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.

http://www. cc. gatech. edu/~turk/bio_sim/articles/metabolic_pathways http://www.cc.gatech.edu/~turk/bio_sim/articles/metabolic_pathways.png

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.

1st 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”

2nd 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 oK 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 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: Food: Renewable energy resource. Unstable bonds 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 1st 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 C6H12O6 + 6 O2 6 CO2 + 6 H2O + 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 CO2 + 6 H2O + Sunlight C6H12O6 + 6 O2

Fig. 5.3

Fig. 5.4

Cellular Respiration Animations Glycolysis http://www. science. smith Cellular Respiration Animations Glycolysis http://www.science.smith.edu/departments/Biology/Bio231/glycolysis.html Krebs Cycle http://www.science.smith.edu/departments/Biology/Bio231/krebs.html Electron Transport Chain http://www.science.smith.edu/departments/Biology/Bio231/etc.html

Photosynthesis Animations Light Dependent Reactions http://www.science.smith.edu/departments/Biology/Bio231/ltrxn.html Calvin Cycle http://www.science.smith.edu/departments/Biology/Bio231/calvin.html