B3 - Biological molecules

Question 1

Biological molecules (4)

Answer 1

Carbohydrates, lipids, proteins, nucleic acids

Question 2

What is the function of biological molecules?

Answer 2

Aids organisms to grow, sustain, and reproduce
- they are involved in building organisms from single cells to complex living beings like humans, by interacting with each other
- the diversity in their shape and structure provides diversity in their functions.

Question 3

Monomer

Answer 3

A simple compound whose molecules can join together to form polymers
- they are the building blocks to substances and make up the structure of biomolecules

Question 4

What are carbohydrates?

Answer 4

Sugars and polymers of sugars (starches)

Question 5

Carbohydrate monomer

Answer 5

• monosaccharide (glucose, fructose)
• disaccharide (maltose, sucrose)
• polysaccharide (starch, glycogen, cellulose)

Question 6

What elements make up carbohydrates?

Answer 6

Carbon, Hydrogen, Oxygen, (CHO) 1:2:1 Ratio

Question 7

What do carbohydrates (such as sugars) do?

Answer 7

An important source and release of energy (both short and long-term)

Question 8

Give examples of carbohydrates (name 3)

Answer 8

bread, beans, milk, potatoes, corn, spaghetti

Question 9

What are lipids?

Answer 9

Substances divided into fats (solids at room temperature) and oils (liquids at room temperature)

Question 10

What do fats do? (2)

Answer 10

• insulate the body
• support and cushion organs

Question 11

What do oils do? (2)

Answer 11

• store energy
• mostly in plants

Question 12

Give properties of lipids (2)

Answer 12

• insoluble
• source of long-term energy once carbohydrates are burnt

Question 13

What are the monomers of lipids?

Answer 13

glycerol and fatty acids (triglycerides)
- one glycerol molecule chemically bonded to three fatty acids

Question 14

What elements make up lipids?

Answer 14

carbon, hydrogen, oxygen (CHO)

Question 15

Give examples of lipids (name 3)

Answer 15

nuts, butter, olives, bacon, beef fat, seeds

Question 16

What are proteins?

Answer 16

They are generically muscle builders that work in the immune system
- play an important role in the structure and efficient function of the body

Question 17

What are the monomers of proteins?

Answer 17

Amino acids
- arranged in any order creating hundreds of thousands of proteins

Question 18

Give examples of proteins (name 3)

Answer 18

lean meats, fish and seafood, eggs, dairy products, poultry

Question 19

What elements make up proteins?

Answer 19

carbon, hydrogen, oxygen, nitrogen (CHON)

Question 20

What are nucleic acids?

Answer 20

Macromolecules such as DNA and RNA

Question 21

What is the monomer of nucleic acids?

Answer 21

Like proteins and carbohydrates, they are polymers (made up of smaller molecules in chains)
- subunits are called nucleotides

Question 22

What elements make up nucleic acids?

Answer 22

carbon, hydrogen, oxygen, nitrogen, phosphorus (CHONP)

Question 23

How do you test for starch?

Answer 23

Iodine turns from orangey brown to blue/black in the presence of starch

Question 24

How do you test for lipids?

Answer 24

Using ethanol as a reagent
- shake the colourless ethanol together with the sample being tested
- positive test forms a cloudy white emulsion

Question 25

How do you test for proteins?

Answer 25

Using a biuret test
- add sodium hydroxide (NaOH) first to raise pH to alkaline levels
- add copper (II) sulphate (CuSO4) for its ions in the reagent to bind the peptide bonds in proteins and aid their identification
- observe as the colours turns from blue to violet/purple for a positive test

Question 26

How do you test for sugars?

Answer 26

• Add Benedict’s reagent to a sample in a water bath at 75C
• If reducing sugars are present, the substance will turn from bright blue to orange/brick red
• The higher the concentration sugars, the greater the colour change

Question 27

Why is water an important solvent?

Answer 27

• It dissolves most small molecules with a charge which is useful for:
  
  • transport of glucose, oxygen, and ions in blood plasma in animals and in phloem sap in plants
• Chemical reactions taking place inside cells (cytoplasm is up to 90% water) and during digestion in the alimentary canal
• Respiration (and photosynthesis) in aquatic organisms - O2 and CO2 can dissolve in water
• Excretion - mixed with urea