2.4.1(Enzymes as biological catalysts)

What is meant by an “Active site”

• Indented area on the surface of an enzyme, with shape that is complementary to the shape of the substrate molecule

What is meant by a catalyst

• Chemical that speeds up rate of reaction by decreasing activation energy and remains unchanged and reusable

What is meant by an enzymes turnover number?

• The number of reactions that an enzyme molecule can catalyse per second

Describe what determines the structure of an enzyme

• The Instructions for making the enzyme are encoded in genes, which is codes for the amino acid structure in its primary structure. The R groups in the amino acid sequence determine its tertiary structure and therefore its shape, which determines its function

What can mutations of genes that code for enzymes cause

• It can can cause a change in the tertiary structure of the enzyme, by altering the primary structure of the amino acids, which prevents the enzyme from functioning correctly

State an example of where mutations of genes that code for enzymes is harmful in mammals

• Because enzymes catalyse the formation of the organsim’s structural components. Some genetic disorders cause malformations of connective tissue and can be very harmful, such as ”stone man syndrome”

Explain why the tertiary structure of enzymes is important

• Because the active site of the enzyme is specific and is only complementary to the shape of it’s substrate. Which means that it can only catalyse a reaction involving the particular type of substrate that is complementary.

• Therefore if the tertiary structure of the enzyme is different, the active site may have a different shape and will not be able to preform its function

State whether enzymes are fibrous or globular proteins

• They are globular proteins

Explain 2 factors affect the enzymes tertiary structure

• Temperature and pH both affect the shape of enzymes

• This is because they both affect the bonds that hold the tertiary structure of the protein

State what metabolites are

• They are reactants, intermediates and products that are part of metabolic pathways

State and define the 2 types of metabolic pathways

1. Catabolic: Metabolites are broken down to smaller molecules and release energy

2. Anabolic: Energy is used to synthesise larger molecules from smaller substrates

State what is meant by an intracellular enzyme and give 2 examples

• An enzyme which catalyses reaction within the cell

• Examples:

  1. Catalase:

  2. Hydrolytic enzymes in lysosomes

State the structure and function of catalase

• Function: This is enzyme which breaks down hydrogen peroxide(H2O2) into O2 and H2O inside the cell

  Structure: A 4 polypeptide chain protein that contains a haem group with iron acting as a cofactor

State the optimum temperature and pH for catalase to operate in both humans and other species

• Humans:

  • Temperature: 45C

  • pH: 7

• Other species:

  • Temperature: varies, but in thermophilic archaea it is 90C

  • pH: varies between 4 and 11

State the function and location of hydrolytic enzymes

• In WBCs, lysosomes fuse with endocytosed pathogens the enzymes break down the pathogens

State what is meant by extracellular enzymes and give 2 examples

• They are enzymes which catalyse reactions out of cells

• Examples:

  • Amylase

  • Trypsin

  • Hydrolytic enzymes in fungi

State and explain how fungi use extracellular enzymes for growth

• Fungi release hydrolytic enzymes from their hyphae.

• These enzymes are able to digest complex organic structures such are proteins, carbohydrates and lipids.

• This then produces glucose, amino acids, and fatty acids, which are absorbed into the fungal hyphae for use in respiration and growth

State and explain how mammals use extra cellular enzymes for growth and repair

• In our digestive system, enzymes are secreted from the cells lining the alimentary canal and into the gut lumen.

• These enzymes extracellularly digest large molecules such as proteins, lipids, carbohydrates and nucleic acids found in food.

• The products of digestion(fatty acids, glucose, amino acids) are then absorbed via microvilli in the gut into the blood stream to then be used for respiration, growth and tissue repair

State the function and production location of amylase in the body

• Function: break down starch into maltose in the mouth and small intestine

• Production location: Salivary glands and pancreas

State the function, production location, location and optimum pH of trypsin in the body

• Function: Break down large polypeptides into smaller ones by hydrolysis of peptide bonds

• Production location: Pancreas

• Location: lumen of small intestine

• Optimum pH: 7.5 and 8.5