Transport across membranes

Question 1

Fluid mosaic model

Answer 1

Describes the lateral movement of membranes
with scattered embedded
intrinsic and extrinsic proteins
membrane contains
glycoproteins, glycolipids,
phospholipids and cholesterol

Question 2

phospholipids in membranes

Answer 2

Phospholipids align as a bilayer
hydrophilic heads are attracted to water
hydrophobic tails repelled by
water

Question 3

cholesterol

Answer 3

Present in eukaryotic organisms to restrict lateral movement of the membranes
adds rigidity to membrane-resistant to high temperatures
& prevents water + dissolved
ions leaking out

Question 4

selectively permeable membrane

Answer 4

molecules must have specific properties to pass through plasma membrane
lipid soluble
very small molecules
non-polar molecules

Question 5

simple diffusion

Answer 5

Net movement of molecules
from an area of higher
concentration to an area of
lower concentration
until equilibrium is reached
passive

Question 6

facilitated diffusion

Answer 6

Passive process using protein
channels/carriers
down the concentration
gradient
used for ions and polar
molecules e.g sodium ions
and large molecules e.g. glucose

Question 7

osmosis

Answer 7

Net movement of water
from an area of higher water
potential to an area of lower
(more negative) water potential
across a partially permeable
membrane

Question 8

water potential

Answer 8

The pressure created by water molecules
measured in kPa and
represented by symbol ψ
pure water has a water potential of 0kPa
the more negative the water
potential, the more solute must be dissolved

Question 9

hypertonic solution

Answer 9

When the water potential of a
solution is more negative than the cell
water moves out of the cell by osmosis
both animal and plant cells will shrink and shrivel

Question 10

Hypotonic solution

Answer 10

When the water potential of a
solution is more positive (closer to zero) than the cell
water moves into the cell by
osmosis
animal cells will lyse (burst)
plant cells will become turgid

Question 11

isotonic

Answer 11

When the water potential of the surrounding solution is the same as the water potential inside the cell
no net movement in water
cells would remain the same
mass

Question 12

role of carrier protein in active transport

Answer 12

when molecule bind to the receptor - ATP will bind to protein on inside of membrane and is hydrolysed to ADP and Pi
protein changes shape and opens inside membrane

Question 12

active transport

Answer 12

the movement of ions and molecules from an area of lower conc to an area of high conc using ATP and carrier proteins
carrier proteins act as selective pumps to move substance

Question 13

co-transport

Answer 13

The movement of two substances across a membrane together, when one is unable to cross the membrane itself
involves a cotransport protein
involves active transport
e.g. absorption of
glucose/amino acids from
lumen of intestines