biological membrane structure + composition

plasma membrane

fluid mosaic (lipids, proteins, oligosaccharides)

1. phospholipid

2. interal protein

3. anchored protein

4. peripheral protein

5. sterol

6. glycolipi/glycoprotein

1. phophsolipid

major component (amphipathic)

• FLUIDITY based on saturation of fatty acid tails

• selective permeability

2. integral protein

• transport

• communication

• enzymes

3. anchored protein

• structural

• enzymes

3. peripheral protein (surface of the membrane)

structure, enzyme function

4. sterol

fluidity

ex. cholesterol- reduces membrane fluidity at moderate temp by reducing phospholipids but hinders solidification at low temp by disrupting packing

oligosaccharides

carbohydrates attached to lipids or proteins

• key factor in cell recognition

• present on the extracellular side of the membrane

PASSIVE TRANSPORT

1. simple diffusion

2. facilitated diffusion

1.Simple Diffusion

• no proteins involved

• through the lipid bilayer

• small or medium nonpolar molecules (O2, CO2)   (steroid, caqrotenoid)

• high to low concentration

2.facilitated diffusion

• uses integral membrane
  PROTEIN (transport proteins)

a. carrier protein

• small or medium, polar/nonpolar molecules

• ALL POLAR MOLECULES
  NEED TRANSPORT
  PROTEINS 

  • POLAR CHARGED: Na+, CL-, amino acids

  • POLAR UNCHARGED: H2o Glucose

b. Channel protein aka ion channel (uniport, symport, antiport)

OSMOSIS

• FACILITATED DIFFUSION OF WATER

THROUGH aquaporin

• isotonic, hypertonic, hypotonic

2. ACTIVE TRANSPORT

ENERGY needed!

• against the concentration gradient
  (LOW to HIGH)

• protein is ALWAYS needed
  1. Primary Active Transport

  • uses ATP directly

  • phosphorylation of the transport protein from ATP hydrolysis changes the shape
    of the protein and allows the transport to happen

2. Secondary Active Transport

• coupled transport

• does not use ATP/energy directly, it depends on primary active transport

LARGE MOLECULE TRANSPORT

1. exocytosis

2. endocytosis

   1. phagocytosis

   2. pinocytosis

   3. receptor mediated

EXOCYTOSIS

rough er → vesicle → golgi → vesicle → plasma mem

ex virsuses, proteins (cholesterol)

ENDOCYTOSIS

1. phagocytosis: macrophages and amoeba engulfing bacteria.

• only specialized cells can do this

• entire cell changes shape and engulfs the substance to break it down with enzymes

2. pinocytosis:cells gulping droplets or extracellular fluid.

3. Receptor mediated endocytosis: specific receptor protein recognize large molecules

• such as cholesterol, change conformation, and engulf into cell for processing

ENERGY SOURCES FOR ACTIVE TRANSPORT

1. ATP

2. MEMBRANE/ACTION POTENTIAL

3. REDOX POTENTIAL

1. ATP

H+ pump and Na+ K+ pump

2. MEMBRANE POTENTIAL

Transport due to electric voltage difference

• seen in voltage gated ion channels

• action potential: rapid reversal of mem potential due to opening/closing of voltage gated Na+ K+ channels

3. REDOX POTENTIAL

OIL RIG: utilized to transport protons to one side of the membrane to generate proton concentration gradient as a form of potential

• energy used to generate ATP.

• ELECTRON TRANSPORT CHAIN