Forces Acting Across the Membrane

Question 1

Function of cell membrane

Answer 1

act as a selective barrier between ECF and ICF

provide binding sites for chemical recognition

differences in membrane proteins are responsible for the varied characteristics of membranes

Question 2

What is diffusion across membranes

Answer 2

occurs through the lipid bilayer or via protein channels, which may be of a number of different types

Question 3

what are the different types of membrane proteins

Answer 3

receptors

transporters

structural

communication

Question 4

What are receptor proteins

Answer 4

integral to membrane structure, penetrate from ECF to ICF, communication of an extracellular signal - ie. neurotransmitter or hormone

Question 5

what are transporter proteins

Answer 5

integral protein

allows movement of ions or molecules across membrane

channels - create pore through membrane where water and ions flow

carrier mediated transport proteins - not continuous pore from ECF - ICF, move longer molecules ie. glucose

Question 6

What are structural proteins

Answer 6

anchor cell membrane to intracellular skeleton

to the extracellular matrix

or to other cells

Question 7

what are communication proteins

Answer 7

glycoproteins act as a marker to tell immune system if cell is our own or foreign

hormones (or drugs) carry extracellular messengers to intracellular environments

Question 8

What is the electrochemical gradient

Answer 8

important in determining the movement of ions across membranes

Question 9

what is meant by carrier mediated transport systems

Answer 9

provide a mechanism for transport across the membrane for larger molecules

either down a concentration/electrochemical gradient = facilitated diffusion

or against such gradients = active transport

Question 10

what is the difference between osmolarity and tonicity

Answer 10

osmolarity = measures the number of solute particles/L of solution

tonicity = the total number of non-penetrating solute particles

Question 11

Significance of osmolarity

Answer 11

if a solute cannot cross the membrane, any change in its concentration produces an osmotic flux, causing net water movement

Question 12

significance of tonicity

Answer 12

only a change in tonicity causes changes in cell volume

Question 13

what is the difference between an isosmotic and an isotonic solution

Answer 13

isosmotic - same total number of solute particles as normal ECF

isotonic - same number of non-penetrating solute particles as normal ECF

Question 14

Process of endocytosis

Answer 14

invagination of cell membrane to form a vesicle which eventually disintegrates on the cytoplasmic surface - releasing content which migrates within cell

common mechanism for terminating signals from extracellular ligands

Question 15

Process of exocytosis

Answer 15

many proteins manufactured in cells are released from those cells