mitochondria

Structure + Adaptations

Double-membraned organelles found in almost all eukaryotic cells.

Outer membrane 

• separates mitochondrial contents from the rest of the cell, creates a specialised compartment for aerobic respiration 

• Permeable to small molecules and ions due to the presence of PORINS  

Inner mitochondrial membrane

• site of oxidative phosphorylation  

• Contains electron transport chain and ATP synthase, which create a proton gradient and use it to produce ATP

• Contains cristae projections to increase the SA for oxidate phosphorylation 

Intermembrane space 

• Between inner and outer membranes 

• Where high concentration of protons are generated by the ETC

• Volume is very small, therefore the concentration gradient increases very quickly across the membrane, readily supplying H+ in the mitochondria. 

Matrix

• Fluid filling compartment inside the inner mitochondrial membrane with ribosomes, enzymes and mtDNA 

• Contains enzymes and substrates for Krebs cycle

• By concentrating enzymes and substrates in a small volume, aerobic respiration can be perfumed more rapidly. 

Key Features

·  Have their own DNA (mtDNA) and ribosomes, allowing them to self-replicate.

·  Inherited maternally.

Functions

ATP production (cellular reproduction): generate ATP via aerobic respiration using glucose and oxygen   

-          Glycolysis (in cytoplasm) – breakdown of glucose into x2 pyruvate

-          Kerbs cycle (in the matrix) – generates NADH and FADH2

-          Electron Transport Chain (in cristae) – produces ATP using oxidative phosphorylation

Protein transport 

Nucleus → RNA proteins → mitochondria

 Ribosomes synthesise unfolded proteins from mRNA

• Unfolded protein (inactive) is chaperoned to a receptor and is pushed through TOM (translocase of outer membrane) to move protein into the intermembrane space 

• In the intermembrane space, a chaperone protein binds to the unfolded protein, and takes it to the next receptor, TIM (translocase of intermembrane)

• From TIM, proteases bind to unfolded protein, to fold it and make it a functional (active protein)