Chapter #15: Introduction to Metabolism Flashcards
What is metabolism?
The processes used by cells to:
- Extract energy from fuels in the environment
- Synthesize complex organic molecules
What is catabolism?
- Extract energy from fuels in the environment
What is anabolism?
- Synthesize complex organic molecules
What is Stage I of Catabolism?
Large molecules of food are broken down into smaller units (digestion) Stage I was the focus of our last lecture: “Catabolism of Biomolecules”
What happens in Stage II of Catabolism?
Numerous small molecules are degraded to a few simple units central to metabolism (glycolysis)
What happens in Stage III of Catabolism?
ATP is produced from the complete oxidation of acetyl CoA
What do we need energy for?
- Physical work
- Synthesize molecules
- Active transport
active transport takes up to 40% of a cell’s energy usage
What is the formula used in metabolism for the reaction A + B → C + D
What is the hydrolysis of ATP?
- The hydrolysis of ATP is exergonic because the triphosphate unit contains two phosphoanhydride bonds that are unstable.
- The energy released on ATP hydrolysis is used to power a host of cellular functions – enzymes recognize it and it is used as the universal energy currency of the cell.
Why does ATP have a high phosphoryl-transfer potential?
- Charge repulsion.
-negative charges on P - Resonance stabilization.
-more resonance = more stability - Increase in entropy
-more molecules = more entropy - Stabilization by hydration.
-more H-bonds = more energy released
Describe endergonic reactions
Describe exergonic reactions
What is the net reaction for the hydrolysis of ATP
What is oxidation?
Loss of electrons
What is reduction?
gain of electrons
How do you find the oxidation state from a Lewis Structure?
- Start with the atom’s valence number (carbon = 4)
- Subtract from it the number of electrons that the carbon “owns”, (the more electronegative atom in the bond “owns” the electrons, or they each get 1 if the bond is comprised of two of the same atom)
- The larger the number, the larger the oxidation of that atom!
How is the oxidation of carbon fuels accomplished?
Carbon fuels are oxidized, and the energy released is used to regenerate ATP from ADP.
How is this accomplished?
1. Creation of compounds with high phosphor transfer potential
2. Creation of an H+ gradient to power ATP synthase
What is homeostasis?
Homeostasis, a stable biochemical environment, is maintained by careful regulation of biochemical processes.
What three regulatory controls are prominent in homeostasis?
- The amount of enzymes present. The quantity of enzyme present can be regulated at the level of gene transcription.
- The catalytic activity of enzymes. Catalytic activity is regulated allosterically or by covalent modification.
- The accessibility of substrates. Opposing reactions, such as fatty acid synthesis and degradation, may occur in different cellular compartments.
What is the take home message for the introduction to metabolism?
- Metabolism is a balance between catabolism (extracting energy from fuels in the environment) and anabolism (synthesizing complex organic molecules).
- Metabolic reactions are often a combination of favorable and unfavorable reactions to follow the law of thermodynamics.
- Unfavorable reaction requires energy provided by favorable reaction (G < 0), thus metabolism is a series of coupled reactions.
- The universal source of energy is ATP.
- Energy synthesis results from redox reactions and a proton gradient.
- The balance between catabolism and anabolism is called homeostasis, and maintains a dynamically stable environment.
