23 - Anabolism and regulation of metabolism Flashcards
Macromolecule
a very large molecule important to biophysical processes (e.g. protein or nucleic acid)
Gluconeogenesis
generation of glucose from non-carbohydrate carbon substrates (esp. pyruvate and lactate)
Amphibolic
biochemical pathway that involves both catabolism and anabolism
Central metabolic pathways
pathways that generate the 12 precursor
metabolites. Includes the glycolytic pathways (i.e. Embden-Meyerhof, Entner-Doudoroff, pentose phosphate) and the TCA cycle
Metabolic channeling
regulation of metabolic pathway activity by localising metabolites and enzymes to specific parts of a cell
Allosteric
regulation of an enzyme by binding an effector molecule (allosteric effector) at a site other than the enzyme’s active site
Feedback inhibition
enzyme inhibition by the end products of a pathway
Level of organisation
Inorganic molecules + carbon source –> precursor metabolites –> Monomers or building blocks –> macromoleucles –> supramolecular systems –> organelles –> cells
Macromolecule examples
Nucleic acids, proteins, polysaccharides, lipids
Anabolism
Synthesis of complex molecules from simple ones.
Turnover
non-growing cells degrade and replace (resynthesise) cellular constituents, requiring ATP
first 3 principles governing biosynthesis
- Macromolecules are synthesised from a limited number of simple structural units (monomers)
- Many enzymes are used for both catabolism and anabolic processes
- Some enzymes function in only one direction in amphibolic pathways
last 3 principles governing biosynthesis
- Anabolism consumes energy (endogonic)
- Anabolic and catabolic reactions can be physically separated
- Anabolic and catabolic reactions use different cofactors
12 precursor metabolites
building blocks of all molecules in cells.
they make up the majority of the intermediates of glycolsis and TCA cycle
termed the central metabolic
Macromolecules are synthesized from a limited number of simple structural units (monomers)
Saves genetic storage capacity, biosynthetic raw material, and energy
Many enzymes are used for both catalytic and
anabolic processes
Most enzymes involved in the glycolysis pathway that produces ATP from glucose are also involved in the gluconeogenesis. Saves materials and energy.
Some enzymes function in only one direction in amphibolic pathways
enables independent regulation of catabolism and anabolism by regulating the activity of pathway-specific enzymes
Anabolic and catabolic reactions can be physically separated
Biosynthesis and catabolic functions are
located in separate organelles (e.g. mitochondria, lysosomes, ER).
Allows some pathways to operate simultaneously but independently
Which cofactors do anabolic and catabolic pathways use
- Catabolism produces NADH (acts as an electron acceptor)
- Anabolism uses NADPH as an electron donor
What does NADPH stand for
nicotinamide adenine dinucleotide phosphate
name 3 Precursor metabolites
Glucose - 6, Ribose - 5, Pyruvate
What is regulation of metabolism important for
- Efficiency (conservation of energy and materials) e.g. no synthesis of enzymes for which no substrate is available or no synthesis of enzymes to produce end products already in abundance
- Maintenance of metabolic balance in response to external changes
3 major ways of metabolism regulation
- Metabolic channelling
- Regulation of gene expression
- Posttranslational regulation of enzyme activity
Metabolic channelling
- metabolic channeling is the physical separation of metabolic pathways in the cell
- compartmentalisation
- common way organisms separate and regulate pathways
-enables better control as key metabolites can be restricted or enhanced to affect the efficeint functioning of the pathway
Advantages of metabolic channelling*
- Facilitates separate operation and regulation of similar pathways
- Enables enhanced pathway control by regulation of delivery of key metabolites to the various compartments.
Regulation of gene expression
- Controls the synthesis of a particular enzyme
- Relatively slow, but conserves energy and the use of cellular materials
- Can occur at transcription or translation
Posttranslational regulation of enzyme activity
- Following synthesis of the enzyme
- Involves direct stimulation or inhibition of the activity of critical enzymes
Three important mechanisms of Posttranslational regulation of enzyme activity
- Allosteric regulation
- Covalent modification of enzymes
- Feedback inhibition
Allosteric regulation
Allosteric effector binds non-covalently at regulatory site changing the shape of the enzyme and alters activity of the catalytic site.
Can be:
- Positive effector increases enzyme activity
- Negative effector inhibits the enzyme
Covalent modification of enzymes
- Covalent bonding of a chemical group to the
enzyme affects its activity - Allows more sophisticated control (Regulation of the enzymes that catalyse the covalent modification adds a second level of control)
Feedback (end product) inhibition
- End products inhibit one or more critical enzymes in a pathway
- Each end product regulates its own branch of a branching pathway
- involves the “pacemaker” enzyme which
catalyses the slowest rate-limiting reaction
