What are the differences between DNA and RNA nucleotides?
- DNA nucleotides have the pentose sugar deoxyribose whereas RNA nucleotides pentose sugar ribose
- DNA have base Thymine and RNA has base Uracil
What are the differences between DNA and RNA molecules?
- DNA is double stranded whereas RNA is single stranded
- DNA is longer and RNA is shorter
What is the structure of DNA related to its functions?
- Double stranded - both strands can act as templates for semi-conservative replication
- Weak hydrogen bonds - unzipped for replication
- Complementary base pairing - accurate replication
- Many hydrogen bonds between bases - stable
- Double helix with sugar phosphate backbone - protects bases
- Long molecule - store lots of genetic information
- Double helix - compact
What is the process of DNA replication?
- DNA helicase breaks hydrogen bonds between bases, unwinds double helix - 2 strands act as templates
- Free floating DNA nucleotides attracted by complementary base pairing, hydrogen bonds form
- DNA polymerase joins adjacent nucleotides by condensation forming phosphodiester bonds
How does DNA polymerase work?
- DNA has antiparallel strands
- DNA polymerase is an enzyme with a specific shaped active site which can bind to substrate with a complementary shape
- Can only bind to and add nucleotides to phosphate 3
What is the evidence for semi-conservative replication?
- Bacteria grown in a nutrient solution containing heavy nitrogen (15N) for several generations
- Nitrogen incorporated into bacterial DNA bases
- Bacteria then transferred to a nutrient solution containing light (14N) nitrogen to grow and divide twice
- During this process DNA from different samples was extracted and spun in a centrifuge
What is the structure of ATP?
- Ribose, a molecule of adenine, 3 phosphate groups
- ADP is the same as ATP but minus phosphate
What is the hydrolysis of ATP?
- Catalysed by the ATP hydrolase
- Provides energy for active transport, protein synthesis
- The inorganic phosphate released can phosphorylate other compounds making them more reactive
What is the condensation of ATP?
- Catalysed by the enzyme ATP synthase
- Happens during respiration and photosynthesis
What are the properties of ATP that make it a suitable immediate source of energy?
- ATP releases small, manageable amounts
- Only 1 bond is hydrolysed to release energy
How does hydrogen bonding occur in water molecules?
- Water is polar (oxygen has a partial negative charge, hydrogen atoms have a partial positive charge)
- Negative oxygens attract slightly positive hydrogens of other water molecules
- So hydrogen bonds form
What are the 5 properties of water?
- High specific heat capacity
- High latent heat of vaporisation
- Cohesive
- Solvent
- Metabolite
What is specific heat capacity and what is its importance in biology?
- Polar so many H bonds form between water molecules
- This allows water to absorb a large amount of heat energy before its temperature changes
- Good for aquatic organisms - maintain constant internal environment
What is specific heat capacity and what is its importance in biology?
- Polar so many H bonds form between water molecules
- This allows water to absorb a large amount of heat energy before its temperature changes
- Good for aquatic organisms - maintain constant internal environment
What is latent heat of vaporisation and its importance in biology?
- Polar so many H bonds form between water molecules
- They can absorb a lot of energy before breaking when water evaporates. Lot of energy used up
- Cooling mechanism - help maintain a constant body temperature
What is cohesion and what is its importance in biology?
- Polar so many H bonds form between water molecules
- So water molecules tend to stick together
- Column of water doesn’t break when pulled up a narrow tube
- Produces surface tension - xylem in transpiration
How is water a solvent and what is its importance in biology?
- Polar
- Can separate ionic compounds
- Can dissolve other substances
- Act as a medium for metabolic reactions
- Act as a transport medium e.g in xylem to transport nitrates to make amino acids
How is water a metabolite and what is its importance in biology?
- Water is reactive
- Condesation releases H20, hydrolysis requires H20 break bonds. Amino acids joined by condensation reactions
What is the role of phosphate ions?
- In DNA, enabling nucleotides to join together forming phosphodiester bonds
- ATP - bonds between these store/ release energy
What is the role of hydrogen ions?
- Maintain pH levels in the body
- Affects rate of enzyme-controlled reactions
What is the role of Iron ions?
- Component of haem group in haemoglobin which is contained red blood cells
- Transports oxygen around the body - oxygen temporarily binds
What is the role of sodium ions?
- Co-transport of glucose and amino acids across membranes
- Involved in generating nerve impulses and muscle contraction
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Section 1: Biological Molecules44
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Section 3: Gas Exchange + Digestion and Absorption35
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Section 3: Mass Transport57
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Section 4: DNA, genes, chromosomes and protein synthesis23
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Section 2: Immunology21
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Section 4 : Genetic Diversity32
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Section 4: Biodiversity18
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Section 2: Cell structure29
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Section 1: Nucleic Acids22
