Question

1- list one similarity and one difference between free and bound ribosomes?

2-List two structural characteristics shared by prokaryotes and eukaryotes?

3-If endosymbiosis resulted in benefits for both partners in the relationship, what were the benefits? Make sure to include both cells in your answer?

Answer 1

Answer 1-  

DIFFERENCES –

Membrane-bound ribosomes are attached to a structure known as the rough endoplasmic reticulum. Free and membrane-bound ribosomes produce different proteins. Whereas membrane-bound ribosomes produce proteins that are exported from the cell to be used elsewhere, free ribosomes produce proteins used inside the cell itself.

SIMILARITIES –

Both free and Bound ribosomes translate the encoded information provided by mRNA in the cell nucleus, then they link the amino acids which are selected and collected by the tRNA from the cytoplasm (however, the order of linking up of amino acids is determined by mRNA). They, then export the polypeptide formed in this process, to the cytoplasm where it will be used to form a functional protein. The proteins synthesized by free ribosomes are sent to the Golgi apparatus for packaging. While the proteins synthesized by bound ribosomes remain in the endoplasmic reticulum.

Answer 2 - Like a prokaryotic cell, a eukaryotic cell has a plasma membrane, cytoplasm, and ribosomes, but a eukaryotic cell is typically larger than a prokaryotic cell, has a true nucleus (meaning its DNA is surrounded by a membrane), and has other membrane-bound organelles that allow for compartmentalization of functions.

Characteristic is shared by both prokaryotes and eukaryotes.

All cells, whether they are prokaryotic or eukaryotic, have some common features. The common features of prokaryotic and eukaryotic cells are DNA, the genetic material contained in one or more chromosomes and located in a nonmembrane bound nucleoid region in prokaryotes and a membrane-bound nucleus in eukaryotes.

Answer 3 - Endosymbiosis.- Endosymbiosis occurs when a symbiont lives inside the body or the cells of another organism. It is a very widespread phenomenon in living things. ... Single-celled forams which include a single-celled alga inside the cell.

The endosymbiotic theory deals with the origins of mitochondria and chloroplasts, two eukaryotic organelles that have bacteria characteristics. ... The theory states that a prokaryotic cell was consumed or engulfed by a larger cell.

Endo = "within"]
[Endocytosis = (cyto = cell) a process of 'cell eating' - cells are engulfed, but then usually digested as food....]
[Endosymbiosis = cells are engulfed, but not digested...cells live together is a mutually benefitting relationship or symbiosis]

Hypothesis originally proposed that:

• mitochondria are the result of endocytosis of aerobic bacteria
• chloroplasts are the result of endocytosis of photosynthetic bacteria
• in both cases by large anaerobic bacteria who would not otherwise be able to exist in an aerobic environment.
• this arrangement became a mutually beneficial relationship for both cells (symbiotic).

• Margulis' original hypothesis proposed that aerobic bacteria (that require oxygen) were ingested by anaerobic bacteria (poisoned by oxygen), and may each have had a survival advantage as long as they continued their partnership.
• Each would have performed mutually benefiting functions from their symbiotic relationship. The aerobic bacteria would have handled the toxic oxygen for the anaerobic bacteria, and the anaerobic bacteria would ingest food and protected the aerobic "symbiote".
• The result = a cell with a double-membrane bound organelle. The inner lipid bilayer would have been the bacterial cell's plasma membrane, and the outer lipid bilayer came from the cell that engulfed it.

Benefits of Endo Symbiosis

The evolution of the eukaryote cell was probably spurred by the benefits that the engulfed bacteria provided. If an anaerobic prokaryote engulfed anaerobic bacteria, it would have acquired the ability to generate energy from nutrients and oxygen. A prokaryote that took up cyanobacteria would acquire the ability to make energy utilizing sunlight. The engulfed aerobic bacteria and cyanobacteria would benefit from the protection and nutrients supplied by the host cell. The extra energy produced by the bacteria may have allowed the primitive eukaryotic cell to enlarge and acquire other bacteria, resulting in a more complex cell. Without the extra energy provided by the bacterial organelles, the primitive eukaryotic cell may not have been able to develop into a multicellular organism.