Metabolism 1 Flashcards
Semester 1 year 1
What is the first and second law of thermodynamics?
-1st law = energy cannot be created or destroyed
-2nd law = entropy always increases
What does metabolism involve?
-making things - anabolism
-breaking things down - catabolism
Are anabolic processes ender or exergonic?
-endergonic
-not spontaneous - +ΔG
Are many catabolic processes ender or exergonic?
-exergonic
-spontaneous - -ΔG
What are metabolic pathways?
A series of linked reactions usually involving a discrete enzyme at each step that catalyses the conversion of 1 molecule in the pathway to another
What must all metabolic pathway be?
-physically possible - all enzymes present + accessible
-thermodynamically likely - net -ive ΔG
-kinetically feasible
-shielded from unwanted side reactions
What are the benefits of metabolic pathways?
-make complex transformations kinetically possible
-allow multiple energy production sites by releasing free energy in manageable ‘packets’
-generate a diverse range of chemical structures
-allow a high level of control
Why do metabolic pathways allow for a higher level of control?
More steps = more potential control sites
What are the common features of metabolism?
-involves many common pathways shared by most living things
-has 6 basic types of reactions
-has common organisational paradigms - each reaction can be divided to different organelles
-involves a common set of regulatory principles
-involves use of common set of cofactors that evolved in RNA world
-uses ATP as an energy source
What are the 6 basic types of reaction?
-oxidation reduction
-ligation requiring ATP cleavage
-isomerisation
-group transfer
-hydrolytic
-addition or removal of functional groups
What happens in an oxidation reduction reaction?
Electron transfer
What happens in a ligation requiring ATP cleavage reaction?
Formation of covalent bonds
What happens in an isomerisation reaction?
Rearrangement of atoms to form isomers
What happens in a group transfer reaction?
Transfer of a functional group from 1 molecule to another
What happens in a hydrolytic reaction?
Cleave bonds by addition of water
What happens in an addition or removal of functional groups reaction?
Addition of functional groups to double bonds or their removal to form double bonds
What can common organisational paradigms have?
-physically separate, soluble enzymes with diffusing intermediates
-a multienzyme complex (metabolons) with substrate channels between them sequentially before product release
-a membrane bound multi-enzyme system
What are the benefits of having organisational paradigms?
-substrate channelling - substrate moved directly from enzyme of 1 active site to the next without releasing it into the bulk solution
-increases rate - effective conc. of enzymes + reactants are increased
-avoids unwanted side reactions + futile cycling
How can we discover and study different pathways?
-cell fractionation
-inhibitors
-radiotracers
-mutants
How can cell fractionation be used to study different pathways?
-homogenise tissue to break open cells
-density gradient ultracentrifugation
-test which components have particular enzyme activity of interest - localisation of pathways
How can inhibitors be used to study different pathways?
-specific compounds can be tested for inhibitive properties
-inhibited step identified due to build up of reactants
-inhibitors sometimes bind irreversibly to proteins, allowing enzyme to be identified
How can radiotracers be used to study different pathways?
-radioactive C14 can be converted to CO2
-can follow which plants incorporate the radioactive carbon into their molecules
How can mutants be used to study different pathways?
-specific genes knocked out, preventing synthesis of the protein it encodes
-allows the step catalysed by the protein to be identified as reactant builds up
How can energy be obtained from reduced carbon sources?
-reactions performed step wise - release energy from source in controlled way
-energy can be captured + stored in activator carrier molecules
-total free energy change the same in both routes
Describe the stability of C-H bonds compared to C-O and C=O bonds
Less stable
