endosymbiosis

Question 1

endosymbiosis summary:

Answer 1

1. mitochondria and chloroplasts derive from once independent prokaryotic cells
2. they were ingested (taken/absorbed) by larger prokaryotic cells (by phagocytosis)
3. the engulfed cell may have been able to photosynthesise (perform function from the cell (becoming chloroplasts) or aerobically respire (becoming mitochondrion) and create a eukaryote

Question 2

what is phagocytosis?

Answer 2

phagocytosis is a cellular process for ingesting and eliminating particles larger than 0.5 μm in diameter

Question 3

how many stages would eukaryotic cells be involved in?

Answer 3

2 stages

Question 4

the two stages of eukaryotes are

Answer 4

• infolding of a membrane to form an endomembrane system which became ER, Golgi body and nuclear membranes
• endosymbiosis, the engulfing of a whole prokaryotic organism into the developing eukaryote. mitochondria and chloroplasts are believed to have been incorporated in this way

Question 5

the endosymbiotic theory suggests that

Answer 5

the engulfing of whole prokaryotic organisms led to the development of eukaryotic cells and mitochondria and chloroplasts are believed to have been free-living cells that were engulfed by larger prokaryotic cells

Question 6

symbiosis means

Answer 6

two different organisms living together for mutual benefit

Question 7

mitochondria are thought to have descended from close relatives of

Answer 7

typhus-causing bacteria

Question 8

endo means

Answer 8

inside

Question 9

true or false: prokaryotic cells have ribosomes in smaller sizes than eukaryotic cells

Answer 9

true

Question 10

where is the evidence of endosymbiosis in the chloroplasts of glaucophytes?

Answer 10

the chloroplasts of glaucophytes still have their cell wall as evidence from cyanobacteria

Question 11

what is some evidence that endosymbiosis can be found in the structure of present day mitochondria in chloroplasts?

Answer 11

• they resemble present day eubacteria in size (very weak evidence)
• they contain a small circular DNA molecule, RNA, and ribosomes that are similar to bacteria/prokaryotes
  they are capable of self-replication by a process similar to binary fission in prokaryotes
• they contain a double membrane as the outer membrane is similar to the plasma in a eukaryotic cell, the inner membrane is similar to lipid composition to that of a bacterial membrane

Question 12

the evidence of endosymbiosis in the structure and function of mitochondria

Answer 12

a single mitochondrion has many copies of mitochondrial RNA (mRNA) and, a eukaryotic cell may have hundreds of mitochondria depending on its type

Question 13

do all cells have the same amounts of mitochondria?

Answer 13

no, all cells have different amounts of mitochondria

Question 14

the evidence of endosymbiosis in the structure and function of chloroplasts

Answer 14

they are only found in green plant cells, and the structure consists of a double surrounding membrane with internal stacked plate-like structures (better known as thylakoids) and contains a green light trapping pigments such as chlorophyll

Question 15

the evidence of endosymbiosis in mitochondria binary fission

Answer 15

mitochondria divide in binary fission in basically the same way as prokaryotes

Question 16

do chloroplasts undergo binary fission?

Answer 16

yes they do, just like prokaryotes

Question 17

describe the fossil evidence that suggests prokaryotic cells existed before eukaryotic cells

Answer 17

• fossil evidence shows that primitive photosynthetic prokaryotes existed in stromatolites.
• the oldest stromatolites have been dated back at around 3.7 billion years old in greenland. but, on the other hand, the oldest recorded eukaryotic fossils date back to only 1.5 billion years ago.

Question 18

explain how the ancestry of most existing eukaryotic cells probably involved endosymbiotic events

Answer 18

• in ancient prokaryotes there was likely variation, which meant that some were able to photosynthesise while others were able to produce ATP using oxygen
• it is believed that larger prokaryotic cells engulfed smaller prokaryotes cells to produce ATP
• instead of the cells being digested, they lived in symbiosis with the larger engulfing cell
• the smaller prokaryotic cell is likely to become a mitochondria, which provides the larger cell with the necessary energy
• some prokaryotes would then go to engulf photosynthetic bacteria in the same way, but turn into chloroplasts instead