1. Year 12 Revision Topic 2: Molecular Biology
2.1 Molecules to metabolism
2.2 Water
2.3 Carbohydrates and lipids
2.4 Proteins
2.5 Enzymes
2.6 Structure of DNA and RNA
2.7 DNA replication, transcription and translation
2.8 Cell respiration
2.9 Photosynthesis

2. Responses must include reference to coolant, transport and habitat to receive full marks.
coolant: lots of energy required to heat water / water has a high specific heat capacity / hydrogen bonding of water molecules; when water evaporates energy is used; cools organism; eg sweating / panting / transpiration;
transport: water is polar / universal solvent; dissolves many organic / inorganic substances; movement of water carries substances around organism; eg blood / phloem / xylem / adhesion / cohesion; medium for external transport (eg gametes);
habitat: Thermal properties of water; water is transparent; allows light through for photosynthetic organisms; organisms live in / on water / surface tension for surface creatures / buoyancy; contains dissolved gases; fish / aquatic organisms survive under ice at surface;
8 max (Plus up to [2] for quality)

3. 2.4 Proteins
Condensation reactions
Protein functions

4. Condensation Reactions
Amino acids 🡪 Polypeptides

5. Condensation Reactions
20 different amino acids means a huge range of proteins can be made

6. Protein Functions
20 different amino acids means a huge range of proteins can be made
Many different combination
Many different functions

7. Protein Functions Catalysis* Muscle contraction Cytoskeletons
Tensile strengthening*
Blood clotting
Transport of nutrients and gas
Cell adhesion
Membrane transport
Hormones*
Receptors*
Packaging of DNA
Immunity*

8. Protein Functions Catalysis Enzymes Muscle contraction
Rubisco: photosynthesis
Muscle contraction
Actin and myosin
Cytoskeletons
Tubulin gives cells shape
Tensile strengthening
Fibrous proteins
Collagen and spider silk
Blood clotting
Plasma proteins
Transport of nutrients and gas
Haemoglobin
Cell adhesion
Membrane proteins
Membrane transport
Facilitated diffusion or active transport
Hormones
Insulin: glucose regulation
Receptors
Binding sites for hormones or neurotransmitters
Rhodopsin: vision
Packaging of DNA
Histones
Immunity
Immunoglobulin: antibody

9. 2.5 Enzymes Structure of enzymes Factors affecting activity
Immobilized enzymes

10. Enzyme structure Active site Specific to a substrate
Lower activation energy for a reaction
Used in most metabolic pathways
Substrate become product

11. Factors affecting enzymes
How it affects enzymes
Graph
Temperature pH
Substrate concentration

12. Factor How it affects enzymes
Temperature
Higher temperatures = more kinetic energy
More collisions
Too high = enzymes denature
Optimum temperatures pH
Substrate concentration

13. Factor How it affects enzymes
Temperature
Higher temperatures = more kinetic energy
More collisions
Too high = enzymes denature
Optimum temperatures pH
Optimum pH
Too high or low pH = enzymes denature
Substrate concentration

14. Factor How it affects enzymes
Temperature
Higher temperatures = more kinetic energy
More collisions
Too high = enzymes denature
Optimum temperatures pH
Optimum pH
Too high or low pH = enzymes denature
Substrate concentration
Fewer substrates = less likely for enzymes and substrate to collide
More substrate = more collisions
Reaches saturation point

15. Immobilized Enzymes Enzymes are unable to move Fixed in position
Substrate poured over enzymes

16. Immobilized Enzymes
Pros
Cons

17. Immobilized Enzymes Pros Cons
Enzyme easily separated from substrate (prevent contamination)
Enzymes recycled
Less likely to denature
Able to stop and start the reaction quickly
Requires time and money to make immobilized enzymes
Extra equipment need to make
Maybe fewer collisions – rate of reaction slower

18. condensation reactions involve joining subunits/molecules/monomers;
with the release of water;
hydrolysis reactions involve splitting molecules into subunits molecules/monomers;
with the addition of water;
example of condensation reaction; (e.g. amino acid + amino acid yields dipeptide + water)
example of hydrolysis reaction; (e.g. disaccharide + water yields two monosaccharides) Examples can be shown in words or chemical form.
5 marks