AS RECALL biological Molecules Flashcards
Describe the chemical reactions involved in the conversion of polymers to monomers and monomers to polymers. Give 2 named examples of polymers and their associated monomers to illustrate your answer.
A condensation reaction joins monomers together and forms a chemical bond and released water.
A hydrolysis reaction breaks a chemical bond between monomers using water.
E.g: POLYMERS: MONOMERS: Protein Amino acid DNA. Nucleotide Starch Alpha glucose
Describe how the structures of starch and cellulose molecules are related to their functions (5 marks)
Starch:CHOOSE 3
- helical shape; compact
- insoluble; osmotically inactive(doesn’t affect water potential)
- Branched; easily accessible by enzymes to break down
- Large; can not leave cell
Cellulose:
- long, straight & unbranched chains of beta glucose…
- Joined by hydrogen bonding to form microfibrils;
- These provide rigidity/ strength
Describe the structure of a cellulose molecule and explain how cellulose is adapted for its function in cells(6marks)
- Made from beta glucose
- Joined by condensation to form glycosidic bond
- 1:4 link
- ‘flipping over’ of alternate molecules
- hydrogen bonds linking long straight chains
- Cellulose makes cell walls strong
- Can resist turgor pressure/ osmotic pressure
- Bond difficult to break
- Resists action of enzymes
Describe the structure of proteins
5marks
- Polymer of amino acids
- Joined by peptide bonds
- That are formed by condensation
- Primary structure is the order of amino acids
- Secondary structure is folding of polypeptide chain due to hydrogen bonding
- Tertiary structure is 3-D folding due to hydrogen bonding and ionic/ disulfide bonds
- Quaternary structure is 2 of more polypeptide chains
ATP is useful in many biological processes. Explain why (4 marks)
- Releases energy in small &easily manageable amounts
- Broken down in a one step reaction which makes sure energy is available readily
- Phosphorylates substances to make them more reactive
- Reformed /made again rapidly
Describe the biochemical tests you would use to confirm the presence of a lipid, non-reducing sugar and amylase in a sample (5 marks)
Lipid
- Add ethanol (alcohol)
- Add water
- Shake ——> white/ milky emulsion
Non Reducing sugar
- do Benedict’s test, if it says blue
- Boil with acid
- Neutralise with alkali
- Heat with Benedict’s ——> red precipitate
Amylase
- Add biuret reagent ——> turns purple
- Add starch test for a reducing sugar
Haemoglobins are chemically similar molecules found in many different species. Differences in the primary structure of haemoglobin molecules can provide evidence of phylogenetic relationships between species. Explain how (5 marks)
- Mutations change base/nucleotide sequence
- Causing a change in the amino acid sequence
- Mutations build up over time
- More mutations/ more differences in primary structure between distantly related species OR
- Fewer mutations/ differences in primary structure in closely related species OR
- Closely related species have recent common ancestor
Describe the role of iron ions, sodium ions and phosphate ions in cells (5 marks)
Iron ions:
-Haemoglobin binds/ associates with oxygen OR it loads/ transports oxygen
Sodium ions:
- Co-transport of glucose / amino acids
- Sodium moves out by active transport
- Creates a sodium concentration/ diffusion gradient
- Affects osmosis/ water potential
Phosphate ions:
- Affects osmosis/ water potential
- Joins nucleotides/ in DNA backbone
- Used to produce ATP
- Phosphorylates other compounds making them more reactive
- Hydrophilic part of phospholipid bilayer
Explain 5 properties that make water important for organisms (5 marks)
- A metabolite in condensation/ hydrolysis/ photosynthesis/ respiration
- A solvent so metabolic reactions can occur
- High heat capacity; buffers changes in temperature
- Large latent heat of vaporisation; provides a cooling effect
- Cohesion; supports columns of water in plants OR produces surface tension support for small organisms
