Cells
Introduction to cells
·
Identify the essential characteristics
of prokaryotic and eukaryotic cells.
·
Eukaryotic
cells are relatively large and complicated
·
·
Eukaryotic
cells have specialised internal structures such as nuclei and mitochondria
·
Has
membrane bound organelles
·
Prokaryotic
cells are smaller and less complicated without obvious internal organisation
such as nuclei.
·
No
membrane bound organelles, e.g. no mitochondria
·
No
complex internal membranes e.g. no golgi
·
DNA
exist as a single large molecule in the form of
a ring (containing no histone(?) proteins)
·
Explain the relationship of individual
cells to the organisation of the whole body.
·
Understanding
how major body systems work and go wrong can be reduced to the level of cellular
function and malfunction.
·
Cells
® Tissues ® Organs ® Organ Systems
® Body
·
Molecules
in the cell are the targets for drug action.
·
E.g.
cancer is a disease of cells
·
Explain how information usually flows
from DNA to protein in eukaryotic cells.
·
The
DNA gene is first isolated, copied to pre-mRNA (transcription)
·
Then
it is processed to mRNA
·
This
mRNA is then used to code for synthesis of protein by ribosomes (translation)
·
DNA ®
pre-mRNA ® mRNA
® Protein
·
Describe DNA, RNA and protein in terms
of their linear polymeric structure.
·
DNA
is composed to two nucleic acid strands running in opposite directions
·
It
contains nucleotides linked by PHOSPHODIESTER bonds
·
A
nucleotide is made up of a DEOXYRIBOSE sugar combined with a nitrogenous base
and a phosphate group.
·
The
two strands are linked by HYDROGEN bonds between adjacent complimentary base
pairs- Adenine- thymine (
·
This
structure forms the characteristic double helix
·
RNA
is single stranded
·
The
sugar in the nucleotides is RIBOSE, it contains URACIL instead of THYMINE and
is less stable than DNA
·
Proteins
are made up of a chain of amino acids, of which there are
·
Each
amino acid is linked by a peptide bond formed by a CONDENSATION reaction
between the carboxylic acid and amine groups on adjacent amino acids.
R
H O H O
Two Amino Acids
N C C + N C C
H OH H OH
H H
R
O
A Dipeptide
H O
N C C N C C
H OH
H H H
·
Recognise the existance of reverse
transcriptase
·
Reverse
transcription is the production of DNA from RNA by the enzyme reverse
transcriptase
·
Describe how amino acids are linked to
form proteins
·
Proteins
consist of one or more polypeptide chains, which themselves consist of chains
of amino acids joined together by covalent bonds (peptide bonds)
·
The
PRIMARY structure of a protein is its
amino acid sequence
·
The
SECONDARY structure is after some folding has taken place; alpha helices or
beta pleated sheets form. These are
stabilised by hydrogen bonding from the H’s and O’s in the peptide bonds.
·
The
TERTIARY structure refers to the folding of polypeptide strands which is stabilised
by interactions between amino acid side chains (R groups).
·
In
general hydrophobic amino acids fill the interior of proteins while polar amino
acids face outwards and hydrogen bonds or charge pairs involving side chains
may contribute to structure.
·
The
QUATERNARY structure are polypeptide chains with any additional non
proteinaceous groups needed. The
quaternary structure is used to describe
the way multiple sub-units in some proteins associate.
·
Explain on the basis of structure why
the range of protein functions is so much larger than that for DNA or RNA.
·
Proteins
can be folded to give precise
·
Proteins
have prosthetic groups (e.g. haemoglobin) and can be covalently modified.
·
Covalent
modification includes:
·
Glycosilation:
Addition of sugar chains at –OH or NH
·
Phosphorylation:
Addition of a phosphate to the –OH group of serine, threonine or tyrosine. This is reversible and often important in
regulating protein function.