Chapter 12 - Mitochondria and Chloroplasts

first major reaction of the mitochondria

citric acid cycle

second major reaction of the mitochondria

electron transport chain

mitochondrial genome

multiple circular

mitochondrial membrane that is impermeable to most ions and small molecules

the inner membrane

mitochondrial membrane that is highly permeable to small molecules

the outer membrane

channels that allow free diffusion of small molecules

porins (in the outer mitochondrial membrane)

location of the citric acid cycle

mitochondrial matrix

phospholipid that restricts proton flow across the membrane to improve oxidative phosphorylation

cardiolipin

first stage of glucose oxidation

glycolysis

location where glycolysis takes place

cytosol

net products of glycolysis

2 pyruvate, 2 ATP, 2 NADH

cell status that inhibits glycolysis

cell has adequate supply of ATP

second stage of glucose oxidation

citric acid cycle

number of pyruvate generated by 1 glucose

2

number of NADH generated by 2 pyruvate

2

in the mitochondria, pyruvate undergoes oxidative decarboxylation in the presence of coenzyme A

formation of acetyl CoA

fate of acetyl CoA

reactant for the citric acid cycle to yield citrate

3rd stage of glucose oxidation

oxidative phosphorylation

net products of glucose oxidation

6 CO₂, 4 ATP, 10 NADH, 2 FADH₂

total ATP yield from glucose oxidation

38 (36 in some cells)

number of ATP yielded from one NADH

3

number of ATP yielded from one FADH₂

2

net products of the citric acid cycle

2 ATP, 8 NADH, 2 FADH₂

number of acetyl CoA generated from 2 carbon atoms

1

number of ATP generated from one molecule of 16-carbon fatty acid

130

location of the complexes for the electron transport chain

inner mitochondrial membrane

electron transport chain complexes used for NADH

I, III, IV, V

electron transport chain complexes used for FADH

II, III, IV, V

site where electrons from NADH enter the electron transport chain

Complex I

electrons are transferred here by Coenzyme Q (ubiquinone)

Complex III

cytochrome c carries electrons here, where they are transferred to O₂

Complex IV

site where electrons from FADH₂ enter the electron transport chain

Complex II

number of protons transferred to the intermembrane space from the NADH electron transport chain

12

number of protons transferred to the intermembrane space from the FADH₂ electron transport chain

8

number of protons transported per pair of electrons

4

pH gradient and electrical potential drive protons back to the matrix across the inner membrane

electrochemical gradient

ATP synthase

Complex V

number of protons required to generate one ATP

4

components of ATP synthase

F₀ and F₁

forms a spinning channel through which protons pass

F₀

spins and harvests free energy by catalyzing the synthesis of ATP

F₁

molecules encoded for by mitochondrial genes

mitochondrial proteins, rRNA, tRNA

number of proteins encoded for by mitochondria

13

UGA codon (in mitochondria)

Trp (tryptophan)

AGA codon (in mitochondria)

stop

AGG codon (in mitochondria)

stop

AUA codon (in mitochondria)

Met (methionine)

blindness caused by mutations in mitochondrial genes for the electron transport chain

Leber’s hereditary optic neuropathy

amino acid sequences that target proteins to the mitochondrial matrix and are removed by proteolytic cleavage

presequences

receptor on the mitochondria that presequences bind to

Tom complex (translocase of the outer membrane)

complex in the inner mitochondrial membrane where proteins are transferred to

Tim complex (translocase of the inner membrane)

unfolds proteins before they enter the mitochondria

Hsp70 chaperones

cleaves the presequence after it enters the mitochondrial matrix

MPP (matrix processing peptidase)

used instead of presequences for proteins with multiple transmembrane domains

internal import signals

laterally inserts inner membrane proteins that were synthesized by the mitochondrial genome

Oxa translocase

outer membrane protein that inserts proteins with single transmembrane domains

Mim1

translocase that mediates insertion of ß-barrel proteins into the outer membrane

SAM (sorting and assembly machinery)

mediates lipid transfer between the ER and the mitochondria

phospholipid transfer proteins

molecules pumped out of the mitochondria by the electrochemical gradient

(ATP)^4-, OH^-

molecules pumped into the mitochondria by the electrochemical gradient

(ADP)^3-, pyruvate, P_i

chloroplasts compared to mitochondria

larger, more complex

first stage of photosynthesis

light reactions

second stage of photosynthesis

dark reactions

internal membrane system of the chloroplast forming a network of flattened discs

thylakoid membrane

internal compartments of the chloroplast

intermembrane space, stroma, thylakoid lumen

area inside the chloroplast envelope but outside the thylakoid membrane, equivalent to mitochondrial matrix

stroma

location of ATP synthesis in chloroplasts

stroma

direction of proton movement in chloroplasts

from the stroma to the thylakoid membrane

sunlight energy drives ATP and NADPH synthesis, coupled to the oxidation of H₂O to O₂

light reactions

ATP and NADPH drive synthesis of carbohydrates from CO₂

dark reactions

photoreactive center that absorbs sunlight

chlorophyll

location where photons of light energy are absorbed

photosystems I and II

generates NADPH (first pathway) or ATP (cyclic electron flow)

function of Photosystem I

generates a proton gradient with cytochrome bf complex that drives synthesis of ATP

function of Photosystem II

number of protons moved in the first light reaction

6

number of protons moved in cyclic electron flow

4

number of ATP generated per pair of electrons in the first light reaction

1.5

number of ATP generated per pair of electrons in cyclic electron flow

1

number of ATP consumed by the Calvin cycle to form one glucose

18

number of NADPH consumed by the Calvin cycle to form one glucose

12

number of electrons needed to convert one molecule of NADP⁺ to NADPH

2

number of proteins synthesized by chloroplast genome

~100

N-terminal sequences of 30-100 amino acids that direct translocation across the chloroplast envelope membranes

transit peptides

removes transit peptides by proteolytic cleavage

SPP (stromal processing peptidase)

transports proteins through the outer membrane of the chloroplast

Toc complex

transports proteins through the inner membrane of the chloroplast

Tic complex

chloroplast proteins have a second signal sequence to cross this location

thylakoid membrane

cleaves the second signal sequence in chloroplast proteins

TPP (thylakoid processing protease)

pathway to translocation proteins into the thylakoid lumen that is ATP dependent - signal sequence is recognized by the SecA protein, protein is unfolded

Sec pathway

pathway to translocate proteins into the thylakoid lumen in which the protein has a twin-arginine signal sequence and energy comes from the proton gradient, protein remains folded

TAT pathway