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Starter. Paramecium is a common freshwater Protista , found in ponds or slow-moving streams. Discuss the relationship between osmosis and contractile vacuole activity in a Paramecium , in its freshwater environment. Answer – Question 1. Starter.
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Starter Paramecium is a common freshwater Protista, found in ponds or slow-moving streams. • Discuss the relationship between osmosis and contractile vacuole activity in a Paramecium, in its freshwater environment.
Starter • Osmosis and active transport are both processes used by cells. Compare and contrast these two processes.
Enzymes • Enzymes are biological catalysts – a molecule made by a cell which speeds up a specific chemical reaction. • Almost all processes in a cell need enzymes in order to occur at a significant rate.
Enzymes • Enzymes lower the energy required for a reaction to occur (activation energy) thus increasing the reaction rate. • Most enzyme reaction rates are millions of times faster than those of comparable un-catalyzed reactions.
Induced Fit Model • Enzymes consist of one or more amino acid chains folded to form a specially shaped pocket called an active site. • The specific molecule that fits into the enzymes active site is called the substrate molecule.
Induced Fit Model • The shape of the enzyme will change when the substrate(s) bond with the active site. • Only one type of substrate molecule will fit into the active site of an enzyme.
Anabolic Reactions Substrates Products Bond to Active Site Enzyme
Catabolic Reactions Bond to Active Site Products Substrate Enzyme
Enzymes • Since enzymes are extremely selective for their substrates and speed up only a few reactions from among many possibilities, the set of enzymes made in a cell determines which metabolic pathways occur in that cell. • Temperature and pH affect the activity of an enzyme.
Hydrogen Peroxide • Hydrogen peroxide (H2O2) is a reactive molecule that can potentially damage proteins, lipids and DNA. • To prevent cellular damage, it must be quickly converted into other, less dangerous substances.
Catalase • The enzymes catalase breaks down hydrogen peroxide into water and gaseous oxygen. 2 H2O2 catalase 2 H2O + O2 • Animals use catalase in every organ, with particularly high concentrations occurring in the liver.
