Nutrients

Question 1

what elements are carbohydrates made up of

Answer 1

carbon (C), hydrogen (H), oxygen (O)

Question 2

4 points

what are the functions of carbohydrates

Answer 2

source of energy

forms supporting structures (e.g. cellulose cell walls)

conversion into other compounds (e.g. amino acids, fats, nucleic acids)

sythesise lubricants in animals and nectar in flowers

Question 3

what are 3 monosaccharides (simple sugars) and their characteristics/functions

Answer 3

glucose:
substrate for cellular respiration (breaks down glucose to release energy)
found in both plants and animals

fructose:
widespread in plants, uncommon in animals

galactose:
component of milk sugar (lactose), formed when digested

Question 4

what are disaccharides (double sugars)

Answer 4

formed when 2 simple molecules are joined together to form a larger molecule, with removal of 1 water molecule

Question 5

describe the formation of maltose, sucrose and lactose

Answer 5

maltose (found in malted cereals, sprouting grains):
join 2 glucose molecules with the removal of 1 water molecule

sucrose (found in sugarcane stems, sweet fruits):
join 1 glucose molecule and 1 fructose molecule with the removal of 1 water molecule

lactose (found in milk of all animals):
join 1 glucose molecule and 1 galactose molecule with the removal of 1 water molecule

Question 6

what are 3 polysaccharides (complex carbohydrates) and their characteristics/functions

Answer 6

starch:
made up of many glucose molecules joined together (long straight chains)
storage form of carbohydrate in plants
(made and stored in plants, but not animals)

glycogen:
made up of numerous glucose molecules joined together to form highly branched chains of glucose molecules
storage form of carbohydrate in animals and fungi, stored mainly in liver and muscles
can be broken down to produce glucose for cellular respiration which releases energy

cellulose:
made up of many glucose molecules joined together (bonds different from starch; cellulose has many straight chains of glucose molecules)
forms greater part of cell walls of plants
humans cannot digest cellulose (serves as dietary fibre preventing constipation)

Question 7

what elements are proteins made up of

Answer 7

carbon (C), hydrogen (H), oxygen (O), nitrogen (N), sometimes sulfur (S)

Question 8

3 points

what are the functions of proteins

Answer 8

synthesis of new protoplasm, for growth and repair of worn-out body cells

synthesis of enzymes and some hormones

formation of antibodies to combat diseases

*body does not store protein but breaks it down

Question 9

3 points

how do amino acids form protein

Answer 9

22 types of amino acids can be arranged differently to form different proteins

amino acids linked by peptide bonds to form polypeptide chains

a polypeptide chain can be folded to form protein

Question 10

what elements are fats (lipids) made up of

Answer 10

carbon (C), hydrogen (H), oxygen (O)

Question 11

5 points

what are the functions of fats (lipids)

Answer 11

efficient source and storage of energy

insulating layer beneath skin

solvent for fat-soluble vitamins and some hormones

essential part of cell membrane

excess stored in adipose tissues under skin and around heart and kidneys

*contains more energy than carbohydrates per unit mass

Question 12

how are fat molecules formed

Answer 12

1 fat molecule made up of 1 glycerol molecule and 3 fatty acid molecules

Question 13

describe the test for the presence of starch

Answer 13

iodine test

procedure:
add a few drops of iodine solution on sample to be tested
observe and record changes in colour of iodine solution

results:
starch present - test sample stained black/blue-black
starch absent - test sample stained brown

Question 14

what are reducing sugars

Answer 14

any carbohydrate capable of being oxidised and causes reduction of other substances without having to be hydrolysed first (e.g. glucose, fructose, galactose, maltose, lactose only)

*sucrose is a non-reducing sugar

Question 15

describe the test for the presence of reducing sugars

Answer 15

Benedict’s test

procedure:
to 2cm³ of sample in a test-tube, add 2cm³ of Benedict’s solution
shake thoroughly to mix
place test-tube in boiling water bath for 5 minutes
remove test-tube from boiling water bath
observe and record any colour changes

results:
reducing sugar present
- brick-red precipitate formed for large amount
- orange precipitate formed for moderate amount
- green/yellow precipitate for traces

reducing sugar absent - mixture remained blue

Question 16

describe the test for the presence of proteins

Answer 16

biuret test

procedure:
to 2cm³ of test sample in a test-tube, add 2cm³ of sodium hydroxide
shake thoroughly to mix
add 1% copper(II) sulfate solution drop by drop, shaking after every drop
observe and record any colour changes

results:
protein present - mixture turned violet/pink/purple
protein absent - mixture turned blue

Question 17

describe the test for the presence of fats (lipids)

Answer 17

ethanol emulsion test

procedure (on liquid food):
to 2cm³ of test sample in a test-tube, add 2cm³ of ethanol
shake thoroughly to mix
add 2cm³ of water and shake thoroughly
observe and record formation of white emulsion, if any

procedure (on solid food):
cut solid food samples into small pieces and place them into a test-tube, add 2cm³ of ethanol
shake thoroughly to mix
allow solid particles to settle before decanting the mixture into another test-tube containing 2cm³ of water
observe and record formation of white emulsion, if any

results:
fats present - white emulsion formed
fats absent - test solution remains clear