PAPER 1 REVISION Flashcards
what element do all biological molecules contain?
carbon
calcium ions Ca2+
involved in muscle contraction and nerve impulse transition
sodium ions Na+
involved in co-transport, reabsorption of water in the kidney and nerves impulse transmission
potassium ions K+
involved in stomatal opening and nerve impulse transmission
hydrogen ions H+
involved in chemiosmosis, pH determination and catalysis of reactions
ammonium ions NH4+
involved in nitrogen cycle, where by bacteria convert ammonium ions into nitrate ions
nitrate NO3-
mineral ion absorbed by plants to provide a source of nitrogen to make amino acids
hydrogencarbonate HCO3-
maintains the pH of the blood
chloride ions Cl-
provide a negative charge to balance to positive sodium ion and potassium ions in cells
phosphate PO4 3-
involved in the formation of phospholipids for cell membranes, nucleic acid and ATP formation and in making bones
hydroxide ions OH-
cations
positive ions
anions
negative ions
water as a biological molecule
- polar, due to uneven charge distribution
- hydrogen bonds form between oxygen and hydrogen atom as the positive and negative regions interact with each other
- covalent bond within molecule, hydrogen bond between multiple molecules
- individual hydrogen bonds are weak, collectively provide strength
water: solvent
polar (hydrophilic)
can interact with other polar molecules
slight positive charge on hydrogen atoms will attract any negative solutes and slight negative charge of oxygen atoms will attract any positive ions in solutes
non-polar molecules (hydrophobic)
hydrophobic
cannot dissolve in water
repelled by water
purpose of cytosol in eukaryotic and prokaryotic cells being mainly water
ensures many solutes can dissolve within the cell and then easily transported
water: transport medium
polar substances dissolve easily and are transported in water around animals (blood) and plants (xylem)c
cohesion
water molecules ‘sticking’ together by hydrogen bonds
*due to cohesion, when water moves up the xylem in plants due to transpiration, it is as a continuous column of water
ADVANTAGE: easier to draw up a column rather than individual molecules
water: coolant
(high specific heat capacity)
water has a high specific heat capacity (lot of energy required to raise the temperature of water) due to energy required to break hydrogen bonds between water molecules
ADVANTAGE: internal temperatures of plants and animals should remain constant - so enzymes do not denature or reduce in activity with temperature fluctuations
water: coolant
(large latent heat of vaporisation)
water has a large latent heat of vaporisation (a lot of energy is required to convert water in its liquid state to gaseous state) due to energy required to break the hydrogen bonds between water molecules to turn it into a gas
ADVANTAGE: for organisms, providing significant cooling effect
e.g. animals sweat, plants transpire
water: habitat
water buffers temperature meaning it provides a stable environment, in terms of temperature, for aquatic organisms
cohesions provides surface tension, enabling small invertebrates to move and live on the surface, providing habitat away from predator within water
ice is less dense than liquid water due to spacing of hydrogen bonds
ice floats on top of water providing a surface habitat for animals
monomer
one (smaller) unit which can create large molecules (polymers)
polymer
made from lots of monomers bonded together
monomer glucose - what polymer?
starch, cellulose, glycogen
monomer amino acid - what polymer?
protein
monomer nucleotide - what polymer?
DNA, RNA
monosaccharides
one sugar unit
(monomer)
glucose, fructose, galactose
disaccharides
two sugars bonded together
(dimer)
sucrose, maltose, lactose
joined by glycosidic bond
formed via condensation reaction
glucose + (gluc/galact/fruct)ose -> (malt/lact/sucr)ose + water
1,4 - glycosidic bond
polysaccharides
many sugars
(polymer)
starch, cellulose, glycogen
ALPHA glucose
C6H12O6
hexagon
symmetrical
isomer
same molecular structure, different structural isomer
BETA glucose
C6H12O6
hexagon
unsymmetrical - hydroxyl on top of carbon 1
condensation reaction
joining two molecules together by removing water (chemical bond formed)
hydrolysis reaction
splitting apart molecules through addition of water (chemical bond broken)
starch
- alpha glucose
- 1,4 - glycosidic bonds (amylose)
1,4 and 1,6 - glycosidic bonds (amylopectin) - store of glucose
- plant cells (chloroplasts)
- 2 polymers: amylose (unbranched helix), amylopectin (branched)
how structure of starch leads to function
- helix can compact to fit a lot of glucose in small space
- branched structure increases surface area for rapid hydrolysis back to glucose
- insoluble - will not affect water potential
cellulose
- beta glucose
- 1,4 - glycosidic bonds
- structure strength for cell wall
- plant cell wall
- polymer forms long, straight chains: chains held parallel by hydrogen bonds to form fibrils, macrofibrils combine to form cellulose fibre
how structure of cellulose leads to its funtion
- many hydrogen bonds provide collective strength
- insoluble - will not affect water potential
glycogen
- alpha glucose
- 1,4 and 1,6 - glycosidic bonds
- store of glucose
- animal cells (muscle and liver)
- highly branched molecule
how structure of glycogen leads to its function
- branched structure increases surface are for rapid hydrolysis back to glucose
- insoluble - will not affect water potential
