biological molecules, enzymes and human nutrition Flashcards
what are biological molecules? state the main 4
chemical substances that make up every living being. carbohydrates, proteins, lipids (fats), nucleic acids
name 2 physical aspects of biological molecules
often very large, made up of many smaller molecules joined together
complete: enzymes are a type of _______
protein
complete: water is also an important ________
molecule
suggest reasons on why we need carbohydrates (4)
energy source, energy store, structural roles (plant cell wall - cellulose), to form larger molecules
state the three different sizes of carbohydrates
monosaccharide (sugar molecule), disaccharide, polysaccharide
what are monosaccharides made of?
glucose, fructose, galactose
what are disaccharides made of?
maltose, sucrose, lactose
what are polysaccharides made of?
starch, glycogen, cellulose
describe this biological molecule: starch (4)
it is the main storage plants (chloroplasts - made here, starch grains - stored here), no effect on water potential, long chains with no branches, the amount of starch stored in the cell does not affect movement of water by osmosis
describe this biological molecule: glycogen (5)
storage polysaccharide in animals, long branched chain (more than starch), side chains, releases glucose quickly, storage in liver and muscle cells
describe this biological molecule: proteins (5)
most abundant molecule, contains carbon, hydrogen, oxygen and nitrogen, may contain sulphur, important for growth and repair in all organisms, made of amino acids
name 5 jobs of proteins
enzymes (catalyse reactions), hormones (chemical messengers), antibodies (immunity), membrane-transport, structural role (e.g. muscle fibres)
describe this biological molecule: lipids (fats and oils) (4)
made out of carbon, hydrogen, oxygen, made up of a molecule of glycerol joined to three molecules of a fatty acid, fats form part of the cell membranes and the membranes that make up organelles, droplets of fat stored in the cytoplasm are also a source of energy
how can you show the presence of starch?
by adding a solution of iodine indicator
how do you know if there is starch present?
the yellow-brown colour turns to a blue-black colour
how can you reduce sugar?
heat it with Benedict’s solution
how do you know if there is sugar present?
the blue changes to a cloudy orange-red colour
how can you show the presence of protein?
by adding Biuret reagent (2-part reagent ‘solution a’ & ‘solution b’)
how do you know if there is protein present?
The colour changes from a pale blue to lilac colour
how can you show the presence of lipids?
by using the ethanol emulsion test, mix this with the sample, add water and shake
how do you know if there are lipids present?
a cloudy white emulsion will form near the top of the water
how can you show the presence of vitamin c?
add 1cm3 of DCPIP solution to a test tube and a small amount of food sample
how do you know if there is vitamin c present?
the blue colour of the dye will disappear
