Nutrients Flashcards

Content • Water and Living Organisms • Carbohydrates, Fats and Proteins • Enzymes

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1
Q

Functions of water

A
  • 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
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2
Q

Define carbohydrates

A

Carbohydrates are organic molecules made up carbon, hydrogen & oxygen (H:O atoms = 2:1)

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3
Q

Monosaccharides eg

A

glucose, fructose, galactose

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4
Q

Disaccharides eg

A

maltose, sucrose & lactose

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5
Q

Define condensation reaction

A

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

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6
Q

Define hydrolytic reaction or hydrolysis

A

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

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7
Q

Test for reducing sugars

A

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

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8
Q

Determining amount of reducing sugar present

A
  1. Solution remained blue: no RS
    Presence of…
  2. Green ppt: Traces amnt of RS
  3. Yellow or orange ppt: Moderate amnt of RS
  4. Brick-red ppt: Large amnt of RS
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9
Q

Why are glycogen & starch suitable as storage materials in cells?

A
  • 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
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10
Q

Functions of carbohydrates

A
  • 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
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11
Q

Define fats

A

Fats are organic molecules made up of carbon, hydrogen & oxygen (much less oxygen in proportion to hydrogen)

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12
Q

What is the result of hydrolysis of fats?

A

One fat molecule will be broken down into glycerol & 3 fatty acid molecules/fatty acid chains
- involves addition of 3 water molecules & enzyme

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13
Q

What are the differences b/w saturated & unsaturated fats?

A

Saturated: fatty acid chain - straight, solid @ RT
Unsaturated: fatty acid chain - have kink/bent, liquid @ RT

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14
Q

How do we test for fats?

A

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

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15
Q

Indication of presence of fats

A

A cloudy white emulsion is formed

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16
Q

Functions of fats

A
  • 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
17
Q

What is amino acid made up of?

A

It is made up of an amino group, an acid group and a side chain, R group, which differentiates the different amino acids.

18
Q

Define proteins

A

Proteins are organic molecules made up of carbon, hydrogen, oxygen, nitrogen(+maybe sulfur)

19
Q

Formation of proteins

A
  1. Amino acids are the building blocks of proteins
  2. Peptide bonds (covalent bonds) link up amino acids to form a polypeptide
  3. 2 or more polypeptide chains fold to form a 3D molecule called proteins
20
Q

How can we test for proteins?

A

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

21
Q

Indication of the presence of proteins

A

Biuret solution changes colour from blue to violet

22
Q

What are the functions of proteins?

A
  • synthesis of new protoplasm for growth & repair of worn out cells
  • synthesis of enzymes & some hormones
  • synthesis of antibodies
23
Q

explain enzyme action in terms of the ‘lock and key’ hypothesis

A
  • 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
24
Q

explain the mode of action of enzymes

A
25
Q

explain the effects of temperature on the rate of enzyme catalysed reactions

A
26
Q

explain the effects of pH on the rate of enzyme catalysed reactions

A