Unit 1.1 (Part One)

Question 1

What are organisms composed of?

Answer 1

Organisms are composed of biological molecules that are fundamental to their functioning.

Question 2

What is an atom?

Answer 2

The smallest unit of matter

Question 3

What is a molecule?

Answer 3

Two or more atoms chemically bonded.
They could be the same or different type of atom.

Question 4

What is an element?

Answer 4

A substance made up of one type of atom only.

Question 5

What is a compound?

Answer 5

Two or more elements chemically bonded.

Question 6

What is an organic compound?

Answer 6

A compound containing one or more carbon atoms, chemically bonded with other elements, usually hydrogen and oxygen.

Question 7

What is an inorganic compound?

Answer 7

A compound that doesn’t contain carbon-hydrogen bonds.

Question 8

What is meant by the term metabolism?

Answer 8

All the organism’s chemical processes.

Question 9

What do living organisms need?

Answer 9

Living organisms need a variety of inorganic ions/electrolytes/minerals to survive.

Question 10

Why are inorganic ions/electrolytes/minerals important?

Answer 10

They are important in many processes in cells, e.g. muscular contraction, nervous coordination and maintaining the osmotic balance in cells and blood.

Question 11

What are the two groups of inorganic ions?

Answer 11

macronutrients: needed in small concentrations e.g. Mg, Fe, Ca, P

micronutrients: needed in minute (trace) concentrations e.g. Cu, Zn

Question 12

Why do living organisms need magnesium?

Answer 12

Magnesium is an important constituent of chlorophyll and is therefore essential for photosynthesis.

Mammals need magnesium for their bones.

Question 13

What are the deficiency symptoms for lack of magnesium?

Answer 13

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.

Question 14

Why do living organisms need iron?

Answer 14

Iron is a constituent of haemoglobin, which transports oxygen in red blood cells.

Question 15

What does lack of iron lead to?

Answer 15

Lack of iron in the human diet can lead to anaemia

Question 16

Why do living organisms need phosphate ions?

Answer 16

Phosphate ions are used for making nucleotides, including ATP, and are a constituent of phospholipids found in biological membranes.

Question 17

What is a nucleotide?

Answer 17

The building blocks of nucleic acids (DNA and RNA)

Question 18

Why do living organisms need calcium?

Answer 18

Calcium is an important structural component of bones and teeth in mammals and is a component of plant cell walls, providing strength.

Question 19

Why is water important?

Answer 19

Water provides a habitat for aquatic organisms and a medium for metabolic reactions.

Question 20

What percentage are all organisms made up of water?

Answer 20

Plants and animals are made up of 65% - 95% water and 70% of human cells are made up of water.

Question 21

Tell me about the structure of water.

Answer 21

1. Each molecule of water has two hydrogen atoms and one oxygen atom, covalently bonded.
2. Water is a small molecule which is polar.
3. The water molecule is a dipole, the hydrogen end is charged slightly positively and the oxygen end is charged slightly negatively. The charges are very small and they are written as delta + and delta - to distinguish them from full charges written as + or -.
4. The negatively charged oxygen atoms of water attract the positively charged hydrogen atoms of neighbouring water molecules forming hydrogen bonds.
   Individual hydrogen bonds are weak but because they are so numerous, water molecules form a lattice and are difficult to separate.

Question 22

Define polar molecule.

Answer 22

A polar molecule is neutral overall but has uneven distribution of charge.

Question 23

List the properties of water.

Answer 23

1. Cohesion
2. High surface tension
3. Solvent
4. A metabolite
5. High specific heat capacity
6. High latent heat of vaporisation
7. High density
8. Water is transparent

Question 24

What is cohesion?
What does it enable to do?

Answer 24

Water molecules can ‘stick together’ by forming hydrogen bonds with each other.

This strong attraction to one another is called cohesion and enables columns of water to be drawn up xylem vessels in tall trees.

Question 25

At what temperatures does water have the highest surface tension?

Answer 25

At ordinary temperatures, water has the highest surface tension of any liquid, except mercury.

Question 26

Why is water having a high surface tension important for living organisms?

Answer 26

The large number of hydrogen bonds between water molecules produce surface tension so that insects such as the pond skater can be supported as if the water has a ‘skin-like’ surface.

Question 27

Why is water a universal solvent?
Why is it important?

Answer 27

Water’s polarity makes it an excellent solvent for ionic and polar molecules.

It will attract other charged particles (ions) e.g. Na+ and Cl- and other polar molecules, e.g. glucose.

These then dissolve in water so chemical reactions take place in solution.

Water acts as a transport medium.
e.g. in animals - blood plasma transports many dissolved substances such as oxygen and carbon dioxide.
in plants - water transports minerals in the xylem and sucrose and amino acids in the phloem.

For aquatic organisms, CO2 and O2 dissolve in water for photosynthesis and/or respiration.

Question 28

Can non-polar molecules dissolve in water?

Answer 28

No, non-polar molecules such as lipids will not dissolve in water as they are hydrophobic.

Question 29

Define hydrophobic.

Answer 29

Does not dissolve in water.
non-polar molecules

Question 30

Define hydrophilic

Answer 30

Dissolves in water.
polar molecules

Question 31

Why is water a metabolite?

Answer 31

Because water is used in many biochemical reactions as a reactant.

Question 32

Give an example where water is a reactant.

Answer 32

In hydrolysis reactions, water is added and splits a molecule

maltose + water —-> glucose + glucose

Water is also a reactant in photosynthesis

Question 33

Give an example where water is a product.

Answer 33

In condensation reactions, water is a product.

glucose + fructose —–> sucrose + water

Question 34

What does it mean when water has a high specific heat capacity?

Answer 34

This means that a large amount of thermal energy is needed to raise the temperature of water.

Question 35

Why does water have a high specific heat capacity?

Answer 35

This is because hydrogen bonds between water molecules restrict their movement, resisting an increase in kinetic energy and resisting an increase in temperature.

Question 36

Why is water’s high specfic heat capacity important?

Answer 36

Because this prevents large temperature fluctuations of water so enzymes are not denatured.

This is important inside cells where enzymes are temperature sensitive and in large bodies of water such as lakes where the temperature remains fairly constant.

Question 37

What does it mean when water has a high latent heat of vaporisation?

Answer 37

A great deal of thermal energy is required to change the state of water from a liquid to a vapour state.

Question 38

Why is water’s high latent heat of vaporisation important?

Answer 38

This is important in temperature control where thermal energy is used to vaporise water from sweat on skin or from the surface of leaves.

As the water evaporates, the surface is cooled.

This also means that aquatic habitats do not disappear easily by evaporation.

Transpiration in plants also has a cooling effect on leaves.

Question 39

What is the benefit of water’s high density?

Answer 39

Water is denser than air and as a habitat for aquatic organisms, provides support and buoyancy.

Ice is less dense than liquid water, so it floats on the surface.
Ice then forms an insulating layer for the water below so that the sea or lake does not freeze solid and allows organisms below the ice to survive.

Question 40

Why is water being transparent important?

Answer 40

This allows light to pass through so that aquatic plants can photosynthesise.