nutrients

Question 1

examples of reducing sugars

Answer 1

glucose, fructose, galactose, maltose, and lactose
SUCROSE IS NOT A REDUCING SUGAR

Question 1

what is the test for reducing sugars

Answer 1

benedict’s test
a brick red precipitate would be produced when reducing sugars are present

Question 2

what are monosaccharides

Answer 2

single sugars that cannot be further digested into smaller molecules. they can pass through cell membranes and be absorbed in the cells
(glucose, fructose, and galactose)

Question 3

where is glucose, fructose, and galactose found

Answer 3

in plants and animals
commonly found in plants, rarely found in animals
in milk sugar in mammals

Question 4

what are disaccharides

Answer 4

double sugars ( 2 molecules of single sugars bonded together ) it can be split into 2 single sugar molecules with an enzyme.
e.g. maltose can be split into glucose with the enzyme maltase
( maltose, sucrose, and lactose)

Question 5

what is hydrolysis

Answer 5

a reaction inwhich a water molecule is needed to break up a complex molecule into smaller moelcules

Question 6

explain benedicts test

Answer 6

1. place 2cm3 of food sample into a test tube
2. add 2cm3 of benedict’s solution to the food sample
3. shake the mixture and place the tube ina boiling water bath for 2-3 minutes
   The presence of reducing sugars is indicated by the colour change of the solution
   blue solution - no reducing sugars
   green solution - traces of reducing sugars
   yellow or orange precipitate - moderate amount of reducing sugar
   brick-red precipitate - large amount of reducing sugar

Question 7

what is a polysaccaharide

Answer 7

a complex carbohydrate consisting of many monosaccharide molecules joined together.
( starch, cellulose, and glycogen)

Question 8

how can we identify starch?

Answer 8

by the iodine test.
add a few drops of iodine solution to the substance. if there is presence of starch, the substance will turn blue-black

Question 9

why are glycogen and starch suitable as storage materials in cells?
(4 points)

Answer 9

1. they are insoluble in water, so they do not change the water potential in the cells
2. they are large molecules which cannot diffuse through cell membranes, so they would not be lost from the cell
3. they can be easily hydrolysed to glucose when needed, e.g. in tissue respiration
4. their molecules have compact shapes so they occupy less space than all the individual glucose molecules that make up a glycogen or starch molecule

Question 10

what are the 6 functions of carbohydrates?

Answer 10

1. used as a substrate for respiration, to provide energy for cell activities
2. to form supporting structures, e.g. cell walls in plants
3. to be converted into other organic compounds such as amino acids and fats
4. for the formation of nucleic acids e.g. DNA
5. to synthesise lubricants, e.g. mucus which consists of a carbohydrate and a protein
6. to synthesise the nectar in some flowers. nectar is a sweet liquid that plants produce to attract insects

Question 11

what do fats consist of

Answer 11

fatty acids and glycerol

Question 12

what are the sources of fats

Answer 12

butter
cheese
fatty meat

Question 13

how do we test for fat

Answer 13

by the ethanol emulsion test
a cloudy white emulsion can be observed

Question 14

explain the ethanol emulsion test

Answer 14

ON LIQUID FOOD
1. add 2cm3 of ethanol to a drop of liquid food in a test tube and shake thoroughly
2. add 2cm3 of water to the mixture
ON SOLID FOOD
1. cut the solid food into small pieces and place the pieces in a test tube. add 2cm3 of ethanol and shake thoroughly
2. allow the solid food particles to settle. carefully decant the ethanol into another test tube containing 2cm3 of water

a cloudy white emulsion indicates the presence of fats
the solution would remain clear in the absence of fats

Question 15

what are the functions of fats?
(5 functions)

Answer 15

1. a source and store of energy
2. an insulating material that prevents excessive heat loss
3. a solvent for fat-soluble vitamins and many other vital substances such as hormones
4. an essential part of protoplasm, esp in cell membranes
5. a way to reduce water loss from the skin surface

Question 16

how can we test for proteins

Answer 16

by the biuret test
the solution turn violet when proteins are present

Question 17

explain the biuret test

Answer 17

1. add 2cm3 of sodium hydroxide solution to 2cm3 of egg white solution in a test tube and shake it thoroughly
2. add 1% copper(II) sulfate solution, drop by drop, shaking after every drop into the solution.
   shake well and allow the mixture to stand for 5 minutes
   biuret solution is originally blue.
   if proteins are present, the solution develops into a violet coulor

Question 18

what are the functions of protein
(3 functions)

Answer 18

1. synthesis of new protoplasm; for growth and repair of worn-out body cells
2. synthesis of enzymes and some hormones
3. formation of antibodies to combat diseases

Question 19

what are the effects of protein deficiency

Answer 19

protein deficiency may lead to a disease called kwashiorkor.

Question 20

where can proteins be found

Answer 20

milk, eggs, seafood, and chicken

Question 21

why do we need food
(3 reasons)

Answer 21

1. it provides energy
2. it is needed for growth and repair of worn-out tisues
3. it keeps us healthy

Question 22

what are the functions of water?
(5 reasons)

Answer 22

1. it is an essential part of protoplasm, lubricants, digestive juices, and blood
2. it is a medium for chemical reactions to occur
3. it transports food substances, excretory products, and hormones from one part of the body to another
4. it is essential for hydrolysis and photosynthesis
5. it helps to control body temperature

Question 23

what are the factors that affect the amount of water needed by the body
(common sense question)

Answer 23

how active the person is
how healthy the person is
environmental conditions
(hot and dry climates need more)

Question 24

what is the function for starch?

Answer 24

the main form of storage for carbohydrates in green plants

Question 25

what is the function for glycogen?

Answer 25

main form of storage for carbohydrates in animals and fungi

Question 26

what is the function for cellulose?

Answer 26

it forms the cell walls in plants
used as fibre in mammals’ diet even though cannot be digested

Question 27

why is water important in plants?
(4 reasons)

Answer 27

1. essential for photosynthesis
2. needed to keep plant cells turgid/provides turgor pressure
3. transports mineral salts from the roots to the leaves
4. transports food substances from the leaves to other parts of the plant/transport medium

Question 27

why is water important in plants?
(4 reasons)

Answer 27

1. essential for photosynthesis
2. needed to keep plant cells turgid
3. transports mineral salts from the roots to the leaves
4. transports food substances from the leaves to other parts of the plant

Question 28

which of the following is a hydrolysis reaction?
breakdown of starch
formation of glucose
formation of lactose
transport of sucrose

Answer 28

breakdown of starch