Monday 12 June 2017

Question 1

Give two types of molecules from which a ribosome is made (1)

Answer 1

• rRNA

- Amino acids

Question 2

Describe the role of a ribosome in the production of a polypeptide. Do not include transcription in your answer. (3)

Answer 2

• mRNA bind to ribosome
• 2 codons/binding sites
• Allows tRNA with anticodons to bind
• Catalyses formation of peptide bond between amino acids
• Moves along (mRNA to the next codon)

Question 3

In a eukaryotic cell, the base sequence of the mRNA might be different from the sequence of the pre-mRNA (2)

Answer 3

• Introns in pre-mRNA

- Removal of sections of pre-mRNA/splicing

Question 4

Describe the structure of glycogen (2)

Answer 4

• Polysaccharide/polymer of a glucose

- Joined by glycosidic bonds/ branched structure

Question 5

Suggest how glycogen acts as a source of energy (2)

Answer 5

• Hydrolysed to glucose

- Glucose used in respiration

Question 6

Suggest and explain two ways the cell-surface membranes of the cells lining the uterus may be adapted to allow rapid transport of nutrients (2)

Answer 6

• Membrane has large surface area to volume ration for fast diffusion
• Large number of protein channels for FD/AT/CO-T

Question 7

Use your knowledge of transport across cell membranes to suggest how NHE3 transports one sodium ion into the cell in exchange for one proton out of the cell (3)

Answer 7

• Co-transport
• Uses hydrolysis of ATP
• Sodium ion and proton bind to the protein
• Protein changes shape to move sodium ion across membrane