Cell Membrane Strucutre 1. Phospholipid bilayer 1. Phospholipid bilayer a. hydrophilic heads point out (phosphate) a. hydrophilic heads point out (phosphate) b. hydrophobic tails in center (fatty acid) b. hydrophobic tails in center (fatty acid) c. amphipathic (both philic and phobic) c. amphipathic (both philic and phobic) c. held together by hydrophobic interactions c. held together by hydrophobic interactions d. capable of d. capable of rapid lateral movement

Selective Permeability A) Molecules can pass through membrane phospholipids on their own A) Molecules can pass through membrane phospholipids on their own i) small or non-polar (H 2 O, O 2, CO 2, Lipids) i) small or non-polar (H 2 O, O 2, CO 2, Lipids) ii) Large polar molecules get through only ii) Large polar molecules get through only very slowly (glucose) very slowly (glucose) iii) ions seldom cross on their own iii) ions seldom cross on their own B) More rapid transport requires proteins B) More rapid transport requires proteins

Cell Membrane Structure 2. Cholesterol 2. Cholesterol a. found in animal cells a. found in animal cells b. maintains membrane fluidity b. maintains membrane fluidity 1. high temp restrains p-lipid movement 1. high temp restrains p-lipid movement 2. low temp: 2. low temp: prevents prevents close packing close packing

Cell Membrane Structure 3. Membrane Proteins 3. Membrane Proteins a. Integral (penetrate into CM) some are transmembrane b. Peripheral May be held in Place by cytoskeleton Or ECM (Extracellular matrix)

Membrane Proteins (p97) 1. Membrane Enzymes a. often grouped in teams a. often grouped in teams b. active in metabolism b. active in metabolism c. bind to cytoplasmic substrates c. bind to cytoplasmic substrates

Membrane Proteins 2. Attachment proteins a. bind to ECM a. bind to ECM b. bind to cytoskeleton b. bind to cytoskeleton c. maintain cell shape and location c. maintain cell shape and location d. non-covalent bonds d. non-covalent bonds

Membrane Proteins 3. Recognition proteins/lipids a. sort cells in embryo a. sort cells in embryo b. immune system self-recognition b. immune system self-recognition c. often glycoproteins (glycolipids) c. often glycoproteins (glycolipids) d. differ between species, individuals, cell types d. differ between species, individuals, cell types e. A B O blood types e. A B O blood types

Membrane Proteins 4. Intercellular Joining a. gap junctions a. gap junctions b. adhering junctions b. adhering junctions

Membrane Proteins 5. Receptor Protiens aid Signal Transduction a. receptors – bind to chemical messenger (hormones, cAMP) (hormones, cAMP) b. binding signal molecule changes protein shape b. binding signal molecule changes protein shape c. signals inside of cell by binding cytoplasmic protein causing transduction c. signals inside of cell by binding cytoplasmic protein causing transduction

Receptor Protein example

G protein example

Membrane Proteins 6. Transport proteins a. channel proteins (aquaporin) a. channel proteins (aquaporin) b. carrier proteins (glucose transporter & b. carrier proteins (glucose transporter & protein pumps) protein pumps) c. all are specific c. all are specific

2 Types of Cellular Transport 1) Passive Transport = no energy needed 1) Passive Transport = no energy needed mol. flow high concentration  low conc. mol. flow high concentration  low conc. 2) Active Transport = 2) Active Transport = takes energy takes energy molecules pumped molecules pumped Low conc.  high conc. Low conc.  high conc. Exocytosis/endocytosis Exocytosis/endocytosis

3 Types of Passive Transport all high conc.  low conc. due to… a) potential energy of concentration gradient a) potential energy of concentration gradient b) thermal energy causing Brownian motion. b) thermal energy causing Brownian motion. 1) Diffusion 1) Diffusion (any molecule, random motion) (any molecule, random motion) 2) Facilitated Diffusion 2) Facilitated Diffusion (diffusion through channel protein) (diffusion through channel protein) 3) Osmosis 3) Osmosis (diffusion of water through membrane) (diffusion of water through membrane)

1. Diffusion Dynamic equilibrium = no net movement Dynamic equilibrium = no net movement

2. Facilitated Diffusion Molecules too big /polar / charged Molecules too big /polar / charged must go through transport protein. Either must go through transport protein. Either Channel protein or carrier protein Channel protein or carrier protein (aquaporin) (glucose carrier) (aquaporin) (glucose carrier) Some channel proteins gated Some channel proteins gated

3. Osmosis Diffusion of water Diffusion of water must cross a membrane must cross a membrane

Tonicity = Ability of surrounding solution to make a specific cell gain or lose water Ability of surrounding solution to make a specific cell gain or lose water No net movement = No net movement = isotonic (same solute) isotonic (same solute) Water moves into cell = Water moves into cell = hypotonic solution (less solute in solution) hypotonic solution (less solute in solution) Water moves out = Water moves out = hypertonic solution (more solute in solution) hypertonic solution (more solute in solution)

Osmoregulation Control of solute and water concentrations inside a cell Control of solute and water concentrations inside a cell Contractile vacuoles Contractile vacuoles aquaporin aquaporin

Diffusion Rates Affected by: 1. concentration 1. concentration 2. size of molecule 2. size of molecule 3. temperature 3. temperature 4. electric gradient 4. electric gradient 5. pressure gradient 5. pressure gradient 6. # pores 6. # pores

3 Types of Active Transport can be low conc.  high conc. All require energy input All require energy input Pumps move individual molecules Pumps move individual molecules Endo/exocytosis do ‘bulk transport’ Endo/exocytosis do ‘bulk transport’

1. Protein Pumps Carrier proteins that require energy Carrier proteins that require energy Protein pushes molecules into areas where they are in high concentration. Protein pushes molecules into areas where they are in high concentration. ATP is the ATP is the energy used energy used Proton pumps Proton pumps Pump H + ions

2. Exocytosis How cells secrete materials like hormones How cells secrete materials like hormones a. transport vesicle buds from a. transport vesicle buds from golgi body golgi body b. vesicle moved to C.M. by motor protein b. vesicle moved to C.M. by motor protein c. vesicle fuses with CM c. vesicle fuses with CM d. contents spill out into extracellular space d. contents spill out into extracellular space

Endocytosis Cell takes in molecules by forming new vesicles at CM Cell takes in molecules by forming new vesicles at CM a. phagocytosis = takes in food a. phagocytosis = takes in food b. pinocytosis = takes in water b. pinocytosis = takes in water c. receptor mediated = triggered by molecule binding to membrane receptor c. receptor mediated = triggered by molecule binding to membrane receptor * helps concentrate rare molecules * helps concentrate rare molecules