Chapter 5: Cell Membrane Flashcards
Fluid mosaic model
Is a model that describes a phospholipid bilayer in which proteins can move about (float in the lipid “lake”)
What are the 3 major functions of fluid mosaic model?
- Move materials through the membrane
- involved in intercellular recognition and adhesion
- receive chemical signals from the cell’s external environment
What does carbohydrate attach to in the fluid mosaic membrane?
They attach to either lipid or protein molecules
Lipid rafts
form from glycolipoprotein lipid microdomains and include more cholesterol (acts like a glue that holds it together and stiffens it)
cholesterol
Is a steroid and is found in the membranes of animals and some bacteria.
What is cholesterol made of?
It is made of multiple linked rings and a hydroxyl group that interacts with hydrophilic heads of phospholipids
Phospholipids may differ in what?
- Hydrocarbon chain length
- degree of saturation
- kinds of polar groups present
What are the 2 important factors in membrane fluidity?
- lipid composition and proteins
Lipid composition
Are types of hydrocarbon tails (Unsaturated or saturated) can increase or decrease fluidity
What are the 2 types of membrane proteins?
- peripheral membrane protein
2. Intergral membrane proteins
Peripheral Membrane Protein
They lack hydrophobic groups and are not embedded in the bilayer
Intergral Membrane Proteins
They are at least partly embedded in the phospholipid bilayer that contain both hydrophilic and hydrophobic groups. Hydrophobic groups anchor the protein in the membrane
Transmembrane Protein
An intergral membrane protein that extends all the way through the phospholipid bilayer and protrudes on both sides are always oriented the same way
glycolipid
They consists of a carbohydrate covalently bonded to a lipid
Glycoprotein
They consists of 1 or more short carbohydrate chains covalently bonded to a protein
Proteoglycan
A protein with even more carbohydrate molecules attached to it
Passive transport
Does not require metabolic energy
Active transport
Requires input of metabolic energy because they involve the movement of a substance against their concentration gradients
Diffusion
is the process of random movement toward a state of equilibrium
Simple diffusion
When molecules that are hydrophobic and soluble in lipids can pass through the membrane
What does diffusion do?
- They have molecules from an area of higher concentration to one of lower concentration
- can occur in any medium (liquid, solid, gas)
- Doesn’t require a semipermeable membrane
Osmosis
The net movement of a solvent across a selective permeable membrane into a region of higher solute concentration
What does osmosis do?
- Can only occur in liquid
- requires a semipermeable membrane
- movement seeks to equalize solvent concentration (although it doesn’t achieve it)
What are the 3 terms used to compare solute concentrations of 2 solutions separated by a membrane?
- Hypertonic
- Isotonic
- Hypotonic
Hypertonic
The solution has a higher solute concentration than the other solution
Isotonic
The solution has an equal solute concentration
Hypotonic
The solution has lower solute concentration than other solution
Channel proteins
Are integral membrane proteins that form channels across the membrane (speeds of diffusion)