Introduction to Metabolism Flashcards
What is metabolism?
The sum of all of the chemical transformations taking place in an organism.
How does metabolism take place?
occurs through series of enzyme-catalyzed reactions that constitute metabolic pathways
What is intermediary metabolism?
the combined activities of all the metabolic pathways
What is a metabolite?
products of low molecular weight
What is the difference between Anabolism and catabolism?
Anabolism- building of large molecules from small ones- energy requiring
Catabolism- breakdown of large molecules to small ones- energy producing
How are anabolic and catabolic reactions linked?
a limited set of energy carriers;
ATP, NADH, NADPH, FADH2
What is ATP?
intermediate in the flow of energy
used for multiple energy-requiring processes (those with + delta G)
ATP drives non-spontaneous reactions by coupling them with the hydrolysis of ATP to make the reaction spontaneous
How does ATP hydrolysis result in a large free-energy change?
- hydrolysis with relief of charge repulsion
- resonance stabilization ** (3- charge)
- ionization
Does the concentration of ATP change?
The concentration remains the same and is not stored
What are NAD and NADP?
soluble electron carriers, derived from niacin
NADH- mostly used for ATP synthesis
NADPH- mostly used in anabolic pathways- generated in the pentose phosphate pathway
Act as coenzymes- bind only transiently to the enzyme
NAD vs. NADP
both present in cells in micro molar concentrations
NAD:
[NAD+]>NADH] involved in oxidative (catabolic) pathways
NADP:
[NADP+]<[NADPH] involved in reductive (anabolic) pathways
How does reduction of NAD+ to NADH occur?
NAD+ accepts a hydride ion (H-) to form NADH
What are some examples of NAD+ reduction?
lactate dehydrogenase:
lactate + NAD+ -> pyruvate + NADH + H+
NAD+ + 2H+ + 2e- –> NADH + H+
Two electrons and one proton/ hydride ion are transferred from lactate to NAD+ to form NADH, one proton released to the aqueous solvent
malate dehydrogenase
What is FAD and FMN?
protein bound electron carriers, derived from riboflavin
tightly to covalently bound to flavoproteins (prosthetic groups)
FADH2 and FMNH2 are the reduced forms
involved in numerous redox reactions
How does reduction of FAD and FMN occur? Give example
accepts two hydrogen atoms during reduction
succinate dehydrogenase reactions
