A level Biology: Post your doubts here!

[Saad (سعد)]

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?

CO2 transport is in the syllabus. They've asked about it in the past papers, I'm sure.

Antibiotics are ineffective against viruses because viruses are entirely different from other life forms in many different ways (there's even a debate about whether viruses are actually living things to begin with). Antibiotics (Greek 'anti-' against and 'bio' life) only affect proper life forms, such as bacteria and fungi, which have internal machinery, can move around, eat, reproduce, grow, etc. Viruses on the other hand are practically dead - they do not reproduce themselves and cannot metabolize - until and unless they come into contact with a living cell. When they infect the cell, they 'hijack' the internal machinery of that cell and use it to carry out their dirty work.

 

[Amaryllis]

Does anyone know if we have to remember the types of immunoglobulins (A, G, M and E) and their functions? Also the 6 different ways antibodies help aid defense?

Type of immunoglobulins...i don't think so (not sure though)
and the 6 diff ways antibodies aid defense....could you please put em up?

i dont think that Type of immunoglobulins are included
6 ways are:
1- antibody combine with viruses and bactrial toxins preventing them entering or damaging cells
2-attach to their flagella so they become less active
3-antibodies with multiple binding sites can cause agglutination of bacteria reducing the chance of spreading trough the body
4-some antibodies punch a hole on the cellwalls of bacteria causing them to burst
5-coating bacteria which makes it easier for phagocytes to ingest
6- combine with toxins neutralising them and making them harmless

 

[Soldier313]

i dont think that Type of immunoglobulins are included
6 ways are:
1- antibody combine with viruses and bactrial toxins preventing them entering or damaging cells
2-attach to their flagella so they become less active
3-antibodies with multiple binding sites can cause agglutination of bacteria reducing the chance of spreading trough the body
4-some antibodies punch a hole on the cellwalls of bacteria causing them to burst
5-coating bacteria which makes it easier for phagocytes to ingest
6- combine with toxins neutralising them and making them harmless

awesome...tx a lot!

 

[Amaryllis]

CO2 transport is in the syllabus. They've asked about it in the past papers, I'm sure.

Antibiotics are ineffective against viruses because viruses are entirely different from other life forms in many different ways (there's even a debate about whether viruses are actually living things to begin with). Antibiotics (Greek 'anti-' against and 'bio' life) only affect proper life forms, such as bacteria and fungi, which have internal machinery, can move around, eat, reproduce, grow, etc. Viruses on the other hand are practically dead - they do not reproduce themselves and cannot metabolize - until and unless they come into contact with a living cell. When they infect the cell, they 'hijack' the internal machinery of that cell and use it to carry out their dirty work.

thank u ...so for c02 transport shall i know the steps of formation of carbamino-haemoglobin ?cuz the teacher didnt mention that . we took the bohr''s effect only

 

[Amaryllis]

awesome...tx a lot!

you're welcome ^^

 

[confused_soul]

Can sum bdy pleaseeee explain me tyical bio p5 questions in which we hav to do T n chi test
I dont get it all

 

[Saad (سعد)]

thank u ...so for c02 transport shall i know the steps of formation of carbamino-haemoglobin ?cuz the teacher didnt mention that . we took the bohr''s effect only

Yup, you gotta know about all three ways in which carbon dioxide is transmitted; carbamino-haemoglobin (10%), bicarbonate ions (85%) and in solution form inside the blood plasma (5%).

If you have the Mary Jones book, read the 'Carbon dioxide transport' article on page 111. Its simple, easy to understand, and comprehensively explained there.

 

[prekshya]

role of tendons and pappillary muscles??? anyone ppllzzz.....

 

[HubbaBubba]

Specimen Paper Paper 2
Q3 (a) (iii) and (d)

The question is:
Q3. An experiment was carried out to investigate the activity of a protease on gelatine (A protein)
Exposed photographic film carries black silver salts which are bonded to it by gelatine. The protease acts upon the gelatine, which releases the salts when the gelatine is hydrolyzed. The photographic film is therefore cleared. Six test-tubes were set up, containing 1cm3 of protease solution, each at a different buffered pH. They were placed in a water bath at 30C for 5 minutes. A small square of exposed film was then placed into each test-tube at the same time, and the time taken for the film to clear was recorded. The results are shown in Fig 3.1

(a) (iii) Explain why a precise value for optimum pH cannot be deduced from these results.
(d) The experiment was repeated at the optimum pH for the protease, with the addition of a solution of lead salt. The film did not clear. Suggest with reference to enzyme structure and function, THREE possible reasons why the film did not clear after incubation with the lead salt.

 

[shan5674]

http://www.xtremepapers.com/papers/...nd AS Level/Biology (9700)/9700_w10_qp_21.pdf

Can someone please explain to me Q2 b(ii)? i dont get how to calculate the tidal volume

 

[aliya_zad]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w10_qp_21.pdf

Can someone please explain to me Q2 b(ii)? i dont get how to calculate the tidal volume

Tidal volume is defined as the volume of air breathed in and out during a single breath.
In this case the athlete has a breathing rate of 11 breaths per minute which took in a volume of 5.5dm3.
11 breaths -------> 5.5dm3
1 breath --------> 0.5dm3

 

[Soldier313]

Could someone please provide an explanation for the tertiary structure and the quaternary structure of a molecule....what is the difference between the two?

 

[littlecloud11]

Could someone please provide an explanation for the tertiary structure and the quaternary structure of a molecule....what is the difference between the two?

Tertiary structure: This refers to the specific 3-dimensional shape of a protein molecule and is determined by the variety of bonding interactions between the side-chains of the amino acids in the molecule. There are 4 main types of bonds responsible for this.
Disulfide bonds (the strongest bonds) - between two cysteine groups.
Hydrogen bond- between two alcohols, or an alcohol and an acid, or two acids, or an acid and an amide.
Hydrophobic interactions- between non-polar side chains
Ionic bonds- between polar groups.

Quaternary structure: It is the final specific structure of the protein formed by the non-covalent interaction between two or more polypeptide chains. the bonds present are same as those in the tertiary structure.

you can use their structure to figure out their differences.

 

[confused_soul]

Can any 1 please explain t test n chi test
Standard error and deviation

 

[raamish]

http://www.xtremepapers.com/papers/...and AS Level/Biology (9700)/9700_s06_qp_2.pdf

In qs 4a) The length 0.5um is not specified, so how do we know its the length of the chloroplast. And why dont we take the width of the entire micrograph rather than the chloroplast b/c its saying magnification of micrograph. Help plzz

 

[angelpari]

AOA.. cn sum1 telme wht r the most imp. chaps..? bcx i hav done wid my syllabus..
i need to revise those chaps. fr paper.. which chaps might cum??

 

[Soldier313]

may sound like an odd qn but...what's the difference between mucous glands and goblet cells?

 

[Jaf]

may sound like an odd qn but...what's the difference between mucous glands and goblet cells?

Goblet cells are a type of a mucous gland.

 

[Soldier313]

Goblet cells are a type of a mucous gland.

owh ryt tx....coz in this paper qn 1b.) they accept mucous gland as an answer and not goblet cells, i don't understand why:S
qp: http://www.xtremepapers.com/papers/...nd AS Level/Biology (9700)/9700_w11_qp_22.pdf
ms: http://www.xtremepapers.com/papers/...nd AS Level/Biology (9700)/9700_w11_ms_22.pdf

 

[geek101]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s06_qp_2.pdf

In qs 4a) The length 0.5um is not specified, so how do we know its the length of the chloroplast. And why dont we take the width of the entire micrograph rather than the chloroplast b/c its saying magnification of micrograph. Help plzz

there the little scale given on the side is the same magnification as the photograph, so you use it to calculate the mag cuz its the same for the same and the photograph...the length of the mini scale is 1.5 cm -> 0.015 m -> 15 000 micrometers. now just divide the 15000 by 0.5 micro meters the actual length, following the formula that magnification = image / actual... you'll get the answer...dont forget to put the x for times.... hope that helps.