Cytochrome C

Question 1

What is Cytochrome C capable of doing?

Answer 1

Accept electrons and then transfer it off to another protein

Capable of undergoing oxidation and reduction

Question 2

What doesn’t Cytochrome C bind?

Answer 2

Doesn’t bind to oxygen

Question 3

What complexes are the electrons transported between?

Answer 3

Complexes III (Coenzymes Q -Cyt C reductase)

IV (Cyt C oxidase)

Question 4

What allows for the electrons to transport between the two complexes?

Answer 4

Co-factors

Question 5

In humans what encodes for Cytochrome C?

Answer 5

CYCS gene

Question 6

How is Cytochrome C involved in Phosphatase phosphorylation?

Answer 6

Involved in the last step

Transfers electrons at the last step in the production of cellular energy

Question 7

How is Cytochrome C involved in the electron transport chain?

Answer 7

Cytochrome C is like a small cellular wire which electrons can flow through

Carries one electron per trip, each time binds to electron and moves across.

Electricity is the flow of electrons within a conductive mater, such as metal wire

Electricity powers many cellular processes

Electrons may be picked up from one particular place, then delivered where needed

Question 8

How are electrons involved with breathing?

Answer 8

Electrons are from breakdown of sugar (Make ATP) and end up being attached to oxygen forming water. This the fate of oxygen we breathe and why we breathe.

Question 9

Which electron carrier is used?

Answer 9

Heme group which is the prosthetic group

Question 10

What is the job of the Heme group?

Answer 10

Pick up and transport electrons

Question 11

What is the protein surrounding the Heme group used for?

Answer 11

Protein is like a scaffold, carrying the heme group

Can change the properties of the prosthetic group

Depending on its environment it will more or less except an electron, or donate differently

Question 12

How does the Heme group attach the electron?

Answer 12

Ion attaches to electron and passes it on

The Ion coordinated to a porphyrin acting as a tetradentate ligand (N), and to one or two axial ligands (amino acids).

Question 13

Where are the electrons gathered from?

Answer 13

From cytochrome bc1 complex and delivers to cytochrome oxidase complex

Question 14

What are the structural features of cytochrome C proteins?

together
loop

Answer 14

100 AA’s (12kDa), high conserved in eukaryotes, differing by only a few residues

Alpha Helical fold

Functionally conserved

Contains characteristic CXXCH (cysteine-any-any-cysteine-histidine) AA’s motif that binds heme

Question 15

How is Cytochrome C involved in Apoptosis?

Answer 15

CytoChrome C is released by mitochondria, in response to pro-apoptotic stimuli (Ca^2+ changes in BCL-2 protein expression, ROS etc).

Diffuses out to interact with proteins (InsP3 receptor, Caspase-9).

Further Ca2+ release stimulates more cytochrome c is released

Question 16

Explain Apoptosis

Answer 16

Release of cytochrome c from mitochondria
binding to protein Apaf-1
Causing it to assemble into seven-fold-ring
Caspases, activated by binding to the ring of CARD domains on the assembled apoptosome

Question 17

How is Apoptosis involved in development?

Answer 17

Normal development
Maintenance of tissues homeostasis
Effective immune system
Disturbance implicated in numerous pathological conditions ranging from degenerative disorders to autoimmunity to cancer

Question 18

What are the characteristic biochemical changes in cells undergoing apoptosis?

Answer 18

1) Chromosomal DNA cleaved into fragments
2) Change in the plasma membrane, For example, Phosphatidylserine in outer leaflet
3) Loss of electrical potential across the inner membrane of the mitochondria
4) Relocation of cytochrome c from intermembrane space of mitochondria to cytosol

Question 19

What are the symptoms of necrosis?

Answer 19

1) Cellular swelling
2) Membranes are broken
3) ATP is depleted
4) Cell lyses, eliciting an inflammatory reaction
5) DNA fragmentation random and smeared
6) Vivo, whole areas of the tissues are affected

Question 20

What are the symptoms of Apoptosis?

Answer 20

1) Cellular condensation
2) Membranes remain intact
3) Requires ATP
4) Cell phagocytosed, no tissue reaction
5) Ladder-like DNA fragmentation
6) In vivo, individual cells appear affected

Question 21

Explain the Apoptotic pathway: Extrinsic pathway

Answer 21

Death lings- Death receptors- Initiator caspase 8- Effect Caspase 3- Programmed cell death

Question 22

Explain the Apoptotic pathway: Intrinsic pathway

Answer 22

DNA damage and p53- Mitochondria/Cytochrome C - initiator Caspase- Effect Caspase 3- Programmed Cell death

Question 23

What are the inhibitors of Cytochrome C?

Answer 23

Cyanide and azide bind tightly to cytochrome oxidase complex, stopping electron transport, reducing overall ATP production.

Question 24

How does the intrinsic pathway of apoptosis depend on the mitochondria?

Answer 24

Release of cytochrome C from mitochondrium

Binds to Apa1, activating Apaf1 with the help of hydrolysis of bound dATP to dADP

Apaf1 forms complex called Apoptosome by the release of dADP in exchange for dATP (or ATP)

Recruitment of other proteins such as procaspase-9 which is activated

The caspase-9 is cleaved, activating executioner procaspase

The caspase cascade is then activated leading to Apoptosis

Question 25

How does pro-apoptotic BH3-only and Anti-apoptotic Bd2 proteins regulate the intrinsic pathway of apoptosis?

Answer 25

Regulates the release of proteins

Found in the mitochondria

Question 26

How is Cytochrome C in relation to Apoptosome?

Answer 26

Cyt c binds apoptotic to peptidase starting factor Apaf-1
Recruits and activates procasepase-1
Caspase-9 activates other caspases
Caspases degrade proteins and active endonucleases

Question 27

Give a brief rundown of the Cytochrome C conclave

Answer 27

Cytochrome c binds to Apaf-1 forming Caspase 9 -> Caspase 3 -> Apoptose substrate -> Cell death

Caspase 3 can also go of to form IAP,, which can produce Smac and omi
It can also go to caspases