Deck 13: Mitochondria, Chloroplasts, and Peroxisomes

Question 1

Mitochondrial and chloroplast proteins are synthesized on

A) ER ribosomes.
B) free cytosolic ribosomes.
C) the Golgi apparatus.
D) peroxisomes.

Answer 1

B

Question 2

Which of the following contain their own genomes?

A) Mitochondria, but not chloroplasts and peroxisomes
B) Chloroplasts, but not mitochondria and peroxisomes
C) Mitochondria and chloroplasts, but not peroxisomes
D) Mitochondria, chloroplasts, and peroxisomes

Answer 2

C

Question 3

Which statement about mitochondria is true?

A) They produce most of the ATP derived from the breakdown of lipids and carbohydrates.
B) They produce all of the ATP derived from the breakdown of fatty acids.
C) They produce all of the ATP derived from the breakdown of carbohydrates.
D) They produce about 10% of the ATP derived from the sunlight.

Answer 3

A

Question 4

The infoldings of the inner mitochondrial membrane are called

A) cisternae.
B) cristae.
C) laminae.
D) lamellae.

Question 5

The inner compartment of mitochondria is called the

A) stroma.
B) intermembrane space.
C) inner membrane space.
D) matrix.

Question 6

Which compound is a product of glycolysis that is transported into the mitochondria?

A) Pyruvate
B) Acetate as acetyl CoA
C) Lactic acid
D) Citric acid

Question 7

The citric acid cycle consists of the oxidation of _______ to produce _______.

A) pyruvate; CO₂, NADH, and FADH₂
B) acetyl CoA; CO₂, NADH, and FADH₂
C) pyruvate; CO₂
D) pyruvate; NADH and FADH₂

Question 8

Most small molecules are permeable across

A) both mitochondrial membranes.
B) the inner, but not the outer, mitochondrial membrane.
C) the outer, but not the inner, mitochondrial membrane.
D) neither mitochondrial membrane.

Question 9

Mitochondria can

A) divide by fission.
B) fuse with one another.
C) be transported to areas of high energy use.
D) All of the above

Question 10

The mitochondrial outer membrane contains channels composed of proteins called

A) porins.
B) aquaporins.
C) connexins.
D) claudins.

Question 11

The outer mitochondrial membrane contains proteins that

A) synthesize ATP.
B) pump protons.
C) transport pyruvate and fatty acids.
D) direct translocation.

Question 12

Electron transport occurs in the mitochondrial

A) outer membrane.
B) intermembrane space.
C) inner membrane.
D) matrix.

Question 13

The process by which mitochondria are thought to have arisen during evolution is called

A) symbiosis.
B) phagocytosis.
C) endosymbiosis.
D) pinocytosis.

Question 14

Most mitochondrial genomes consist of

A) a single linear DNA molecule.
B) several linear DNA molecules.
C) several circular DNA molecules.
D) a single circular DNA molecule.

Question 15

The organisms most similar to mitochondria are

A) progenotes.
B) $\alpha$ -proteobacteria.
C) cyanobacteria.
D) purple sulfur bacteria.

Question 16

Mitochondria contain

A) no genes of their own.
B) genes for mitochondrial proteins.
C) genes for mitochondrial proteins and rRNAs.
D) genes for mitochondrial proteins, rRNAs, and tRNAs.

Question 17

In what way does the mitochondrial genetic code differ from the "universal" genetic code?

A) Some codons code for different amino acids.
B) There are no stop codons.
C) It accommodates less wobble.
D) All of the above

Question 18

The proteins encoded by the human mitochondrial genome function in

A) mitochondrial ribosomes.
B) mitochondrial DNA polymerases.
C) respiratory complexes and oxidative phosphorylation.
D) helicases.

Question 19

Mitochondrial DNA is inherited by means of

A) maternal transmission.
B) paternal transmission.
C) random assortment.
D) Mendelian genetics.

Question 20

Which of the following is a mitochondrial disease?

A) Lou Gehrig's disease
B) Retinoblastoma
C) Leber's hereditary optic neuropathy
D) Crohn's disease

Question 21

Most mitochondrial proteins are synthesized on

A) mitochondrial ribosomes from nuclear mRNAs.
B) cytoplasmic ribosomes; they are imported co-translationally as they are being synthesized.
C) cytoplasmic ribosomes; they are imported after they are completely synthesized.
D) mitochondrial ribosomes from mitochondrial mRNAs.

Question 22

Mitochondrial targeting presequences usually consist of a

A) hydrophobic $\alpha$ helix.
B) hydrophobic random chain.
C) negatively charged $\alpha$ helix.
D) positively charged $\alpha$ helix.

Question 23

Tim and Tom are

A) twin brothers with the same mitochondrial disease.
B) chaperones.
C) protein translocators in mitochondrial membranes.
D) transporters of small molecules across the mitochondrial membranes.

Question 24

The mitochondrial protein presequence is cleaved off by a protease called

A) signal peptidase.
B) presequence protease.
C) ubiquitin-targeted protease.
D) matrix processing peptidase.

Question 25

Mitochondrial inner membrane single-pass transmembrane proteins are inserted into the inner membrane

A) through a transporter called Oxa translocase.
B) through Tim.
C) through Tim and Tom.
D) directly from the matrix into the lipid bilayer.

Question 26

Most mitochondrial phospholipids are synthesized in the

A) mitochondrial matrix.
B) mitochondrial intermembrane space.
C) ER.
D) Golgi apparatus.

Question 27

Which of the following is not involved in the initial transport of a protein across the mitochondrial outer membrane from the cytosol?

A) Hsp70
B) Tim23
C) Tom
D) ATP

Question 28

Which of the following is not involved in targeting a protein from the intermembrane space into the inner mitochondrial membrane?

A) Tim9
B) Tim10
C) Tim22
D) Tom

Question 29

The import of mitochondrial matrix proteins from the cytoplasm requires

A) an electrochemical gradient across the inner membrane.
B) a potassium gradient across the inner membrane.
C) ATP and a proton gradient across the inner membrane.
D) ATP and a potassium gradient across the inner membrane.

Question 30

The energy required to drive the transport of small molecules into and out of mitochondria is provided by the

A) chemiosmotic gradient.
B) hydrolysis of ATP.
C) electrochemical gradient.
D) negative charge of small molecules.

Question 31

Which of the following phospholipids contains four fatty acid chains and is associated with a restriction in proton flow?

A) Phosphatidylcholine
B) Cholesterol
C) Sphingolipid
D) Cardiolipin

Question 32

Chloroplasts differ from mitochondria in that chloroplasts

A) do not generate ATP.
B) do not originate by endosymbiosis.
C) do not replicate by division.
D) synthesize their own amino acids and fatty acids.

Question 33

Chloroplasts are similar to mitochondria in that both

A) have a porous outer membrane.
B) contain light sensitive pigments.
C) require presequence amino acids on proteins for import.
D) require folded cristae as the site of electron transport.

Question 34

Chloroplasts synthesize

A) elaioplasts.
B) amino acids.
C) peroxisomes.
D) catalase.

Question 35

The chloroplast genome contains about _______ genes.

A) 20
B) 150
C) 1,500
D) 3,000

Question 36

Chloroplast tRNAs translate

A) all mRNA codons according to the universal code.
B) all the amino acids according to the universal code but have different stop codons.
C) some codons as amino acids that differ from the universal code but use the same stop codons.
D) some codons as amino acids that differ from the universal code and use some different stop codons.

Question 37

Most chloroplast proteins are synthesized on

A) free ribosomes in the cytosol.
B) RER membranes in the cytoplasm.
C) ribosomes bound to the outer chloroplast membrane.
D) ribosomes in the chloroplast stroma.

Question 38

The transport of proteins across the outer and inner chloroplast membranes occurs through complexes called

A) Tim and Tom.
B) Tic and Toc.
C) Sec and Tat.
D) import complexes.

Question 39

Many proteins incorporated into the thylakoid lumen are synthesized

A) in the thylakoid lumen.
B) in the stroma and transported across the thylakoid membrane.
C) on the outer chloroplast membrane and transported across the thylakoid membrane by way of its hydrophobic signal sequence.
D) in the cytosol, imported into the stroma, and transported across the thylakoid membrane by way of a second signal sequence.

Question 40

Carotenoids are stored in

A) chloroplasts.
B) chromoplasts.
C) amyloplasts.
D) elaioplasts.

Question 41

All plastids, including chloroplasts, develop from

A) chromoplasts.
B) etioplasts.
C) elaioplasts.
D) proplastids.

Question 42

An amyloplast is a plastid that

A) stores starch.
B) stores lipid.
C) is arrested in chloroplast development by lack of light.
D) stores pigment.

Question 43

The major function of peroxisomes is to

A) oxidize certain organic molecules and degrade the H₂O₂ produced by these reactions.
B) produce hydrogen peroxide for cells.
C) digest old organelles.
D) digest macromolecules taken up by endocytosis.

Question 44

Peroxisomes contain the enzyme _______, which breaks down H₂O₂ into H₂O and oxygen.

A) peroxidase
B) catalase
C) peroxigen
D) glyoxylate

Question 45

Which of the following is the human disease caused by mutations in the proteins required for importing functional proteins into peroxisomes?

A) Turner's syndrome
B) Zellweger syndrome
C) I-cell disease
D) Leber's hereditary optic neuropathy

Question 46

Most peroxisomal proteins are synthesized on

A) free ribosomes in the cytosol.
B) RER membranes in the cytoplasm.
C) ribosomes bound to the outer peroxisome membrane.
D) ribosomes inside the peroxisome.

Question 47

New peroxisomes form by

A) budding from the Golgi apparatus.
B) budding from preexisting peroxisomes.
C) de novo assembly from proteins synthesized in the cytosol.
D) budding of vesicles from the ER and growth and division of preexisting peroxisomes.

Question 48

The citric acid cycle produces two reduced cofactors, _______ and _______.

Question 49

To enter the mitochondria, precursors of the $\beta$ -barrel proteins pass through the _______ complex into the intermembrane space; there, they are recognized and transported to a second complex, called the _______complex, and inserted into the outer membrane.

Question 50

Chloroplasts have three membranes: the inner membrane, the outer membrane, and the _______ membrane.

Question 51

In terms of its role in the generation of metabolic energy, the thylakoid membrane of chloroplasts is equivalent to the _______ of mitochondria.

Question 52

Chloroplasts contain their own genetic system, reflecting their evolutionary origins from photosynthetic _______.

Question 53

Although chloroplasts encode more of their own proteins than mitochondria, about 3,000 or 95% of chloroplast proteins are still encoded by _______ genes.

Question 54

Once through the Toc complex in the outer membrane of the chloroplast, proteins are transferred to the _______ in the inner membrane.

Question 55

Proteins can be targeted to the thylakoid membrane by at least _______ different pathways.

Question 56

In chloroplasts, the _______ pathway is related to the pathway used to translocate proteins into the endoplasmic reticulum.

Question 57

In addition to _______ from the ER, new peroxisomes can be formed by the growth and division of old peroxisomes.

Question 58

All mitochondria use the universal genetic code.

Question 59

Most mitochondrial proteins are coded for by the mitochondrial genome.

Question 60

Mitochondria lacking mitochondrial DNA are soon unable to make ATP by oxidative phosphorylation.

Question 61

Mitochondria contain about 1,500 different proteins.

Question 62

Most proteins are imported into mitochondria in their fully folded state.

Question 63

A mitochondrial matrix protein is maintained in its unfolded state by an Hsp70 chaperone protein before transport across the mitochondrial membrane.

Question 64

Some proteins destined for insertion into the inner membrane are transported from the matrix compartment.

Question 65

Mitochondrial phospholipids are delivered to mitochondria by phospholipid transfer proteins.

Question 66

In mitochondria, the pH of the matrix is higher than the pH of the intermembrane space.

Question 67

Chloroplasts are only one of a much larger family of plant organelles called plastids that all contain the same genome.

Question 68

Where in mitochondria does each of the following processes or events occur?
-Synthesis of mitochondrial ribosomal RNAs

Question 69

Where in mitochondria does each of the following processes or events occur?
-Diffusion of small molecules via porin-formed channels

Question 70

Where in mitochondria does each of the following processes or events occur?
-The citric acid cycle

Question 71

Where in mitochondria does each of the following processes or events occur?
-Oxidative phosphorylation of ATP

Question 72

What are some of the reasons evolutionary biologists believe mitochondria came from bacteria through endosymbiosis?

Question 73

What would be the effect of a mutation in the Tim23 complex?

Question 74

Where does the energy for phosphate transfer across the mitochondrial inner membrane to the matrix come from?

Question 75

Both mitochondria and chloroplasts use a proton gradient to drive ATP synthesis, but in different locations. What is the major structural difference, that is related to the proton gradient, between mitochondria and chloroplasts, and where is ATP generated in each?

Question 76

What effect would a functional mutation in the Toc complex have on chloroplasts?

Question 77

Translocase proteins such as Toc have channels that are just barely wider than a single amino acid. Since most mature proteins have significant secondary and tertiary structure, how do they fit through the narrow channels of these translocases?

Question 78

What are the two mechanisms by which peroxisomes can be formed?

Question 79

Mitochondria differ from other organelles such as lysosomes and the Golgi apparatus in that they

A) contain enzymes specific to their function.
B) contain their own genomes.
C) do not contain proteins that are imported from the cytosol.
D) are not membrane-bounded.

Question 80

What is the major site of energy production in the form of ATP in human cells?

A) The mitochondrial matrix
B) The cytoplasm
C) The outer mitochondrial membrane
D) The inner mitochondrial membrane