Chapter eight: introduction of metabolism

Q1: what is metabolism?

A1: The totality of an organism’s chemical processes.

Q2: how does metabolism work in living things?

A2: catabolic and anabolic pathway that release or gain energy.

Q3: what is energy?

A3: the ability of work

Five Facts:

1. an organism's metabolism transforms matter and energy, subject to the laws of thermodynamics.

2. the free-energy change of a reaction tells us whether or not the reaction occurs spontaneously

3. ATP powers cellular work by coupling exergonic reactions to endergonic reactions

4. enzymes speed up metabolic reactions by lowering energy barries

5. regulation of enzyme activity helps control metabolism

Figure

if the reaction goes from higher free energy to lower free energy, there will be a negative ΔG, and the reaction will be spontaneous. However, if the reactants have a lower ΔG than the products, there will be an increase in free energy, and the reaction is nonspontaneous. In this situation, some form of energy (in the form of heat, light, etc.) will be required for the reaction to take place. It should be noted that a spontaneous reaction will not necessarily occur on its own. This is because an initial activation energy is needed in order to start the reaction and thus even a spontaneous reaction may need some form of energy input. A good example of this is the very exergonic combustion of octane, which still needs a flame in order to initiate.

Summary:

Metabolism is the totality of an organism’s chemical processes, concerned with managing the material and energy resources of the cell.A metabolic pathway begins with a specific molecule, which is then altered in a series of defined step, resulting ina centain product. Catabolic pathway is breakdown pathway. Anabolic pathways consume energy to build complicated molecules from ones. Also called biosynthetic pathway. energy released from the downhill reactions of catabolic pathways can be stored and then used to drive the uphill reactions of anabolic pathways.

Kinetic energy is energy of motion. Potential energy is stored enegy or th ecapacity to work. Activation energy needed to convert potential energy into kinetic energy. The study of the energy transformation that occur in a collection of matter is called thermodynamics: 1)Energy can be transferred and transformed, but it cannot be created or destroyed.2)Each energy transfer or transformation increases the entropy of the universe.Entropy is the measure of disorder. Free energy is the portion of a system's energy that can perform work when temperature and pressure are uniform throughout the system. If the system has more free energy, it is less stable, it has greater work capacity. Exergonic reaction is chemical reactions with a net release of free energy. Endergonic: chemical reactions that absorb free energy from the surroundings. Living cell is not in equilibrium. ATP contains sugar ribose, adenine, and three phosphate groups. Atp can be broken by hudrolysis. Energy released from ATP drives anabolic reactions.Energy from catabolic reactions “recharges” ATP. enzymes cause rate of a chemical reaction to increase and lower the activation energy for a chemical reaction to take place. environment, cofactors, coenzymes, and inhibitor are some factors can effect enzyme.

Key Terms:

1. active site-The specific portion of an enzyme that binds the substrate by means of multiple weak interactions and that forms the pocket in which catalysis occurs.
2. allosteric regulation-The binding of a regulatory molecule to a protein at one site that affects the function of the protein at a different site.
3. catalyst-A chemical agent that increases the rate of a reaction without being consumed by the reaction.
4. coenzyme-An organic molecule serving as a cofactor. Most vitamins function as coenzymes in metabolic reactions.
5. cofactor-Any nonprotein molecule or ion that is required for the proper functioning of an enzyme. Cofactors can be permanently bound to the active site or may bind loosely with the substrate during catalysis.
6. competitive inhibitor-A substance that reduces the activity of an enzyme by entering the active site in place of the substrate whose structure it mimics.
7. feedback inhibition-A method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.
8. induced fit-Induced by entry of the substrate, the change in shape of the active site of an enzyme so that it binds more snugly to the substrate
9. noncompetitive inhibitor-A substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing the enzyme’s shape so that the active site no longer functions effectively
10. bioenergetics-(1) The overall flow and transformation of energy in an organism. (2) The study of how energy flows through organisms.

Video:

http://www.youtube.com/watch?v=V4OPO6JQLOE

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