Enzymes AS Biology 2015 New Spec OCR

HideShow resource information





(a)The role of enzymes in catalysing reactions that affect metabolism at a cellular and whole organism level

To include the idea that enzymes affect both structure and function

-Speeds up a reaction without being used in it

-Enzymes are globularproteins

-with a specific tertiary structure

-catalyse metabolic reactions at a cellular and whole organism level

-2 metabolic reactions

-Anabolic(Build-up of larger more complex molecules from smaller simpler ones) – This process requires energy

-Catabolic(The breakdown of complex molecules into smaller simpler ones) – Thisprocess releases energy

-Instructions are encoded in the genes

-If a mutation happens this will alter the sequence of amino acids and this will alter the enzymes tertiary structure. This will prevent the enzyme from functioning

-If a metabolic reaction is deficient a metabolic disorder results

-Enzymes also catalyse the formation of organisms structural components e.g collagen in bones



(b) the role of enzymes in catalysing both intracellular and extracellular reactions

To include catalase as an example of an enzyme that catalyses intracellular reactions and amylase and trypsin as examples of enzymes that catalyse extracellular reactions.


-An example is catalyse

-Catalyse is formed in nearly all living organisms that are exposed to air

-It is important as it breaks down hydrogen peroxide into oxygen

-Hydrogen peroxide is a harmful by-product in many metabolic reactions, to water and oxygen

-Catalyse consists of 4 polypeptide chains and contains a haem group with iron

Extracellular-works outside the cell

-Amylase is produced in the salivary glands and acts in the mouth to digest the polysaccharide starch to the disaccharide maltose

-It is also made in the pancreas, and acts to catalyse the same reaction in the lumen of the small intestine

Trypsin is made in the pancreas, and acts in the lumen of the small intestine to digest proteins into smaller peptides by hydrolysing peptide bonds.

-Its optimum PH is between 7.5 and 8.5


(c) the mechanism of enzyme action

To include the tertiary structure, specificity, active site, lock and key hypothesis, induced-fit hypothesis, enzyme-substrate complex, enzyme-product complex, product formation and lowering of activation energy.

Lock And Key Hypothesis

-Enzymes have an active site complementary to its substrate molecule

-Enzymes have kinetic energy and are constantly moving randomly

-If a substance molecule successfully collides with the active site, non-covalent forces such as hydrogen bonds hold the substrate molecule together forming an enzyme substrate complex

-The substrate molecule is either broken down or build up into product molecules forming an enzyme product complex

-The product molecule leaves the active site

-The enzyme molecule is now able to form another enzyme substrate complex, so a small amount of enzyme molecules can convert a large amount of substrate molecules

E+S – ESC – EPC – E+P

The Induced-fit Hypothesis

-When a substrate molecule fits into the enzymes active site, the active site changes shape slightly to mould itself around the substrate molecule

-This moulding allows the substrate…


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Enzymes resources »