Biology - Things I got Wrong in tests completed

Given the molecular masses of Carbon, Hydrogen and Oxygen are 12, 1, 16 respectively…

Explain why the molecular mass of one glucose molecule is 180

Because the molecular formula of one glucose molecule is C6H12O6, and 12×6 + 1×12 + 16×6 = 180

Give 2 differences between the structure of a ribose molecule and the structure of a glucose molecule

1) Ribose is a pentose sugar, meaning it has only 5 carbons, whereas glucose is hexose, meaning it has 6 carbons

2) Ribose has 2 less Hydrogen and 1 less Oxygen molecule, giving it the formula C5H10O5, where the glucose formula is C6H12O6

When Benedict’’s solution is mixed with a molecule, what would indicate the molecule is a reducing sugar?

Formation of red precipitate

An experiment is carried out using different concentrations of glucose, to see how much precipitate is formed when added to same mass of benedict’s solution. Explain why there would be an initial linear increase, that then plateaus.

Increase Initially because all glucose is reacting, and since there is more of it, more reaction can happen, so more precipitate forms

Plateau as Benedict’s concentration becomes limiting, and no more reaction can happen without adding more Benedict

When investigating the effect of glucose concentration on mass of red precipitate formed when mixed with Benedict’s solution, how could you reduce error of results. (4 ways)

1) Repeat measurements more times to reduce standard deviation

2) Increase drying time to ensure all water is removed

3) check calibration of balance to increase accuracy of mass measurement

4) Rinse all precipitate off filter paper to ensure all precipitate is collected and measured

Why can common cold viruses not infect cells if they land on unbroken skin?

Skin cells do not have receptor cells that are complimentary for the virus to bind to, meaning the viruses cannot infect skin cells. The virus also cannot pass through the skin which acts as a primary defence barrier due to the keratin it contains.

Why does the common cold not infect cells if they enter the blood through a cut in the skin?

Viruses can only infect cells with complimentary receptors that they can bind to. The blood cells do not have these specific receptors, and so the virus cannot infect blood cells. The virus is also likely to be destroyed by the high concentration of phagocytes in the blood.

Describe the Structure of a Ribosome

It is composed of two subunits and can be either 70 or 80s in prokaryotic and eukaryotic cells respectively. They are made of protein and RNA.