Properties of water [9]
- Solvent; metabolic reactions can occur
- Metabolite in condensation & hydrolysis
- Transparent; allows light penetration for aquatic plants to photosynthesis
- Strong cohesion; supports columns of water e.g. transpiration stream
- Strong cohesion; creates surface tension which supports small organisms
- High heat capacity; buffers change in temperature
- High latent heat of vaporisation; provides cooling effect via evaporation, only a small amount needed to cool down higher body temp
- High adhesion; hydrogen bond between xylem wall supports transpiration stream
- Solid form is less dense than water; ice floating protects aquatic life under it
Two properties of water that are useful in cytoplasm
- Solvent; metabolic reactions occur faster in solution
- Polar molecule; acts as a universal solvent
- Reactive; takes place in hydrolysis and condensation
What are hydrogen bonds
Attractions between delta positive hydrogen atom in one molecule of water, and delta negative oxygen in another
What are inorganic ions
- Ions that do not contain carbon
Where are inorganic ions found
- In the cytoplasm
- In bodily fluids of organisms
What is the role of hydrogen ions
- pH is calculated based on the concentration of H+ ions in the environment
- Enzyme controlled reactions are affected by pH
What is the role of iron ions
- Haemoglobin carries oxygen in RBC
- Haemoglobin is made up of 4 polypeptide chains, each has a Fe2+ ion at the centre
- Fe2+ binds to oxygen
What is the role of sodium ions
- Co transports glucose and amino acids across cell surfaces
- Needed for the transmission of nerve impulses
What is the role of phosphate ions
- Key components of DNA, RNA and ATP
- Bonds between phosphate groups in ATP store energy
- Phosphate groups in nucleotides allow them to join and form polynucleotides
Define monosaccharide and give examples
- Single, simple sugar
- alpha-glucose
- beta-glucose
- fructose
- galactose
What is the difference between a-glucose and b-glucose
a-glucose’ s carbon 1 bond is H then OH
b- glucose’s carbon 1 bond is OH then H
List the uses of the monosaccharides
- Glucose: main substrate in respiration
- Fructose: found in nectar and many plants, attracts insects for pollination and flower dispersal
What are the disaccharides and what monomers are they made up of
- Maltose: glucose + glucose
- Sucrose: glucose + fructose
- Lactose: glucose + galactose
List the uses of the disaccharides
- Maltose: breakdown of starch, used to provide energy for (the embryos of) germinating seeds
- Lactose: sugar found in milk, provides energy for suckling mammals
- Sucrose: transported through plants via the phloem
How are disaccharides formed
Two monosaccharides join together to form a C1-4 glycosidic bond in a condensation reaction, releasing a molecule of water in the process.
Name the three types of sugars (-ose)
- Hexose
- Pentose
- Triose
How to test for reducing sugars
- Add copper III sulfate to sample
- Bring to a boil for a few minutes
- Observe colour of precipitate (if formed)
How to test for non reducing sugars
- Add hydrochloric acid to sample to break down the sugar into its monomers
- Bring to a boil for a few minutes
- Add sodium hydrogencarbonate to neutralise acid
- Test pH using litmus or pH probe
- Add more sodium hydrogencarbonate to make sample alkaline
- Carry out Benedict’s test
Name the polysaccharides
- Starch - amylose and amylopectin
- Glycogen
- Cellulose
Structure of amylose
- Chain of alpha glucose
- Branches and free ends
- Chain of 1-4 bonds
- 1-6 bonds every 25-30 bonds
Structure of amylopectin
- Helix structure
- Chain of 1-4 bonds
Function of amylose
- Compact - fit a lot of glucose molecules in a small space
- Insoluble and too large - not as easily lost from the cell
- Insoluble - does not affect water potential
- Free ends allow quick hydrolysis
Function of amylopectin
- Compact - fit a lot of glucose molecules in a small space
- Insoluble and too large - not as easily lost from the cell
- Insoluble - does not affect water potential
