The origins and functions of mitochondria and chloroplasts

Question 1

Compare mitochondria and chloroplasts

Answer 1

• membrane-bound sub-compartments of eukaryotic cells
• full of internal membranes (increase SA of compartment)
• responsible for much of energy production in eukaryotic cells

Question 2

In eukaryotes … of total cellular protein is in the mitochondrion

Answer 2

about 5%

Question 3

In plants … of total cellular protein is in the chloroplast

Answer 3

~70% (~20-50% is rubisco)

Question 4

Chloroplasts

Answer 4

• occupy a high percentage of the total volume of a plant cell
• move about inside cells in response to light

Question 5

Describe the links between chloroplasts and cyanobacteria (Microcystis)

Answer 5

• descendents
• look much the same under an electron microscope
• both have large amounts of internal membranes

Question 6

Mitochondria

Answer 6

• descendants of an alphaproteobacterium
• undergone proliferation of internal membranes
• reticulate network inside metazoan cells is highly dynamic

Question 7

Describe the dynamism of the mitochondrial reticulate network inside metazoan cells

Answer 7

moving, branching and fusing

Question 8

When did mitochondrial endosymbiosis occur?

Answer 8

before the radiation of the eukaryotes

Question 9

Describe the inheritance of mitochondria and chloroplasts in all eukaryotes

Answer 9

maternal

Question 10

Describe the mitochondrial genome across the tree of life

Answer 10

• 13 protein coding genes (humans)
• 35 protein coding genes (plants)
• 62 protein coding genes (Reclinomonas)

Question 11

Describe mitochondrial gene retention

Answer 11

• retained genes involved in energy production

Question 12

Describe the human mitochondrial genome

Answer 12

• circular genome
• involved in oxidative phosphorylation
• rRNA genes (but not any ribosomal proteins)
• tRNAs

Question 13

Describe the genome of free-living alphaproteobacterium (e.g. Magnetococcus)

Answer 13

~5000 protein coding genes

Question 14

Describe the genome of an endosymbiotic alphaproteobacterium (e.g. Rickettsia)

Answer 14

~1000 protein coding genes

Question 15

Describe the plant mitochondrial genome

Answer 15

• extra proteins for cytochrome c biogenesis
• extra ribosomal proteins for information processing
• a maturase and a two transporters

Question 16

Describe the genome of a free living cyanobacterium (e.g. Microcystis)

Answer 16

~6000 protein coding genes

Question 17

Describe the genome of an endosymbiotic cyanobacterium (e.g. Nostoc)

Answer 17

• ~7600 protein coding genes
• gene acquisition

Question 18

Describe the chloroplast genome across phylogeny

Answer 18

• 80 protein coding genes (land plants)
• 100 protein coding genes (glaucophytes)
• 220 protein genes (red algae)

Question 19

Chloroplast has been an endosymbiont for

Answer 19

1 billion years

Question 20

Mitochondrion has been endosymbiont for

Answer 20

2 billion years

Question 21

Describe the chloroplast gene retention

Answer 21

retained genes for energy production and information processing

Question 22

Describe the chloroplast genome of the Embryophytes

Answer 22

• circular genome
• rRNA genes
• tRNA genes
• NADH dehydrogenase-like complex (Complex I)
• Cytochrome b6f complex (Complex III)
• ATP synthase (Complex V)
• Ribosomal protein genes
• Photosystem genes (PSI and PSII)
• Rubisco large subunit
• Some other bits and pieces

Question 23

Describe the gene-protein relationship of mitochondria

Answer 23

• 13 – 60 genes
• 3000 different proteins

Question 24

Describe the gene-protein relationship of chloroplasts

Answer 24

• 60 – 200 genes
• 3000 different proteins

Question 25

Describe how gene transfer to the nucleus is fine

Answer 25

• genes transcribed in nucleus
• proteins translated in cytosol
• imported into chloroplast/mitochondrion

Question 26

Describe the genome copy number per cell

Answer 26

Nuclear genome: 2
Mitochondrial genome: 200
Chloroplast genome: 5000
(significantly different in H. sapiens for ATP)

Question 27

Describe the function of the mitochondria

Answer 27

• ATP
• NADH
• NH3
• BCAA
• Lipids