Bio paper 1

Describe and explain 2 features you would expect to find in a cell specialised for absorption 2marks

M1 Folded membrane/ microvilli hence large surface area

M2 Many/large number of carrier proteins so fast rate of absorption

Describe the role of micelles in the absorption of fats into the cells lining the ileum 3marks

1. Micelles include bile salts and fatty acids;

2. Make the fatty acids (more) soluble in water;

3. Bring/release/carry fatty acids to cell/lining (of the ileum);

4. Maintain high(er) concentration of fatty acids to cell/lining (of the ileum);

5. Fatty acids (absorbed) by diffusion;

Describe how an enzyme can be phosphorylated 2marks

1. Attachment/association of (inorganic) phosphate (to the enzyme);

2. (Released from) hydrolysis of ATP

OR

(Released from) ATP to ADP + Pi;

Define ‘non-coding base sequence’ and describe where the non-coding multiple repeats are positioned in the genome 2marks

1. DNA that does not code for protein/polypeptides

OR

DNA that does not code for (sequences of) amino acids

OR

DNA that does not code for tRNA/rRNA;

2. (Positioned) between genes;

Describe how a polypeptide is formed by translation of mRNA 6marks

1. (mRNA attaches) to ribosomes

OR

(mRNA attaches) to rough endoplasmic reticulum;

2. (tRNA) anticodons (bind to) complementary (mRNA) codons;

3. tRNA brings a specific amino acid;

4. Amino acids join by peptide bonds;

5. (Amino acids join together) with the use of ATP;

6. tRNA released (after amino acid joined to polypeptide);

7. The ribosome moves along the mRNA to form the polypeptide;

Define ‘gene mutation’ and explain how gene mutation can have - no effect on an individual - a positive effect on an individual 4marks

(Definition of gene mutation)

1. Change in the base/nucleotide (sequence of chromosomes/DNA);

2. Results in the formation of new allele; (Has no effect because)

3. Genetic code is degenerate (so amino acid sequence may not change);

OR

Mutation is in an intron (so amino acid sequence may not change);

4. Does change amino acid but no effect on tertiary structure;

5. (New allele) is recessive so does not influence phenotype;

(Has positive effect because)

6. Results in change in polypeptide that positively changes the properties (of the protein)

OR

Results in change in polypeptide that positively changes a named protein;

7. May result in increased reproductive success

OR

May result in increased survival (chances);