Nutrients Flashcards
Content • Water and Living Organisms • Carbohydrates, Fats and Proteins • Enzymes
Functions of water
- as a solvent for chemical reactions that take place
- a key component in cells, tissue fluid, digestive juices & blood
- helps to control body temp. through sweating - as water in sweat evaporate of skin surface, latent heat of vaporisation is removed, cooling down the body
- transport dissolved substances such as digested products & waste products
Define carbohydrates
Carbohydrates are organic molecules made up carbon, hydrogen & oxygen (H:O atoms = 2:1)
Monosaccharides eg
glucose, fructose, galactose
Disaccharides eg
maltose, sucrose & lactose
Define condensation reaction
A condensation reaction is a chemical reaction in which 2 simple molecules are joined tgt to form a larger molecule with the removal (release) of 1 molecule of water
Define hydrolytic reaction or hydrolysis
Hydrolysis or a hydrolytic reaction is a reaction in which 1 water molecule is needed to break up a complex molecule into smaller molecules
- use an enzyme
Test for reducing sugars
Carry out the Benedict’s test
- Add 2 cubic cm of Benedict’s solution to 2 cubic cm of food sample in test tube (1:1)
- Shake the mixture
- Heat contents in a boiling water bath for 2-3 minutes
Determining amount of reducing sugar present
- Solution remained blue: no RS
Presence of… - Green ppt: Traces amnt of RS
- Yellow or orange ppt: Moderate amnt of RS
- Brick-red ppt: Large amnt of RS
Why are glycogen & starch suitable as storage materials in cells?
- insoluble in water so they do not change the water potential in cells
- large molecules - cannot diffuse through CSM so they will not be lost from cell
- easily hydrolysed to glucose when needed
- molecules have compact shapes so they occupy less space than individual glucose molecules
Functions of carbohydrates
- to provide energy for cell activities
- to form supporting structures such as cell walls (cellulose)
- to be converted into other organic compounds such as amino acids & fats
- to form nucleic acids in DNA
- to synthesise lubricants
- for nectar production in flowers
Define fats
Fats are organic molecules made up of carbon, hydrogen & oxygen (much less oxygen in proportion to hydrogen)
What is the result of hydrolysis of fats?
One fat molecule will be broken down into glycerol & 3 fatty acid molecules/fatty acid chains
- involves addition of 3 water molecules & enzyme
What are the differences b/w saturated & unsaturated fats?
Saturated: fatty acid chain - straight, solid @ RT
Unsaturated: fatty acid chain - have kink/bent, liquid @ RT
How do we test for fats?
ethanol emulsion test
1. Add 2 cubic cm of ethanol to 2 cubic cm of food sample in a test tube
2. Shake contents vigorously
3. Decant 2 cubic cm of water into test tube & shake the mixture
Indication of presence of fats
A cloudy white emulsion is formed
Functions of fats
- as a source & store of energy
- as an insulating material - prevents excessive heat loss
- as a solvent for fat soluble vitamins & hormones
- to form the main part of cell membranes (lipids)
- to help reduce water loss from skin surface
What is amino acid made up of?
It is made up of an amino group, an acid group and a side chain, R group, which differentiates the different amino acids.
Define proteins
Proteins are organic molecules made up of carbon, hydrogen, oxygen, nitrogen(+maybe sulfur)
Formation of proteins
- Amino acids are the building blocks of proteins
- Peptide bonds (covalent bonds) link up amino acids to form a polypeptide
- 2 or more polypeptide chains fold to form a 3D molecule called proteins
How can we test for proteins?
Biuret test
1. Add 2cm3 of sodium hydroxide to test tube containing 2cm3 of food sample & shake well
2. Add 1% copper(II) sulfate solution drop by drop to test tube. Shake the test tube after each drop
3. Leave the test tube to stand for 5 minutes
Indication of the presence of proteins
Biuret solution changes colour from blue to violet
What are the functions of proteins?
- synthesis of new protoplasm for growth & repair of worn out cells
- synthesis of enzymes & some hormones
- synthesis of antibodies
explain enzyme action in terms of the ‘lock and key’ hypothesis
- an enzyme has a specific 3D shape
- only substrate with a 3D shape complementary to that of active site can fit into the enzyme, forming an enzyme-substrate complex (the enzyme is like a lock and substrate a key; ‘lock-and-key’ hypothesis)
- while substrate is attached to the active site, chemical reaction occurs & substrate is converted into products
- products leave the active site, enzyme remains chemically unchanged
explain the mode of action of enzymes
