Lecture 5 Flashcards
What does a plasma membrane do?
1.Protects and separates a cell from its environment
2. It is selectively permeable (so it lets in the right things and not the wrong things)
Why does the phospholipid bilayer not need to be bonded together?
Because the phospholipids want to form a layer with the tails on the inside and the heads on the outside.
Why is it important that the phospholipid bilayer is not bonded together?
Because it allows it to be flexible and allows things to go in and out of the cell.
What is the fluid mosaic model?
The model where proteins float in or on the fluid phospholipid bilayer.
What are 4 components of cellular membranes?
- Phospholipid bilayer
- Transmembrane proteins (proteins in membrane)
- Interior protein network (proteins on inside)
- Cell surface markers (proteins on the outside)
Types of proteins in membrane?
- Transporters
- Enzymes
- Cell-surface receptors
- Cell-surface identity markers
- Cell-to-cell adhesion proteins
- Attachments to the cytoskeleton
What are anchoring molecules?
Modified lipids that have nonpolar regions that insert into the lipid bilayer and chemical bonding domains that link to proteins.
What are 2 types of membrane proteins?
- Integral membrane proteins - go all the way through the lipid bilayer
- Transmembrane domain - spans the lipid bilayer
What types of things can move freely through the lipid bilayer?
- nonpolar molecules
- small polar molecules
What are 3 types of transport through the plasma membrane (cell membrane)?
- Passive transport - no energy is required
- Active transport
- Bulk transport
What are 2 types of passive transport?
- Diffusion
- Osmosis
What is diffusion?
When molecules move through a semipermeable membrane to where there is more space (lower concentration).
What is osmosis?
When water moves through a semipermeable membrane to an area with a higher solute concentration.
What is osmotic pressure?
pressure required to oppose osmosis.
What is tonicity?
relative concentration of solutes in two fluids.
What is isontonic?
When extracellular and intracellular solute concentrations are equal and there is no net movement of water.
What are 3 types of tonicity?
- Hypertonic
- Hypotonic
- Isotonic
What is hypertonic?
When the concentration of solutes outside a cell is higher than inside the cell. It causes the cell to shrink.
What is hypotonic?
When the concentration of solutes outside a cell is lower than inside the cell. It causes the cell to swell.
What are aquaporins?
Specialized channels for water in cell membrane that facilitate osmosis.
Is energy required for passive transport?
no.
What are 3 ways that diffusion can occur?
- Directly through the lipid bilayer
- Through protein channels
- Through facilitated transport
What are 2 types of proteins that can be involved in facilitated transport?
- Channel proteins
- Carrier proteins
What are three conditions that determine the direction that molecules move through channel proteins?
- Concentration on either side of the membrane
- Voltage differences across membrane
- whether the gated channel is open or closed
Are carrier proteins specific or nonspecific?
They are specific to the molecule they transport and bind to it.
Does active transport require energy?
yes.
Does passive transport move molecules to where there is higher concentration or lower concentration?
Lower concentration.
Does active transport move molecules to where there is higher concentration or lower concentration?
Higher concentration.
What is an example of active transport?
Sodium-potassium pump.
What are 2 types of bulk transport?
- Endocytosis
- Exocytosis
What is endocytosis?
It brings substances into a cell by surrounding it in a membrane bound vesicle.
What is exocytosis?
It expels substances from the cell by surrounding it with a membrane bound vesicle and fusing to the membrane.
How is information transferred through a plasma membrane?
Receptor proteins span membrane and transfers information.
