nutrients Flashcards
examples of reducing sugars
glucose, fructose, galactose, maltose, and lactose
SUCROSE IS NOT A REDUCING SUGAR
what is the test for reducing sugars
benedict’s test
a brick red precipitate would be produced when reducing sugars are present
what are monosaccharides
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)
where is glucose, fructose, and galactose found
in plants and animals
commonly found in plants, rarely found in animals
in milk sugar in mammals
what are disaccharides
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)
what is hydrolysis
a reaction inwhich a water molecule is needed to break up a complex molecule into smaller moelcules
explain benedicts test
- place 2cm3 of food sample into a test tube
- add 2cm3 of benedict’s solution to the food sample
- 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
what is a polysaccaharide
a complex carbohydrate consisting of many monosaccharide molecules joined together.
( starch, cellulose, and glycogen)
how can we identify starch?
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
why are glycogen and starch suitable as storage materials in cells?
(4 points)
- they are insoluble in water, so they do not change the water potential in the cells
- they are large molecules which cannot diffuse through cell membranes, so they would not be lost from the cell
- they can be easily hydrolysed to glucose when needed, e.g. in tissue respiration
- their molecules have compact shapes so they occupy less space than all the individual glucose molecules that make up a glycogen or starch molecule
what are the 6 functions of carbohydrates?
- used as a substrate for respiration, to provide energy for cell activities
- to form supporting structures, e.g. cell walls in plants
- to be converted into other organic compounds such as amino acids and fats
- for the formation of nucleic acids e.g. DNA
- to synthesise lubricants, e.g. mucus which consists of a carbohydrate and a protein
- to synthesise the nectar in some flowers. nectar is a sweet liquid that plants produce to attract insects
what do fats consist of
fatty acids and glycerol
what are the sources of fats
butter
cheese
fatty meat
how do we test for fat
by the ethanol emulsion test
a cloudy white emulsion can be observed
explain the ethanol emulsion test
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
what are the functions of fats?
(5 functions)
- a source and store of energy
- an insulating material that prevents excessive heat loss
- a solvent for fat-soluble vitamins and many other vital substances such as hormones
- an essential part of protoplasm, esp in cell membranes
- a way to reduce water loss from the skin surface
how can we test for proteins
by the biuret test
the solution turn violet when proteins are present
explain the biuret test
- add 2cm3 of sodium hydroxide solution to 2cm3 of egg white solution in a test tube and shake it thoroughly
- 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
what are the functions of protein
(3 functions)
- 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
what are the effects of protein deficiency
protein deficiency may lead to a disease called kwashiorkor.
where can proteins be found
milk, eggs, seafood, and chicken
why do we need food
(3 reasons)
- it provides energy
- it is needed for growth and repair of worn-out tisues
- it keeps us healthy
what are the functions of water?
(5 reasons)
- it is an essential part of protoplasm, lubricants, digestive juices, and blood
- it is a medium for chemical reactions to occur
- it transports food substances, excretory products, and hormones from one part of the body to another
- it is essential for hydrolysis and photosynthesis
- it helps to control body temperature
what are the factors that affect the amount of water needed by the body
(common sense question)
how active the person is
how healthy the person is
environmental conditions
(hot and dry climates need more)
what is the function for starch?
the main form of storage for carbohydrates in green plants
what is the function for glycogen?
main form of storage for carbohydrates in animals and fungi
what is the function for cellulose?
it forms the cell walls in plants
used as fibre in mammals’ diet even though cannot be digested
why is water important in plants?
(4 reasons)
- essential for photosynthesis
- needed to keep plant cells turgid/provides turgor pressure
- transports mineral salts from the roots to the leaves
- transports food substances from the leaves to other parts of the plant/transport medium
why is water important in plants?
(4 reasons)
- essential for photosynthesis
- needed to keep plant cells turgid
- transports mineral salts from the roots to the leaves
- transports food substances from the leaves to other parts of the plant
which of the following is a hydrolysis reaction?
breakdown of starch
formation of glucose
formation of lactose
transport of sucrose
breakdown of starch
