A level Biology: Post your doubts here!

[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!

 

[soccerprinc3]

Thanks.

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

Primary response
1) the pathogen invades the body
2) it damages or weakens body cells
3) the weakened body cells produce proteins called histamines
4) the phagocytes in the blood are attracted to these proteins...(chemotaxis)
5) the phagocytes (macrophages) engulf the pathogen by phagocytosis and display the non self antigens on its surface
6) the T helper cells with the complementary receptors goes and recognizes the antigens of the pathogen, and secretes chemicals which cause the bone marrow to form T Killer cells, and secretes cytokines (hormone-like)
7) B lymphocytes with the complementary surface receptors are activated due to these cytokines and divide by mitosis to produce B-memory cells and Plasma cells.
8) The B memory cells further divide to produce more memory cells and plasma cells.
9) the plasma cells release anitbodies with the variable region (antigen binding site) complementary to the antigens of the pathogen. These antibodies destroy the pathogens.
10) The T killer cells (cytotoxic T cells) with the specific complementary receptors release chemicals such as hydrogen peroxide or punch holes in the infected body cells to remove and kill any remaining weakened body cells, and the remaining debris.
11) The memory B and memory T cells remain circulating in the blood.
Secondary response:
The memory cells which are in the blood on the encounter of the pathogen with the antigens complementary to their receptors, divide rapidly producing plasma cells which secrete antibodies (more than the primary response) and the pathogens are destroyed in a short time.

Correct me if im wrong

this helped me out..hope it helps you too