BI203 Lecture 18: Mitochondria, the ETC, and Peroxisomes

Question 1

The primary function of the mitochondria is to _____ _____ from the breakdown of sugars (esp. glucose).

Answer 1

generate ATP

Question 2

During glucose catabolism (such as during glycolysis), many of the reactions release _____ that is “captured” in the form of _____ or _____ (& _____).

Answer 2

energy, ATP, NADH, FADH2

Question 3

Glycolysis takes place in the _____.

Answer 3

cytosol

Question 4

The Citric Acid Cycle (Kreb’s Cycle) takes place in the _____ of the _____.

Answer 4

matrix, mitochondria

Question 5

_____ takes place in the cytosol.

Answer 5

glycolysis

Question 6

The _____ _____ _____ (or _____ _____) takes place in the matrix of the mitochondria.

Answer 6

citric acid cycle, Kreb’s cycle

Question 7

The net gain of glycolysis is _____ _____ and _____ _____.

Answer 7

2 ATP, 2 NADH

Question 8

The net gain of the citric acid cycle is _____ _____, _____ _____, and _____ _____.

Answer 8

2 ATP, 8 NADH, 2 FADH2

Question 9

The resulting 10 NADH and 2 FADH2 of both glycolysis and the citric acid cycle go through _____ _____ in order to produce 34 ATP.

Answer 9

oxidative phosphorylation

Question 10

The resulting 10 NADH and 2 FADH2 of both glycolysis and the citric acid cycle go through oxidative phosphorylation in order to produce _____ _____.

Answer 10

34 ATP

Question 11

The resulting _____ _____ and _____ _____ of both glycolysis and the citric acid cycle go through oxidative phosphorylation in order to produce 34 ATP.

Answer 11

10 NADH, 2 FADH2

Question 12

Mitochondria are surrounded by a _____ system.

Answer 12

double-membrane

Question 13

The inner and outer membranes of the mitochondria are separated by the _____ _____.

Answer 13

intermembrane space

Question 14

The inner membrane of mitochondria has many folds (_____), which extend to the interior (_____).

Answer 14

cristae, matrix

Question 15

The outer membrane of the mitochondria is highly _____, while the inner membrane of the mitochondria is highly _____.

Answer 15

permeable, impermeable

Question 16

Oxidative phosphorylation (ETC) takes place in the _____ _____ of the _____.

Answer 16

inner membrane, mitochondria

Question 17

_____ _____ takes place in the inner membrane of the mitochondria.

Answer 17

oxidative phosphorylation (ETC)

Question 18

The _____ of mitochondria contains its genetic system as well as enzymes for both the citric acid cycle and oxidative phosphorylation.

Answer 18

matrix

Question 19

Oxidative phosphorylation:

High-energy electrons from NADH and FADH2 are transferred through a series of _____ in the membrane to molecular oxygen.

The energy from this is converted to potential energy stored in a _____ _____, which drives _____ _____.

Answer 19

carriers, proton gradient, ATP synthesis

Question 20

Most mitochondrial proteins are translated in the _____ and _____ post-translationally.

Answer 20

cytosol, imported

Question 21

The mitochondrial genome consists of _____ DNA molecules (like bacteria) in _____ copies.

Answer 21

circular, multiple

Question 22

Mitochondrial proteome:

1000 - 1500 different proteins.
_____% encoded by the nuclear genome.

Answer 22

99%

Question 23

The human mitochondrial genome encodes _____ proteins involved in the ETC.

Plus _____ and _____ rRNAs; and _____ tRNAs, which are required for translation of the proteins.

Answer 23

13, 16S, 12S, 22

Question 24

The mitochondrial genetic code is _____ from the universal code (mitochondria’s codon table is _____).

Answer 24

different

Question 25

U in the tRNA anticodon can pair with any of the bases in the third codon position of mRNA; thus _____ codons are recognized by a single tRNA.

Some codons specify _____ amino acids in mitochondria than in the universal code.

Answer 25

four, different

Question 26

_____, which leads to blindness, is caused by mutations in mitochondrial genes that encode components of the electron transport chain.

Answer 26

LHON (Leber’s Hereditary Optic Neuropathy)

Question 27

Mutations causing LHON reduce mitochondrial capacity to carry out _____ _____ and generation of ATP.

Answer 27

oxidative phosphorylation

Question 28

LHON most greatly affects cells in the _____, such as the brain and optic nerve.

Answer 28

CNS (Central Nervous System)

Question 29

Proteins are targeted to the matrix of the mitochondria by _____ [ amino-terminal sequences with _____ residues ] that are removed by proteolytic cleavage after import.

Answer 29

presequences, positively-charged

Question 30

Presequences bind to outer membrane receptors on the mitochondria that are part of a protein complex (_____ of the outer membrane; the _____ _____).

Proteins are then transferred to another complex in the inner membrane (_____ of the inner membrane; the_____ _____).

Answer 30

translocase, Tom complex, translocase, Tim complex

Question 31

Following passage through the Tom complex, the pre-sequence binds to the _____ _____ in the inner membrane

Answer 31

Tim23 complex

Question 32

Protein translocation requires the _____ potential established across the inner membrane during electron transport.

Proteins must also be unfolded, requiring _____ chaperones.

Answer 32

electrochemical, Hsp70

Question 33

Presequences are cleaved by _____ _____ _____, and the polypeptide is bound by other Hsp70 chaperones which facilitate folding.

Answer 33

matrix processing peptidase (MPP)

Question 34

Some proteins with multiple transmembrane domains have _____ _____ _____ instead of presequences:

After translocation across the outer membrane, they are bound by _____-_____ chaperones, which bring them to _____.

_____ _____ _____ halt translocation, and the protein is transferred laterally into the inner membrane.

Answer 34

internal import sequences, Tim9-Tim10, Tim22, internal stop-transfer sequences

Question 35

Some inner membrane proteins are encoded by the mitochondrial genome:

They are synthesized in mitochondrial ribosomes in the matrix and targeted to the _____ _____ in the inner membrane.
They then exit _____ _____ laterally to insert into the inner membrane.

Answer 35

Oxa1 translocase

Question 36

Proteins destined for the outer membrane or intermembrane space also pass through the _____ _____.

β-barrel proteins pass through Tom, are bound by _____-_____ and carried to another translocon called the _____.
_____ mediates their insertion into the outer membrane.

Answer 36

Tom complex, Tim9-Tim10, SAM (Sorting & Assembly Machinery).

Question 37

Proteins with single transmembrane domains (destination is outer membrane, but it is a single-domain protein) are inserted in the outer membrane protein _____.

Answer 37

Mim1

Question 38

The machinery of oxidative phosphorylation: The _____ _____ _____.

Answer 38

electron transport chain (ETC)

Question 39

The electron transport chain couples the released energy stored in the _____, to pump H+ _____ its gradient.

Answer 39

carriers (NADH, FADH2), against

Question 40

Components of the electron transport chain are organized into _____ complexes in the inner mitochondrial membrane.

Answer 40

four

Question 41

_____ _____ and The Electron Transport Chain (ETC):

A series of electron carriers in the inner mitochondrial membrane.

Answer 41

chemiosmotic coupling

Question 42

NADH is produced in the Krebs cycle in the _____; electrons from NADH enter the electron transport chain at _____ _____.

Electrons are transferred to _____ _____ by _____ _____ (ubiquinone).

_____ _____ then carries electrons to _____ _____ (cytochrome oxidase), where they are transferred to O2.

The energy-yielding electron transfers at each step are coupled to ATP synthesis.

Answer 42

matrix, complex I, complex III, Coenzyme Q (ubiquinone), Cytochrome c, complex IV (cytochrome oxidase)

Question 43

_____ _____ receives electrons from the citric acid cycle intermediate, _____.
These electrons are transferred to _____ instead of NADH, and then to _____ _____.

Answer 43

complex II, succinate, FADH2, Coenzyme Q

Question 44

_____ _____: Channel protein which couples the flow of protons down their gradient to the synthesis of ATP. (H+ goes from _____ _____ to the _____)

Answer 44

ATP synthase, intermembrane space, matrix

Question 45

ATP synthase consists of two components:

_____ forms a spinning channel through which protons pass.
_____ spins and harvests the free energy by catalyzing the synthesis of ATP.

Answer 45

F0, F1

Question 46

ATP synthesis requires continuous transport of:

1) _____ out of matrix.
2) _____ & _____ into matrix.

Answer 46

ATP, ADP & Pi

Question 47

The mitochondrial outer membrane is highly permeable to small molecules, because it has _____.

Answer 47

porins

Question 48

Transport of ATP and ADP across the mitochondrial inner membrane is mediated by an integral membrane protein, the _____ _____ _____.

Answer 48

adenine nucleotide translocator

Question 49

The adenine nucleotide translocator:

ATP carries a more negative charge than ADP (_____ compared to _____), so exchange is driven by the voltage component of the electrochemical gradient.

Pi is brought in as _____ (H2PO4-) in exchange for _____ ions (OH-).

This exchange is electrically neutral, but is driven by the _____ _____ _____.

Answer 49

-4, -3, phosphate, hydroxyl, proton concentration gradient

Question 50

ATP/ADP exchange is driven by _____.

Pi (H2PO4-) import is coupled to OH- export, which is driven by _____ difference.

Answer 50

voltage, pH

Question 51

_____ - Small single-membrane organelles containing enzymes involved in many metabolic reactions incl. fatty acid oxidation, lipid biosynthesis; they do not have their own genomes like mitochondria.

Answer 51

peroxisomes

Question 52

Peroxisomes:

Many substrates are broken down by oxidative reactions in peroxisomes, which leads to production of hydrogen peroxide.
_____ converts hydrogen peroxide to water or uses it to oxidize another organic compound.

Answer 52

catalase

Question 53

Peroxisomes:

Peroxisomes are also involved in synthesis of lipids.
In animal cells, _____ and _____ are synthesized in peroxisomes and in the ER.
In the liver, peroxisomes are involved in synthesis of bile acids from cholesterol.

Answer 53

cholesterol, dolichol

Question 54

Peroxisomes:

Peroxisome transmembrane proteins are transported from the ER, including _____ or _____ _____ involved in peroxisome assembly.

Answer 54

peroxins, Pex proteins

Question 55

Peroxisomes:

Mutations in peroxins are associated with _____ _____ _____ that result from defective peroxisome assembly.
The recessive genetic disorders are RCDP type 1 and Zellweger spectrum disorders.
Mutations that completely destroy Pex protein function result in severe disease; mutations that only reduce function of the mutated Pex protein cause less severe forms.

Answer 55

peroxisome biogenesis disorders

Question 56

Peroxisomes:

_____ _____ _____ are translocated into the ER and inserted into the ER membrane.
These proteins then bud in vesicles.

Answer 56

peroxisome transmembrane proteins

Question 57

Peroxisomes:

_____ different types of vesicles containing different classes of peroxins fuse to form a functional peroxisome.

Answer 57

2

Question 58

Peroxisomes:

_____ _____ _____ are synthesized on free ribosomes and imported as folded polypeptides.
Most are targeted to peroxisomes by a PTS1 signal, recognized by a Pex5 receptor.
The Pex5/cargo complex binds to a docking complex on the peroxisome.

Answer 58

peroxisome matrix proteins

Question 59

Peroxisomes:

Peroxisomes can be formed by two distinct mechanisms:

1) _____ budding from the ER (peroxisomes have new content).
2) Growth and division of _____ peroxisomes (more rapid)

Answer 59

vesicle, existing