evidence of bacterial origins of chloroplasts

Question 1

define: endosymbiosis

Answer 1

symbiotic relationship in which one organism lives inside another.

Question 2

describe how the first photosynthetic eukaryotes were formed

Answer 2

o A free-living photosynthetic microbial cell (ie. the original chloroplast) was, ages ago, engulfed by another microbial cell. This event soon gave rise to the first photosynthetic eukaryotes.

Question 3

how was this engulfment endosymbiotic?

Answer 3

 The engulfed cell gained a protective environment and an additional energy source when sunlight wasn’t available.
 The large cell gained a source of carbohydrate production.

Question 4

DNA evidence for chloroplasts’ bacterial origin?

Answer 4

o DNA not enclosed in nuclear membrane, and in form of circular DNA molecule – like in bacteria cells.

Question 5

ribosomal evidence for chloroplasts’ bacterial origin?

Answer 5

o Have their own ribosomes (like bacteria), and are smaller than those present in cytosol of host cells.
o ribosomes are sensitive to the same antibiotics that target bacterial ribosomes (but these don’t affect eukaryotic ribosomes)

Question 6

reproductive evidence for chloroplasts’ bacterial origin?

Answer 6

o Chloroplasts divide by binary fission, like bacteria cells

Question 7

general structure evidence for chloroplasts’ bacterial origin?

Answer 7

o Chloroplasts enclosed within double membrane envelope, similar to outer and inner membranes in some bacteria cell walls.
o Size similar to bacterial cells