Cell Membrane

Front 1

Roles of the plasma membrane

Back 1

1. Maintains stable cell environment
2. Receptor mediated cell signaling
3. Ion gradients
4. Secretion and endocytosis
5. Cell-matrix adhesion
6. Cell-cell adhesion and communication

Front 2

Roles of internal membranes

Back 2

1. Maintain integrity of organelle
2. Protein and molecule transport
3. Energy production
4. Protein synthesis

Front 3

Fluid Mosaic Model

Back 3

1. The foundation of the biological membrane is the phospholipid bilayer
2. Embedded in bilayer are integral and peripheral membrane proteins that diffuse freely

Front 4

Components of lipid bilayer

Back 4

1. Phospholipids
2. Cholesterol
3. Glycolipids

Front 5

Amphiphatic

Back 5

Having both a non-polar and polar end.

Front 6

Phosphoglycerides

Back 6

Glycerol backbone linked to two fatty acid chains and a phosphate group. Head is usually serine, inositol, or choline.

Front 7

Tm

Back 7

The transition temperature for the bilayer.

Front 8

Length of fatty acid tails

Back 8

Longer the acyl tails, the higher the Tm

Front 9

Level of unsaturation

Back 9

The more double bonds, the lower the Tm

Front 10

Presence of sterols

Back 10

Cholesterol has a rigid ring system and a short branched hydrocarbon tail with one polar hydroxyl group.

Broadens the transition of the membrane preventing packing at low temperature and fast movement at high temperature.

Front 11

Phosphatidylcholine, sphingomyelin

Back 11

Phospholipids found in outer leaflet of plasma membrane.

Front 12

Phosphatidylethanolamine, phosphatidylserine

Back 12

Found in inner leaflet of plasma membrane

Front 13

Glycolipids

Back 13

Found exclusively on outer half of membrane

Front 14

Flippase

Back 14

Catelyzes flip-flop in membranes where lipid synthesis occurs.

Front 15

Peripheral membrane proteins

Back 15

Soluble proteins that associate with lipid head groups of membrane through electrostatic interactions. They can be easily dissociated with salt or pH.

Front 16

Integral membrane proteins

Back 16

Insoluble proteins that penetrate or transverse the lipid bilayer one or multiple times. Can be dissociated with detergent.

Usually have alpha helixes.

Front 17

Lipid-anchored proteins

Back 17

Covalently attached lipid anchor that inserts into the bilayer:
1. Fatty acid
2. Isoprenoid
3. GPI

Front 18

Factors that restrict protein mobility in membranes

Back 18

1. Some membrane proteins are linked to underlying cytoskeleton
2. Membrane proteins can be clustered by interactions
3. Enrichment in specific lipids that restrict lateral diffusion
4. Strong interactions between membrane proteins that junction between adjacent cells.

Front 19

Simple (passive) diffusion

Back 19

1. Spontaneous from the thermal motion of molecules
2. Doesn't require membrane proteins
3. No energy required
4. Molecule travels down concentration gradient

Front 20

Parameters affecting passive diffusion

Back 20

1. Concentration difference
2. Lipid solubility
3. Membrane thickness, surface area
4. Temperature increases velocity of molecules

Front 21

Osmosis

Back 21

Movement of a solvent through a semipermeable membrane from a less concentrated solution to a more concentrated one.

Front 22

Intracellular compartment

Back 22

Contains 2/3rds of the body's total fluid in cells.

Front 23

Extracellular compartments

Back 23

Spaces between individual cells (interstitial and blood plasma). The other 1/3rd of water.

Front 24

Solvent

Back 24

Substance present in greatest amount.

Front 25

Solute

Back 25

Substance present in least amaount.

Front 26

Donnan Effect

Back 26

The water flow is generally into the cell, causing volume changes requiring active removal of solutes and water.

Front 27

Tonicity

Back 27

Effect of extracellular solution on volume of cell

Front 28

Isotonic

Back 28

Term applied to two solutions with equal solute concentrations

Front 29

Hypertonic

Back 29

A solution having a high concentration of solute.

Front 30

Hypotonic

Back 30

A solution having a low concentration of solute.

Front 31

Main processes of the kidney

Back 31

1. Filtration
2. Reabsroption
3. Secretion

Front 32

Passive transport (facilitated diffusion)

Back 32

1. Require membrane proteins: pores carriers
2. No energy utilized. Molecules move down electro-chemical gradient
3. Saturable. Rate proportional to concentration gradient but limited by number of protein channels available.
4. Selective. Molecules interact with proteins so they can be specific
5. Integral multi-pass proteins with hydrophilic residues towards channels and hydrophobic in the lipid bilayer.

Front 33

Permeases (Carriers)

Back 33

1. Bind to substrate and move it across the membrane, undergoing a conformational change
2. Cannot be controlled by gates
3. Cell controls their activity by inserting them into or removing them from the plasma membrane

Front 34

Channels

Back 34

Form aqueous pores in the membrane to allow water or ions to flow through.

Front 35

Active Transport

Back 35

1. Moves molecules up against the electro-chemical gradient
2. Requires the input of energy
3. Specific
4. Commonly used to generate a membrane potential
5. Saturable
6. Molecules pass through transmembrane by two mechanisms:
a. Uniport - one molecule transported
b. Cotransport - 2 molecules are transported

Front 36

Symport

Back 36

Two molecules are transported in the same direction

Front 37

Antiport

Back 37

Two molecules are transported in the opposite direction

Front 38

Na+/K+-ATPase

Back 38

Predominant pump in the cell using ~25% ATP of the cell. Uses energy to maintain high K+ in the cell and high Na+ outside the cell. Moves 2 K+ into the cell and 3 Na+ out of the cell.

Front 39

Ouabain

Back 39

Steroid-like drug that specifically blocks Na+/K+-ATPase.

Front 40

Cellular roles of Na+/K+-ATPase

Back 40

1. Regulation of osmotic balance and cell volume
2. Production of a voltage gradient

Front 41

Secondary active transport

Back 41

Involves using energy to establish a gradient across the cell membrane and then utilize that gradient to transport a molecule of interest up its concentration gradient.

Front 42

Na+-glucose secondary transport mechanism

Back 42

1. Uses the Na+/K+ pump to generate a strong Na+ gradient across cell membrane
2. Na+ gradient provides driving force to transport glucose into the cell with glucose-Na+ symport

Front 43

Congestive heart failure (Dropsy)

Back 43

Failure of heart to circulate sufficient blood volume. Treated with cardiac glycosides.

Front 44

Digitalis

Back 44

Inhibits Na+/K+ ATPase and increases force of heart contraction due to altered Ca2+ homeostasis.

Front 45

Digoxin

Back 45

Inhibits Na+/K+ ATPase and increases force of heart contraction due to altered Ca2+ homeostasis.

Front 46

ABC (adenosine triphosphate binding cassettes) transporters

Back 46

Largest family of membrane transporters. Bind and hydrolyze ATP inducing conformational changes that are transmitted to allow translocation of substrate form one side of membrane to another.

Front 47

Cystic Fibrosis

Back 47

Most common fatal genetic disease caused by mutation in CFTR gene, a Cl- channel. Affects the sweat glands, pancreas, male reproductive tract, and lungs.

Front 48

Multidrug resistance proteins

Back 48

P-glycoproteins that have been implicated in antibiotic and cancer drug resistance due to ability to extrude antibiotics and cytotoxic chemotherapy agents.

Front 49

Gated ion channels

Back 49

Exist in either closed or open conformations. Gating is regulated in response to electrical, mechanical, or chemical signaling allowing flux of ions. Passive transport.

Front 50

Nongated ion channels

Back 50

Leak channels that are always open and not influenced by extrinsic signals. Maintaining the resting membrane potential.

Front 51

Ligand gated channels

Back 51

Noncovalent, reversible binding of chemical ligand induces conformational change for opening or closing.

Front 52

Voltage-gated channels

Back 52

A change in membrane potential causes movement of charged regions in channel, altering conformation and leading to opening or closing.

Front 53

Mechanosensitive channels

Back 53

The stretching or deformation of the plasma membrane can induce shape changes in the channel thus triggering channel opening or closing.

Front 54

Membrane potential

Back 54

Separation of charge = voltage difference between the inside and outside of the cell. Provides an electrical force similar to the concentration gradient that drives the movement of ions across a membrane.

Front 55

Electrochemical gradient

Back 55

Difference in ion concentration and electric charge that exists across the plasma membrane.

Front 56

K+ leak channels

Back 56

Help set up the membrane potential by slowly leaking K+ out of the cell.

Front 57

Nernst equation

Back 57

Predicts the equilibrium potential for any concentration gradient of a particular ion across a membrane.

Front 58

Resting potential

Back 58

The potential across the membrane when the cell is at rest.

Front 59

Polarized state

Back 59

The state the cell is in when at resting potential.

Front 60

Depolarization

Back 60

A reduction of the charge separation.

Front 61

Hyperpolarization

Back 61

An increase in charge separation

Front 62

"action potential"

Back 62

The membrane potential changes that occur during nerve impulse propagation.

Front 63

Threshold potential

Back 63

The level where an action potential is fully triggered.

Front 64

Refractory period

Back 64

Period when the Na+ voltage gated channels are inactivated.

Front 65

Delayed rectifier channels

Back 65

K+ channels in nerve impulse that are slower to open than Na+ channels.

Front 66

Increase in axonal diameter

Back 66

Increases the speed conduction rate because it decreases internal resistance.

Front 67

Myelin sheath

Back 67

Produced by Schwann cells to wrap nerve in lipid membrane insulating from ion leakage and increasing the speed of action potential propagation.

Front 68

Schwann Cell

Back 68

Makes the myelin sheath in the peripheral nervous system.

Front 69

Nodes of Ranvier

Back 69

Myelination is interrupted at these regular intervals which are the locations of ion flux into and out of the cell.

Front 70

Saltatory conduction

Back 70

Due to nodes of Ranvier, action potential jumps down the axon from node to node.

Front 71

Autoimmune disease

Back 71

Immune system attacks nerves.

Front 72

Multiple Sclerosis

Back 72

Demyelination in CNS - delayed or blocked conduction in some nerves.

Front 73

Lidocaine

Back 73

Local anesthetic that blocks Na+ channels and inhibits action potentials blocking conduction of pain fibers.

Front 74

Tetrodotoxin

Back 74

Puffer fish toxin that inhibits Na+ channels blocking action potentials.

Front 75

Smallest water compartment in the body

Back 75

Plasma

Front 76

Largest water compartment in the body

Back 76

Intracellular fluid

Front 77

Concentration of Na+ inside the cell

Back 77

14 mEq/L

Front 78

Concentration of Na+ outside the cell

Back 78

140 mEq/L

Front 79

Concentration of K+ inside the cell

Back 79

120 mEq/L

Front 80

Concentration of K+ outside the cell

Back 80

4 mEq/L

Front 81

Concentration of Ca2+ inside the cell

Back 81

1 x 10^-4 mEq/L

Front 82

Concentration of Ca2+ outside the cell

Back 82

2.5 mEq/L

Front 83

Concentration of Cl- inside the cell

Back 83

10 mEq/L

Front 84

Concentration of Cl- outside the cell

Back 84

105 mEq/L