mitochondria

traits of endosymbiotic theory of mitochondrial origin (4)

• own circular genome

• double membrane

• similar in size to prokaryotic cells

• divide by binary fission

how many mitochondria do most cells have

several hundred

what type of cells have the most mitochondria and how many

liver cells - 2500

mitochondral membrane

inner and outer membrane

• inner membrane folded into cristae

mitochondrial compartments

• 2

• matrix inside the inner membrane and intermembrane space between the inner and outer membranes

mitochondria distribution

• moved to areas of high atp consumption like myofibrils of muscle cells by microtubules of cytoskeleton

mitochondrial outer membrane

• similar to other eukaryotic membranes

• protein is porin

• large aqueous channels

mitochondrial inner membrane

3 types of major membrane

• electron transport chain

• atp synthase

• specific transporters of metabolites which vary according to cell/tissue type

mitochondrial cristae

• increase membrane surface areas

• energy transducing

• impermeable to most small ions

mitochondrial matrix

• enzymes which catalyse the krebs cycle and fatty acid oxidation

• ribosomes

• mitochondrial dna

3 atp uses

• transport = phosphorylates transport proteins for conformational change

• mechanical = atp phosphorylates motor proteins

• chemical = atp phosphorylates key reactants

what bonds have the highest energy electrons

C-H

electron carriers function

link organic molecules oxidation to the electron transport chain

electron carriers link (4)

• NAD+ is e- carrier

• accepts high energy e-

• donates them to ETC

• cannot be transported to/from mitochondria so must be regenerated

where does glycolysis occur

• in cytosol

glycolysis overview

• in cytosol

• small amount of energy released

• 2 molecules of pyruvate formed

glycolysis brief steps

• substrate with high energy phosphate bonds

• transferred to adp →atp

• glucose → 2x pyruvate

• net 2 atp

• nad+ → NADH

krebs cycle location

mitochondrial matrix

krebs cycle brief steps

• high energy e- (acetyl group) → nad+ or FAD (FAD for lower energy)

• small amount atp produced

ETC location

inner membrane - FAD and NAD collect e- from krebs and carry to membrane

ETC steps

• ions pumped across unner membrane and gradient used by ATP synthase

• stepwise extraction of energy from high energy e-

• NO ATP MADE DIRECTLY BUT USED TO PRODUCE H+ GRADIENT

redox

• redox = reactant losing e- oxidised, reactant giving reduced

ETC

multiprotein complexes embedded in inner membrane of mitochondria

ETC characteristics

• each component of etc is slightly more electronegative

• proteisn with prosthetic groups

  • first protein is always a flavoprotein

order of proteins in ETC

• flavoprotein

• iron sulphur protein

• ubiquinone

• series of carriers called cytochromes

• oxygen (picks up 2 h+ to make h2o

what are cytochromes

• 4 organic rings surrounding an iron atom

• in the ETC

chemiosmosis proteins

ATP synthase

F0

F1

atp synthase

• lots in inner membrane

• large multiprotein complex

F0 protein

H+ channel

F1 protein

head is site if ATP synthesis

what happens when h+ move through F0

• rotation of rotor and central stalk while stator keeps F1 stationary

• sequential conformational changes in central stalk and F!

• provides energy for atp synthesis

• 10H+ moving to matrix generate 3 ATP

• h+ ion gradient between opposite sides of inner membrane

name 2 mitochondrial poisons

cyanide

1,4-dinitrophenol

effect of cyanide

prevents passage of e- to one of the cytochromes, blocking ETC

• one of the fastest poisons known to man

2,4- dinitrophenol effect

makes inner membrane leaky so h+ gradient not established

ETC still works but energy released as heat

brown fat (3)

• type of adipose tissue

• mitochondria in brown fat produce heat

• lots of BF in newborns

thermogein

• H+ channel in inner membrane of brown fat mitochondria

• H+ leak bac out without passing through ATP synthase → no ATP produced

• energy in ETC released as heat

myoclonic epilepsy and ragged red fibre disease

• mitochondrial genetic diseases

• mutation in trna lys gene in mitochondria

• affects mitochondrial proteins

• affects muscle and nerves → epilepsy and muscle weakness

• no cure

• mitochondria are only inherited from the mother

• ivf technique developed to prevent the passing of defective mitochondria