Biological Molecules.

Question 1

What two types of molecules do living organisms contain and give examples of both?

Answer 1

Living organisms contains inorganic molecules (water, iron and calcium) and organic molecules obtained by nutrition (carbohydrates, lipids, proteins and DNA).

Question 2

What do all organic molecules contain?

Answer 2

Organic molecules all contain carbon.

Question 3

Why do organisms need organic molecules?

Answer 3

Organisms need organic molecules (food) for all the chemical reactions that take place in the cells of the body (metabolism).

Question 4

Give five examples that go with the statement organisms need organic molecules for metabolism.

Answer 4

• Release energy in respiration for muscle contraction.
• Provide raw materials for the growth and repair of cells and tissues.
• Protein synthesis.
• Maintaining good health (efficient metabolism).
• Maintaining body temperature (37°C).

Question 5

What are the chemical elements that make up carbohydrates?

Answer 5

Carbohydrates are made of the chemical elements carbon (C), hydrogen (H) and oxygen (O).

Question 6

What large molecules are formed when many small glucose molecules join together?

Answer 6

When lots of glucose molecules join together starch, glycogen or cellulose can form (a polysaccharide).

Question 7

What happens when 2 glucose molecules join together?

Answer 7

When 2 glucose molecules join together maltose is formed (a disaccharide).

Question 8

There are two main classes of carbohydrates. Name them.

Answer 8

Simple sugars (glucose C₆H₁₂O₆ (( a monosaccharide) (soluble)) and complex sugars (are built up from small simple sugars such as glucose).

Question 9

What are the 1 steps of using the iodine test for starch and the colour change for a positive test?

Answer 9

• Add drops of iodine solution to the food sample on a white tile.

A positive test will show a colour change from orange-brown → blue-black.

Question 10

What are the 3 steps for using Benedict’s solution test for reducing sugars/glucose and the colour change for a positive test?

Answer 10

• Grind the food and add water to make a food solution.
• Add an equal amount of Benedict’s reagent to the unknown solution.
• Heat the mixture in a water bath for 2 to 3 minutes.

A positive test for glucose will show a color change from blue → green → orange → red-brown.

Question 11

What are the chemical elements that makeup fats or lipids?

Answer 11

Lipids are made of the chemical elements carbon (C), hydrogen (H), and oxygen (O).

Question 12

What small molecules make up the large molecules called fats and oils (insoluble)?

Answer 12

Fats and oils from fatty acids and glycerol.

Question 13

What are the 3 steps for using the ethanol emulsion test for fats and oils and the colour change for a positive test?

Answer 13

• Add 2cm³ ethanol to 2cm³ of the unknown food solution.
• Shake the mixture gently.
• Add the mixture to distilled water.

A positive test for fats and oils will show a color change from colourless → milky white emulsion.

Question 14

What are the building blocks of lipids?

Answer 14

Glycerol + 3 fatty acids.

Question 15

What small molecules make up the large molecule called protein?

Answer 15

Proteins (enzymes and antibodies) from amino acids.

Question 16

What are the chemical elements that make up proteins?

Answer 16

Proteins are made of the chemical elements carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sulphur (S).

Question 17

What are the 2 steps for using the Biuret test for proteins and the colour change for a positive test?

Answer 17

• Add a few drops of Biuret solution to 2cm³ of the unknown solution.
• Shake the mixture gently.

A positive test for protein will show a color change from blue → purple.

Question 18

What are the elements that makeup DNA?

Answer 18

Carbon, hydrogen, oxygen, nitrogen, phosphorus.

Question 19

Describe the structure of a DNA molecule (4 characteristics).

Answer 19

• Two strands coiled together to form a double helix.
• Each strand contains chemicals called bases.
• Bonds between pairs of bases hold the strand together.
• The bases always pair up in the same way: A with T and C with G.

Question 20

What are the characteristics of organisms which share a more recent ancestor?

Answer 20

Organisms that share a more recent ancestor are more closely related and have base sequences in DNA that are more similar to those that share only a distant ancestor.

Question 21

Scientists can now sequence the DNA of particular genes in nuclei to help identify and classify different species of many animals. The sequence they find are called “barcodes”. What do these help to do?

Answer 21

These help to identify an animal accurately and are useful if distinguishing characteristics is difficult and it can help identify unknown or endangered species.

Question 22

What is glycogen’s use in animals (insoluble)?

Answer 22

The energy stored in animal cells can be easily broken down by enzymes to glucose to release energy (glycogen is usually stored in liver and muscle cells).

Question 23

What is starch’s use in plants (insoluble)?

Answer 23

A very important energy store in plant cells (found in rice, potatoes and bread).

Question 24

What is the use of cellulose in plants (insoluble)?

Answer 24

Forms plant cell walls.

Question 25

What are the 2 steps for using the DCPIP test for Vitamin C and the colour change for a positive test?

Answer 25

• Add 1cm³ of DCPIP solution to a test tube.
• Add a small amount of food sample (as a solution).

A positive test for vitamin c will show a color change from blue → colorless.

Question 26

What are the chemical elements that makeup DNA?

Answer 26

DNA is made of the chemical elements carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and phosphate (P).