3.1.7/8 Water and Ions

Question 1

Give a property of water

Answer 1

polar, solvent, metabolite

Question 2

Why is it useful to living organisms that water is polar?

Answer 2

acts as a universal solvent so metabolic reactions can occur

Question 3

why is it useful to living cells that water is a solvent?

Answer 3

metabolic reactions occur faster in solution

Question 4

why is it useful to living cells that water is reactive?

Answer 4

metabolite in hydrolysis and condensation reactions

Question 5

name an important ion

Answer 5

hydrogen, sodium, iron, phosphate

Question 6

how do water and ions enter cells?

Answer 6

they can move down a concentration gradient
both move through channel proteins
ions can move against a concentration gradient by active transport

Question 7

Name 3 properties of water that are important in biology

Answer 7

Is a metabolite
Is a solvent
Has a (relatively)high heat capacity
Has a (relatively)largenlatent heat of vaporisation/ evaporation
Has cohesion / hydrogen bonds between molecule

Question 8

Why is it important that water has a high specific capacity?

Answer 8

To buffer changes in temperature

Question 9

Why is it important that water has a high latent heat of vaporisation?

Answer 9

Provides a cooling effect through evaporation

Question 10

Why does ‘water is a metabolite’ mean?

Answer 10

Has a role in chemical reactions like condensation and hydrolysis

Question 11

What is cohesion?

Answer 11

Attraction of water molecules to each other, caused by hydrogen bonds

Question 12

Why is cohesion important to organisms

Answer 12

Forms a continuous column of water in the xylem

Surface tension for organisms to move on bodies of water

Question 13

Describe the role of Fe2+ ions in humans

Answer 13

Found in haemoglobin, binds to oxygen

Question 14

Describe a role of Na+ in organisms

Answer 14

Na+/K+ pump in co-transport

Question 15

Describe a role of H+ ions in organisms

Answer 15

Affects pH
Generating chemiosmotic gradients in photosynthesis and respiration (Year 2 content)

Question 16

Describe a role of phosphate ions in organisms

Answer 16

Phosphate group in DNA , RNA or ATP
Phosphate group in phospholipid bilayer

Question 17

List all the ions and their functions you study in A level Biology

Answer 17

H+ For Chemiosmosis and Oxidative phosphorylation and maintaining pH
Fe2+ Haemoglobin
Na+ Co-transport, depolarisation, sodium potassium pump in action potentials
K+ For sodium potassium pump
Ca2+ For NMJ, synaptic transmission and sliding filament
PO43- For phospholipid bilayer, DNA, RNA and ATP
NO3- For N-cycle and Nitrogen containing compounds e.g. amino acids, DNA, ATP etc