Explain how inhibitors affect the rate of enzyme-
controlled reactions. (6 marks)
Competitive
Similarity of shape of inhibitor and substrate;
Inhibitor can enter/bind with active site (of enzyme);
Non-competitive
Affect/bind to enzyme other than at active site;
Distorts shape of active site;
Inhibitors
Prevent entry of/binding of substrate to active site;
Therefore fewer/no enzyme-substrate complexes
formed;
, Describe the structure of a plasma membrane and
explain how different substances are able to pass
through the membrane by diffusion. (6 marks)
Phospholipids forming bilayer/two layers;
Details of arrangement with “heads” on the outside;
Two types of protein specified: channel/carrier
proteins
Reference to other molecule e.g. cholesterol or
glycoprotein;
Substances move down concentration gradient/from
high to low concentration;
Water/ions through channel proteins/pores;
Small/lipid soluble molecules/examples pass between
phospholipids/ through phospholipid layer
Carrier proteins involved with facilitated diffusion;
controlled reactions. (6 marks)
Competitive
Similarity of shape of inhibitor and substrate;
Inhibitor can enter/bind with active site (of enzyme);
Non-competitive
Affect/bind to enzyme other than at active site;
Distorts shape of active site;
Inhibitors
Prevent entry of/binding of substrate to active site;
Therefore fewer/no enzyme-substrate complexes
formed;
, Describe the structure of a plasma membrane and
explain how different substances are able to pass
through the membrane by diffusion. (6 marks)
Phospholipids forming bilayer/two layers;
Details of arrangement with “heads” on the outside;
Two types of protein specified: channel/carrier
proteins
Reference to other molecule e.g. cholesterol or
glycoprotein;
Substances move down concentration gradient/from
high to low concentration;
Water/ions through channel proteins/pores;
Small/lipid soluble molecules/examples pass between
phospholipids/ through phospholipid layer
Carrier proteins involved with facilitated diffusion;
