NOTES FOR BIOLOGY 1201

Section 001

Spring 2005

DR. STEVEN POMARICO

Bioenergetics: The Laws of Thermodynamics - 2.8.1

>>>>>The chemistry of life is organized into metabolic pathways

---Metabolism

-Uptake of matter and energy

-Conversion to usable form

-Synthesis of cellular materials

-Elimination of waste products

Two types of metabolic pathways:

Catabolic pathways and anabolic pathways

---Catabolism

-degradation, releases energy

---Anabolism

-synthesis, consumes energy

>>>>>Organisms transfer energy

---Energy

Review types of energy

---Potential energy

---Kinetic energy

>>>>>Energy transfers are subject to the laws of thermodynamics

---First Law of Thermodynamics

---Second Law of Thermodynamics

---Entropy (S)

Thermodynamics can determine whether or not a chemical reaction will occur in the cell, and how much energy it will consume or release

>>>>>Free energy and spontaneous reactions

---Free energy (G)

---Total energy (H)

G = H - TS

In a chemical reaction the energy change (ΔG) between the reactants and the products is the amount of useable energy that can be harvested to do work.

ΔG = ΔH - TΔS = G_{final products} - G_{starting material}

>>>>>Free energy and chemical equilibrium

-As a chemical reaction approaches equilibrium the free energy (ΔG) of the system decreases.

-When a reaction is pushed away from equilibrium, the free energy (ΔG) of the system increases.

-At chemical equilibrium, ΔG=0. When ΔG=0 no work can be done.

Free energy and Metabolism

---Exergonic reactions

---Endergonic reactions

EXERGONIC REACTIONS	ENDERGONIC REACTIONS
Chemical products have less free energy than the reactant molecules	Products store more free energy than reactants.
Reaction is energetically downhill	Reaction is energetically uphill
Spontaneous reaction	Non-spontaneous reaction (requires an energy source)
ΔG is negative	ΔG is positive
-ΔG is the maximum amount of work the reaction can perform	+ΔG is the minimum amount of work the reaction requires to occur.

-Metabolic disequilibrium

-Many biological reactions are reversible; therefore they have the possibility of reaching equilibrium.

-However, in the cell the chemical reactions are kept from reaching equilibrium because the products of one reaction are the reactants for another reaction.

-The linking of chemical reactions makes up metabolic pathways and results in metabolic disequilibrium.

-In a cell when equilibrium is reached, the cell is dead.

Activation Energy - 2.8.2

>>>>>Enzymes speed up metabolic reactions by lowering energy barriers

---Catalyst

---Enzymes

---Activation energy

---Transition state

---Energy profile of a reaction

Enzyme Characteristics - 2.8.3

Enzyme Action: The Induced-Fit Model - 2.91

>>>>>Enzymes are substrate-specific

---Substrate

---Active site

---Induced fit

>>>>>Enzymes active site is a catalytic center

---Steps in the catalytic cycle of enzymes

>>>>>A cell’s chemical and physical environment affects enzyme activity

---Effect of temperature and pH

---Cofactors

---Coenzymes

Enzyme Regulation: Allosteric Regulation - 2.9.2

Feedback Inhibition and Cooperativity 2.9.3

>>>>>Enzyme inhibitors

---Competitive inhibitors

---Noncompetitive

>>>>>Metabolic order of the cell’s regulatory systems and structure

---Feedback inhibition

ATP Structure and Function - 4.1.1

>>>>>ATP powers cellular work by coupling exergonic reactions to endergonic reactions

The Structure and Hydrolysis of ATP

---ATP (Adenosine Triphosphate)

Types of work driven by ATP

1. Mechanical work

2. Transport work

3. Chemical work

Phosphorylated Intermediates - 4.1.2

>>>>>How does ATP drive work?

-Phosphorylated or activated intermediates

>>>>>ATP is continually regenerated