Plasma membrane: Composition & Functions

Question 1

Plasma membrane

Answer 1

• Boundary separates living cells from surround
• Barrier to prevent contents of the cell from escaping nutrient in waste out (selective permeable)

Question 2

Fluid mosaic model

Answer 2

• Dynamic and complex structure of plasma membrane that contains glycolipids, sterols, proteins and glycoproteins embedded
• Lipid molecules 2d move along the plane of the bilayer (fluidity dependant on composition of bilayer)

Question 3

Movement of Phospholipid membrane

Answer 3

• Rapid lateral movement
• Spin in its place
• Flexion contract movement
• Flip flop side to side
• Protein anchored by cytoskeleton

Question 4

Cholesterol

Answer 4

• Only in animal cell
• Modulates stability & improves it
• Stiffen membrane less soluble & fluid reduce molecule passage
• Glycolipids sugar group always facing exterior

Question 5

Membrane protiens

Answer 5

• Synthesised in rough ER
• Mostly transmembrane proteins
• Hydrophobic region has coiled alpha helices interior
• Other proteins are embedded in the membrane exclusively
• Peripheral proteins either side of membrane covalently attached to membranes lipids

Question 6

Function of membrane proteins

Answer 6

• Transport of molecules
• Enzyme activity
• Cell communication
• Support and attachment of extracellular membrane

Question 7

Definition

Passive transport

Answer 7

• Selectively permeable
• Without expenditure of energy
• Move down concentration gradient
• High to low conc until equilibrium is reached

Question 8

Diffusion

Answer 8

• Free movement of particles across lipid bilayer (net)
• No energy required down concentration gradient
• Uncharged polar molecules and CO2 and O2 urea & ethanol
• Organic molecule too large to diffuse

Question 9

Osmosis

Answer 9

• Spontaneous passive transport of water across a semipermeable membrane high to low water potential
• Water potential inverse to solute conc
• Hydrostatic pressure required to stop net flow of water across membrane water flow in and out via aquaporins

Question 10

Isotonic

Answer 10

Same concentration of solute in and out of cell (normal cell)

Question 11

Hypertonic

Answer 11

Solution higher solute conc outside cell compare to inside (shrivel cell)

Question 12

Hypotonic

Answer 12

higher solute con inside than outside cell (burst cell)

Question 13

Facillitated diffusion

Answer 13

• Passive movement down conc grad via transport proteins
• Channel protein and protein carrier
• Highly specific and no energy require
• Reversible
• Specific ions hydrophilic glucose

Question 14

Uniport

Answer 14

• Shift and transport a single type of molecule
• Specific confirmational change protein when entering channel
• Slower rate than other channels

Question 15

Symports

Answer 15

Moves 2 different molecules across the cell in the same direction

Question 16

Antiporters

Answer 16

Move 2 distinct proteins opposing directions Na+ and K+ pump 3 in and 2 out

Question 17

Active transport

Answer 17

• Moves substance against concentration gradient
• Energy ATP required
• Specific protein embedded in membrane enabling stockpiling
• Specific bind site can be saturated and inhibited and catalysed

Question 18

Endocytosis

Answer 18

• Uptake of macromolecules
• Form intracellular membrane-bound vesicle containing extracellular fluid

Question 19

Exocytosis

Answer 19

• Secretion and excretion insulin by pancreatic cell
  Transport molecules migrate to plasma membrane fuse release content