Lecture 24: Intro to Metabolsim Flashcards
living organisms require a continual input of free energy for 3 major purposes:
- mechanical work
- active transport of molecules and ions in/out of cells
- making biomolecules and their building blocks
what is metabolism?
highly integrated network of chemical pathways that enables a cells to get and use energy from the environment
phototrophs
get energy by capturing sunlight in its chemical form
chemotrophs
get energy by oxidation of carbon fuels
fuels are degraded and large molecules are made step by step in a series of linked reactions called ___
metabolic pathways
an energy currency common to all life-forms is ___ and links what 2 pathways?
ATP; energy-releasing and energy-requiring
____ powers the formation of ATP
oxidation of carbon fuels
t/f a limited number of types of reactions and intermediates are common to many pathways
true
metabolic pathways are highly regulated to allow __ and coordinate ___
efficient use of fuels; biosynthetic processes
what are the 2 major divisions of metabolism?
catabolism and anabolism
catabolism
process that breaks down fuels into cellular energy
anabolism
processes that use energy to make biomolecules
what are the 3 stages of a metabolic pathway?
- interconversion of polymers with monomeric intermediates
- interconversion of monomers with still simpler organic metabolic intermediates
- the ultimate degradation to or synthesis from inorganic compounds
metabolic pathways are __ -dependent
inter
metabolic pathways are regulated and controlled in 3 ways
- control enzyme amounts
- regulation of catalytic activities of many enzymes
- compartmentalization
how are the enzyme amounts controlled?
regulation of the rate of their synthesis and degradation
how is the regulation of catalytic activities achieved?
by allosteric interactions and by covalent modification
what is compartmentalization?
movement of many substrates into cells and sub cellular compartments
a pathway must satisfy 2 criteria:
- individual reactions are specific
2. the entire set of reactions must be thermodynamically favoured
how are individual reactions made specific?
specificity of enzymes
a thermodynamically unfavourable reaction can be driven by __
being coupled with a thermodynamically favourable reaction
delta G (free energy) depends on __ and ___ of the reactants
nature and concentration
t/f overall free energy change = sum of free energy changes for each step
true
ATP is energy rich because its triphosphate contains 2 __
phosphoanhydride linkages
an otherwise unfavourable reaction can be made possible by coupling to __
ATP hydrolysis
t/f ATP shifts equilibrium. of coupled reactions
true
amount of ATP in the body __ and amount used daily__
250g; 60-80 kg
ATP and ADP differ due to 4 factors that make ATP an efficient energy currency
- electrostatic repulsion (ATP has 4- charge resulting in repulsion, reduced by creating ADP)
- resonance stabilization of othrophosphate
- increase entropy of the products
- stabilization due to hydration of ADP and Pi (makes reverse rxn less likely)
t/f there is no special reason why ATP is used and not other NTPs, they all have ~ the same delta G, cells have just evolved to use ATP
true
t/F ATP is typically in higher concentrations in the cell than other NTPs
true
carbon fuels are mainly __
glucose and fats
t/f there is considerable energy released by the conversion of glucose to CO2
true
in the catabolism of glucose under aerobic conditions, 3 pathways occur
- glycolysis
- pyruvate oxidation
- critic acid cycle
glycolysis converts ___ to ___
1 glucose to 2 pyruvate
pyruvate oxidation converts ___ to __ and __
2 pyruvate to 2 acetyl CoA and 2 CO2
the citric acid cycle converts ___ to __
2 acetyl CoA to 4 CO2
carbon oxidation is paired with __
reduction
in aerobic oxidation of carbon fuels into CO2, electrons are removed from __ and passed to __
carbon to O2
t/f the more reduced a carbon is to begin with, the more free energy it will release when oxidized
true
why are fats a more efficient fuel source than carbohydrates?
because the carbons are more reduced to begin with and will release more energy when oxidized
what is an activated carrier?
a small molecule carrying activated functional groups that can be donated to another molecule
what are 3 examples of activated carriers in metabolism?
ATP, NADH and acetyl CoA
the reactions that activated carriers participate in are always enzyme catalyzed
true
many activated carriers function as ___ and are derived from vitamins
co-enzymes
