Biology Higher Unit 2 (Part 1)

1. Identify the most accurate description of the membrane structure from the given responses:

Jason : The walls of the membrane are pretty solid. Not many substances can pass through the walls as only certain molecules are required. There are proteins which can accept some specific ions or molecules and the cell membrane has channels.
Henry: The phospholipid bilayer follows the fluid-mosaic model and protein pumps energise the molecules from the inner membranes in active transport from higher to lower concentration. The membrane will have pores which allow diffusion of products.
Amy : The membrane will contain ion channels which will allow the diffusion of ions and the entire membrane is selectively permeable with a double layer of phospholipid and pumps penetrating through the bilayer enabling active transport.
Hanna : Well the membrane consists of phospholipid, protein and enzyme molecules and the protein pores generate an electrical gradient enabling the transport of certain molecules. The whole membrane is characterised by its fluidity and permeability.

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it assumes that the enzyme is influenced by the substrate in such a way that its structure is modified which is incorrect.
in reality the shape of the enzyme is altered slightly when the enzyme-substrate complex forms which causes the substrate to attatch to the active site even more tightly as illustrated by the induced fit model..
it assumes that the substrate orientation does not affect the ability of the substrate to bind with the enzyme unlike in the induced fit model.
in reality the shape of the substrate is altered slightly which allows the substrate to bind to the active site even more tightly as illustrated by the induced fit model.