Nucleic Acids, ATP, water & inorganic ions Flashcards
Draw the structure of a nucleotide
http://www.a-levelnotes.co.uk/biology-ocr-as-notes-foundations-in-biology-nucleotides-and-nucleic-acids.html
Which bases are present in RNA nucleotides?
Adenine, URACIL, guanine, cytosine
Describe the structure of DNA. (6 marks))
- Sugar-phosphate backbone and double helix structure SO provides strength
- Large molecule SO stores a lot of information
- Helical SO compact
- Base sequence ALLOWS information to be stored
- Double stranded SO semi-conservative replication can occur BECAUSE each strand acts as a template
- Complementary base pairing ALLOWS accurate replication
- Hydrogen bonds FOR replication / strand separation
- Many weak Hydrogen bonds SO stable / strong molecule
Q
Describe Semi-Conservative Replication. (6 marks)
A
1. DNA helicase moves along DNA molecule
2. Breaking Hydrogen bonds between complementary bases and the two strands separate
3. Each strand acts as a template
4. Free DNA nucleotides attracted
5. To exposed complementary bases - adenine with thymine and guanine with cytosine
6. DNA polymerase joins adjacent nucleotides together forming phosphodiester bonds by condensation reactions
7. New DNA molecule contains one old strand and one new strand
Describe the role of DNA polymerase in the semi - conservative replication of DNA. (3)
- Joins (adjacent DNA) nucleotides
- By condensation reactions
- Forming phosphodiester bonds
Name the two scientists who proposed models of the chemical structure of DNA and of DNA replication.
Watson and Crick
Q
Give two features of DNA and how each one is important in the semi - conservative replication of DNA. (2)
- Weak hydrogen bonds between bases ALLOWS two strands to separate
- Two strands SO both can act as templates
- Complementary base pairing ALLOWS accurate replication
ATP is an energy source used in many cell processes. Give two ways in which ATP is a suitable energy source for cells to use. (2)
- Releases relatively small amounts of energy
- Releases energy instantaneously
- Phosphorylates other compounds making them more reactive
- Can be rapidly re-synthesized
- Does not leave the cells
Give two ways in which then hydrolysis of ATP is used in cells (2)
- Phosphorylates other compounds making them more reactive
- Provides energy for (named process) - active transport, protein synthesis, semi-conservative replication
Describe how an enzyme can be phosphorylated (2)
- Attachment of inorganic phosphate (Pi) to enzyme
- Hydrolysis of ATP OR ATP to ADP + Pi
Describe how ATP is re-synthesized in cells. (2)
- ADP + Pi
- By ATP synthase
- In respiration
Compare the structures of ATP and a nucleotide found in DNA to give two differences. (2)
- ATP has ribose sugar and DNA nucleotide has deoxyribose sugar
- ATP has 3 phosphate groups and DNA nucleotide has 1 phosphate group
- ATP base is always adenine and DNA nucleotide base can be different
Explain five properties that make water important for organisms (5)
- Metabolite SO allows condensation and hydrolysis reactions to occur
- Solvent SO allows transportation of substances within organisms
- High specific heat capacity SO buffers changes in temperature
- Large latent heat of vaporisation SO provides a cooling effect (through evaporation)
- Cohesion SO provides surface tension supporting organisms
Give two properties of water that are important in Biology. Explain the importance of each property you identify. (4)
- Polar
- Dissolves charged particles / acts as a solvent
OR - Metabolite
- Involved in metabolic reactions such as condensation and hydrolysis
OR - Cohesion between water molecules
- Provides surface tension
OR - High specific heat capacity
- Buffers changes in temperature
OR - High latent heat of vaporisation
- Provides cooling effect through evaporation
Describe the roles of iron ions, sodium ions, and phosphate ions in cells. (6)
A
Iron Ions
1. Haemoglobin loads/binds with oxygen
Sodium Ions
2. Co - transport of glucose into cells
3. Sodium moved out by active transport / Na-K pump
4. Creates a sodium concentration gradient
5. Affects osmosis
Phosphate ions
6. Affects osmosis
7. Joins nucleotides / in phosphodiester bonds
8. Used to produce ATP
9. Phosphorylates other compounds making them more reactive
10. Hydrophilic part of phospholipid bilayer