Chemical Elements & Biological Compounds

Question 1

What are other names for inorganic ions

Answer 1

• electrolytes

- minerals

Question 2

Why do living organisms need a variety of inorganic ions to survive?

Answer 2

• muscle contraction
• nervous coordination
• maintaining water potential in cells and blood

Question 3

What are the two main types of nutrients (inorganic ions)

Question 4

Describe the importance of magnesium in plants and mammals

Answer 4

Plants:
-An important constituent of chlorophyll and is therefore essential for photosynthesis.
- plants without magnesium in their soil cannot make chlorophyll and so the leaves are yellow, a condition known as chlorosis.
- growth is often stunted from lack of glucose
Mammals:
- need magnesium for their bones

Question 5

Describe the importance of iron in the human body

Answer 5

• A constituent of haemoglobin, which transports oxygen in red blood cells
• A lack of iron in the diet can lead to anaemia

Question 6

Describe the importance of phosphate ions

Answer 6

• Are used for making nucleotides, including ATP and are a constituent of phospholipids, found in biological membranes

Question 7

Describe the importance of calcium ions

Answer 7

An important structural component of bones and teeth in mammals and is a component of plant cell walls providing strength

Question 8

Why is water classed as a dipole?

Answer 8

It has a positively charged end (hydrogen) and a negatively charged end (oxygen). A molecule with separated charges is polar (these charges are very small)

Question 9

Describe water’s properties as a solvent

Answer 9

• because water molecules are dipoles, they attract charged particles
• these dissolve in water; chemical reactions take place in solution
• water acts as a transport medium

Question 10

Water as a solvent, its effect on plants and animals:

Answer 10

Plants: 
- water transports minerals in the xylem
-water transports sucrose and amino acids in the phloem 
Animals:
- plasma transports dissolved substances

Question 11

Waters properties as a metabolite

Answer 11

- water is used in many biochemical reactions as a reactant 
Hydrolysis:
Maltose + water ---> glucose + glucose
Condensation:
Glucose + glucose ---> maltose + water

Question 12

Why is water said to have a high specific heat capacity?

Answer 12

A large amount of energy is needed to raise 1g of water by 1 degree

• hydrogen bonds restrict their movement
• resisting an increase in kinetic energy
• prevents large fluctuations in temperature

Question 13

Waters high specific heat capacity and it’s affect in plants and animals

Answer 13

Plants & animals:

• keeps aquatic habitats stable so organisms do not have to adapt to extremes in temperature
• allows enzymes to work efficiently

Question 14

Why is water said to have a high latent heat of vaporisation

Answer 14

A lot of heat energy is needed to change it from a liquid to a vapour

Question 15

Waters high latent heat of vaporisation and its affects in plants and animals

Answer 15

Plants:
Heat is used to vaporise water from a leafs surface

Animals:
Water is used to vaporise sweet from the surface of the skin and as the water evaporates the body cools

Question 16

What is cohesion?

Answer 16

• Water molecules attract each other forming hydrogen bonds

- individually the bonds are weak but because there are many of them the molecules stick together in a lattice

Question 17

How is cohesion useful in plants?

Answer 17

It allows columns of water to be drawn up xylem vessels in plants

Question 18

How is surface tension created?

Answer 18

• cohesion between water molecules at the surface produces surface tension

Question 19

How can surface tension be useful for some animals:

Answer 19

The body of an insect (e.g a pond skater) is supported

Question 20

What temperature does water have its maximum density?

Answer 20

4 degrees

Question 21

Why does ice float on water?

Answer 21

Ice is less dense than water because hydrogen bonds hold the molecule further apart than they are in a liquid. So ice floats in water.

Question 22

Why is waters density important for organisms?

Answer 22

• it’s a good insulator and prevents large bodies of water loosing heat and freezing completely
• so organisms beneath can survive

Question 23

Why is waters transparency an important property?

Answer 23

• it lets aquatic plants photosynthesise effectively