Biological Molecules

Which option shows the three main elements from the Periodic Table that are present in most molecules in living organisms?

• Carbon, oxygen, nitrogen

• hydrogen, carbon, oxygen

• oxygen, sulfur, carbon

• hydrogen, carbon, nitrogen

The drawing shows a food test being carried out in a laboratory.

• Biuret test for reducing sugar

• DCPIP test for vitamin C

• Benedict's test for proteins

• None of the above

3 statements about proteins are given below. Which of the statements are true?

• Different sequences of amino acids give different shapes to protein molecules,

• Amylase is made from a sequence of amino acids joined together forming a non-specific 3D shape.

• When mixed with Biuret solution, there is a colour change from blue to violet.

• Excess proteins are deaminated in the liver.

The table below lists three large molecules found in living organisms. Which row correctly describes the smaller molecules these substances are made from?

• A

• B

• C

• D

Four statements about large biological molecules are given below. Which of the statements is/are false?

• Proteins are made from a number of different amino acids.

• Oils are made of glycerol only.

• Fats are made from glycogen and fatty acids.

• Lipids are made from glycerol and fatty acids.

A student carried out two food tests on solution F to determine what food groups it contains.

Name a food molecule that is definitely found in solution F.

A student mixes a food reagent with solution X in a test-tube. They observe a positive test results when a cloudy emulsion forms. Which row of the table below identifies the reagent used and molecule present in Solution X?

• A

• B

• C

• D

The image shows two molecules before and after chemical digestion by enzymes in the alimentary canal. Which letter(s) identify the products of digestion in the mouth?

• E

• F

• G

• H

Which row of the table correctly describes the role of cellulose, proteins and water in living organisms?

• A

• B

• C

• D

The presence of vitamin C can be tested using the DCPIP test. When vitamic C is present, the blue DCPIP will turn colourless. Four foods were tested with Benedict's reagent, biuret solution, ethanol-water, DCPIP. Which food possibly contains sucrose, and fats?

• A

• B

• C

• D