CHEMISTRY AND LIFE One unromantic but productive way of viewing life is to see it as a set of coordinated chemical reactions. This leads to an obvious question – What determines which chemical reactions are possible?

CHEMICAL REACTIONS Whether a chemical reaction will or won’t occur under particular conditions is determined by the laws of thermodynamics. If the overall amount of order is decreased by a reaction, the reaction is favoured Keeping it simple - Generally, if energy is released in a reaction, the reaction is favoured

The Direction of Spontaneous Reactions (and what it takes to go the other way)

Life Requires Lots of Unfavourable Reactions – How Is This Possible? By coupling favourable to unfavourable reactions. favorable reactions unfavorable reactions

The “Nature of Life” – Coupling Favourable to Unfavourable Reactions

ATP – LIFE’S ENERGY CURRENCY ATP = Adenosine Triphosphate Energy is released when ATP is hydrolyzed (broken down by water) to ADP. ATP is restored from ADP and an input of energy. ATP’s energy is used to drive endergonic (energy-requiring) reactions.

ENZYMES SPEED UP CHEMICAL REACTIONS Enzymes are biological catalysts – substances that speed a reaction without being altered in the reaction. Most enzymes are proteins. Enzymes are essential for life. Model of the surface of an enzyme.

Enzymes Lower a Reaction’s Activation Energy

ENZYME ACTION

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The Fit Between Enzyme and Substrate is Critical and Precise Hexokinase, an enzyme (blue), binding its substrate, glucose (yellow).

ENZYME DEFICIENCY AND HEALTH Most genetic disorders are due to a deficiency in enzyme function. This archival photo shows three children with the enzyme deficiency that causes phenylketonuria.

What is it? Phenylketonuria (PKU) is a hereditary disease that is caused by the lack of a liver enzyme required to digest phenylalanine. Phenylalanine is an amino acid that is most commonly found in protein-containing foods such as meat, cow's milk, over the counter infant formulas (both regular and soy) and breast milk. Signs & Symptoms Newborns affected by PKU usually do not show any signs of the disease at birth. But within the first few weeks of life they begin to show neurologic disturbances such as epilepsy. Signs also include skeletal changes such as a small head, short stature, and flat feet. PKU sufferers may also have a skin disorder called eczema. Long Term Effects PKU-affected children who are not diagnosed and do not eliminate phenylalanine from the diet will suffer from irreversible brain damage and mental retardation. Properly treated individuals should live a normal, healthy life. Treatment Treatment of PKU is the elimination of phenylalanine from the diet. Phenylalanine is commonly found in protein-containing foods such as meat. Babies who are diagnosed with PKU must immediately be put on a special milk/formula substitute. Later in life, the diet is mainly vegetarian.

 A phenylketonuria (PKU) test is done to check whether a newborn baby has the enzyme needed to use phenylalanine in his or her body. Phenylalanine is an amino acid that is needed for normal growth and development. If a baby's body does not have the enzyme that changes phenylalanine into another amino acid called tyrosine, the phenylalanine level builds up in the baby's blood and can cause brain damage, seizures, and mental deficiencies.phenylketonuria (PKU)

Enzyme Activity is Often Regulated Feedback inhibition - a common form of enzyme regulation in which the product inhibits the enzyme.

 Temperature and pH effect enzyme action

 Enzyme and substrate concentrations