Nucleic Acids Flashcards
1
Q
DNA (Deoxyribonucleic Acid)
A
- Stores genetic information
- Made up of a deoxyribose sugar, a phosphate group and nitrogenous base
- Double helix structure - the 2 strands in DNA are antiparallel
2
Q
RNA (Ribonucleic Acid)
A
- Transfers genetic information from the nucleus to the ribosomes
- Made up of a ribose sugar, a phosphate group and a nitrogenous base
- Short, polynucleotide chain structure
- RNA is single stranded, unlike DNA
3
Q
Polynucleotide
A
- Long chain of nucleotides joined in condensation reactions
- Held together by phosphodiester bonds
- Bond formed between the sugar of one nucleotide and the phosphate of the adjacent nucleotide
- Chain of sugars and phosphates formed is known as a sugar-phosphate backbone
4
Q
Complementary Base Pairings
A
- Bases are joined by hydrogen bonds
- Adenine (A) joins with thymine (T)
- A and T form 2 hydrogen bonds
- Guanine (G) joins with cytosine (C)
- G and C form 3 hydrogen bonds
- In RNA, Adenine (A) joins with uracil (U)
5
Q
Why is DNA a stable molecule?
A
- Sugar phosphate backbone protects nitrogen bases, which are more chemically reactive
- There are 3 hydrogen bonds between C and G making the molecule more stable when there is a higher proportion of these bonds
6
Q
Process of DNA Replication
A
- DNA Helicase breaks the hydrogen bonds between the complementary bases on the 2 strands of DNA, causing them to separate
- Free nucleotides form hydrogen bonds between their complementary bases on the template strand
- DNA polymerase forms phosphodiester bonds between the adjacent nucleotides forming the sugar phosphate backbone on the new strand
7
Q
Antiparallel Strands
A
- DNA strands run in opposite directions parallel to one another
- Each strand has a 3’ end and a 5’ end
- Only the 3’ end can bind with the active site of polymerase
- The polymerase enzyme travels in opposite directions on each strand
8
Q
Conservative Theory
A
DNA molecule is copied and a 2nd new DNA molecule is made
9
Q
Dispersive Theory
A
- DNA molecule is cut at various sections with each section being copied
- The new sections reattach to the original sections of DNA to produce 2 DNA molecules
- Both DNA molecules have a mix of the old and the new DNA
10
Q
Semi-Conservative Theory
A
- 2 strands separate and each strand acts as a template strand to copy a new strand
- The old strands and the new strands would reattach to create 2 new DNA molecules
- Both DNA molecules have 1 old strand and 1 new strand
11
Q
Meselson and Stahl E-coli Experiment
A
- Grew E-coli in a sample of N-15 and then centrifuged it to show it was heavy
- Left E-coli to divide in a sample of N-14 (less dense than N-15) and then centrifuged the E-coli again
- After division 1, 100% of the DNA in the E-coli was a mix of N-14 and N-15 (disproves conservative theory)
- E-coli was left to divide in N-14 again and centrifuged again
- After division 2, 50% of the DNA was N-14 and 50% was a mix of N-14 and N-15 (disproves dispersive model)
12
Q
ATP (Adenosine Triphosphate)
A
- 3 phosphates, a ribose sugar and an adenine base
- Nucleotide derivative (modified form of a nucleotide)
- Provides energy for chemical reactions within the cell (energy isn’t directly from glucose)
- Synthesised from ADP and inorganic phosphate using energy from reactions (e.g. breakdown of glucose)
- ADP + P(i) –> ATP + H2O (condensation reaction)
13
Q
ADP (Adenosine Diphosphate)
A
- Phosphorylated during respiration
- When energy is needed in a cell, ATP is broken down into ADP and P(i)
14
Q
Properties of Water
A
- Metabolite - can be used/formed in condensation and hydrolysis reactions
- Solvent - can transport substances
- Large Specific Latent Heat - allows animals to cool down via evaporation (sweating)
- Cohesive (polar) molecule - creates surface tension to support small organisms
- High Specific Capacity - acts as a buffer to temperature (lots of energy can be gained/lost without there being a temperature change)
