Exam Revision

Question 1

Osmosis

Answer 1

Osmosis is the diffusion of water from a dilute to a more concentrated solution through a partially permeable membrane that allows water molecules through

Question 2

What type of reaction is cellular respiration?

Answer 2

Exergonic and catabolic.

Question 3

What type of reaction is photosynthesis?

Answer 3

Anabolic and endergonic.

Question 4

Structures of proteins.

Answer 4

• primary
• secondary
• tertiary
• quaternary

Question 5

What’s the primary structure;

Answer 5

The sequence of amino acids.

Question 6

What’s the secondary structure?

Answer 6

How the polypeptide chain is folded. It may form an alpha helix it a beta fold or pleated sheets, these are held by hydrogen bonds.

Question 7

Tertiary structure;

Answer 7

Further folding of the polypeptide chain. It is held by

1. Hydrogen bonds
2. Hydrophobic interactions
3. Disulphide bridges
4. Ionic bonds.

Question 8

Quaternary structure;

Answer 8

The holding of more than one polypeptide chain together.
This is also done by; hydrogen bonds, hydrophobic interactions, disulphide bridges and ionic bonds.
Eg. Haemoglobin, collagen,

Question 9

Steps of transcription in protein synthesis.

Answer 9

Occurs in nucleus

1. DNA unwinds
2. Pre- RNA sequence forms under control of RNA polymerase enzyme.
3. Introns are cut out leaving a shorter RNA strand- Exons left.
4. Resulting mRNA moves across nuclear membranes to ribosomes in the cytoplasm, carrying genetic info from DNA template.

Question 10

Steps of translation in protein synthesis.

Answer 10

Occurs in cytoplasm at ribosomes.
1. mRNA attaches to a ribosome and a start codon must be read (usually aug)
Each mRNA codon pairs with an anti-codon of tRNA.
2. Next tRNA molecule moves in and matches with the mRNA codon while the amino acids form a polypeptide bond.
3. Previous tRNA detaches and mRNA shifts/moves for the next tRNA molecule to come in.
4. Protein grows until stop codon is reached.

Question 11

Process of pre-mRNA to mRNA

Answer 11

Introns are removed, and remains exons have a methylated cap at the 5’ end and a poly-A-tail at the 3’ end.

Question 12

Semi conservative replication of one DNA molecule.

Answer 12

Original strand splits into two new strands.

Question 13

Factor which is most likely to affect the gene pool of a population.

Answer 13

A reduced population, only a few individuals leaving can affect proportions of alleles significantly.

Question 14

Immune response to allergen

Answer 14

Allergen will have a specific shape which will bind to antibody on surface of specific B cell and as a result the B cell will divide.

The B cells will differentiate into plasma cells and produce many antibodies against the allergen (antigen)