Definitions: 1. Metabolism – A term which refers to all the chemical reactions of a cell. 2. Enzymes – A protein catalyst. (Speeds up certain reactions) a. Apoenzyme – Protein portion -- Its shape accounts for an enzymes ability to run only a single type of reaction. b. Coenzyme – Non-protein portion -- Can donate or accept atoms to or from a reaction. -- Our body often cannot make coenzymes, so we need them in our diet. Example: Vitamins Enzymes

Definitions: 1. Metabolism – A term which refers to all the chemical reactions of a cell. 2. Enzymes – A protein catalyst. (Speeds up certain reactions) a. Apoenzyme – Protein portion -- Its shape accounts for an enzymes ability to run only a single type of reaction.

b. Coenzyme – Non-protein portion -- Can donate or accept atoms to or from a reaction. -- Our body often cannot make coenzymes, so we need them in our diet. Example: Vitamins

Enzymes often require coenzymes. Apoenzyme coenzymes = holoenzyme

3. Substrate – A reactant (raw material) in an enzyme -- Controlled reaction. 4. Activation Energy Many reactions will not occur unless the energy is added to start them off. Example: A piece of wood needs an input of energy to start it burning. This input energy is called activation energy or energy of activation.(Ea)

***Enzymes bring the substrate close enough together so that the reaction can occur without as much activation energy.*** Thyroxin: The thyroid gland, located in the neck, accumulates iodine in order to produce thyroxin. Thyroxin is a protein hormone that is secreted into the blood stream by cells of the thyroid. It attaches to a receptor site on the surfaces of our body cells where it governs the rate that cells consume oxygen, thus having an overall impact on the body’s metabolism.

Thyroxin does not have a target organ; it stimulates most of the cells of the body to metabolize at a faster rate. The number of respiratory enzymes increases, as does oxygen uptake. Thyroxin helps regulate growth and development. Thyroglobulin is the storage form of Thyroxin. Iodine is required for thyroglobulin to be made. No iodine, the thyroid gland will increase activity as a mechanism to produce more thyroxin. Unfortunately no Iodine, no thyroxin.

Simple Goiter: A simple goiter occurs when the thyroid gland is unable to meet the metabolic demands of the body through sufficient hormone production. The thyroid gland compensates by enlarging, which usually overcomes mild deficiencies of thyroid hormone.

Exophthalmic Goiter: Graves' disease. Condition characterized by excessive production of thyroid hormone. Characterized by an enlarged thyroid gland, protrusion of the eyeballs, tachycardia and nervous excitability. Example of the eyes of a serious Exophthalmic Goiter patient

Symptoms of Hypothyroidism Low thyroxin in the blood -Fatigue -Weakness -Coarse, dry hair -Dry, rough pale skin -Hair loss -Constipation -Depression -Cold intolerance (can't tolerate the cold like those around you) -Weight gain or increased difficulty losing weight -Muscle cramps and frequent muscle aches -Irritability -Memory loss -Abnormal menstrual cycles -Decreased libido

Common symptoms and signs of hyperthyroidism (high thyroxin in the blood) -Palpitations -Heat intolerance -Nervousness -Insomnia -Breathlessness -Increased bowel movements -Light or absent menstrual -periods -Fatigue -Fast heart rate -Trembling hands -Weight loss -Muscle weakness -Warm moist skin -Hair loss -Staring gaze

LOCK AND KEY THEORY OF ENZYME ACTION A.In order for a reaction to occur, the reactants (substrates) must be brought close together. B. The substrates bond to the active site on the enzyme, and are brought close together. Sometimes the active site changes shape to bring the substrates together. C. The reaction occurs and the product(s) are released. The enzyme goes back to its normal tertiary configuration. (shape)

Review of LOCK AND KEY According to this analogy, an enzyme acts like a key by combining with a specific substrate and “unlocking” the substrate for further activity of the cell.

This is a useful analogy because the key (enzyme) must have the correct shape to fit the lock (substrate). After the lock has been opened (reaction takes place) the key (enzyme) is freed and unchanged so that it may be used repeatedly in the same manner. The portion of the enzyme that is involved in the reaction is called the active site.

Note: Example of a Metabolic Pathway A--->B--->C--->D A= beginning substrate B,C= intermediate products/reactants D= final product Number = Enzymes

ROLE OF COENZYMES Coenzymes – (non-protein portion of enzymes) -- Can participate in a reaction by accepting or contributing atoms to the reaction. SIGNIFICANCE OF VITAMINS Many coenzymes are vitamins. Our bodies cannot make many of those that we require – we must get them in our diet. They are vital for efficient metabolism. We only need small quantities, because as part of enzymes, they can be used over and over again.

FACTORS AFFECTING ENZYME ACTIVITY A. Heavy metals: Such as Pb+2 (lead) or Hg+2 (mercury) These metals can bond with parts of enzymes and cause them to change shape (denature them). This bonding is called noncompetitive inhibition. noncompetitive inhibition. The enzyme is inactive – no products form. This is explained by a process in which the inhibitor fits into a place (site) on the enzyme, which is different from the active site. When this happens, the folding of the enzyme changes a little bit, and the active site is distorted in a way, which makes it a less effective catalyst.

B. Competitive Inhibition : Some molecules are shaped like a substrate and compete with the substrate for the enzyme’s active site. Example: Carbon Monoxide (CO) competes with Oxygen (O2) Since some of the enzymes get bonded to the “wrong” substrate, the amount of “correct” product is reduced. Sometimes these molecules only bond temporarily with the enzyme, but sometimes they bond permanently. For the life of the enzyme, it is useless.

-If too many important enzymes are inactivated, the organism may die. -A molecule, which fits into the enzyme's active site but doesn't react with anything there, is called a competitive inhibitor. If this molecule (an inhibitor) is in the active site, a substrate molecule can't get in, and that particular enzyme molecule is inactive until the inhibitor falls off.

C. Temperature: Cold temperature slows down enzymatic reactions. Warm temp to around 40  C - speed up reactions High temp – denature enzymes and cause reactions to stop. If we increase the temperature of the solution the enzyme is operating in, we will typically see an increase in the reaction rate until a point is reached at which the enzyme starts to unfold. This is a result of breaking hydrophobic bonds and salt bridges as the increase in temperature causes the enzyme's structure to "wiggle" around

D. pH: Each enzyme operates best at a preferred pH level. Any other pH affects tertiary structure and slows down reactions. Too much of a change stops the reaction. Since salt bridges depend on ionic charges for their "bonding" power, anything, which neutralizes such a charge, will destroy the salt bridge and make the folded structure of the enzyme less stable. Increase of pH (more basic) will take an H+ from an NH3+ group and neutralize its charge. Similarly, decrease in pH will put an H+ on a COO-. This means that each enzyme has an optimum pH at which its folded (active) structure is most stable. It has its maximum catalytic power at that pH.

E. Substrate Concentration: The more concentration of substrate, the greater the rate of reaction. If we do a series of experiments arranged so the concentration of the enzyme is always the same, but the substrate (reactant) concentration is increased from one experiment to the next, we find that in the low substrate concentration experiments the rate increases as we increase substrate concentration, but as the experiments involve higher and higher substrate concentrations, we find that we reach a maximum reaction rate. More substrate doesn't increase the rate any more. At this point, we say that the enzyme is saturated (it can't handle any more). To increase the rate again, we'd need more enzyme

Example: 800 H O > 2 H 2 O 800 H O > 800 H 2 O

overview F. Enzyme concentration – more enzyme, greater rate of reaction. What happens if we change the concentration of an enzyme? More catalyst means a faster reaction, so the reaction rate increases. (Reaction rate is basically "how much substrate reacts in a particular amount of time, usually a second.)