A level Biology: Post your doubts here!

[angelpari]

Hey, do we also have to do the electrocardiogram as well, besides the usual pressure graph for cardiac cycle???

i don't think so..
but if yes..then do let me knw too

 

[geek101]

Hey, do we also have to do the electrocardiogram as well, besides the usual pressure graph for cardiac cycle???

i don't think so..
but if yes..then do let me knw too

i checked up the syllabus and it mentions all the normal things in this chapter but the last line says...''use the knowledge gained in this section in new situations or to solve related problems'' so i guess the electrocardiogram and the pressure graphs come in the related stuff. no harm in doing it...exams are unpredictable

 

[angelpari]

i checked up the syllabus and it mentions all the normal things in this chapter but the last line says...''use the knowledge gained in this section in new situations or to solve related problems'' so i guess the electrocardiogram and the pressure graphs come in the related stuff. no harm in doing it...exams are unpredictable

yea ryt.. its just a lil concept.. better to do this

 

[rogue94]

i checked up the syllabus and it mentions all the normal things in this chapter but the last line says...''use the knowledge gained in this section in new situations or to solve related problems'' so i guess the electrocardiogram and the pressure graphs come in the related stuff. no harm in doing it...exams are unpredictable

hmmm, thanks for the insight! better do it then! also, uses of ions are no longer in our syllabus except for nitrates and magnesium, no harm in doing them as well i guess!

 

[haroon740]

hi
why is the antibiotics non effective on viruses?
and is the co2 transport included in the syllabus or i should only know the bohr's effect?

Heyy man, first thing Viruses are are not living cells and they r just Proteins which require a hist in which they multiply so basically they do not have cell walls and antibiotics affect cell wall synthesis so they have no effect on viruses and as far as CO2 transport is concerned I advice you to go through Bohr's effect in addition to little bit Information of reactions of Co2 in redblood cells like formation of Carbonic acid and dissassociation of into HCO3-1 and H+ ions ....soo juss have an overall idea

hope this helped

 

[samwickz]

Explain how sucrose is transported in the phloem along the stem from the leaf to the
fruit?
d marking scheme ans s kinda in point form and pretty confusing so any help btw its m/j 06 pretty plzzzzzzzzzzzzzzzzz

thanx

 

[rogue94]

Explain how sucrose is transported in the phloem along the stem from the leaf to the
fruit?
d marking scheme ans s kinda in point form and pretty confusing so any help btw its m/j 06 pretty plzzzzzzzzzzzzzzzzz

thanx

At source (leaf) proton pumps of transfer/companion cells pump protons (H+) to surrounding mesophyll cells via active transport, using energy from ATP. The protons then diffuse back into the transfer cells, down their concentration gradient, carrying sucrose along with them which is known as co-transport. Sucrose moves into the transfer cells via the co-transporters (a type of transport protein in cell membrane). Sucrose then diffuses down its concentration gradient to the sieve tube element via the plasmodesmata, which lowers the water potential of the element with water entering the cell via osmosis. This leads to build up of hydrostatic pressure at source. At sink, the sucrose is either hydrolysed or stored, which increases the water potential of those cells so that there is less hydrostatic pressure at sink. This pressure difference between the source and the sink results in mass flow of solution/phloem sap from source to sink (mass flow means that it flows altogether, all at once).

 

[Fizz911]

Re: Stuck in Biology?? Post your doubts here!!

What are polar molecules???

Due to da difference in electronegativities between 2 covalently bonded atoms, one atom have a partially positive charge and da othr have a partially negative charge......
This partial charge arises becoz electrons in da bond tend stay near to da more electronegative element in da bond giving it a partially negative charge and da othr a partially positive charge.
Due to dis property polar molecules r soluble in water as water is itslf polar....

Hope dat clears out your confusion

 

[farhan143]

[Advertising. No place for that. G.Mod edit]

 

[raamish]

what is bacterial cell wall made out of?

 

[Jaf]

what is bacterial cell wall made out of?

Peptidoglycan.

 

[raamish]

Why does vaccination help in making us immune against a disease. If the disease strikes us later we will still produce antibodies to destroy them, so what is the use of vaccination?

 

[Saad (سعد)]

Why does vaccination help in making us immune against a disease. If the disease strikes us later we will still produce antibodies to destroy them, so what is the use of vaccination?

Vaccination causes our antibodies to produce faster if a disease strikes us after its administered; so fast, that we don't feel the symptoms of the disease at all. The pathogen is destroyed almost instantaneously upon entering.

Basically, in vaccination, a disabled form of the pathogen is (usually) injected into us. Our Immune System therefore becomes active against the pathogen; memory B-cells store information regarding that pathogen and move around in the body. When a live pathogen invades our body, as the memory B-cells of that pathogen are already present, an immune response is initiated as soon as they recognize the pathogen and then they destroy it before it can do any considerable damage.

If vaccination is not administered, then should a pathogen invade us, the entire immune response would have to occur from scratch. In this case, first the pathogen would have to be detected, then B-cells that can produce the antibodies required to destroy that pathogen would have to divide and form an army; and this takes time. Enough for the pathogen to make us sick in the meanwhile.

Basically, this can be explained with the help of a war-similitude;

With Vaccination: Evil invaders, invade country at night, thinking they could sneak by and capture that country, only to find that the Intelligence of that country already had their Wanted Posters, and recognized them immediately once they showed up on active radar. The Intelligence immediately alerts the Armed Forces; and then bang! explode! kaboom! krzzzkrzzz! dishkewn!!! Invader eliminated before they could do much.

Without Vaccination: Evil invaders, invade country at night, thinking they could sneak by the border-posts and capture that country, and to their delight, the Intelligence neither has any information on them nor is their radar detecting them! They invade and capture several of country's important cities; by then, the Armed Forces have become aware that something invasion-y is going on. They rally up their troops; an entire war ensues with the Armed Forces trying to take back the captured cities and the Invaders putting up intense resistance. bang! explode! kaboom! krzzzkrzzz! dishkewn!!! Sooner or later, the Armed Forces win, either on their own, or with Foreign Aid (medicine/antibiotic ref.), but the country has suffered incredible damage, and it took a while for all the Invaders to be eliminated.

... I hope that helps, insha' Allah.

 

[raamish]

But in vaccination sometimes a live virus is used as well. And its apparently the most effective form of vaccination so why?

 

[raamish]

Vaccination causes our antibodies to produce faster if a disease strikes us after its administered; so fast, that we don't feel the symptoms of the disease at all. The pathogen is destroyed almost instantaneously upon entering.

Basically, in vaccination, a disabled form of the pathogen is (usually) injected into us. Our Immune System therefore becomes active against the pathogen; memory B-cells store information regarding that pathogen and move around in the body. When a live pathogen invades our body, as the memory B-cells of that pathogen are already present, an immune response is initiated as soon as they recognize the pathogen and then they destroy it before it can do any considerable damage.

If vaccination is not administered, then should a pathogen invade us, the entire immune response would have to occur from scratch. In this case, first the pathogen would have to be detected, then B-cells that can produce the antibodies required to destroy that pathogen would have to divide and form an army; and this takes time. Enough for the pathogen to make us sick in the meanwhile.

Basically;

With Vaccination: Evil invaders, invade country at night, thinking they could sneak by and capture that country, only to find that the Intelligence of that country already had their Wanted Posters, and recognized them immediately once they showed up on active radar. The Intelligence immediately alerts the Armed Forces; and then bang! explode! kaboom! krzzzkrzzz! dishkewn!!! Invader eliminated before they could do much.

Without Vaccination: Evil invaders, invade country at night, thinking they could sneak by and capture that country, and to their delight, the Intelligence neither has any information on them nor is their radar detecting them! They invade and capture several of country's important cities; by then, the Armed Forces have become aware that something invasion-y is going on. Of course, they got informed a bit late, so an entire war ensues with the Armed Forces trying to take back the captured cities and the Invaders putting up intense resistance. bang! explode! kaboom! krzzzkrzzz! dishkewn!!! Sooner or later, the Armed Forces win, either on their own, or with Foreign Aid (medicine/antibiotic ref.), but the country has suffered incredible damage, and it took a while for all the Invaders to be eliminated.

... I hope that helps, insha' Allah.

Also do we have to learn the sizes of all the different structrues such as cell surface membrane etc.

 

[Saad (سعد)]

Also do we have to learn the sizes of all the different structrues such as cell surface membrane etc.

Have a general idea. They've asked questions referring to that several times.

 

[raamish]

hmmm ok

 

[raamish]

do u know which sizes to learn. can u note dem down plzz

 

[hihi]

does anyone have a short summary of genetic control, because my book dosnt have that part and it requird in syllabus ??

 

[KurayamiKimmi]

does anyone have a short summary of genetic control, because my book dosnt have that part and it requird in syllabus ??

DNA and RNA are polynucleotides ,made up of long chains of nucleotides.A nucleotide consists of a pentose sugar,a phosphate group and an nitrogen-containing base

.A DNA molecule consists of two polynucleotide chains ,linked by hydrogen bonds between the bases.Adenine always bonds with thymine and cytosine with guanine
.RNA which comes in several different forms , has only one polynucleotide chain ,although this may be twisted back onto itself like in tRNA .In RNA the base thymine is replaced by uracil.

DNA molecules replicate during interphase .The hydrogen bonds between the bases break ,allowing free nucleotides to fall into position beside their complementary bases on each strand of the original DNA molecule .Adjacent nucleotides are then linked ,through their phosphates and sugars ,to form new strands .Two complete new molecules are thus formed from one old one ,each new molecule containing one old strand and one new .

The sequence of bases on a DNA code for a amino acids in a protein (or polypeptide) .Each amino acid is coded for by three bases .A length of DNA coding for one complete protein or polypeptide is a gene.

During protein synthesis , a complementary copy of the base sequence on a gene is made by building a molecule of mRNA against one DNA strand .The mRNA then moves to a ribosome in the cytoplasm.
tRNA molecules with complementary triplets of bases temporarily pair up with the base triplets on the mRNA ,bringing appropriate amino acids .As two amino acids are held side by side ,a peptide bond is formed between them .The ribosome moves along the mRNA molecule , so that appropriate amino acids are linked together , following the sequence laid down by the base sequence on the mRNA

That should pretty much sum up the whole chapter .Hope this helps!