Chapter 15: Metabolism Flashcards
3 Stages of generation from food
- Large molecules in food broken down into smaller molecules by digestion (no useful energy yet)
- Small molecules are processed into key molecules of metabolism (small amount of ATP)
- ATP is produced from complete oxidation (lot of ATP)
Why living organisms need free energy?
- Performance of mechanical work
- Active transport
- Synthesis of macromolecules and other biomolecules
Catabolism
Large molecules broken down to smaller molecules
Release energy, exergonic
Usually involved in oxidation
Anabolism
Small molecules react to give rise to larger ones
Requires energy, endergonic
Usually involved in reduction
△G under set of conditions depend on
- value of △G°
- concentration of reactants and products
Criteria for constructing metabolic pathways
- Individual reactions must be specific
- pathway in total must be thermodynamically favorable
How do thermodynamically unfavorable reactions become favorable?
By coupling reactions that are more favorable
ATP Hydrolysis
ATP + H20 –> ADP + Pi
Proces is exergonic
△G°= -30.5 kJ/ mol
ATP (Adenine Triphosphate)
Universaly currency of free energy
Energy derived from light of fuels is converted into ATP
Great intermediate for carrier of phosphoryl groups
Rank stability of ATP, AMP, ADP from least stable to most stable
ATP ( - 4) –> ADP (-3) –> AMP (-2)
Why is ATP least stable between AMP and ADP?
Has 4 negative charges and electrostatic repulsion
Phosphate transfer potential
Standard free energy of hydrolysis
Means of comparing tendency of organic molecules to transfer a phosphoryl group to an acceptor molecule
4 Key Factors why ATP has high phosphoryl transfer potential
- Charge repulsion: 4 Negative charges in close proximity
- Resonance stabilization: free Pi has greater resonance stabilization than any of phosphates in ATP
- Increase in entropy: when one molecule of ATP –> ADP + Pi
- Stabilization by hydration: ATP hydrolysis are more effectively stabilized by association with water than ATP
ATP Synthesis
ADP + Pi –> ATP + H20
Requires energy for catabolism
Endergonic
The more reduced a carbon, the more _____ is released by its oxidation
free energy
More energy of carbon molecules is:
Higher △G°
More CH bonds
More energy released
Less reduced
Less energy of carbon molecules is:
Lower △G°
Less CH bonds
More energy released
More reduced
ATP Synthesis Couple with Carbon Oxidation
- Essence of catabolism is capturing energy of CO2 as ATP
- the energy that is released when Carbon that is oxidized to CO2 is used to regenerate ATP from ADP and Pi
- Energy of oxidation is initially trapped as high phosphoryl transfer potential compound
Activated Carriers
Small molecule carrying activated functional groups that can be donated to another molecule
Compounds that have high phosphoryl transfer potential
- Phosphoenol pyruvate (PEP)
- 1,3 Biphophoglycerate (1, 3 BPG)
- Creatine phosphate
Will donate phosphate to ADP for ADP to phosphate ATP
Activated Carrier characteristics
- carriers that are kinetically stable in absence of specific catalysts
- metabolsim of activated groups is accomplished with small number of carriers
NAD+ reduced to NADH
Gain of e-
Nicotinamide ring accepts a hydrogen ion and 2 electrons
ATP is activated carrier of
phosphoryl groups
NAD+
Universal oxidizing agent for catabolsim as it picks up electrons during oxidatin of food
NAD+ and FAD are activated carriers of
carry electrons from oxidation of fuels
NADH
- After receiving electrons, acts as activator carrier to electron transfer chain and regenerate to NAD+
- Cofactor for many enzymes that catalyze redox reactions
Redox dehydrogenation Reaction
Oxidation and Reduction happen at same time
Use enzyme dehydrogenase
The electrons are carried by ____ componet of FAD and FADh2
Isoalloxazine Ring
Coenzyme A
Activated carrier of acyl groups
Transfer of acyl group is exergonic because thioester is unstable
Biotin (B7)
Activated carrier of CO2
Coenzyme: Biotine lysine adducts
ATP dependent carboxylation and carboxyl group transfer
Many activated carriers are derived from
Vitamins
Riboflavin (B2 Vitamin)
Coenzyme: FAD
Oxidation Reduction rxn
Whichvitamin functrions as coenzymes
B Vitamins
Nicotinic Acid (niacin, B3)
Coenzyme: NAD+
oxidation reduction rxn
Pantothenic acid (B5)
Coenzyme A
Acyl group transfer
Metabolic Processes/ Homeostatsis is regulated by:
- Amount of enzymes present: regulated by gene level transcription
- Catalytic activity of enzymes: regulated allosterically or by reversible covalent modification, hormones cordinate metabolic activity
- Accessibility of substrates
Energy Status
Important regulator of enzyme activity
2 ways to assess energy status:
- energy change
- phosphorylation potential
Energy change formula
[ATP] + 1/2 [ADP] / [ATP] + [ADP] + [AMP]
Phosphorylation formula
[ATP] / [ADP] + [Pi]
