Cell Membrane Components 07/01

What are the primary lipid components of plasma membrane

Glycerol based phospholipids, sphingolipids, cholestrol

What is the role of cisternae?

Protein synthesis and modification. They give space for ribosomes to attach and synthesize proteins

What leaflet are glycerol based phospholipids on

Inner and outer leaflet

What leaflet are sphinglipids on

Outer leaflet

What leaflet are cholestrol on

Embedded within phospolipid bilayer, outer leaflet

What is diff between phosphoglyceride and sphingolipid backbone

Phosphoglycerides use glycerol and sphingolipids use sphingosine

Function of phosphoglycerides

Maintain structure of bilayer, responsible for allowing things to/not to pass through

Function of sphingolipids

Maintain structure of membrane, act as signaling molecules, and help with cellular processes like growth, apoptosis, and differentiation. Make up lipid rafts

How are membrane phospholipids synthesized

Synthesized in cytosolic leaflet of smooth ER by fatty acid building blocks from cytosol or food

How are membrane phospholipids trafficked

Transported via vesicles by proteins that are specific for transport to/from a certain organelle or by lipid exchange proteins

Role of lipid exchange proteins

Move lipids from one membrane to another

How are membranes asymmetric

Membranes have different concentrations of lipids types on outer vs inner leaflets

What lipids types are more common on inner leaflet

Phosphodylynserine and Phosphoethanolamine

What phospholipid types are more common on outer leaflet

Phosphodylyncholine and sphingomyelin

Flippase vs. scramblase

Flippase moves lipids form outer leaflet to inner leaflet with the help of ATP whereas scramblase swaps 2 lipids for each other without help of ATP

Why are membranes fluid and why do they need to be fluid?

Membranes are fluid because cell conditions are constantly changing, you need to be able to move lipids and proteins around to meet cell needs at the moment.

What increases or decreases membrane fluidity

1. Cholestrol - stabilizes membrane by making it less fluid during high temp and more fluid during low temp

2. Length of fatty acid tails - shorter tails interact less. andmake membrane more fluid

3. Double bonds - absence of double bonds makes membrane less fluid because it can pack more tightly together

Peripheral vs. integral membrane proteins

Noncovalent vs. covalent attachment. Peripheral can also be attached to phospholipid head

Types of integral membrane proteins

Transmembrane - span membrane

Lipid anchored- covalently attached to lipid that is attached to bilayer

Simple diffusion

Move with gradient from high to low concentration directly through membrane, no ATP

Facilitated diffusion

Move with gradient from high to low concentration with the help of a channel, no ATP

Example of facillitated diffusion

Glucose transporter

Active transport

Move against concentration gradient from low to high concentration, requires ATP

Describe the movement of water via osmosis

Water will move from low concentration of water to high concentration of water until the amount of solute to amount of water distribution matches

Hypotonic, hyperotnic, isotonic

1. water moves into cell, cell bulges

2. water moves out of cell, cell shrivels

3. concentration is equal on both sides of cell

Channel vs. transporter proteins

Channel proteins open/close, allowing molecules to pass without binding whereas transporter proteins enact conformational change due to substrate binding

Uniporters vs. symporters vs. antiporters

1. A single solute molecule moves in one direction

2. 2 solutes move in same direction

3. 2 solutes move in opposite directions

Why are ion channels highly specific

Ion channels have charged amino acid residues that only allow certain molecules to pass through. They open and close as needed and move with the concentration gradient

Primary active transport vs secondary active transport

Primary active transport uses ATP to move things against the concentration gradient, like the sodium potassium pump. Secondary active transport uses the electrochemical gradient created by by primary active transport to move things against concentration gradient

Purpose of K+ channel selectivity filter

It is responsible for dehydrating the ions so they can pass through

Action potential: resting potential

Na/K gradient is maintained by Na/K ATPase

Action potential: rapid depolarization

Voltage gated AN channels open and NA flows into the cell

Action potential: depolarization

Na channels close and Ca channels open. Ca flows into cell

Action potential: plateau

Ca channel opening and Ca inflow is balanced by K channel opening and K outflow

Action potential: repolarization

Other K channels open to allow K outflow and Ca channels close