Lecture 22 Flashcards
(26 cards)
What happens during the second step?
It is the oxidation of reduced coenzyme Q. It is where QH2 is oxidized and transfers electrons through heme groups cytochrome b/c or Fe-S and then reduce two molecules to cytochrome c.
What is complex III? What happens here?
It is where it takes and passes the electrons from QH2 to cytochrome C through the heme pathway known as the Q cycle
What initiates the Q cycle?
he Q-cycle is initiated when QH2 diffuses through the bilipid layer to the QH2 binding site (Q0 site). There are also two binding sites.
What is true about the copper hemes?
They only accept one electron at a time. During this time electrons bound around.
How does the electron transfer work here? What is the process?
It happens when QH2 binds to Q0 and it is oxidized. One electron travels to heme bL group and then to heme bH, then coenzyme Q and then Q1 and reducing to semiquinone.
What happens during the third step?
It is the final stage of electron transport and is carried out by Complex IV, or cytochrome C oxidase. Here the elctrons from III are passed and accepted and are directed to 4 electron reduction of O2 to form 2 molecules of water.
What happens when oxygen is bound to electrons and not released?
This is dangerous and is known as reactive oxygen species (ROS). This is caused by peroxide ion or superoxide ion. Cytochome c makes sure that it holds oxygen tight to avoid ROS
What is the defense mechanism against ROS?
Superoxide dismutase which is an enzyme that gets rid of ROS. It can come in oxidized or reduced. Oxi, grabs the ROS and converts to oxygen. If it is reduced then it forms hydrogen peroxide.
What happens when hydrogen peroxide forms?
It uses catalase to break apart the hydrogen peroxide to something safer like water
What is the chemiosmotic theory?
Where electron
transport and ATP synthesis are coupled by a proton gradient across
the inner mitochondrial membrane
What are the requirements for the chemiosmotic theory?
- intact inner membrane
- electron transport through ETC generates proton gradient
- ATP synthase catalyzes phospho. of ADP in a reaction driven by movement of H across inner membrane
What are the two gradients formed from the chemiosmotic theory?
chemical and charge gradient
What happen in complex V?
It has two assemblies of F0 and F1.
Where does F0 complex sit?
sits in the membrane and forms the proton channel
Where does F1 complex sit?
contains the catalytic activity, and protrudes into the mitochondrial matrix
What proteins are in F1 unit?
a3, b3, gamma, delta, epsilon
superoxide
peroxide
Where does Q transfer electrons to?
cytochrome C
What does superoxide dismutase generate?
H2O2
What does catalase do? What does it yield?
(catalyzes the reduction of hydrogen peroxide
How many subunits are in F0?
10-14 c like a ring
What makes up the chemiosmotic theory? What are the two components?
chemical(pH) and charge gradient
How are F0 and F1 connected?
y/e and a/b/delta
