biological molecules PMT

Question 1

describe the effect of a high temperature on the structure of cell membranes

Answer 1

-phospholipids have more kinetic energy
-this increases the number of gaps in the membrane
-the bilayer becomes more fluid and melts
-proteins/ glycoproteins are denatured

Question 2

what are the function of cell membranes within cells

Answer 2

-compartmentalisation
-site of processes/ reactions
-provide a surface for attachment of enzymes
-control what substances enter and leave

Question 3

what are the functions of glycoproteins/ glycolipids

Answer 3

they are on the surface/ sticking out from surface for cell signalling receptor sites or for stabilising

Question 4

explain how a cell surface membrane contributes to the process of cell signalling

Answer 4

• a signal molecule can be released by exocytosis
  -proteins/ glycoproteins/ glycolipids act as/have receptors
  -receptor/ signal is specific
  -shape of receptor and signal is complimentary
  -attachment of signal molecule causes change on the cell surface
  -cell surface membrane causes entry of some signal molecules

Question 5

state 3 roles of membranes inside cells

Answer 5

-create concentration gradients
-compartmentalisation
-site of attachment for enzymes
- provide selective permeability

Question 6

outline how vesicles are moved from one organelle to another

Answer 6

-cytoskeleton provides a pathway for movement
-vesicles move along microfilaments/ microtubules
-microtubule extended/ broken down
-uses ATP/ metabolic energy

Question 7

what type of protein does active transport use

Answer 7

uses a carrier protein

Question 8

state examples of active transport in cells

Answer 8

-active transport of potassium ions into the cell
-mineral ions into root hair cell
-sodium ions out of neuron
-potassium ions into neuron
-sodium ion out of loop of Henle
-hydrogen ions for chemiosmosis in respiration*
-calcium ions out of pre-synaptic bulb

Question 9

explain why plant cells do not burst when when they are left in pure water

Answer 9

-they have a cellulose cell wall which provides strength

Question 10

how could the procedure using onion epidermis be made more reliable

Answer 10

-observe more pieces of onion epidermis
-count more cells in each piece of onion epidermis
-calculate a mean
-ignore anomalous results
-repeats

Question 11

how could the procedure using onion epidermis be made more accurate

Answer 11

-use more intermediate concentrations within an existing range
-use a narrower range around area investigated
-take photographs and mark cells as counting