guys biology paper 2 is on 29 of may ...i need some help

[littlecloud11]

and what are the things we should learn in core G?
transport in plant :
xerophyte,
transport of water in xylem,
transport of sucrose in phloem
role of companion cell
transpiration

transport in mammal :
arteries, vein capillaries
how co2 is transported
bohr shift + haemoglobin
cardiac cycle
structure of heart

is that it? just to make sure...

Yeah, that pretty much covers it.

 

[littlecloud11]

what about explain how heart action is initiated and controlled

It's initiated by SAN (sino-atrial node) which send a wave of electrical excitation across the atrial wall that causes the atrial muscle to contract and bring about atrial systole. A band of insulating fiber in the median septum prevents this impulse from reaching the ventricle. This allows a time delay for the atrial systole to complete before the ventricles start contracting.
The AVN then acts as a relay station and send another impulse to the ventricle via the purkyne tissues. The purkyne tissues conducts the impulse to the base of the ventricle wall so that it contracts from the bottom upwards.

 

[littlecloud11]

and what is a mass flow? sorry i'm asking too much questions here :s i'm pretty nervous about my exam which is tomorrow.

Mass flow is basically the bulk movement of matter through a tube.
No problem, i have bio tomorrow as well.
Good luck!

 

[KurayamiKimmi]

and what is a mass flow? sorry i'm asking too much questions here :s i'm pretty nervous about my exam which is tomorrow.

Mass flow means that all the water molecules (along with any solute molecules-as in translocation) move together ,as a body of liquid .This is helped by two properties of water molecules -cohesion and adhesion
cohesion-water molecules are attracted to each other
adhesion:water molecules are attracted to the lignin in xylem vessels (or to the walls of sieve tube -in translocation)
cohesion and adhesion help to keep water moving as a continous column

 

[eyamwir]

Mass flow is basically the bulk movement of matter through a tube.
No problem, i have bio tomorrow as well.
Good luck!

you as well best of luck! i'm sure you'll do fine since you taught me so much :') i have to say thank you and i am so grateful to you

 

[sahania]

amy do you have notes like this for physics?

http://www.xtremepapers.com/community/threads/physics-p5.16548/#post-285403

 

[littlecloud11]

you as well best of luck! i'm sure you'll do fine since you taught me so much :') i have to say thank you and i am so grateful to you

It was my pleasure.

 

[eyamwir]

what should we know in core H?

 

[Ashleyxoxo93]

can anyone explain the transport in plant in detail?? im always confused with the sucrose, sieve tube and companion cell thingy. And what kind of transport stuff do we have to know about xylem vessel???

 

[eyamwir]

and what does carcinogen do to the lungs?

 

[Ashleyxoxo93]

damage the DNA and causes uncontrolled division of cells...resulting in the growth of tumour

 

[samin390]

and what does carcinogen do to the lungs?

carcinogen causes mutation..which results in abnormal cell division and tumor develops

 

[biba]

this might help contains all the topics for AS biology..

thanxx alot!!!!!!!
u r a life saver!!!

 

[Amy farvin]

thanx
make dua for me if u want to save my life if i really saved yours...

 

[Nawaf Dandachi]

People who took paper 21 : Check this thread out : http://www.xtremepapers.com/community/threads/biology-9700-paper-21.16955/