Unit 3.5 (metabolism) Flashcards
What is Metabolism? (overview)
The overall process by which living organisms acquire and utilize the free energy they need to carry out their various functions
What are metabolites?
Small molecule intermediates in the degradation and synthesis of biopolymers
What 2 processes does metabolism consist of?
Catabolism: Degradative pathways (exergonic oxidation)
Anabolism: Biosynthetic pathways (endergonic processes)
What kind of end products does catabolism result in? What about anabolism?
Catabolic pathways converge to a few end products (The energy released is preserved in compounds such as ATP)
Anabolic pathways use a few substrates and diverge to synthesize many biomolecules
What is an amphibolic pathway?
Pathway that serves in both catabolism and anabolism
What are the roles of NADH and NADPH in metabolism?
NADH - Supports ATP synthesis
NADPH - Used for anabolism
What is a metabolic pathway? (general overview)
A series of consecutive enzymatic reactions that produce specific products (~4000 metabolic reactions occurring in a typical cell)
Are metabolic pathways reversible?
No, metabolic pathways are irreversible (overall), but have reversibility of some individual steps
What is significant about the first step in a metabolic pathway?
Highly Exergonic (very favorable … highly committal …. cannot go back!)
Thus, this is a regulation/control point (rate-determining step)
At what points in a metabolic pathway is control available?
Any step with a very large, negative deltaG (very favorable!)
Can the process of a metabolic pathway be “undone”, even if the pathway is irreversible
What are the 2 kinds of negative feedback present in metabolic pathways?
(1) Feedback Inhibition: The product (often end product) of a metabolic pathway inhibits an enzyme further upstream in the pathway (often the first enzyme)
(2) Product Inhibition: (a subset of feedback inhibition) the product of an enzyme cat. reaction binds to the enzyme, inhibiting its activity
Define Feed Forward Activation
A metabolite early in a metabolic pathway activates an enzyme further down the pathway
What are the central reactions of metabolism? (2)
(1) Glycolysis
(2) Citric Acid Cycle (TCA)
What is the overall strategy of Metabolism?
To harness chemical energy (!) stored in C-H, C-C, and C-OH bonds!
Cells can use the energy generated from oxidizing carbon (with O2) to do work/make ATP
How much energy is stored in the bonds of fatty acids from a triacylglycerol? What about from glucose?
Where is energy primarily stored in ATP?
In the phosphoanhydride bonds (-30.5 kJ/mol of energy per phosphoanhydride bond broken)
Explain the 3 factors that contribute to the release of energy when ATP is hydrolyzed
(1) Relieves electrostatic repulsion
(2) The Pi (inorganic phosphate) released by hydrolysis has better resonance stabilization than it had on ATP
(3) Greater degree of solvation of products further stabilizes
What is the deltaG°’ of the first Phosphate bond broken off of ATP (energy release)
-30.5 kJ/mol
Why is it significant that Free Energies (G) are additive?
Describe Phosphate Transfer Potential. What is the cutoff in kJ/mol for an energy rich compound vs. an energy poor compound? How can these two different kinds of compounds interact?
Describe (in detail) Substrate-Level Phosphorylation
Coupled Reaction
What five high energy compounds drive the formation of ATP by substrate level phosphorylation?
(1) Acetyl Phosphate
(2) 1,3-BPG
(3) PEP (the GOAT)
(4) Phosphocreatine
(5) Thioesters
Describe (in detail) how Acyl Phosphates and 1,3-BPG can be used to make ATP
Describe (in detail!!!!) the mechanism that PEP (the GOAT) undergoes to help make ATP by substrate-level phosphorylation
Describe (in detail) how Phosphocreatine can be used to make ATP
Describe how Thioesters (ex. Acetyl CoA) can be used to make ATP
Explain what it means for free energy changes to be concentration dependent
Explain (in detail) how NADH and FADH2 can be used to make ATP via oxidative phosphorylation
What is the general process for the Elucidation of Metabolic Pathways
(1) Sequences and Energetics
(2) Control Mechanisms (regulation)
(3) Enzymes mechanisms
Describe how Metabolic Inhibitors/Mutants can be used for figure out metabolic pathways
Describe how Pathway Labeling with Isotopes can be used to figure out metabolic pathways
