Biology Chapter 2 Flashcards
What does a phosphodiester bond consist of?
Phosphate group and 2 ester bonds
Describe the differences of DNA and RNA
DNA:
- Deoxyribose sugar
- A,T,G,C
- Nucleotides form double polynucleotide strands
- Longer strands
RNA:
- Ribose sugar
- A,U,G,C
- Nucleotides form single polynucleotide strands
- Shorter strands
Describe DNA replication
- DNA helicase breaks the hydrogen bonds between the bases on the two polynucleotide DNA strands. This makes the ‘helix’ unwind to form two single strands of DNA
- Each original single strand acts as a template for a new strand. Complementary base pairing means that free-floating DNA nucleotides are attracted to their complementary exposed bases on each original template strand
- Condensation reactions join the nucleotides of the new strands together, which are catalysed by DNA polymerase. The active site of DNA polymerase is only complementary to the 3’ end of the newly forming DNA strand. This means that the enzyme can only add nucleotides to the new strand at the 3’ end. This means that the new strand is made in a 3’ to 5’ direction and that DNA polymerase moves down the template strand in a 3’ to 5’ direction. Hydrogen bonds form between bases on the original and new strands. Each new DNA molecule contains one strand from the original DNA and one new strand
What is the evidence for semi-conservative replication?
- 2 samples of bacteria grown for many generations, one in a nutrient broth containing heavy nitrogen and one in a nutrient broth containing light nitrogen. As the bacteria reproduced they took up nitrogen from the broth to help make nucleotides from the DNA. So the nitrogen gradually became part of the bacteria’s DNA
- Sample of DNA taken from each broth, spun in centrifuge. Heavy nitrogen bacteria = lower down the tube. Light nitrogen bacteria = higher up the tube
- Bacteria grown in heavy nitrogen were taken out and put in broth containing light nitrogen only. The bacteria were left for round one of DNA replication, and then another DNA sample was taken out and spun in the centrifuge
- If DNA replication was conservative the original heavy DNA would settle at the bottom and new light DNA would settle at the top. If replication was semi-conservative the new bacterial DNA molecules would contain one strand of old DNA and one strand of the new DNA. The DNA would, therefore settle out between where the light nitrogen DNA and the heavy nitrogen DNA settled out
- DNA settled out in the middle, therefore replicated semi-conservatively
What is ATP made from?
Adenine
Ribose sugar
3 phosphate groups
Where is ATP stored?
In high energy bonds between phosphate groups
What is ATP broken down into during hydrolysis
ADP
Inorganic phosphate
What is the enzyme which catalyses hydrolysis of ATP
ATP hydrolase
What is phosphorylation?
When inorganic phosphate is added to another compound which makes it more reactive
how is ATP resynthesised?
In a condensation reaction between ADP and inorganic phosphate during respiration and photosynthesis
What enzyme catalyses the resynthesis of ATP?
ATP synthase
What are the 4 functions of water?
- Metabolite in loads of metabolic reactions (including hydrolysis and condensation reactions)
- Solvent (substances dissolve in it and most metabolic reactions take place in solution)
- Helps with temperature control due to its high latent heat of vaporisation and a high specific heat capacity
- Water molecules are very cohesive, which helps water transport in plants and other organisms
What is the structure of water?
Oxygen = slightly negative charge Hydrogen = slightly positive charge
Hydrogen bonding between molecules
Why is water an important metabolite?
Hydrolysis requires water to break a bond, condensation releases water as a new bond is formed)
Why is water a good solvent?
Water is polar so ions get totally surrounded by water molecules so useful dissolved substances can be transported around the organism’s body
