CHEM AND BIO HELP AND TIPS HERE

[nid404]

Guys,
        These r my subjects. So if u have any doubts or want to share some tips, pls go ahead. I'll try to answer all ur questions asap........others can join in to help(of course).
There's no common thread for these subjects and so I thought of having one. It'll be easier.

[jkiam11]

A question set by my teacher, not sure where he got it and I have no clue about it.

The allele for a normal haemoglobin is In. The allele for a sickle cell haemoglobin production is Is. Explain why under  some circumstances people who are heterozygous for this condition have a greater chance of survival than homozygous people.

[nid404]

This is pretty easy. Sickle cell anaemia is caused by a mutation in the blood. When the faulty haemoglobin is present the red blood cells become sickle-shaped, especially when oxygen levels in the blood become low. So these cells r less efficient in transporting oxygen and more likely to get stuck in the capillary, preventing blood flow. The faulty allele is dominated by the normal haemoglobin but has some effect in a heterozygous genotype.(not life-threatening)

Malaria is a life-threatening disease caused by a parasite that invades red blood cells. A person who is heterozygous has a protection from malaria, because the parasite is unable to invade and reproduce in these cells.  A person who is homozygous for sickle cell also has high protection but is likely to die from sickle cell anaemia whereas a person with normal haemoglobin is at a high risk of contracting malaria.

The distributions of malaria and sickle cell on the map coincide in tropical areas because of the selective advantage of the sickle cell allele in providing protection against malaria.

I hope u've understood

[jkiam11]

K thanks

[nid404]

my pleasure

[kawyn]

can u explain the functions of the lymphatic system?

[nid404]

for our syllabus this is all we need to know. Lymphatic system is really complicated if u try goin' into details. So here it is
Three functions
-The return of tissue fluid to the blood in the form of lymph fluid. This prevents fluid build-up in tissues.
-The production of lymphocytes(very imp). These r made in the lymph glands such as the tonsils, adenoids and spleen. The glands become more active during the time of an infection because they r producing and releasing large no of lymphocytes.
-The absorption of fatty acids and glycerol from the small intestine. Each villus contains a lacteal- a blind ending lymph vessel which absorbs the fatty acids and glycerol.

This is all u need to know. Don't get urself confused by trying to unlock the whole working of the lymphatic system. It's there in detail in the A levels. For now this is it. Hope uve got the functions.

[magician007]

Could you help in details about the kidney tubule (nephron)?

Like the glomerulus, and stuff?

[2009scared]

cud nid404 help me wit nov 01 p6 of bio..its urgent..please
i m not sure of my answers..

[SGVaibhav]

nid404
the biology specialist
looks like he wants to go in medical

[nid404]

yup. I can help u with the process.
Blood is got to the kidney via renal artery. The renal artery divides into a great number of arterioles and capillaries, mostly in the cortex. Each arteriole leads to a glomerulus. The pressure in the glomerulus causes part of the blood plasma to leak the capillary walls. The RBC's and proteins in plasma r too big to pass out. The fluid that moves out contains mainly water with dissolved salts, urea, glucose and uric acid. The process by which the fluid is filtered out of the blood by the glomerulus is called ultrafiltration. The filtrate from the glomeruls collects in the renal capsule and trickles down the renal tubule. As it does so, the capillaries which surround it absorb the substance the body needs. All the glucose is absorbed, with much of the water(depends on the state of hydration). The some salts r taken back to keep the correct con in the blood. This process of taking back the required substances is called selective reabsorption.

Substances that r not needed pass further down to the collecting duct into the pelvis of the kidney. From here the fluid, now called urine, passes down the ureter to the bladder.


Nephron- A single glomerulus with its renal artery, renal tubule and blood capillaries

visit the site for a good animation http://www.biologymad.com/resources/kidney.swf

[nid404]

nid404
the biology specialist
looks like he wants to go in medical

y do ull change ma gender all the time. By the way i want to work for conservation of wildlife. And w8 help in nov 2001 do u want 2009scared???

[nid404]

guys i will get back to u later. sorry 2009 scared i can't ans rightaway but i promise to get back. Please tell me the questions ur having difficulties with.

[angell]

thanks nid!

[nid404]

ur welcome and thanks to u too for acknowledging