Another Barron's Problem

[dane4695]

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I'm just curious if anyone knows why this is the case... the quesiton says something like which of the following are "true cells"

Leucocytes
Erythrocytes
Plateles

Then gives answers like.
1 only
2 only
1 and 3
1 and 2
1 2 and 3

I obviously dont' completely understand the definition of "true cell." I was thinking tha since eryth. lack nuclei, they probably weren't a "true cell" since eukaryotic cells are typically nucleiated. Three is obviously wrong and 1 is obiviously right. Any insights as to why B is considered a true cell? I hope i'm not being dumb 🙂

 

[DrTacoElf]

erythrocytes are considered a true cell for a couple reasons.

1) they initally have all organelles however through maturation they lose these in order to become optimized for gas exchange. However the plasma membrane is retained.

2) they get energy from anaerobic respiration

platlets on the other hand are not "alive" they are fragemented cells which require no energy for upkeep.

 

[Sprgrover]

The reason why two answer choices are true cells, and one is not, has to do with erthyrocyte and blood platelet formation. Platelets are formed from the budding of a megakaryocyte's cytoplasm and never contain all of the organelles that a true cell has. An erythrocyte is formed as a complete cell - nucleus and all. In humans it circulates in the blood for a while before enucleating and turning into a 'normal' rbc. Another clue is that the question doesn't state which species is under consideration as some animal's erythrocytes, such as those of birds, don't lose their nucleus (though it is inactivated). For these reasons, two of the options are true cells (at least sometime in their development) and that leaves B as the logical choice. You're not dumb at all - the question is just tricky.

 

[dane4695]

Thanks guys -- clear as day. For some reason I thought the fact that it loses its nucleus / organelles would matter 🙂 But i guess not!

 

[sinned]

from what I just gathered on the internet including this pdf file from UIC...it seems as though erythrocytes are NOT true cells, leukocytes are true cells and platelets are not as well...leaving us only with leukocytes being the only true cell...

http://www.uic.edu/ahp/knad/ppt/252_082_components_of_blood.pdf

 

[Sprgrover]

Good observation, sinned. Perhaps another explaination for why an erythrocyte is considered a true cell is in order. For example, a tunicate is considered a chordate. For a long time scientists were puzzled by this strange creature and didn't know quite how to classify it. The reason why it is considered to be a chordate (there is still some debate if it should be in its own phylum - Urochordata - or if it should be with Chordata but that is beside the point) is because it displays the four hallmarks of chordates at least some point along its developmental pathway. Same thing with an erythrocyte. Keep in mind that in some animals erythrocytes retain their organelles, though they may not function after a certain period of time.
At some point they are functional cells, though they undergo differentiation.

Check out this link:
http://education.vetmed.vt.edu/Curriculum/VM8054/Labs/Lab6/Examples/exbrdrbc.htm .

Your link is a pdf file an I have a feeling it was a slide show meant to accompany an entry level science course. Often times instructors, when faced with an audience of glassy-eyed freshment, will make generalizations so as not to overwhelm students and get them thoroughly confused. I hope this helps!

 

[dane4695]

Blah. I don't feel like I am completely satisfied either way. Perhaps it's a bad question.

 

[sinned]

Yea, saw that link as well, I will get the correct answer for you guys...