What is the purpose of the citric acid cycle?
What is a quick summary of the CAC?
- Acetyl CoA goes through the cycle, causing 2 carbons to be lost as CO2, eight electrons to be captured by electron carriers (NAD+, FAD)
- GTP is created, but if ATP is needed, it can be converted to phosphate
Can all amino acids be fed into the pathway?
- but acetyl CoA is produced by the addition of 2 acetyl groups to CoA
Where is the location of all of these things?
in the matrix is the CAC
inner mitochondrial membrane: pyruvate can't get through on its own--> pyruvate translocase
outer mitochondrial membrane: has pores, such as porin; certain size, restricting some and allowing others; pyruvate passes through
How can pyruvate get into the matrix?
transfports pyruvate against the gradient into the matrix; energy source is protons
- proton concentration outside membrane higher than concentration inside
- --> proton moves with gradient; pyruvate against (both inside)
What is the final product in the CAC that begins the step?
oxaloacetate (4 C), which combines with 2 carbons to fourm a 6 carbon ring, to start the cycle
What is oxidative decarboxylation?
removing one carbon and simultaneously capturing e-
NAD+ to NADH
What is the purpose of the ETC?
to pump protons as electrons are passing dowm
36 H+ per glucose. These H+ proton gradient power production of ATP by similar protein to bacterial flagellar motor
All enzymes in the ETC are where?
in the mitochondria
they are transmembrane integral proteins
electrons were shuttled directly to ETC, where oxygen acts as the final acceptor, forming water
What is stage 2 of cellular respiration?
stage 2: remove CO2, capture electrons, get acetyl CoA
What is pyruvate dehydrogenase complex?
made of 3 different types of enzymes
- pyruvate dehydrogenase component
- dihydrolipoyl transacetylase
- dihydrolipoyl dehydrogenase
What is the simplified version of the reaction?
pyruvate+ CoA+NAD+--> acetyl CoA+CO2+ NADH
pyruvate dehydrogenase complex
- Number of chains: 24
- prosthetic group: TPP
- reaction catalyzed: oxidative decarboxylation of pyruvate
- Number of chains: 24
- prosthetic group: Lipoamide
- reaction catalyzed: transfer of acetyl group to CoA
- Number of chains: 12
- prosthetic group: FAD
- reaction catalyzed: regeneration of the oxidized form of lipoamide
1) important part
- 1) important part is the ring
- 2) highly acidic/ can use a proton and bind to pyruvate
we attach it to the end of a lysine residue, allowing it to flop around--> delivery system
disulfide bond at the end of a large hydrophobic chain; can be broken; we can attach things it
pyruvate to acetyl CoA
pyruvate--> decarboxylation --> oxidation--> transfer to CoA--> acetyl CoA
What is special about the carbanion of TPP?
it lost a proton so its in carbanion form.
It can then attack the carbonyl carbon of pyruvate to produce hydroxyethyl-TPP
- A covalent bond forms, doing two things:
- ---1) captures energy associated with decarboxylation
- ---2) allows decarboxylation to happen
In ring structure, __.
What about Decarboxylation ?
nitrogen is positively charged, drawing electrons so decarboxylation can take place
Decarboxylation would not have occurred if it wasn't added to enzyme
Energy conserved in bond between the prosthetic group
2 carbons we want to transfer to CoA
can form a high energy bond with two carbons
can flip between active sites
What happens in the pyruvate dehydrogenase component?
S-S bond breaks
one side accepts the electrons
the other side accepts acetyl CoA
high energy thioester bond
Active site of E2 (Dihydrolipoyl transacetlyase)
CoA brought in
high energy bond holding acetyl group
electrons reduced to disulfide bonds
Active site E3
allows electrons to transfer up the ladder
FADH2 transfers electrons to NAD+, becoming NADH
There are ___ through which pyruvate enters--> what happens?
gets trapped; nothing can escape and become wasteful