Chapter 3: Nutrients Flashcards
(33 cards)
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?
- Provide an immediate source of energy
- Form supporting structures (e.g. cell walls in plants)
- For conversion into other organic compounds (e.g. amino acids in plants & fats in plants and animals)
- 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.
