Exam PPQ's

Question 1

Glycogen and cellulose are both carbohydrates.

Describe two differences between the structure of a cellulose molecule and a glycogen molecule. (2)

Answer 1

• Cellulose is made up of β-glucose (monomers) and glycogen is made up ofα-glucose (monomers).
• Cellulose molecule has straight chain and glycogen is branched.
• Cellulose molecule has straight chain and glycogen is coiled.
• Glycogen has 1,4- and 1,6- glycosidic bonds and cellulose has only 1,4-glycosidic bonds.

Question 2

Identify the test which would be used to show the presence of starch. (1)

Answer 2

Iodine/potassium iodide.

Question 3

Hydrogen bonds are important in cellulose molecules. Explain why. (2)

Answer 3

• Holds chains / cellulose molecules together / cross links / forms microfibrils, providing strength or rigidity.
• Hydrogen bonds strong in large numbers.

Question 4

A triglyceride is formed through the condensation of how many molecules? (1)

Answer 4

4 (1 glycerol molecule and 3 fatty acids).

Question 5

A starch molecule has a spiral shape. Explain why this shape is important to its function in cells. (1)

Answer 5

• Compact / occupies small space / tightly packed.

- (as a storage molecule).

Question 6

Some seeds contain lipids. Describe how you could use the emulsion test to show that a seed contains lipids. (3)

Answer 6

• Crush / grind.
• With ethanol / alcohol.
• Then add water.
• Forms emulsion / goes white / cloudy.

Question 7

DNA is a polymer. What is the evidence from the diagram that DNA is a polymer? (1)

Answer 7

Repeating units / nucleotides / monomer / molecules.

Question 8

A polypeptide has 51 amino acids in its primary structure.

What is the minimum number of DNA bases required to code for the amino acids in this polypeptide? (1)

Answer 8

153, (51 x 3).

Question 9

The gene for this polypeptide contains more than this number of bases, explain why. (1)

Answer 9

Introns / Start codons / Stop codons.

Question 10

Name the type of chemical bond that joins two monomers to form maltose. (1)

Answer 10

(α 1,4) Glycosidic.

Question 11

Name the monomers from which a maltose molecule is derived. (1)

Answer 11

Glucose (+ glucose).

Question 12

Name the monomers that form a cellulose molecule. (1)

Answer 12

β / Beta glucose.

Question 13

Give one way in which the structure of cellulose is linked to its function. (2)

Answer 13

• H-bonds / micro / macro fibrils / fibres.

- Strength / rigidity / inelasticity.

Question 14

Describe how a saturated fatty acid differs in molecular structure from an unsaturated fatty acid. (2)

Answer 14

• absence of a double bond.

- in the (hydrocarbon) chain.

Question 15

The structure of a phospholipid molecule is different from that of a triglyceride. Describe how a phospholipid is different. (2)

Answer 15

• Phosphate / PO4.

- Instead of one of the fatty acids / and two fatty acids.

Question 16

A starch molecule has a spiral shape. Explain why this shape is important to its function in cells. (1)

Answer 16

• Compact / occupies small space / tightly packed.

Question 17

For which of the following substances is this statement true?
- Starch.
- Glycogen.
- Deoxyribose.
- DNA Helicase.
“Substance contains only the elements carbon, hydrogen and oxygen.” (1)

Answer 17

• Starch
• Glycogen
• Deoxyribose

Question 18

For which of the following substances is this statement true?
- Starch.
- Glycogen.
- Deoxyribose.
- DNA Helicase.
“Substance is made from amino acid monomers.” (1)

Answer 18

• DNA Helicase.

Question 19

For which of the following substances is this statement true?
- Starch.
- Glycogen.
- Deoxyribose.
- DNA Helicase.
“Substance is found in both animal cells and plant cells.” (1)

Answer 19

• Deoxyribose.

- DNA Helicase.

Question 20

Ribonuclease is an enzyme, it is 127 amino acids long. What is the minimum number of DNA bases needed to code for ribonuclease? (1)

Answer 20

381, (127 x 3).