WRONG Qs Paper 1

Question 1

Describe how a student could make a 1 in 10 dilution and then use this to make a 1 in 1000 dilution (3 marks):

Answer 1

1. Add 1 part bacteria to 9 parts sterile liquid to make 10^-1 dilution
2. Mix well
3. Add 1 part 10^-1 suspension to 99 parts sterile liquid to make 10^-3 dilution

Question 2

Explain the advantages for larger animals of having a specialised system that facilitates oxygen uptake (2 marks)

Answer 2

1. Larger organisms have a smaller SA:Vol ratio
2. Overcomes long diffusion pathway so faster diffusion

Question 3

Need to remember for protein synthesis:

Answer 3

• RNA polymerase- phosphodiester bonds between adjacent nucleotides
• ribosome attaches to mRNA
• ribosome covers 2 mRNA codons
• ribosome attaches to start codon- AUG
• ribosome moves along to next codon
• ATP used when amino acid attaches to tRNA
• pre- mRNA spliced to remove INTRONS

Question 4

Differences between mRNA and tRNA (6 marks)

Answer 4

1. mRNA has no hydrogen bonds, tRNA has hydrogen bonds
2. mRNA is linear/ straight chained, tRNA is clover leaf shaped
3. mRNA has no amino acid binding site, tRNA has an amino acid binding site
4. mRNA has more nucleotides than tRNA
5. Different mRNAs have different lengths, tRNA is all similar/ the same length
6. mRNA has codons, tRNA has anticodons