Mitochondria

(h) explain, with the aid of diagrams and electron micrographs, how the structure of mitochondria

enables them to carry out their functions;

On your diagram, can you label....

• Inner and outer phospholipid membrane• The envelope• Cristae• Intermembrane space• Matrix• Stalked particles (ATP synthase)

Stages of Respiration

1. Glycolysis (Cytoplasm)

2. Link Reaction (Mitochondrial Matrix)

3. Krebs Cycle (Mitochondrial Matrix)

4. Oxidative Phosphorylation (electron carriers, oxygen and mitochondrial cristae)

Mitochondrial Structure and Function – The Matrix

Link reaction and Krebs Cycle• Enzymes are present to catalyse the above reactions• Coenzyme NAD is present• Oxaloacetate present – accepts acetate from the link

reaction• Mitochondrial DNA – codes for some of the enzymes

and proteins required• Mitochondrial ribosomes – to assemble the above

proteins

Mitochondrial Structure and Function – The Outer Membrane

The outer membrane contains proteins.• Some of these proteins form channels or

carriers to allow the passage of molecules such as pyruvate (from glycolysis)

• Enzymes are also present in the membrane

Mitochondrial Structure and Function – The Inner Membrane

• Impermeable to most small ions including protons (hydrogen ions). Has a different lipid composition to the outer membrane.

• Is folded into cristae to give a large surface area

• Has many ATP synthase enzymes and electron carriers embedded in it. The electron carriers are protein complexes arranged in electron transport chains

Krebs Cycle

e-e-

e-e-

H+H+

H+H+H+H+

H+H+

Cyt Ce-e-

H+H+H+H+O2 H+H+H+H+H2O

ADP ATP

Cyt C

e- Q

H+`H+H+`H+

NADHNADH

NAD+NAD+

H+H+H+ H+ H+H+

H+

H+ H+ H+H+

H+

Cyt C

H+` H+`

e-

e-e-

IN

OUT

Animated by Peter RabinovitchBackground after Mandavilli et al, Mutation Research 509 (2002) 127–151

Mitochondrial Electron Transport Chain

2OH-2OH- OH-OH-

Electron transport chains• Each electron carrier is an enzyme and has a

cofactor associated with it. Cofactors are haem groups and contain an iron atom

• Iron atoms can become reduced to Fe2+ or oxidised to Fe3+ by accepting and donating electrons

• The carriers are oxidoreductase enzymes as they are involed in oxidation and reduction reactions

• Some electron carriers also have a coenzyme that pumps (using energy from the passage of electrons) protons from the matrix to the intermembrane space, building up a proton gradient

P86-87 Structure of ATP Synthase

• Remember protons flow DOWN the proton gradient NOT along

http://www.americanchildneurologyuae.com/files/neurological-diseases/NEUROMETABOLIC/Mitochondrial-DO-Nature%202012%5b1%5d.pdf