Introduction to Metabolism Energy & Enzymes

Ms. NapolitanoHonors Biology

11/22 – Do Now• Please get your clickers!• Think about and answer the following questions:

What is energy?

Why do we, as humans, need energy?

What are some different types of energy?

What is the 1st and 2nd Laws of Thermodynamics?

Metabolism

• Metabolism – total of all chemical reactions that take place within an organism• Metabolic/biochemical pathway – series of chemical

reactions, catalyzed by enzymes• The product of one reaction becomes the reactant of the

next reaction

Types of Metabolic Pathways

• Catabolic pathways – break down complex molecules into simpler molecules• E released

• Anabolic pathways – build complicated molecules from simpler molecules• E consumed

Physics Review

• Energy• Kinetic• Thermal• Potential• Chemical

• The Laws of Thermodynamics• 1st Law• 2nd Law

Chemical Reactions Absorb or Release Energy

• Exergonic reactions release free energy

• Activation Energy (Ea) is the E required to start the reaction

Chemical Reactions Absorb or Release Energy

• Identify A, B, C, D

• Endergonic reactions absorb free energy

Catalyst

• Catalyst – reduces the activation energy to speed up the chemical reaction

• Enzyme – catalytic protein• Specific substrate binds to active site on enzymes...

called induced fit• Enzymes reduce Ea• Reaction occurs, products are formed• Enzyme can be reused

Enzyme-Substrate Complex

Effect of Enzymes on Reaction Rate

External Factors can Affect Enzyme Activity

• Factors that affect enzyme shape will affect its function

•Different enzymes have different optimal conditions

Adenosine Triphosphate (ATP)• Unstable molecule

• E coupling uses exergonic process to power an endergonic process

• Mediates most E coupling by providing E to power cell work

• E coupled by transferring PO4

- to another molecule (phosphorylated)

Cofactors

• Cofactors – non-protein helpers that bind to enzymes• Inorganic vitamins• Ex: Zn, Cu, Fe

• Coenzymes – organic cofactors• Ex: Vitamins A, B12, C

Cofactors

Enzyme Inhibitors

• Inhibitors prevent an enzyme from catalyzing a reaction• Competitive inhibitors – block

substances from entering active sites• Noncompetitive Inhibitors –

bind to another part of the enzyme, causing the enzyme to change shape and become inactive• Regularly present to regulate

activity

Allosteric Regulation

• Allosteric Regulation – controls metabolic pathways, so they are not always “on” or always “off” in enzymes without quaternary structure• Activators – stabilize active site• Inhibitors – stabilize inactive form of active site

• Cooperativity – amplifies enzyme activity (allows additional substrate)

• Feedback inhibition – the product binds to an enzyme early in the metabolic pathway inhibiting the enzyme

The chemical equation for cellular respiration is:C6H12O6 + O2 CO2 + H2O + Energy

This is an example of an anabolic process. F

Which of the following statements is NOT correct?A metabolic pathway...A. Has an orderly sequence of reaction stepsB. Is mediated by only one enzyme that starts itC. May be anabolic or catabolicD. All of the above are incorrect

An enzyme...E. Is a proteinF. Lowers the activation energy of a reactionG. Is destroyed by the reaction it catalyzesH. 1 and 2

What happens to an enzyme when it denatures?A. The activation energy of the reaction is doubledB. The activation energy of the reaction is loweredC. It’s optimal conditions for temperature of the enzyme are

doubledD. The shape of the enzyme molecule is changed

The chemical equation for cellular respiration is:C6H12O6 + O2 CO2 + H2O + Energy

This is an example of an exergonic process. T