chemical elements of crabohydrates
carbon, hydrogen and oxygen
protein
carbon, hydrogen, oxygen, hydrogen and nitrogen and sometimes sulfur
lipids
carbon, hydrogen and oxygen
Food test for glucose (a reducing sugar)
AddBenedics solutioninto sample solution in test tube
Heatat 60 - 70 °c in water bath for5 minutes
Take test tube out of water bath and observe the colour
A positive test will show a colour change fromblue to orange or brick red
Food test for starch
We can useiodineto test presence or absence of starch in food sample.
Add drops ofiodine solutionto food sample
A positive test will show colour change fromorange-brown to blue-black
Food test for protein
Add drops ofBiuret solutionto food sample
A positive test show colour change fromblue to violet / purple
Food test for lipids
Food sample mixed with2cm 3 of ethanoland shaken
The ethanol added to equal volume ofcold water
A positive test will show cloudy emulsionforming
Food test for vitamin C
Add1cm 3 of DCPIP solutionto test tube
Add small amount of food sample (as solution)
A positive test show theblue colour of the dye disappearing
carbohydrates are long chains of
simple sugars
glucose in a carbohydrate is
monosaccharide (simple sugar)
When2 glucose molecules join together
maltose is formed(a disaccharide)
Whenlotsof glucose molecules join togetherwhat can form
starch, glycogen or cellulosecan form (a polysaccharide)
Most fats (lipids) in the body are made up of
triglycerides
Glycogen, cellulose and starch are all made from
glucose molecules
fatty acids vary in
size and structure
Their basic unit (fats)
1 glycerol molecule chemically bonded to 3 fatty acid chains
Lipids are divided into
fats and oils
Proteins
Long chains of
amino acids
how many amino accids are there
20
what do they 20 amino acids contain
thesame basic structurebut the‘R’ group is different for each one
how can amina acids be arranged
in any order, resulting in hundreds of thousands of different proteins
