Chapter 3: Nutrients Flashcards
What are the 3 types of nutrients?
-Carbohydrates
-Fats
-Proteins
Why do we need nutrients in food?
-Provide energy for vital activities
-Supply raw materials to make new protoplasm for cell growth, reproduction and repair of worn-out tissues
Carbohydrates are organic compounds made of…?
-Carbon
-Hydrogen
-Oxygen
Where Hydrogen:Oxygen=2:1
What are the three main groups of carbohydrates? (+examples)
Monosaccharides
- Glucose
- Fructose
- Galactose
Disaccharides
- Maltose (Glu-Glu)
- Sucrose (Glu-Fru)
- Lactose (Glu-Gal)
Polysaccharides
- Starch
- Cellulose
- Glycogen
Which monosaccharide/ disaccharide is NOT a reducing sugar?
Sucrose!
(Everything else is a reducing sugar)
Name the (main) properties of monosaccharides.
- Basic unit of carbs, cannot be further digested into smaller molecules
- [Of those in syllabus] Small enough to pass through cell membranes (and other ppms)
- [Of those in syllabus] Same chemical formula (C6 H12 O6), but diff. arrangements, giving them diff. properties
Name the (main) properties of disaccharides.
- Formed when 2 monosaccharides join tgt in a condensation reaction
- [Of those in syllabus] Same chemical formula (C12 H22 O11), but in diff. arrangements, giving them diff. properties
What is a Condensation Reaction?
A chemical reaction in which 2 monosaccharides are joined tgt to form a disaccharide +water
(e.g. glucose+glucose-> maltose+ water)
What is Hydrolysis [of disaccharides] (/hydrolytic reaction)?
A chemical reaction in which water is needed to break up disaccharide into 2 monosaccharides
(e.g. water+ maltose—> glucose+glucose [catalysed by maltase])
What is the test for reducing sugars?
Benedict’s test
[Describe Procedure]
Procedure of Benedict’s test?
(+Solid food sample modifications & result indication)
{glucose, fructose, galactose, maltose, lactose}
- Add 2cm^3of Benedict’s solution to 2cm^3 of food sample in a test tube
- Shake the mixture
- Heat contents in a boiling water bath for 2-3 mins
Solid food sample modification:
1. Crush food w/ mortar & pestle
2. Add water to the crushed food to dissolve the nutrients
3. Decant the mixture to a new test tube
[Proceed w/ og step 1]
Blue- No reducing sugar
Green colouration- Traces of reducing sugar
Yellow/orange colouration- Moderate amnt of reducing sugar
Brick-red precipitate- Large amnt of reducing sugar
Examples of polysaccharides?
Starch
Cellulose
Glycogen
Structure, role and occurrence of starch?
Structure: Several thousand glucose molecules joined tgt
Role: Storage form of carbs in plants
Occurrence: Storage organs of plants (e.g. potato tubers/tapioca)
Structure, role and occurrence of cellulose?
Structure: Many glucose molecules joined tgt, but bonded diff. from starch
Role: Cellulose cell walls protect plant cells, also serves as dietary fibres to prevent constipation
Occurrence: Cell walls of plants
Structure, role and occurrence of glycogen?
Structure: Branched molecule of many glucose molecules joined tgt
Role: Storage form of carbs in animals
Occurrence: Stored in liver & muscles of mammals
[Application]
How are glycogen and starch suitable as stores of glucose?
-Insoluble in water
-Large molecules that cannot diffuse thru ppm
-Easily hydrolysed to glucose when needed
-Have compact shapes, so they occupy less space
[Application]
Describe the hydrolysis of starch.
- Starch is broken down into maltose by amylase
- Maltose is broken down into glucose by maltase
What is the test for starch?
Iodine test
[Describe Procedure]
Procedure of Iodine test?
(+Solid food sample modifications & result indication)
- Add 2cm^3 of food sample to a clean test tube
- Add a few drops of iodine solution to the test tube
Solid food sample modification:
1. Crush food w/ mortar & pestle
2. Add a few drops of iodine solution directly onto the crushed food
Blue-black colouration observed- +ve result
Sol. remains yellowish-brown- -ve result
Why do we need carbohydrates?
1. Provide an immediate source of energy
2. Form supporting structures (e.g. cell walls in plants)
3. For conversion into other organic compounds (e.g. amino acids in plants & fats in plants and animals)
4. To form nucleic acids (in DNA & RNA)
Fats are organic compounds made of…?
Carbon
Hydrogen
Oxygen
With less oxygen in proportion to hydrogen, but with no fixed proportions
What is a fat MOLECULE made up of?
3 fatty acids
1 glycerol
What is the difference between saturated and unsaturated fats?
Saturated- Unhealthy
Unsaturated- Healthier
Saturated- Straight fatty acid chain
Unsaturated- Fatty acid chain has kinks
Describe hydrolysis of fats.
Fats are broken down into fatty acids and glycerol by hydrolysis.
Why do we need fats?
-As a source of energy
-As an insulating material that prevents excessive heat loss
-Surround organs for protection
-Help reduce water loss from skin surface
What is the test for fats?
Ethanol emulsion test
[Describe Procedure]
Procedure of ethanol emulsion test?
(+Solid food sample modifications & result indication)
- Add 2cm^3 of ethanol to 2cm^3 of food sample in a test tube
- Shake the contents of the tube vigorously
- Add 2cm^3 of water into the test tube and shake the mixture
Solid food sample modification:
1. Crush food w/ mortar & pestle
2. Add ethanol to the crushed food to dissolve the nutrients
3. Shake and decant the mixture to a new test tube
4. Proceed w/ step 3
Cloudy white emulsion is observed- +ve result
Sol. remains clear- -ve result
Proteins are organic compounds made of…?
Carbon
Hydrogen
Oxygen
Nitrogen
(sometimes + sulfur)
Amino acids are made up of…?
-Amino group
-Acid group
-Side chain
Relationship betw. amino acid and protein?
Amino acids (held tgt by peptide bonds)
->Polypeptide
->Protein
Why do we need proteins?
-Synthesis of new protoplasm for growth and repair of cells
-Synthesis of enzymes and some hormones
-Synthesis of antibodies
What is the test for proteins?
Biuret test
[Describe Procedure]
Procedure of biuret test?
(+Solid food sample modifications & result indication)
- Add 2cm^3 of biuret solution to 2cm^3 of food sample in a test tube
- Shake the contents of the tube thoroughly
- Wait for a few minutes
Solid food sample modification:
1. Crush food w/ mortar & pestle
2. Add water to the crushed food to dissolve the nutrients
3. Decant the mixture to a new test tube
4. Proceed w/ step 1
Purple/violet colouration observed- +ve result
Sol. remains blue- -ve result
