2020 a level paper 1

• explain the function of atp hydrolase

  atp is phosphorylated to adp + pi to release energy.

  this realse of energy allows for active transport of na+
• The movement of Na+ out of the cell allows the absorption of glucose into the cell lining the ileum.

  generates a concentration gradient for na+, when na+ moves in it brings glucose with it via facilitated diffusion.
• Describe and explain two features you would expect to find in a cell specialised for absorption.

  1. microvilli allows for a large surface area for absorption
  2. large number of channel proteins which allow for increased rate of absorption.
• Describe how amino acids join to form a polypeptide so there is always NH2 at one end and COOH at the other end. You may use a diagram in your answer.

  one amine groups joins a carboxyl group to form a peptide bond, so each amino acid is orientated in same direction as chain