A level Biology: Post your doubts here!

[fayzaan]

i wrote the same as u but i do not think it is good enough for 4 marks

 

[fayzaan]

i think i will lose marks here are there and most probably get above 48 or 49. Praying that i am thinking right )))))

 

[A*****]

i wrote the same as u but i do not think it is good enough for 4 marks

Well I'm not too good in biologybut atleast we would get 2 or maybe 3 marks for that

 

[A*****]

i think i will lose marks here are there and most probably get above 48 or 49. Praying that i am thinking right )))))

Me too

 

[fayzaan]

there was also question about the penicilin

 

[A*****]

there was also question about the penicilin

Mode of action: prevents cross links from developing
Then I wrote that peptidoglycan is not on the external surface and the outer layer prevented it from reaching inside and there are no transport proteins for its transport

 

[A*****]

What did u write about why proteins were considered genetic molecules?

 

[fayzaan]

did u mention about the carbohydrate sidechains?!
because u had to refer the diagram

 

[fayzaan]

because it contains aminoacids which are formed by nitrogeneous bases

 

[A*****]

Then I wrote that peptidoglycan is not on the external surface and the outer layer prevented it from reaching inside and there are no transport proteins for its transport

This is a reference from the diagram

 

[fayzaan]

look the question was that why does it attack g something positive and not g negtive

 

[fayzaan]

its because g positive has the complementary carbohydrate side chains

 

[A*****]

its because g positive has the complementary carbohydrate side chains

The question clearly mentioned that positive did NOT have outer membrane but only a thick layer of peptidoglycan

 

[A*****]

And penicillin does not bind to those chains

 

[anastasia grey113]

guys
i know this is not the right thread to ask this question but v got the highest pre med audience here so yh
is there anyone here who is from Pakistan and has completed their A Levels just this year?

 

[Krisarmy]

What important points do we need to remember for practicals? Is knowing the position of xylem and phloem and knowing the procedures enough ??

 

[Kanekii]

https://imgur.com/a/jDutIgR
Need help on this question

 

[cellular_automata]

Hello all. Here are some websites that I found useful for the histology part of paper 3.

respiratory system:
https://www.histology.leeds.ac.uk/respiratory/conducting.php
medcell.med.yale.edu/histology/respiratory_system_lab.php (scroll down to the 'slides' section
blood:
https://www.histology.leeds.ac.uk/blood/blood_wbc.php
plants(has other stuff too, but it is plant micrographs that are relevant):
http://www.sttss.edu.hk/biology/photomicrograph/bio photo.htm

I'm posting this based off of the following points in the sullabus:

-observe and draw plan diagrams of the structure of the walls of the trachea, bronchi, bronchioles and alveoli indicating the distribution of cartilage, ciliated epithelium, goblet cells, smooth muscle, squamous epithelium and blood vessels

-observe and draw the structure of red blood cells, monocytes, neutrophils and lymphocytes using prepared slides and photomicrograph

-make annotated drawings, using prepared slides of cross-sections, to show how leaves of xerophytic plants are adapted to reduce water loss by transpiration

-draw and label from prepared slides the structure of xylem vessel elements, phloem sieve tube elements and companion cells and be able to recognise these using the light microscope

-draw and label from prepared slides the cells in the different tissues in roots, stems and leaves of herbaceous dicotyledonous plants using transverse and longitudinal sections

-draw and label from prepared slides plan diagrams of transverse sections of stems, roots and leaves of herbaceous dicotyledonous plants using an eyepiece graticule to show tissues in correct proportions (see 1.1c)

-observe and draw the mitotic stages visible in temporary root tip squash preparations and in prepared slides of root tips of species such as those of Vicia faba and Allium cepa

 

[A*****]

Hello all. Here are some websites that I found useful for the histology part of paper 3.

respiratory system:
https://www.histology.leeds.ac.uk/respiratory/conducting.php
medcell.med.yale.edu/histology/respiratory_system_lab.php (scroll down to the 'slides' section
blood:
https://www.histology.leeds.ac.uk/blood/blood_wbc.php
plants(has other stuff too, but it is plant micrographs that are relevant):
http://www.sttss.edu.hk/biology/photomicrograph/bio photo.htm

I'm posting this based off of the following points in the sullabus:

The last link is not working...can u plz post a screenshot of it?

 

[cellular_automata]

The last link is not working...can u plz post a screenshot of it?

Fixed the link.