1.1 Mitochondria are structures in cells
where respiration happens. Ribosomes
are too small to see using the light
microscope. Chromosomes are made
from DNA. Genes are short sections of
DNA. Each gene is a set of coded
instructions for making a particular
1.2 Mitochondria are tiny structures found in cells (one is
called a mitochondrion). Respiration, the chemical
reaction that releases energy from glucose, happens
in mitochondria. This provides energy for life process
such as movement and growth. Tissues and organs
that need a lot of energy have large numbers of
mitochondria in their cells. For example, liver cells
and muscle cells contain a lot of mitochondria.
1.3 Chromosomes The cell's nucleus
contains chromosomes. These
are long, coiled molecules of
DNA, divided up into regions
1.4 DNA The information contained in
genes is in the form of coded
instructions called the genetic code.
The genetic code controls cell activity,
which means that it also controls
some characteristics of the organism.
1.4.1 DNA controls the production of
different proteins. These are
needed for the growth and
repair of cells.
1.5 Two scientists, James Watson and
Francis Crick, worked out the
structure of DNA. By using data
from other scientists they were able
to build a model of DNA. The data
they used showed that bases
occurred in pairs. Further x-ray data
showed that there were two chains
wound into a double helix.
1.6 A double helix DNA shown as a double twisted string
with interlinking parts Base pairs on a DNA molecule
Each strand of DNA is made of chemicals called bases.
Do not confuse these with the bases you meet when you
study acids and alkalis in chemistry. There are four
different types of bases, shown as A, T, C and G
1.7 Protein structure is determined by the DNA
base code. Proteins are made from lots of
amino acids joined together. Each amino acid
is coded by the sequence (order) of three
bases. For example, GGT codes are found in
glycine but TCA codes are found in serine, a
different amino acid.
1.8 Messenger RNA (mRNA)
1.8.1 mRNA from DNA is called
transcription. Proteins from mRNA
is called translation
2 Proteins and mutations
2.1 Proteins are made from long chains
of different amino acids. Enzymes are
a type of protein that speeds up the
chemical reactions inside cells. Each
type of enzyme does a specific job.
Enzymes work best at optimum
temperatures and pH values.
Mutations can affect the ability of a
protein to work properly.
2.2 Proteins are polymers, relatively large
molecules made from many smaller
molecules. Each protein molecule is
built up from amino acids, smaller
monomer molecules that join end to end
to make the protein polymer molecule.
2.3 Different types of protein have different functions.