Enzymes A cells toolbox Ch 6 4 high

Enzymes A cell’s toolbox (Ch 6. 4)

high activation energy without catalyst energy content of molecules activation energy with catalyst reactants products low progress of reaction

• An enzyme is a protein that • catalyzes a chemical reaction in living cells. • is not consumed in the reaction.

Enzyme structure Many enzymes have both active sites and allosteric regulatory sites. allosteric regulatory site

active site of enzyme 1 Substrates enter active site in a specific orientation. 3 Substrates, bonded together, leave enzyme; enzyme ready for new set of substrates. 2 Substrates and active site change shape, promoting reaction between substrates.

Lactase Lactose (milk sugar) is a disaccharide. Lactase breaks lactose down into two monosaccharides, which can be absorbed in the small intestine.

Why would the genetic “error” causing lactose tolerance (the ability to drink milk all your life) be selected for in some parts of the world and not in others?

Amylase breaks ____ (amylose) apart into monosaccharides Iodine turns black when ______ is present. How does the test in this picture demonstrate amylase activity?

Pepsin is a protease which breaks apart _______ chains into smaller chains or single ______.

Enzyme regulation Allosteric inhibition Competitive inhibition allosteric regulator molecule An allosteric regulator molecule causes the active site to change shape, so the substrate no longer fits. A competitive inhibitor molecule occupies the active site and blocks entry of the substrate.

Regulation controls enzyme pathways. If one enzyme in the chain were missing, could the end product, G, be made? If Product G came from another source, such as from consumed food, what would be its effect on this system?

Regulation may be through competitive or noncompetitive inhibition.

MTHFR gene: methylenetetrahydrofolate reductase enzyme. Located on the p arm of chromosome 1 in humans, this gene codes for an enzyme involved in the methylation of folic acid, a necessary B vitamin. Methylated (folate) and non-methylated (folic acid) forms are found in leafy greens, beans, and whole grains.

MTHFR is just one enzyme among many that convert certain nutrients into usable forms and convert waste into non-toxic forms.

• Lack of the MTHFR enzyme causes buildup of homocysteine and/or folic acid, which can cause damage to the heart, blood vessels, and thyroid over time. More information on the MTHFR gene on: • http: //www. stopthethyroidmadness. com/mthfr/ • http: //ghr. nlm. nih. gov/gene/MTHFR • Homocysteine is normally converted to glutathione, one of the body’s chief antioxidants. People with a defective MTHFR enzyme lose the protection of this important antioxidant.

p. H influences enzyme activity salivary amylase pepsin enzyme activity acidic p. H basic If you ate a lot of antacids, could that affect your digestion? Why?

Temperature influences enzyme activity Enzyme activity increases enzyme activity Maximum activity at optimal temperature. High temperatures distort enzyme structure. temperature What is one reason why high fevers can be dangerous?

Recap • Enzymes are proteins that catalyze chemical reactions in living systems. • Each enzyme does one job, but does that job over and over again. This is referred to as enzyme specificity.