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biological molecules (Alex) (enzyme as a protein (properties (all enzymes…
biological molecules (Alex)
fats(lipids/oil)
composition
elements: carbon, hydrogen, oxygen
three fatty acids + one glycerol
functions
energy storage: fats in mammals, oils in plants
heat insulation
make cell membrane
testing: ethanol emulsion test
positive result: white and opaque emulsion
Ethanol dissolves fats and the fat-ethanol mixture breaks into droplets which mixed in water
negative result: solution remains transparent
energy: more than twice of carbohydrate per gram
protein
functions
Repair
enzyme for metabolic reaction
Growth
composition
elements: Nitrogen, sulphur, carbon, hydrogen, oxygen
basic unit = Amino acids (20kinds)
in humans
insoluble keratin in hairs and nail
soluble haemoglobin in blood
testing: Biuret test
positive result: blue to purple
Negative result: remain blue
carbohydrates
composition
elements: carbon, hydrogen, oxygen (H:O = 2:1)
monosaccharide
glucose: C6H12O6 (sweet and soluble in water)
disaccharide: sucrose, maltose
polysaccharide: starch in plants; glycogen in liver and muscles
function
To provide energy through respiration
to store energy (starch in plant, glycogen in humans)
to maintain shape of plant cell (cellulose)
testing
Benedict's solution: to test for reducing sugar (NOT starch)
Positive result: colour change from blue to brick-red precipitate
negative result: remains blue
iodine solution:to test starch
positive result: brown to blue black
negative result: remains brown
enzyme as a protein
definition
a catalyst inside a living organism that changes the rate of chemical reaction and is not change by the reation
how does it work?
each enzyme has an active site for substrate to bind to lower the activation energy of the chemical reaction
Works best at optimum temperature and/or optimum pH
factors affecting its activity
pH, temperature, concentration
Denature
high temperature
extreme pH
enzyme molecules lose shape and its active sites no longer fits the substrate so the enzyme no longer catalyse the reaction
inactivate
low temperature: low kinetic energy, less collision, less change for substrate to bind to the active site
properties
all enzymes are proteins
enzymes are catalysts
enzymes denature at high temperature
enzymes work best in optimum temperature
enzymes work best in optimum pH
examples
carbohydrase (amylase): starch --> maltose
catalase: hydrogen peroxide --> water + oxygen
protease: protein --> amino acids
Water
Importance as a solvent
provide a medium for metabolic reaction
transportation
digestion: to dissolve enzymes and nutrients in guts