Term
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Definition
| The breakdown of energy containing nutrients into energy depleted nutrients, and generation of energy (ATP) and reducing equivalents in the process |
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Term
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Definition
| The expenditure of energy harvested from catabolism to convert precursor molecules into cell macromolecules |
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Term
| What are the three types of nonlinear metabolic pathways and which does anabolism and catabolism fall under? |
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Definition
1. Converging
2. Cyclic
3. Diversing
Anabolism is diverging
Catabolism is converging |
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Term
| What is meant by "metabolic pathways are interconnected" |
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Definition
| A metabolic pathway cannot be thought of as existing in isolation. Changes in one pathways will have widespread effects on both other metabolic pathways and the overall homeostasis of an organism |
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Term
| What are the six key reactions that can occur in metabolic pathways? |
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Definition
1. Redox - electron transfer
2. Ligation - Formation of covalent bonds
3. Isomerization - Rearrangement of atoms to isomers
4. Group transfer - transfer of a functional group from one molecule to another
5. Hydrolytic - cleavage of bonds by addition of water
6. Addition/removal of function groups - addition to double bonds or removal to make double bonds |
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Term
| What type of molecules are the precursors for many of the essential activated carriers in metabolism |
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Definition
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Term
| Why are metabolic pathways irreversible? |
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Definition
1. The simultaneous occurrence of anabolism and catabolism would be energy-wasteful
2. Catabolic and anabolic pathways that connect the same two endpoints must have at least 1 different enzyme step then the alternative path, and this serves as regulation
3. Matabolic pathways have one or more highly endergonic steps that make them irreversible |
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Term
| What is meant by a committed step in a metabolic pathway? |
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Definition
| A step that commits the product of the reaction to continue down the pathway to completion. It is usually the rate limiting step as well |
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Term
| How are metabolic pathways regulated? |
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Definition
| Usually through controlling the rate of the rate limiting step through altering the activity of the enzyme catalyzing the reaction |
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Term
| What is product inhibition? |
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Definition
| The product of a reaction inhibits enzyme activity, preventing its further production |
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Term
| What is feedback inhibition? |
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Definition
| The final product in a series of reactions alters activity at its branch point |
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Term
| Describe the different mechanisms for regulating enzymes (we discussed 6 total in this lecture) |
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Definition
1. isoforms - different isoforms of an enzyme in different locations of the body have different chemical properties
2. Substrate concentrations - most pathway reactions operate at equilibrium to altering substrate concentrations is a good way to regulate enzyme activity
3. Product inhibition - Product of a reaction inhibits the enzyme
4. Allosteric regulation - binding of an effector molecule to a site on the enzyme altering its ability to catalyze reactions
5. covalent modification - covalently adding another group to an enzyme (PRK-2 for example)
6. Change in enzyme concentration - Induction, repression, sequestration, degradation |
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Term
| How does cAMP activate Protein Kinase A and what type of enzyme regulation does this perform? |
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Definition
1. cAMP binds to regulatory subunits of cAMP-dependent protein kinase
2. Active catalytic subunits are released from the complex
The catalytic units are capable of covalent modification by phosphorylation |
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Term
| What is energy charge and what is it used as an estimate of? |
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Definition
Energy charge = ( [ATP] + 0.5[ADP]) / ( [ATP] + [ADP] + [AMP ] )
It is a measure of the high energy bonds in a cell
When energy charge is high, anabolism dominates activity, when it is low, catabolism dominates |
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Term
| What is meant by metabolic pathways are compartmentalized? |
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Definition
| Within cells, metabolic reactions only occur in certain, specific locations (ex. cytosol or mitochondria) |
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