Definitions + basics of biological molecules

Question 1

Atom

Answer 1

Basic unit of matter with dense central nucleus and cloud of negatively charged electrons surrounding it

Question 2

Molecule

Answer 2

At least two atoms held together by covalent bonds

Question 3

Organic

Answer 3

Substances / compounds containing carbon excluding ones with only carbon + oxygen

Question 4

Inorganic

Answer 4

Substances/ compounds not containing carbon and the carbon oxides

Question 5

Element

Answer 5

Substance made of only one type of atom → all same atomic number

Question 6

Compound

Answer 6

Substance made of at least 2 elements chemically bonded together /

Question 7

What are the most common elements in living compounds

Answer 7

Carbons oxygen hydrogen nitrogen

Question 8

Describe test of starch and positive test

Answer 8

Add few drops of iodine solution and mix well → goes from yellow-brown to blue-black

Question 9

Describe test for reducing sugars like glucose

Answer 9

Add Benedict’s solution, boil/heat at 90 - 100°C goes from blue → brick red precipitate

Question 10

Describe test for non -reducing sugars like sucrose

Answer 10

Add hydrochloric acid and boil to hydrolyse glycosidic bonds and break down into reducing simple sugars and then neutralise with alkali like sodium hydrogen carbonate then add Benedict’s solution and boil/heat90 - 100°C for 1 minute goes from blue → brick red precipitate

Question 11

Describe test for protein

Answer 11

Add biuret’s solution and shake gently goes from blue → purple

Question 12

Describe test for lipids

Answer 12

Emulsion test → Add ethanol then equal volume of water and shake vigorously goes from colourless → milky cloudy white emulsion → ethanol dissolves all fats/lipids and dissolved lipids are insoluble in water

Question 13

Why are food tests semi-quantitative

Answer 13

No number but idea of how much there is due to colour intensity