Chapter 8 An Introduction To Metabolism Metabolism All

Chapter 8 An Introduction To Metabolism

Metabolism • All the chemical reactions in an organism • Concerned with managing the matter and energy resources of the organism.

Catabolic Pathways • Pathways that break down complex molecules into smaller ones, releasing energy. • Example: Cellular Respiration

Anabolic Pathways • Pathways that consume energy, building complex molecules from smaller ones. • Example: Photosynthesis

Anabolic vs Catabolic

Energy • Ability to do work. • The ability to rearrange a collection of matter. • Forms of energy: • Kinetic • Potential • Activation

Kinetic Energy • Energy of action or motion.

Potential Energy • Stored energy • Can be in chemical bonds!

Activation Energy • Energy needed to convert potential energy into kinetic energy. Activation Energy Potential Energy

Energy Transformation • Governed by the Laws of Thermodynamics.

1 st Law of Thermodynamics • Energy can be transferred and transformed, but it CANNOT be created or destroyed. • Also known as the law of “Conservation of Energy”

2 nd Law of Thermodynamics • Each energy transfer or transformation increases the entropy of the universe.

Entropy • Measure of disorder. • High entropy = high disorder

Free Energy Changes

Question? • How does Life go against Entropy? • By using energy from the environment or external sources (e. g. food, light).

Summary • The quantity of energy in the universe is constant, but its quality is not.

Gibbs Free Energy • Free energy = The portion of a system's energy that can perform work. • “usable energy”

Free Energy of a reaction ΔG = ΔH – TΔS Δ = Change (final – initial) G = free energy of a system H = enthalpy = total energy of a system T = temperature in o. K S = entropy of a system

• Reactions will move from unstable states to stable states

Free Energy Changes

Reaction Types • Exergonic: chemical reactions with a net release of free energy. • ΔG = NEGATIVE VALUE • Spontaneous • catabolic • Endergonic: chemical reactions that require free energy from the surroundings. • ΔG = POSITIVE VALUE • Spontaneous • Anabolic

Biological Examples • Exergonic - respiration • Endergonic - photosynthesis

How does the cell perform endergonic reactions? • Couples an exergonic process to drive an endergonic one. • ATP is used to couple the reactions together.

ATP • Adenosine Triphosphate • Made of: - Adenine (nitrogenous base) - Ribose (pentose sugar) - 3 phosphate groups

Adenine Phosphates Ribose

Key to ATP • Is in the three phosphate groups. • Negative charges repel each other and makes the phosphates unstable.

ATP • Works by energizing other molecules by transferring phosphate groups.

ATP vs Food • ATP: • Renewable energy resource. • Unstable bonds • Food: • Long term energy storage • Stable bonds

ATP Cycles • Energy released from ATP drives endergonic reactions. • Energy from exergonic reactions “recharges” ATP.

ATP in Cells • A cell's ATP content is recycled every minute. • Humans use close to their body weight in ATP daily. • No ATP production equals quick death.

Enzymes • Biological catalysts made of protein. • Cause the rate of a chemical reaction to increase.

Enzymes • Lower the activation energy for a chemical reaction to take place.

free energy

Enzyme Terms • Substrate - the material and enzyme works on. • Enzyme names: Ex. Sucrase - ase name of an enzyme 1 st part tells what the substrate is. (Sucrose)

Control of Metabolism • Is necessary if life is to function. • Controlled by switching enzyme activity "off" or "on” or separating the enzymes in time or space.

Structural Order • Separation of enzymes and metabolic pathways in time or space by the cell's organization. • Example: enzymes of respiration

Summary • Recognize that Life must follow the Laws of Thermodynamics. • The role of ATP in cell energy. • How enzymes work.

Cellular Respiration and Photosynthesis • You will need to know the inputs and outputs of each reaction • Where is each reaction taking place • Understand what the “goal” of each reaction is • What is the role of the major molecules • Connect back to previous material (facilitated diffusion, active transport, exergonic, endergonic)

Rs - Equation C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + ATP The energy is released from the chemical bonds in the complex organic molecules.

Oxidation - definitions • Loss of electrons. • Loss of energy.

Reduction - definitions • Gain of electrons. • Gain of energy.

Photosynthesis Equation 6 CO 2 + 6 H 2 O + Sunlight 6 O 2 C 6 H 12 O 6 +

Fig. 5. 3

Fig. 5. 4

Cellular Respiration Animations Glycolysis http: //www. science. smith. edu/departments/Biology/Bio 231/glycolysis. html Krebs Cycle http: //www. science. smith. edu/departments/Biology/Bio 231/krebs. html Electron Transport Chain http: //www. science. smith. edu/departments/Biology/Bio 231/etc. html

Photosynthesis Animations Light Dependent Reactions http: //www. science. smith. edu/departments/Biology/Bio 231/ltrxn. html Calvin Cycle http: //www. science. smith. edu/departments/Biology/Bio 231/calvin. html