apply knowledge of proteins to explain the effects on enzyme activity of pH, temperature, substrate concentration, enzyme concentration, competitive inhibitors, and non-competitive inhibitors including heavy metals.
devise an experiment using the scientific method (e.g., to investigate the activity of enzymes). Liver catalase experiment!
Describes the constantly occurring chemical reactions in a cell necessary for life.
E.g., the chemical reactions involved in the processes of cellular respiration, DNA replication, protein synthesis, dehydration synthesis and hydrolysis, chemical digestion, intracellular digestion, O 2 /CO 2 transport, etc. ALL require molecules called enzymes .
Induced Fit theory explains how an enzyme must have the correct shape to fit substrate. A change in shape & temporary bonding occurs between the E & S. After the reaction takes place, the product no longer fits on the enzyme, and is freed. The enzyme returns to original shape so that it can be used again.
E.g. Co-enzyme NAD contains niacin, vitamin B1. (NAD+ functions in cellular respiration by carrying two electrons from one reaction site to another in the cytoplasm and mitochondria, i.e. NAD+ + 2H ® NADH + H+ )
Inhibitors are used by many metabolic pathways, for feedback inhibition of products on early stages of the pathway to modulate enzyme activity, e.g. cellular respiration in the mitochondria cristae (malonic acid competing for succinic dehydrogenase
Many medicines are enzyme inhibitors, e.g. sulfa drugs, penicillin to block metabolic pathways of pathogenic bacteria, kidney stone medication, anti-HIV drugs, cancer chemotherapy and even viagra!
Others can be toxic & poisonous, e.g. deadly nerve gas, hydrogen cyanide (competes for cytochrome oxidase), insecticides (parathion, DFP)….
Ethanol & bad methanol or bad ethanol glycol (antifreeze)’ E + Bad I EI complex E + formaldehyde = blindness or oxalic crystals in kidneys--ouch! They all compete for alcohol dehydrogen ase. Doctors give ethanol to methanol-poisoned or antifreeze victims---competes for active site blocking formaldehyde product or kidney tissue damage by oxalic crystals!
Chemicals/inhibitors that bind to an enzyme at a place other than the active site, (i.e. ‘no competition at the active site’), which changes the active site so the substrate can’t bind and slows the reaction rate!
The graph above shows the addition of Hg or Pb reduces the amount of product produced over time; the rate slows, lowers, decreases etc. (Note: if the graph becomes less steep, fewer products are being produced per time unit)
Enzyme Activity Labs One molecule of catalase can break 40 million molecules of hydrogen peroxide each second. No wonder so many bubbles!!!
Thyroid gland accumulates iodine by active transport in order to produce thyroxin (Recall B9). It is secreted into the blood stream and affects the rate of metabolism of the body cells by attaching to receptor proteins on the CM.
http://highered.mcgraw-hill.com/sites/0072421975/student_view0/chapter6/ (Mader’s Student Edition Website Support for Chapter 6; Essential Study Partner: Cells Unit/Metabolism/ Enzymes) or… http://www.mhhe.com/biosci/genbio/espv2/data/cells/004/index.html (Metabolism: Energy of Activation & Enzymes)