SYLLABUS 11-12: Bioenergetics Flashcards
what does oxidative phosphorylation do
converts energy derived from oxidation of glucose, fatty acids, and amino acids to ATP’s high-energy phosphate bonds
where does oxidative metabolism take place
mitochondria
function and location of the electron transport chain?
oxidizes energy, from oxidation of fuels in TCA cycle and B-oxidation of fatty acids, conserved in NADH and FADH2,
via a series of enzymes embedded in mito inner membrane
what is final acceptor of H’s from NADH and FADH2 in the etc?
oxygen
makes H2O
how does structure of the mito impact ETC?
outer membrane is permeable to everything
folded inner membrane contains respiratory/ETC and its enzymes - which are linked to enzymes that make ATP, the ATP synthesis enzymes
how are electrons transferred, broadly, in mito resp chain?
e- are transferred from NADH/FADH2 via **ubiquinone, coenzyme Q, **and cytochromes to molecular O2
molecular O2 is **reduced to H2O **
energy from **oxidation of NADh and FADH2 by O2 **is used to **produce ATP **from ADP + Pi by **ATP synthase, **FoF1 ATPase complex
what is chemiosmotic model
explains how energy from transport of electrons to O2 is transformed into the high energy bonds of ATP
what kind of rxns cause transfer of e- in the etc?
oxidation-reduction steps as electrons pass through complexes of proteins that span the mito inner membrane
what generates electrochemical gradient across mito inner membrane?
as e- pass through complexes in inner mito membrane, pumping of protons from mito matrix to cytosolic side of inner mito membrane
what comprises delta-P?
electrochemical gradient across mito inner membrane
= a membrane potential beacuse of pumping positive charges out of the mito
AND a proton gradient b/c of pumping protons out of the mito
what is the ratio of H+ pumped/e- passing through for each of the complexes of the etc?
Complex I: 4H+ pumped per electron
Complex III: 2H+ per electron
Complex IV: 4H+ per electron
this generates electrochemical gradient across membrane
structure of the ATP synthase?
a proton pore through the inner membrane and a catalytic head-piece that protrudes into the matrix
how does ATP synthase function?
protons that were pumped out during e- transport to O2 re-enter via the proton pore of the ATP synthase complex
this causes conformation change in catalytic headpiece
this change releases ATP bound to 1 site, and catalyzes formation of a new ATP from ADP + Pi at another site
the newly formed ATP is transferred to the bound site, will be released by next proton entering the proton pore
how can we categorize the process that the ATP synthase complex facilitates?
oxidative phosphorylation - transfer of e- and pumping of protons is coupled to synthesis of ATP
what defines the rate of respiration in the etc?
1) transfer of electrons
2) reduction of O2
what regulates the rate of respiration in the etc?
1) rate of ATP synthesis
2) delta-P
3) other bioenergetic work functions which utilize the delta-P
what is difference in effect on etc action between if delta-P is utilized/not utilized?
if delta-P is not utilized, rate of e- transfer or O2 uptake decreases b/c of back pressure exerted on respiratory chain by high accumulated delta-p
if delta-p is utilized for ATP synthesis or bioenergetic work functions, the rate of e- transfer becomes faster in order to keep generating the delta-P
how does the permeability of the mito inner membrane impact the respiration rate?
membrane’s impermeability to protons means that protons are pumped out only at discrete sites in complexes I, III, IV, and pumped back in through proton pore of ATP syntase (links oxidation-phosphorylation)
what can make mito inner membrane permeable?
what’s the impact?
damage or chemical modification by uncoupling agents to mito inner membrane makes it leaky to protons
a delta-P will be immediately dissipated, since pumped-out protons non-specifically re-enter the mito rather than re-enter through proton pore of ATP synthase
what are uncoupling agents
proteins that form channels through the mito inner membrane for protons to pass from the intermembrane (cytosolic) space to the matrix
thus short-circuits the ATP synthase
what happens to the delta-P and respiratory chain in the presence of an uncoupling agent?
lose delta-p beacuse discharge the gradient by carrying protons back into the mitochondria
respiratory chain still is working, so get movement of e- through the chain, but do not make any ATP
this **uncouples phosphorylation and oxidation **
UCP1 action?
associated w/ heat production in brown adipose tissue
important for infants to maintain body temp and for animals to hibernate
UCP3 action?
in skeletal muscle
drug target for obesity - idea that if find activators of UCP3 to “waste” the delta-P as heat rather than use it to support fat synthesis reactions
