Ch 12: Anabolism The Use of Energy in Biosynthesis
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76 Terms
What is anabolism?
Metabolic pathways that build complex molecules (e.g., proteins, lipids) using energy
How does anabolism differ from catabolism?
Anabolism consumes energy (ATP/NADPH) to build molecules; catabolism breaks molecules to release energy (ATP/NADH)
Why are catabolic and anabolic pathways not identical?
To avoid futile cycles; they may share enzymes but are regulated separately and occur in different compartments
What are precursor metabolites?
Small molecules (e.g., pyruvate, acetyl-CoA) from central metabolism used in biosynthesis.
What are the two major CO₂ fixation pathways?
Calvin-Benson cycle (plants/cyanobacteria) and reductive TCA cycle (anaerobes)
Where does the Calvin cycle occur in eukaryotes vs. cyanobacteria?
Eukaryotes: chloroplast stroma; Cyanobacteria: carboxysomes
What enzyme fixes CO₂ in the Calvin cycle?
RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase)
How many ATP/NADPH are needed per CO₂ in the Calvin cycle?
3 ATP + 2 NADPH per CO₂ (18 ATP + 12 NADPH per glucose)
What is the output of the reductive TCA cycle?
Oxaloacetate (from 4 CO₂)
How does gluconeogenesis differ from glycolysis?
Synthesizes glucose from non-carbohydrate precursors and uses unique enzymes; glycolysis breaks down glucose into pyruvate.
Name pacemaker enzymes in glycolysis.
Hexokinase
Name pacemaker enzymes in gluconeogenesis.
Pyruvate carboxylase
Why can't glycolysis and gluconeogenesis occur simultaneously?
Futile cycles waste energy; reciprocal regulation prevents this
What is UDP-glucose (UDP-G)?
An activated form of glucose used in glycogen and peptidoglycan biosynthesis.
How is NAM-pentapeptide synthesized?
UDP-NAM gains 3 amino acids → binds bactoprenol → forms Lipid II with NAG → incorporated into peptidoglycan
What is bactoprenol's role?
Lipid carrier that transports NAM-NAG subunits across the membrane for peptidoglycan synthesis
Rank the nitrogen sources from most reduced to most oxidized.
NH₃ (or R-NH₂) < N₂ < NO₂⁻ < NO₃⁻
What is nitrogen fixation?
The conversion of atmospheric nitrogen gas (N₂) into ammonia (NH₃) by the enzyme nitrogenase, requiring 16 ATP and 8 electrons.
How is ammonia incorporated at high vs. low concentrations?
High NH₃: GDH (no ATP); Low NH₃: GS-GOGAT (ATP needed)
How is sulfate (SO₄²⁻) assimilated?
SO₄²⁻ → PAPS → H₂S → cysteine (for amino acids/coenzymes)
Which amino acids contain sulfur?
Cysteine and methionine
What precursor makes lysine and threonine?
Aspartate is the precursor for lysine and threonine.
How are aromatic amino acids (Trp, Phe...) made?
From chorismate, which is synthesized from E4P and PEP.
How is biosynthesis regulated?
By feedback inhibition, allosteric regulation, and gene expression to prevent waste and maintain balance.
Purine vs. pyrimidine synthesis: key differences?
Purines: built on ribose 5-P; Pyrimidines: bases built first. Purines need folic acid/glutamine
How is deoxyribose made?
From ribonucleotides by ribonucleotide reductase using thioredoxin.
What converts U → T?
Methylation of uracil (in dUMP) to form thymine (in dTMP) by folate derivatives.
How do bacterial/eukaryotic lipids differ from archaeal lipids?
Bacteria/Eukaryotes: fatty acids (acetyl-CoA → malonyl-CoA). Archaea: isoprenoids (IPP/DMAPP)
What is LPS made of?
Lipid A (endotoxin)
How is LPS synthesized?
UDP-NAG → KDO → bactoprenol → transported via Lpt proteins
What does nitrogenase require?
Mo/Fe cofactors
What is thioredoxin's role?
Reduces ribonucleotides to deoxyribonucleotides
Assimilatory vs. dissimilatory pathways?
Assimilatory: incorporate S/N into biomass; Dissimilatory: use S/N as terminal electron acceptors
True or False: Phosphorous is needed for nucleotide synthesis.
True (inorganic phosphate → ATP → nucleotides)
What provides the energy for anabolic pathways?
Energy from catabolism (ATP and NADPH)
What is meant by enzymes doing 'double duty'?
Some enzymes function in both catabolic and anabolic reactions
Where do most precursor metabolites come from?
Central metabolic pathways such as glycolysis
What are precursor metabolites used for?
To synthesize amino acids
What are three other carbon fixation pathways (besides Calvin and rTCA)?
The 3-hydroxypropionate cycle, 3-hydroxypropionate/4-hydroxybutyrate cycle, and the reductive acetyl-CoA (Wood–Ljungdahl) pathway.
Are glycolysis and gluconeogenesis identical but reversed?
No
What is a branching pathway in amino acid biosynthesis?
A pathway where one precursor (e.g., aspartate) gives rise to multiple amino acids (e.g., lysine, methionine, threonine).
Which two molecules form chorismate?
Erythrose-4-phosphate (E4P) + Phosphoenolpyruvate (PEP)
What is the role of periplasmic phosphatases in phosphorus assimilation?
They hydrolyze organic phosphate groups in the environment to release Pi
Where are phosphate-assimilating enzymes located in Gram-negative bacteria?
In the periplasmic space
What is required for bacterial/eukaryotic fatty acid synthesis?
Acetyl-CoA
What building blocks are used in archaeal lipids?
Isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP)
What are the two LPS synthesis branches?
Lipid A-core (UDP-NAG → KDO) and O-antigen polymerization; both transported via Lpt proteins.
What is feedback inhibition in amino acid biosynthesis?
End-products inhibit their own biosynthetic pathways to prevent overproduction
How do aerobic vs anaerobic organisms make unsaturated fatty acids?
Aerobes: NADPH + O₂ → H₂O; Anaerobes: dehydrate hydroxyl fatty acids
How is LPS transported from the inner to the outer membrane?
Via Lpt proteins after synthesis in the cytoplasm
What amino acids can be made from α-ketoglutarate?
Glutamate
What are the two major branches of lipid biosynthesis?
Synthesis of triacylglycerol and phospholipids
What is the first phase of the Calvin cycle?
Carboxylation – CO₂ is fixed by RuBisCO to form 3-phosphoglycerate (3-PGA)
What is the second phase of the Calvin cycle?
Reduction – 3-PGA is reduced to glyceraldehyde-3-phosphate (G3P) using ATP and NADPH.
What is the third phase of the Calvin cycle?
Regeneration – RuBP is regenerated from G3P using ATP to continue the cycle.
What are the precursor metabolites from Glycolysis?
G6P, F6P, G3P, 3-PGA, PEP, pyruvate
What are the precursor metabolites fom PPP?
ribose-5P, erythrose-4P
What are the precursor metabolites from TCA?
acetyl-CoA, α-ketoglutarate, oxaloacetate, succinyl-CoA
What is an amphibolic pathway?
A pathway that functions in both catabolism and anabolism, like the TCA cycle or glycolysis.