Biological Molecules- Part Two- Nucleic Acids, Atp, Watee Flashcards
Describe a nucleotide
Pentose sugar- ribose, deoxyribose
Phosphoric acid
Organic base
Describe a nucleotide
Pentose sugar- ribose, deoxyribose
Phosphoric acid
Organic base
What is the difference between a purine and Pyrimidines base
Purine- double ringed
Adenine and guanine
Pyrimidines- single ringed
Thymine and cytosine
What does antiparallel mean
Two dna strands run alongside each other
But in opposite directions
Different shape nucleotides, enzymes; specific active site. Complementary shapes
What are the adaptations of DNA
- Sugar- phosphate backbone gives strength
- Coiling - compact shape
- Sequence of bases allows information to be stored
- Long molecule/ coiling stores large amounts of information
- Complementary base pairing enables information to be replicated/ transcribed
- Double helix protects weak hydrogen bonds/ double helix makes molecule stable
- Many hydrogen bonds together give molecule stability; prevents code being corrupted
- Hydrogen bonding allows chains to split for replication/ transcription OR molecule unzips easily for replication/ transcription
Describe semi-conservative replication
When cells divide the daughter cell must receive an exact copy of the genetic material from the parent. In order for this to happen the DNA must be replicated or copied
Semi-conservative replication -
1. Replication starts at a specific sequence on the DNA molecule.
2. DNA helicase unwinds and unzips DNA, breaking the hydrogen bonds that join the base pairs, and forming two separate strands. Each chain acts as a template (enzymes)
3. The new DNA is built up from the four nucleotides (A, C, G and T) that are abundant in the nucleoplasm. (free, floating around)
4. These nucleotides attach themselves to the bases on the old strands by complementary base pairing. Where there is a T base, only an A nucleotide will bind, and so on.
+ 5. DNA polymerase (enzyme)joins the new nucleotides to each other by strong covalent bonds
T. (phosphodiester bond), forming the phosphate-sugar backbone. (binds to 3 prime end.)
• joins backbone, not joins A and T, catalyses
6. winding enzyme winds the new strands up to form double helixes.
7. The two new molecules are identical to the old molecule.
What is the difference between conservative and semi-conservative replication
One strand of original dna molecule is contained din the new dna molecule
Describe the meselson and stahl’s experiment
Bacteria were cultured on a heavy nitrogen (N15) medium; (1 mark]
• The bacteria took up this nitrogen and used it to synthesise DNA bases; (1 mark]
• After the DNA is extracted and spun in a centrifuge it settled near the bottom of the tube; Il mark]
• The bacteria is then transferred to light nitrogen (N14)medium; [1 mark]
• (After a period of time) the DNA was extracted and centrifuged, it settled in an intermediate position / between the positions of N14and N15 [1 mark]
Describe the structure of DNA
Polymer of nucleotides
Each nucleotide - deoxyribose, phosphate, organic base
Phosphodiester bonds
Double helix- held by hydrogen bonds
A+T, C+G
What is the structure of atp
Adenosine triphosphate
Adenine, ribose, 3 phosphate
What are the advantages of ATP
Releases relatively small amount of energy/ little energy lost as heat (little danger of thermal death to cell)
Releases energy instantaneously
Phosphorylates other compounds, makes them more reactive (lower activation energy)
Can be rapidly re-synthesises
Not lost form cell
Uses of ATP
Provide energy for other redaction
Adds phosphate and makes them more reactive/ changes shape
Metabolic processes: provides energy to build up macromolecules from their basic units-anabolic reaction
• Movement: provides energy for muscle contraction
• Active transport: Provides energy to change the shape of the carrier proteins in plasma membranes so molecules can be moved against their concentration gradients
• Secretion: needed to form lysosomes
• Activation of molecules: When a phosphate molecule is transferred from AlP to another molecule it makes it more reactive. It therefore allows enzyme-catalysed reactions to occur more quickly
• Bioluminescence
Explain 5 properties of water
A metabolite in condensation/hydrolysis/ photosynthesis/respiration;
A solvent so (metabolic) reactions can occur
A solvent so allowing transport of substances:
High (specific) heat capacity so buffers changes in temperature;
For ‘buffer accept ‘resist.
Large latent heat of vaporisation so provides a cooling effect (through evaporation):
Reject latent heat of evaporation
Cohesion (between water molecules) so supports columns of water (in plants);
For ‘columns of water’ accept transpiration stream.
Do not credit transpiration’ alone but accept description of ‘stream’.
For columns of water’ accept ‘cohesion-tension (theory):
Cohesion (between water molecules) so produces surface tension supporting (small) organisms;
For cohesion accept hydrogen bonding
Ignore reference to pH. Allow other suitable properties but must have a valid explanation.
For example
• ice floating so maintaining aquatic habitat beneath
• water transparent so allowing light penetration for photosynthesis
Give two properties of water that are important in the cytoplasm of cells.
Polar- acts as a universal solvent
Solvent- reacitons occur fast Erin solution
Reactive- takes place in hydrolysis, condensation
