Metabolism (Chapter 6)

Bioenergetics - energy flow in systems Metabolism = all the chemical reactions that take place within cells

Carbohydrates Breakdown of glucose (respiration) C6H12O6 + 6O2→ 6CO2 + 6H2O + energy Synthesis of glucose (photosynthesis) 6CO2 + 6H2O +energy → C6H12O6 + 6O2

Anabolic vs Catabolic Pathways

Potential vs Kinetic Energy Energy of position Energy of motion

Endergonic reactions require energy. (pushing a ball up a hill) Exergonic reactions release energy. (rolling a ball down a hill) Activation Energy = the energy required to start a chemical reaction.

First Law of Thermodynamics Second Law of Thermodynamics Energy can be transformed, but it can never be created or destroyed. Second Law of Thermodynamics The state of entropy of the entire universe will always increase over time. (Entropy is a measure of “randomness”)

Adenosine Triphosphate (ATP)

Enzymes - catalyze biochemical reactions Reactions occur faster and with less activation energy needed

Enzymes bind to substrates at the active site Induced fit model of enzyme function (also called the “lock and key” model

Properties of Enzymes: Enzymes are made of proteins. They are needed only in small amounts They remain unchanged after each reaction and can therefore be reused Each enzyme is specific for a substrate

Degradation vs Synthesis breaking down vs building

Biology Pro-Tip Most enzyme names end in the letters -ase The enzyme that breaks down sucrose is ….. SUCRASE The enzyme that breaks down lactose (milk sugar) is… LACTASE

Factors Affecting Enzymatic Speed 1. Substrate concentration 2. Temperature & pH * 3. Enzyme concentration Enzymes can be denatured - they change shape so much that they are no longer effective. High temp or pH can cause denaturation. 

Siamese cats have an enzyme that works at lower temperatures only, causing the nose and ears to become a darker color than the rest of the body.

Enzymatic Inhibition - when a substance binds to an enzyme and decreases its activity. (Usually reversible) Competitive Inhibition  Noncompetitive Inhibition (allosteric site) **Both are forms of feedback inhibition

Some inhibitors are NOT reversible - poisons like cyanide, lead poisoning all affect enzymes QUESTION: What type of inhibition is pictured below?

Feedback Inhibition

Enzyme Lab(s) 2H2O2 --------> 2H2O + O2 Hydrogen Peroxide is broken down by the enzyme: catalase within cells.    To determine the speed of a reaction you can either A) measure the amount of products produces (oxygen) B) measure the amount of substrate (hydrogen peroxide) is left over when the reaction is stopped

The activity of catalase can be seen by the bubbling of oxygen during the reaction

Virtual Labs with Enzymes McGraw Hill Lab

Enzyme Animation (Tutorial) http://www.stolaf.edu/people/giannini/flashanimat/enzymes/prox-orien.swf Enzyme Quiz http://www.sciencegeek.net/Biology/review/U2Enzymes.htm