Zusammenfassung der Ressource
Nucleic Acids
- Structure of RNA and DNA
- Nucleotide Structure
- made up of 3 components
- a pentose sugar
- a phosphate group
- a nitrogen containing organic base
- A/T/C/G/U
- A is complementary to T and
C is complementary to G
- the pentose sugar, organic
base and phosphate group
are joined by a
condensation reaction
- forms a mononucleotide
- bond between two
mononucleotides is a
phosphodiester bond
- dinucleotide
- RNA - ribonucleic acid
- polymer made
up of nucleotides
- single relatively
short polynucleotide
chain
- pentose
sugar is
always
ribose.
Organic
bases are
A,G,C,U.
- one type of RNA
transfers genetic
info. Another is
involved in protein
synthesis.
Ribosomes are
made of another
type
- DNA structure
- pentose sugar is
deoxyribose.
Organic bases are
A,T,C,G
- DNA is made of 2 strands of nucleotides
- they are both very long and joined by hydrogen bonds.
- double helix forms
a structural
backbone
- DNA stability
- the phosphodiester
backbone protects the more
chemically reactive bases
- hydrogen bonds link the bases
- C-G = 3 A-T = 2
- DNA function
- hereditary material responsible
for passing genetic information
from cell to cell and generation
to generation
- almost infinite variety of sequences of bases
- leading to increased genetic variation
- rarely mutates and very stable
- two strands
joined by
hydrogen bonds
meaning it can
separate during
replication
- large molecule and carries lots of genetic information
- genetic information is
protected from chemical and
physical forces becuause it is
located within the
phosphodiester backbone
- DNA replication
- cell division occurs in two ways
- nuclear division =
nucleus divides
(mitosis/meiosis)
- cytokinesis = follows nuclear division
and the whole cell divides
- semi-conservative replication
- needs... the
nucleotide
bases, both
strands of DNA
to act as a
template, DNA
polymerase,
source of
chemical energy
- 1. DNA helicase breaks the hydrogen bonds
- 2. helix unwinds and separates into two strands
- 3. each exposed polynucleotide chain acts as a template
- 4. nucleotides are joined together in condensation reactions by DNA polymerse
- 5. each new DNA molecule has one original strand and one new one
- Energy and ATP
- Structure = adenine, ribose and phosphates
- ATP has 3 phosphate groups
- the bonds between them are
unstable and lave low activation
energy
- they are easily broken and release lots of energy when they do
- usually only the terminal phosphate is removed
- ATP + H2O -> ADP + Pi + E
- water is used to
convert AP to ADP,
this is known as
hydrolysis. The
reaction is catalysed
by ATP hydrolase
- this is a reversible
reaction. That is a
condensation reaction
and is catalysed by ATP
synthatse
- this can occur in three ways
- photophosphorylation
- oxidative phosphorylation
- substrate-level phosphorylation
- ATP is a good immediate energy
source because it is instable
- ATP is a better immediate energy source than
glucose because the amount of energy released is
more manageable and the hydrolysis of ADP to
ATP is a single reaction
- ATP is involved in
energy-requiring processes in
cells
- metabolic processes - provides the energy needed to build up
macromolecules from their basic sub-units
- movement - provides energy for muscle
contraction and the energy for filaments to slide
past one another
- active transport - energy to change the shape of carrier proteins
- secretion - needed to form lysosomes
- activation of molecules - Pi released
during hydrolysis can be used to
phosphorylate other compounds to
make them more reactive
- Water
- Dipolar
- oxygen atoms are slightly
negative and hydrogen
slightly positive, so the
molecule has positive and
negative poles
- Hydrogen bonding
- opposite poles attract and the attractive forces between them is a hydrogen bond
- individually the bonds are weak
- SHC
- water molecules bond together meaning it takes more energy to break the bonds
- latent heat of vaporisation
- hydrogen bonding between
water molecules means that
it requires a lot of energy to
evaporate 1 gram of water
- cohesion and surface tension
- the tendency of molecules to stick together is known as cohesion.
- with its hydrogen bonding, water has large cohesive forces and these allow it to be pulled through a tube, such as a xylem vessel
- water in metabolism
- used to break down complex molecules by hydrolysis
- produced in
condensation reactions
- chemical reactions take place in aqueous medium
- major raw material in photosynthesis
- solvent
- water readily dissolves other substances such as gases, wastes,
inorganic ions and enzymes
- important
features
- evaporation cools organisms
- not easily compressed so provides support
- transparent so aquatic plants can photosynthesise
- inorganic ions (iron, phosphate ions, hydrogen ions, sodium ions)