Advanced Biology

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  • Created on: 04-05-13 17:49
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Biological Molecules
The atom
The 3 different particles that make up an atom are protons, neutrons and electrons
The protons and neutrons are in the nucleus and the electrons circle around the nucleus in
The number of protons equals the number of neutrons
The atomic number of an element is the number of protons contained in the nucleus
The mass number of an element equals the number of protons plus the number of neutrons
A molecule consists of 2 or more atoms joined up together chemically
Molecules can be made up from atoms of the same element (O2) or from different elements
joined up together (CO2)
A molecule that is made up of different atoms is called a compound e.g. carbon dioxide
Ions are charged particles are formed when atoms or groups of atoms gains or loses
Atoms that gain electrons will be negative (anions)
Atoms that lose electrons will be positive (cations)
Atoms of the same element always contain the same number of protons but the number of
neutrons may change and this would result in a different mass number
N is a heavy, non-radioactive isotope. (Normal form 14N). This isotope has been used to
label the nitrogen in DNA to find out how DNA was made.
Acids and Bases
The PH of a solution is a measure of the concentration of hydrogen ions present. The higher
the concentration of hydrogen ions present, the more acidic the solution
On the PH scale, the value 1 indicates a strong acid and value 7 is a neutral level and value 14
indicates a strong alkali.
The PH scale is logarthromic i.e. PH1 is ten times more acidic than PH2 is ten times more
acidic than PH3.
An acid is a substance that dissolves into ions when in solution, releasing hydrogen ions e.g.
hydrochloric acid is a product of hydrogen ion and chlorine base
The stronger the acid, the more hydrogen ions it releases
When a base accepts a hydrogen ion, it forms into an acid
Living organisms have their cells at a stable PH because their enzymes only work effectively
over a narrow PH range
Some chemicals in the cytoplasm are able to : (other substances can do both)
Act as bases by mopping up hydrogen ions to help neutralize an alkali solution
Chemicals that can act as bases as well as acids are called buffers
Plasma proteins act as buffers to keep the blood PH constant

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When acids and bases react together, they form salts
Chemical bonds
Ionic bonding is when a metal gives one of its electrons to a non metal. After this has
happened, the ions will become charged and will attract each other. The Electrostatic forces
draw these ions together, forming an ionic compound. Ionic compounds usually form
inorganic compounds
Covalent bond is when an atom shares it's electrons with another atom. This occurs in order
to make the element more stable
Hydrogen bonds occur in water molecules.…read more

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Dissacharides or double sugars (formed from 2 monosaccharides)
Polysaccharides (polymer chain of many hundreds of monosaccharides)
Monosaccharides are the simplest forms of carbonhydrates. They are the building blocks for
larger carbohydrate molecules and provide cells with an energy source.
The name of monosaccharide depend upon the carbon atom in the molecule e.g.…read more

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Polysaccharides are made up of hundreds of monosaccharide units
A condensation reaction occurs in-between each monosaccharide unit
Long chains of monosaccharides are held together by glycosidic bonds (it can be
STORAGE polysaccharides are folded to give a compact molecule e.g. starch
STRUCTURAL polysaccharides are coiled or straight chained e.g.…read more

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Fatty acids are organic with one carboxyl (-COOH) group at one end and they have a long
hydrocarbon tail
The way that fatty acids reacts with glycerol depends on:
The length of the hydrocarbon tail
How saturated the molecules
Saturated fatty acids only have C-C bonds only and unsaturated fatty acids have one double
bond at least
Polysaccharides have more than 1 double bond and triglycerides have 1 molecule of glycerol
and 3 fatty acid molecules.…read more

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An amino acid have an amino group (-NH2) at one end of the molecule and a carboxyl group
(-COOH) at the other end of the group. The R group is the only thing that differed in an amino
acid.…read more

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Globular proteins are compact molecules which are twisted polypeptide chains rolled up into
a ball
The shape of a globular protein is a result of the hydrophobic R groups pointing at the centre
of the molecule.…read more

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Alkalinophiles can survive a PH of 10+ and are found in soda lakes rich in sodium
carbonate and sodium chloride
Acidophiles- are bacterium and able to tolerate pH below 1
The cell theory:
Organisms that are made up of one cell are unicellular
Mulitcellular organisms are made up of millions of cells
Prokaryotic cells
They have no nucleus or have distinct cell organelles
Organisms made up of prokaryotic cells are called prokaryotic organisms made up of
eukaryotic cells
Prokaryotes are relatively simple organisms e.g.…read more

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Cellulose cell wall
Plant cell walls are made up of microifibrils glued together by a mixture of polysaccharides
Provides cell support, allows it to be turgid- when water enters cell by osmosis, cell wall
Provides mechanical strength to support cell.…read more

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To form an extensive transport system throughout the cell
Production and packaging of protein (rough ER)
Syntheisis of lipids and steroids (smooth ER)
Collection, storage and distribution of these materials
Are small, dense organelles found in huge numbers in all cells, are 20nm in diameter in
eukayotic cells but slightly smaller in prokaryotic cells
Occur free in cytoplasm where they synthesise enzymes that are used in cytoplasm, such as
those enzymes involved in glycolysis (the first stage of respiration)
Most of the cell's ribosomes…read more


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