Bio Problems

[rz123]

describe the role of centrioles in animal cells.

 

[libra94]

centrioles helps in nuclear division and therefore cell division and therefore cell growth by mitosis.
its made up of 9 triplets of microtubules (which are made up of protein tubulin)
cilia, is also made up of microtubules (same material used for centrioles)

 

[workinghard]

describe the role of centrioles in animal cells.

centrioles are involved in both kinds of cell divisions ie. meiosis and mitosis and thus play vial role in growth and reproductio
they form spindle fibres that seperate the chromosomes during these divisions

and other than this the struc described by libra94 is right

 

[rz123]

and what about its role in anaphase , metaphase, prophase and telophase. how does it take part in these stages of cell division.

 

[hassam]

well all u have to remember is the word MTOCs....i.e microtubule organising centre......then u have to make links......
just b4 nuclear division they replicate and start moving towards opposite pole and generate spindle fibres.these fibres attach to centromere at the kinetochores...centrioles role in anaphase is that the centromere division and chromosome being pulled apart all happens due to contraction of spindle fibres.....these spindle fibres are also responsible for elongating the cell to such an extent that at cytokinesis the membrane just fuses off.....

 

[workinghard]

and what about its role in anaphase , metaphase, prophase and telophase. how does it take part in these stages of cell division.

in metaphase the chromosomes lie up on the eq of spindle fibres formed from dese centrioles
in anaphase the spindle fibres are pulled back by the centrioles and this causes either the whole chromosomes (meiosis) or chromatids (mitosis) 2 be pulled apart and move to the opp poles
in telophase these fibres break up and centrioles move back to their original positions
helped? :?:

 

[workinghard]

dont' thank me so much
i'm more dan glad 2 help
feel free 2 ask n forget bout thankin
u'll make me blush!!!!!!!!!!

 

[rz123]

haha dats nice, i like the spirit of helpin well then tell me may june 2010 paper mcqz problems: 9, 13, 20, 22, 32 and 38, explain me the right option.
q.4 b and c part paper 22 may june 2010,

 

[rz123]

DNA is said to be replicated in a semi-conservative way. results of Meselson and Stahl's experiments gave overwhelming support to this theory. they used E.Coli which has a generation of 50 minutes. explain me their results which shows experimental evidence for the semi-conservative replication of DNA.

 

[hassam]

 

[maybeitwasnoone]

Had a doubt on this one for weeks. Thanks

 

[rz123]

hmm good brief summary thanks.

 

[rz123]

suggest and explain how the flow of blood in a person with patent ductus arteriosus differes from that of a person with a healthy heart. may/jue 2010 q.2 c

 

[workinghard]

hey i jat saw ur ques ll ans dem 2nite!

 

[rz123]

k i will wait tnx

 

[workinghard]

did u mention da component? as in 11, 12 or 13 or 21 22 or 23???????

 

[rz123]

state why it is important for enzymes such as lysozome to possess a tertiary structure. may/june 2010 q 4 c part also if anyone can answer

 

[libra94]

for the heart one.........
patent ductus is when a link between the pulmonary artery and the aorta fails to close, which means the pulmonary carrying deoxygenated blood mixes with the oxygenated blood in the aorta and therefore the floww of blood decreases cuz the blood with high pressure(in aorta-when the ventricles are contracted) will move into the pulmonary artery..

it is important for enzymes such as lysozome to possess a tertiary structure to help in maintaining its shape, the active site! the strong ionic, hydrogen bonds can keep the shape in a fixed position

 

[workinghard]

suggest and explain how the flow of blood in a person with patent ductus arteriosus differes from that of a person with a healthy heart. may/jue 2010 q.2 c

Patent ductus arteriosis
*Oxygenated and deoxygenated blood ll b mixd since pulmonary artery carries deoxygenated blood and aorta carries oxygenated blood
*Blood volume to lungs ll increase since blood will flow from aorta into the pulmonary artery – high pressure in aorta ll force the blood out in pulmonary artery
*The diffusion gradient for gaseous exchange ll decrease since the blood arriving in the lungs ll have oxygenated blood mixed with deoxygenated

And if u want to run ur imagination wild…
*The capillaries in the lungs could burst if the volume is increased 2 much
*And since pressure in aorta ll decrease because of the flowing out of blood heart ll have 2 pump harder
*Moreover the volume of bloodin aorta ll also be decreased as a result of blood flowing out so u could say that heart ll have to work harder to ensure supply of blood 2 da whole body

*4m wat I pickd up 4m med book
• as the person grows older, the differential b/w the high pressure in the aorta and the lower pressure in the pulmonary artery progressively increases with the backward flow of blood from the aorta into the pulmonary artery. Also the high aortic blood pressure usually causes the diameter of the partially open ductus to increase with time making condition even worse
• one half to two thirds of the aortic blood flows backward through the ductus into the pulmonary artery, then through the lungs and finally back into the left ventricle and aorta passing through the lungs and left side of the heart two or three more times for every one time it passes through the systemic circulation
• heart could fail and lungs could become congested later in life
• in early part of life blood is usually more oxygenated than the normal ppl
• decreased cardiac and respiratory reserve – net blood flow through the rest of the body during exercise can never increase to the levels required for the strenuous exercise – person can feel weak or faint from momentary heart failure!
• High pressure in the pulmonary vessels cus pulmonary congestion and oedma – excessive load on heart – these ppl can die b/w ages of 20 and 40
• A harsh blowing sound is produced during systole

I think I overloaded da info here!? Did i?

 

[rz123]

yeah the question was of only 3 marks but this detail info helped refine the concepts. thanks a lot