2nd test Flashcards
glycolysis
first step of respiration
starts with glucose ends with pyruvate and 2 molecules of ATP
Harden and Young
dialysis of yeast extract
small molecules diffuse out and big molecules stayed in bag (enzymes) - activity lost when molecules separate
zymaseis the large molecules inactivated by heat
co-zymase is the small molecules which are heat stable
add 2 molecules back together and activity restored so zymase needs cozymase to work
inorganic cofactors
organic
metal ions
NAD
FAD
ATP
respiration vs combustion
respiration is better because it has lots of steps so more controlled and can harvest energy easier
control points
usually at start of pathways
have large negative delta G so are physiologically irreversible
intermediates can be used in other pathways: Glucose-6-P
store E as glycogen and ribose-5-P for DNA and RNA synthesis
oxidation
electron transfer
ligation requiring ATP cleavage
formation of covalent bonds
isomerization
rearrangment of atoms to form isomers
group transfer
transfer of functional group from 1 molecule to another
hydrolytic
cleavage of bonds by addition of water
addition or removal of functional groups
to double bonds or removal from double bonds
major activated carriers: carry energy, electron, carbon
ATP NAD+ FAD NADPH CoA
react slowly in absence of enzymes
difference between NAD and NADP
derived from niacin/vitamin B3
both nicotinamide + ribose + adenosine (but different R groups in adenosine)
R group of NAD is hydrogen
R group of NADP is phosphate
FAD structure
derived from riboflavin/vitamin B2
in vitro approach
like the yeast extract bag
defined conditions and quantitative results
but loss of compartmentation and spatial and temporal organisation
instability of components
in vivo approach
measure process in vivo and modify it and measure results with assays/indicators/labelled compounds
modify with inhibitors/mutations/molecular methods
number of steps in glycolysis
key steps
10
investment (2ATP used)
payout (oxidation, 4ATP produced, 1NADH produced, require NAD- and Pi)
stoichiometry
of glycolysis
using relationships between reactants and/or products in a chemical reaction to determine desired quantitative data
glucose+2ADP+2Pi+2NAD^+ —-> 2 pyruvate + 2ATP+2NADH+2H^+ +2H20
Harden and Young reaction stopped but adding more substrate (sucrose) did nothing, needed to add inorganic phosphate so each part is a limiting factor
regeneration of NAD+
what about anaerobic?
in oxidative phosphorylation, under aerobic
fermentation: organic compounds act as electron donors and acceptors
glucose oxidised to pyruvate
no oxygen as final electron acceptor so pyruvate reduced
makes lactate or ethanol
fate of pyruvate
acetyl CoA
lactate
acetaldehyde to ethanol
energetics of glycolysis
steps 1,3,10 have strong negative delta G so pushes glycolysis forward
these steps have regulatory points because large negative deltaG means irreversible and always forward and energy is released in reaction
regulatory steps
step1: not main regulatory step because other entry points and glucose needed in other pathways
most substrates come in as G6P so don’t need regulation of getting glucose to enter
step3: main regulatory point, phosphofructokinase
step10: not main one, needed as metabolic branch point
hexokinase
phosphofructokinase
pyruvate kinase
feedback inhibition: shut down if G6P accumulating
AMP upregulates it and ATP down regulates it, so responds to energy status of cell
also regulated by metabolic intermediates
feedforward activation, before needed, signals to make it (remember lab)
