A level Biology: Post your doubts here!

[shan5674]

well i dont think so -i think it's enough to knowantigen-antibody- neutrophils -macrophages-B and T lymphocytes and their actions

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w09_qp_22.pdf

then could you explain to me how to answer Q1 - b? and C too please

 

[Peter Check]

i hope this diagram helps...there's alot of irrelevant data on it but just look at the stuff thats on our syllabus

thnx! (Im a chelsea fan too! )

 

[Peter Check]

i dont think so, J is the nucleolus, this is where the ribosomes are manufactured. while transcription is the formation of the mRNA molecule..this takes place in the nucleoplasm (nucleus) >> H.

I think he referring to the third(excluding the already printed answer). If not then you are right.

 

[angelpari]

-In an antibody, does the sugar chain attached influence the specificity of the antibody?
-What are the exact definitions for *nitrification* and *nitrogen fixation*?
Please help

Nitrogen fixation: This is the process which converts gaseous nitrogen by the help of enzymes nitrogenase, into forms such as amonia, which can be used by plants.

Nitrification: This is the process which oxidises amonia into nitrates in the presence of oxygen.

 

[KurayamiKimmi]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w09_qp_22.pdf

then could you explain to me how to answer Q1 - b? and C too please

for question b
Bacteria have proteins on their cell surface membrane which are identified as antigen/foreign by the phagocyte's receptor -glycocalyx acts as receptor . The phagocyte then flows around the bacteria or sticks to it by binding to its antigens and thus engulfs the bacteria into a vacuole

 

[KurayamiKimmi]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w09_qp_22.pdf

then could you explain to me how to answer Q1 - b? and C too please

as for c
Lysosomes fuse with the phagocytotic vacuole and then secrete hydrolytic enzymes that catalyse the breakdown of either the bacterial murein which makes up the cell wall -or by catalysing the breaking down its DNA

 

[hm12]

how do leguminous plants survive in nitrogen deficient soils?

 

[KurayamiKimmi]

how do leguminous plants survive in nitrogen deficient soils?

they have nitrogen fixing bacteria in their nodules called Rhizobium which convert the nitrogen into NH4+ for the plants to use They do this under anaerobic conditions so the plant regulates a protein called legahaemoglobin in the root nodules where the bacteria live , coz this protein efficiently mops up any oygen that enters the root nodules

 

[hm12]

they have nitrogen fixing bacteria in their nodules called Rhizobium which convert the nitrogen into NH4+ for the plants to use They do this under anaerobic conditions so the plant regulates a protein called legahaemoglobin in the root nodules where the bacteria live , coz this protein efficiently mops up any oygen that enters the root nodules

thanks

 

[Soldier313]

when is carbamino-haemoglobin formed and when is carboxy-haemoglobin formed??? please help urgently....tx

 

[SalamH]

when is carbamino-haemoglobin formed and when is carboxy-haemoglobin formed??? please help urgently....tx

carbamino haemoglobin is formed when co2 combines with Hb.carboxyhaemoglobin forms when carbon monoxide combines with haemoglobin

 

[Amaryllis]

when is carbamino-haemoglobin formed and when is carboxy-haemoglobin formed??? please help urgently....tx

when co2 combine directly with the -NH2 group (amine group) without that reaction that involve carbonic anhydrase enzyme >>> carbo amino haemoglobin is formed
while when carbon monoxide combine with haemoglobin ,,carboxyhaemoglobin is formed

 

[geek101]

when is carbamino-haemoglobin formed and when is carboxy-haemoglobin formed??? please help urgently....tx

Carboxyhaemoglobin is when haemoglobin reacts with CO (carbon monoxide)...
and carbino haemoglobin is when some of the CO2 inside the RBCs reacts with the amine -NH2 groups in haemoglobin. 10% of carbon dioxide is transported in this form.

 

[Soldier313]

Thanx people bt the pro is check out mj/11 p21 the ms says that CO2 combines with Hb and carboxyhaemoglobin is formed! Please check it out and explain...thanx soo much and God bless you all!

 

[Saad (سعد)]

Urgent.

What's the function of the enzyme helicase and the enzyme DNA Polymerase.

 

[geek101]

Urgent.

What's the function of the enzyme helicase and the enzyme DNA Polymerase.

hilicase: breaks the H bonds between the bases when ''unzipping'' occurs before replication.
DNA polymerase: it attaches every incoming nucleotide to the previous strand being formed complementary to the template. (forms the sugar-phosphate backbone)

 

[soccerprinc3]

Thanx people bt the pro is check out mj/11 p21 the ms says that CO2 combines with Hb and carboxyhaemoglobin is formed! Please check it out and explain...thanx soo much and God bless you all!

yeah i saw tha earlier and wanted to come ask aswell..but when you come to look at it..there's a "/" between the two answers so maybe that meant it was another idea and wasn't referring to the CO2 and Hb combining?

 

[Saad (سعد)]

Thanks.

Can someone please tell me an outline of the sequence in an Immune Response.

 

[soccerprinc3]

thnx! (Im a chelsea fan too! )

lol Long live the Blues..goodluck with your exams tomorrow bro

 

[Soldier313]

yeah i saw tha earlier and wanted to come ask aswell..but when you come to look at it..there's a "/" between the two answers so maybe that meant it was another idea and wasn't referring to the CO2 and Hb combining?

Nah I don't think it's another idea....I feel there's a point I am missing there....maybe something to do with the part of Haemoglobin the CO2 combines with......people please help out....tx a lot!