All paper 1 content

Define atom

The smallest part of a substance that cannot be chemically broken down

What are atoms made of?

Protons, neutrons, electrons

Define molecule

A collection of atoms bonded together chemically with covalent or ionic bonds

Define compound

Made from atoms of two or more elements and can include metals and non-metals or simply non-metals

Define ion

Can be positively charged (lost electrons leading to an overall positive charge) or negatively charged (gained electrons leading to an overall negative charge)

Define non-polar

When the ions within a molecule have charge but the overall molecule is not charged

Define polar

When the ions within a molecule are all charged and the molecule has an overall charge

Define pure

A substance cannot be broken down into smaller parts without chemical or nuclear reactions taking place

Define mixture

A substance which is not pure, is not chemically bonded and can be divided by physical means

What type of liquid can non-polar compounds dissolve in?

In lipids not water, as they are lipid soluble

What type of particle do charged particles attract?

Oppositely charged particles as they have important roles within the structure of lipids, in making covalent or hydrogen bonds

What elements are the main components of all organic molecules?

Carbon, hydrogen, oxygen, nitrogen (CHON)

Where are CHON molecules found?

In amino acids and nucleic acids

What non CHON elements are vital for life?

Calcium, phosphorus, iron, magnesium

What is the role of calcium in the body?

It strengthens teeth, bones and nerves in animal cells, and strengthens cell walls in plants

What is the role of phosphorus in the body?

It is present in cell membranes, ATP and nucleic acids

What is the role of magnesium in the body?

It is required by plants as a component of chlorophyll and is used in enzyme function

What is the role of iron in the body?

It is used in oxygen transport and the production of haemoglobin in animals

What is the difference between organic compounds and inorganic compounds?

Organic compounds may contain carbon, hydrogen, oxygen and nitrogen (but not necessarily with oxygen and nitrogen). Inorganic compounds may have any of these

What constitutes an inorganic compound?

Inorganic ions mare made without the involvement of living organisms

Why is water so important?

Water is the most abundant compound in any organism, making up 70% of the mass of humans. It is essential for biochemical reactions since these all take place is aqueous solutions.

What is the charge of a molecule of water?

It is a polar molecule with no overall charge - although the two sides of the molecule have charge; the hydrogen atoms have a partial positive charge and the oxygen atom has a partial negative charge

What bonds are present in a molecule of water?

Solid lines represent covalent bonds, since both atoms are non-metals, and vertically dashed lines between two water molecules represent hydrogen bonds

How do bonds form between polar water molecules?

The polarity of water means that individual molecules can form hydrogen bonds with up to four other water molecules, and that charged particles can dissolve easily in water

How strong are hydrogen bonds?

Individually they are weak, but collectively they form strong bonds

What angle do atoms in water molecules meet at and why?

104.5 degrees due to the difference in size and electronegativity of the atoms

Give the titles of the properties of water

Solvent properties, high specific heat capacity, high latent heat of vaporisation, molecular mobility, cohesion and surface tension, density and freezing properties, colloid formation

Give the titles of the biological importance of water

Transport medium, thermoregulation, osmosis, the transpiration stream, supportive role, lubricant properties, ice floats, metabolic functions, volatility and stability, transparency

What are the solvent properties of water?

The polarity of water makes it an excellent solvent for other polar molecules. The electrostatic attractions between polar water molecules and ions are greater than the electrostatic attractions between the anion and the cation (which are types of ion), causing ions to become hydrated in aqueous solution. Such polar substances, which dissolve in water, are hydrophilic (water loving). However, the polarity of water molecules means that non-polar (hydrophobic, or water hating) substances do not readily dissolve in water. Instead, these non-polar molecules arrange themselves to expose the minimum possible surface area to the water molecules

How does water’s solvent properties result in water being biologically important?

It is a universal solvent (since so many substances dissolve in it) and it allows water to act as a transport medium for polar solutes

Give an example of how water acts as a transport medium

The movement of minerals to lakes and seas, transport via blood and lymph in multicellular organisms, the removal of metabolic wastes such as urea and ammonia in urine

What is the high specific heat capacity of water?

The amount of heat energy, measured in joules, required to raise 1kg of water by 1 degree Celsius is very high. Much of the heat absorbed is used to break the hydrogen bonds holding water molecules together

How does the high specific heat capacity of water result in it being biologically important?

It means that bodies composed largely of water (like humans, since our cells are around 70% water) are very thermostable so are less prone to damage by heat due to changes in environmental temperatures

What is the high latent heat of vaporisation of water?

Hydrogen bonds which attract molecules of liquid water to one another make it difficult for the molecules to escape as vapour. This means that a high input of energy is required to vaporise water, causing water to have a much higher boiling point than other molecules of the same size

How does the high latent heat of vaporisation of water result in water being biologically important?

It means that an organism can be considerably cooled with a minimal loss of water

Give an example of when high latent heat of vaporisation is useful

It is used extensively by mammals during sweating and reptiles in gaping, and it may be important in cooling transpiring leaves

What is the molecular mobility of water?

The weakness of hydrogen bonds means that individual water molecules continually jostle each other whilst in a liquid state

How does the molecular mobility of water result in the biological importance of water?

It allows osmosis to take place, which is vital for the uptake and movement of water, especially in plants

What is the cohesion and surface tension of water?

Hydrogen bonding causes water molecules to stick together and stick to other molecules (cohesion). At the surface of a liquid, the inwardly acting forces of cohesion produce surface tension as the molecules are attracted to one another

List reasons for the biological importance of water due to its cohesive forces and surface tension

The transpiration stream, supportive role, lubricant properties

How does the cohesive and surface tension of water result in the transpiration stream?

The continuous column of water is able to move up the xylem due to cohesion (between two water molecules) and adhesion (between water and the walls of the xylem vessels)

How does the cohesion and surface tension of water result in it having a supportive role?

The cohesive forces of water means that water is not easily compressed so is an excellent medium for support

Give an example of how water provides a supportive role

The hydrostatic skeleton of earthworms, turgor pressure in the herbaceous parts of plants, amniotic fluid which supports and protects the mammalian foetus, and it is a general supportive medium - particularly for large aquatic mammals such as whales

How does the cohesion and surface tension of water result in it having lubricant properties?

It means that water is viscous (it can flow) so is a useful lubricant in biological systems

Give an example of how water has lubricant properties

Synovial fluid lubricates many vertebrate joints, pleural fluid minimises friction between the lungs and thoracic cage (ribs) during breathing, mucus permits the easy passage of faeces down the colon and lubricates the penis and vagina during intercourse

What are the density and freezing properties of water?

As water cools towards its freezing point (0 degrees Celsius), the individual molecules slow down sufficiently for each one to form its maximum number of hydrogen bonds. To do this, water molecules in liquid water must move further apart to give enough space for all four hydrogen bonds to fit. As a result, water expands as it freezes. This makes ice less dense than liquid water and so it floats on the surface of water

How do the density and freezing properties of water result in water being biologically important?

Since ice floats, it forms at the surface of ponds and lakes to insulate the organisms in the water below it, as ice is a poor conductor of heat. It also allows the ice to thaw rapidly when temperatures rise. Changes in density also maintain circulation in large bodies of water, helping nutrient cycling. Floating ice also means that penguins and polar bears still have a habitat and somewhere to stand

What temperature is the maximum density of water?

4 degrees Celsius at a liquid state

What is the colloid formation of water?

Some molecules have strong intermolecular forces which prevent their solution in water, but have charged surfaces which attract a covering of water molecules. This ensures that the molecules remain dispersed throughout the water rather than forming huge aggregates which could then settle out. The dispersed particles and liquid around them collectively form a colloid

List reasons for the biological importance of water due to its colloid formation

Function in metabolism, volatility and stability, transparency

How does the colloid formation in water result in water being biologically important in metabolism?

Water is used directly as a reagent (a source of reducing power) in photosynthesis to hydrolyse macromolecules to their subunits. Water is also the medium in which all biochemical reactions take place

Give an example of when water hydrolyses macromolecules to their subunits

Digestion

How does the colloid formation in water result in water being biologically important in volatility and stability?

Water is liquid at most temperatures on earth so that the water cycle is maintained

What are the main stages in the water cycle?

Evaporation, transpiration, precipitation

How does the colloid formation in water result in water being biologically important in transparency?

Water permits the passage of visible light, meaning that photosynthesis and it associated food chains are possible in relatively shallow aquatic environments