
- Carbohydrates
- Proteins
- The type and amount affect function
What is the fluid mosaic model?
- The structure of the plasma membrane is described to be a mosaic of phospholipids, proteins, cholesterol, glycoproteins, and glycolipids
- These molecules can move around in the cell membrane
What is the primary component of membranes?
- Phospholipids
What direction do the head and tail of the phospholipids face and why?
- Head faces the outside because they are hydrophilic
- Tails face the inside of the cell because they are hydrophobic
What molecules do the phospholipid bilayer not allow through and why?
- Polar molecules
- The hydrophobic tails do not allow polar molecules to diffuse through the membrane
- large molecules
- Too big to fit through the membrane
How do phospholipids differ in strucutre?
- Fatty acid chain length
- Degree of saturation
- Kinds of polar groups present
How are cholesterol molecules imbedded in the cell membrane?
- Hydroxyl groups interreact with the polar heads of the phospholipids
- The rest of the cholesterol interacts with the tails of the phospholipids
- Pretty much like a phospholipid, jus the hydroxyl group of the cholesterol is the head
What is cholesterols function in the cell membrane?
Modulating membrane fluidity
What structure makes the membrane fluid?
Fatty acids
What influences membrane fluidity?
- Saturation (unsaturated increases fluidity)
- Length (short increases fluidity)
- Temperature (heat increases fluidity)
Why do unsaturated lipids increase fluidity in a cell membrane?
The kinks and bends in the structure of a lipid creates more space for molecules to move in the cell membrane
What are the types of proteins found in the phospholipid bilayer?
- Peripheral membrane proteins
- Integral membrane proteins
- Anchored membrane proteins
- Transmembrane proteins
What is a peripheral membrane protein?
Proteins that lack a hydrophobic group and are not embedded in the bilayer,
- Found on the surface of the plasma membrane, either inside or outside of the cell
What is an integral membrane protein?
Proteins with a hydrophobic group that are at least partly embedded into the bilayer
- Interact extensively in the bilayer
What is an anchored membrane protein?
Proteins with hydrophobic lipid components that anchor them to the bilayer,
- the hydrophobic component has to stay inside the bilayer with the lipid tails, so the rest of the protein can be free from being embedded into the membrane while having an anchor secure inside
What are transmembrane proteins?
Proteins that extend through the bilayer, they have areas with functions inside and outside of the membrane
How are proteins distributed on the plasma membrane?
Asymmetrically, this is because proteins cannot flip from facing the inside of the cell to the outside, so they need to have proteins facing inside and outside of the cell,
- There is not necessarily an equal amount of proteins facing each direction, they are just not ordered to face one way
Can all molecules move in the phospholipid bilayer?
No, some can while some are restricted, the cytoskeleton and other proteins inside the cell can restrict some membrane proteins from moving
What is the function of carbohydrates in the bilayer?
Communication/ identification
What carbohydrates can be found in the bilayer?
- Glycolipid
- Glycoprotein
- Proteoglycan
What is a glycolipid?
Carbohydrates covalently bonded to a lipid
What is a glycoprotein?
One or more oligosaccharides (small carbohydrates) covalently bonded to proteins
What are proteoglycans?
Proteins with more and longer carbohydrates bonded to it
What is an oligosaccharide?
Oli-go-saccharide
- A small chain of monosaccharides/ small carbohydrates
How do cells attach to each other?
Proteins and carbohydrates can connect to each other across membranes and keep the cells close to each other
Are cell membranes ever inactive?
No, they are constantly forming, transforming into other types, fusing, and breaking down
What is plasmolysis?
The detaching of the cell membrane from the cell wall, and constriction of the membrane when a plant cell is in a hypertonic solution
What is a selectively permeable membrane?
When the membrane only allows certain molecules to diffuse through, will others are unable to.
What is a carrier protein?
A protein that changes shape in order to facilitate the diffusion through a cell membrane across a concentration gradient
What is a channel protein?
A type of integral protein, a hollow protein that allows molecules to pass through across the plasma membrane.
What is a concentration gradient?
The direction in which molecules move, from a high concentration of molecules to a lower one
