-
· __ facilitate exchange across the inner membrane
· One function of the chain is to __
o NADH cannot simply __because the inner mitochondrial membrane is impermeable to NADH an NAD+. The solution is that __
- Transport proteins
- regenerate NAD+ for use in glycolysis
- pass into mitochondria for oxidation by the respiratory chain
- electrons from NADH, rather than NADH itself, are carried across the mitochondrial membrane
-
§ One of several means of introducing electrons from NADH into the ETC is the __
· The first step in this shuttle is the __ on the outer surface of the inner mitochondrial membrane by a __
o An __is transferred to an __ in this enzyme to form __
§ This reaction also regenerates __
- G3P shuttle
- transfer of a pair of electrons from NADH to dihydroxyacetone phospahate
- membrane-bound isozyme of G3P dehydrogenase
- electron pair from G3P
- FAD prosthetic group
- FADH2
- dihydroxyacetone phosphate
-
· The reduced flavin transfers its electrons to the __, which then enters the respiratory chain as __.
o When cytoplasmic NADH transported by the __ is oxidized by the respitaroy chain, __ rather than __ are forme
§ The yield is lower because __
- electron carrier Q
- QH2
- G3P shuttle
- 1.5 rather than 2.5 molecules of ATP
- FAD rather than NAD+ is the electron acceptor in mitochondrial glycerol 3-phosphate dehydrogenase
-
o The use of FAD enables electrons from cytoplasmic NADH to be __
§ The price of this transport is __
· This G3P shuttle is prominent in muscle and enables it to sustain a very high rate of __
- transported into mitochondria against an NADH concentration gradient
- one molecule of ATP per two electrons
- oxidative phosphorylation
-
· In the heart and liver, electrons form cytoplasmic NADH are brought into mitochondria by the __, which is mediated by __ and __
o Electrons are transferred from NADH in the cytoplasm to __, forming __, which traverse the inner mitochondrial membrane in exchange for __ and is then reoxidized by __ in the matrix to form __in a reaction catalyzed by the __
- malate-aspartate shuttle
- two membrane carriers and four enzymes
- oxaloacetate
- malate
- alpha-ketoglutarate
- NAD+
- NADH
- CAC enzyme malate dehydrogenase
-
§ The resulting oxaloacetate does not do what and so a __reaction is needed to form __, which can be transported to the cytoplasmic side in exchange for __, which donates an __ to __, forming __ and __.
- readily cross the inner mitochonodrial membrane
- transamination
- aspartate
- glutamate
- amino group
- oxaloacetate
- aspartate and alpha-ketoglutarate
-
· In the cytoplasm, aspartate is __to form __and the cycle is restarted
· The major function of oxidative phosphorylation is to generate ATP from ADP
o ATP and ADP do not diffuse freely across the __
§ __ enabels the molecules to transverse this permeability barrier
- deaminated
- oxaloacetate
- inner mitochondrial membrane
- ATP-ADP translocase
-
· The flows of ATP and ADP are coupled
o explain
§ The process is carried out by the __, an __
- ADP enters the matrix only if ATP exits, and vice versa
- translocase
- antiporter
-
· __ is highly abundant, constituting about 15% of the protein in the inner mitochondrial membrane
o The abundance is a manifestation of the fact that human beings exchange the equivalent of their weight in ATP each day
§ The 30-kd translocase contains a __ that alternately faces the matrix and the cytopaslmic side of the membrane
- ATP-ADP translocase
- single nucleotide-binding site
-
· ATP and ADP bind to the __without __, and ATp has one more __ than that of ADP
o Thus, in an actively respiring mitochondrion with a positive membrane potential, __ and __ are favored
§ This __ is energetically expensive; about a quarter of the energy yield from electron transfer by the respiratory chain is consumed to do what?
· This inhibition of this process leads to the subsequent inhibition of cell resp
- translocase
- Mg2+
- negative charge
- ATP transport out of the mitochondrial matrix and ADP transport into the matrix
- ATP-ADP exchange
- regenerate the membrane potential that is tapped by this exchange process
-
· ATP-ADP translocase has __ of a 100-amino-acid module, each of which appears to have __
o The transmembrane helices form a tepeelike structure with the __ (marked by a bound inhibitor) lying in the center
§ Each of the three repeats adopts a similar structure
- three repeats
- two transmembrane segments
- nucleotide-binding site
-
· __ is but one of many mitochondrial transporters for ions and charged metabolites
o The __ mediates the electroneutral exchange of __ for __
§ The combined action of these two transporters leads to the __(owing to the transport of one OH- out of the matrix)
· These two transporters, which provide ATP synthase with its substrates, are associated with the synthase to form a large complex called the __
- ATP-ADP translocase
- phosphate carrier
- H2PO4- for OH-
- exchange of cytoplasmic ADP and Pi for matrix ATP at the cost of the influx of one H+
- ATP synthasome
-
· Other homologous carriers also are present in the inner mitochondrial membrane
o The __ enables malate, succinate, and fumarate to be exported from the matrix in exchange for Pi
§ The __ exchanges citrate and H+ for malate
· Pyruvate in the cytoplasm enters the mitochondrial membrane in echange for OH- by means of the __
- dicarboxylate carrier
- tricarboxylate carrier
- pyruvate carrier
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