Nutrients

Question 1

Why do all water molecules have hydrogen bonding?

Answer 1

The unequal sharing of electrons in a water molecule results in the oxygen having a partial negative charge, while the hydrogen has a partial positive charge

Question 2

List all the properties of water

Answer 2

Good solvent: mineral salts and food transported while dissolved in plants, blood plasma in humans
Cohesion (btw water molecules) and Adhesion (with other molecules): transpiration pull
High heat of vaporisation: evaporative cooling, sweating
Reactant: raw material for photosynthesis and hydrolysis of food during digestion
Incompressible: provides turgor pressure, amniotic fluid protects foetus
High specific heat capacity: allows large bodies of water to maintain relatively constant temperatures despite surrounding changes

Question 3

State all monosaccharides, disaccharides and polysaccharides and their components

Answer 3

Monosaccharides: glucose, fructose, galactose
Disaccharides—
Sucrose: fructose + glucose
Lactose: glucose + galactose
Maltose: glucose
Polysaccharides: starch, cellulose, glycogen

Question 4

Composition of carbohydrates

Answer 4

Carbon, hydrogen, oxygen (H:O=2:1)

Question 5

What are carbon molecules in glucose used for?

Answer 5

Synthesis of other molecules like amino acids or fatty acids

Question 6

Reactions for nutrients (hydrolysis and condensation)

Answer 6

Hydrolysis (digestion): 1 large molecule + water = many small molecules
Condensation: many small molecules = 1 large molecule + water

Water is a raw material in hydrolysis (large to small), but a product in condensation (small to large)

Question 7

What is the bond in disaccharides and triglycerides?

Answer 7

Disaccharides: covalent, glycosidic linkage
Triglycerides: 3 ester bonds/linkages between glycerol and fatty acids

Question 8

Describe the structure of polysaccharides

Answer 8

Starch and cellulose and linear, but cellulose is alternate. Glycogen is branched

Question 9

Functions of all carbohydrates

Answer 9

Glucose: raw material of respiration
Starch (in plants) and glycogen (in animals): large and insoluble storage materials (polysaccharides)
Cellulose: structural material in plants, makes up the cell wall
Deoxyribose and ribose sugars: makes up DNA and mRNA

Question 10

What are lipids (triglycerides) and its composition

Answer 10

One glycerol molecule joined to 3 fatty acids: carbon, hydrogen, oxygen

Question 11

What has more oxygen in proportion to hydrogen?

Answer 11

Lipids not saccharides

Question 12

Hydrolysis of triglycerides

Answer 12

Each triglyceride can be hydrolysed into 1 glycerol and 3 fatty acids by the enzyme lipase

Question 13

What are saturated and unsaturated fats?

Answer 13

Saturated fats have the maximum possible amount of hydrogen molecules and are solid at rtp.
Unsaturated fats have less than the maximum possible amount of hydrogen molecules and are liquid at rtp

Question 14

Functions and types of lipids

Answer 14

Storage molecules, insulating material, steroid and some hormone synthesis, solvent for fat-soluble vitamins
Types: phospholipids, steroids, carotenoids

Question 15

Structure (subunits of proteins) of amino acids

Answer 15

Alpha carbon (C) connected to:
Side chain (R)
Animo group (H-N-H)
Carbonyl group (O=C-OH)

Question 16

How many types of and elements in animo acids

Answer 16

Twenty types, depending on the R group

Elements found: carbon, hydrogen, oxygen, nitrogen, (sulphur)

Question 17

Hydrolysis of proteins

Answer 17

Protein + water (catalysed by protease) = amino acids

Question 18

Function of proteins

Answer 18

Enzymes (biological catalysts), antibodies, haemoglobin, collagen (structural), hormones (eg. insulin, glucagon)

Question 19

Structure and conformation of proteins, and their denaturisation

Answer 19

Polypeptide chains in unique 3D conformation (amino acid sequence determines protein type). Bonds between amino acids are strong, bonds that hold structure together are weak.

Due to extreme temperature or pH, permanent.

Question 20

What has a lower proportion of hydrogen, phospholipids or carbohydrates?

Answer 20

Phospholipids molecule, not carbohydrates

Question 21

Food test for starch

Answer 21

Add a few drops of iodine solution to the test sample.
Positive: iodine solution changes from brown to blue-black
Negative: iodine solution remains brown

Question 22

Food test for reducing sugars (Benedict’s test)

Answer 22

Reducing sugars are all disaccharides and polysaccharides except for sucrose.

Place 2cm^3 of food sample in a test tube
Add 2cm^3 of Benedicts solution to the food sample and mix
Heat in a boiling water bath for 2-3 minutes
Positive: mixture changed from blue to red/orange/yellow/green (different concentration = range of colours)
Negative: mixture remains blue

Question 23

Food test for non-reducing sugars (polysaccharides and sucrose)

Answer 23

Boil food sample with hydrochloric acids, causing the hydrolysis of the glycosidic bond in the non-reducing sugar if present

Carry out Benedict’s test
Place 2cm^3 of food sample in a test tube
Add 2cm^3 of Benedicts solution to the food sample and mix
Heat in a boiling water bath for 2-3 minutes
Positive: mixture changed from blue to red/orange/yellow/green (different concentration = range of colours)
Negative: mixture remains blue

Question 24

Food test for proteins (Biuret test)

Answer 24

Add 2cm^3 of NaOH (sodium hydroxide) to 2cm^3 of the food sample and shake thoroughly.
Add 1% copper sulfate solution dropwise, shaking after every drop
Positive: mixture changed from blue to VIOLET
Negative: mixture remains blue