~AS Bio doubts Here !!~

[filza94]

DESCIBE THE PROCESS OF GASEOUS EXCHANGE BTWEEN AIR IN THE AVEOLI AND THE BLOOD

 

[nidzzz09]

Ok guys temme which year was the hardest


challenge

 

[nidzzz09]

DESCIBE THE PROCESS OF GASEOUS EXCHANGE BTWEEN AIR IN THE AVEOLI AND THE BLOOD

hey WHY WHY WHY dont you Open your book EVERYTHNG wat you are askin Is CLEARLY written honey :no:

 

[Xthegreat]

- blood flowing into the lungs have higher partial pressure of CO2 and lower partial pressure of O2.
- alveoli is higher in partial pressure of O2 and lower in partial pressure of CO2.
- CO2 and oxygen moves down the concentration gradient.
- O2 diffuses into the moist surface of the alveoli then move across endothelium cells of the blood capillaries and into the blood.
- CO2 diffuses into across the blood capillaries and into the alveoli.

ps. do u even read your textbook? or even finish off your past years?

 

[filza94]

cox m confused wat to rite how to rite answerss i know evrything bt when it cums to rite i dont knw

 

[Xthegreat]

Ok guys temme which year was the hardest


challenge

from 2002 to 2010, everything seems to be on the same scale.

 

[Xthegreat]

cox m confused wat to rite how to rite answerss i know evrything bt when it cums to rite i dont knw

i know itz kinda late, but u should really read the marking schemes!

 

[filza94]

im reading it almost gona finish!!!

 

[girlscampisra]

please someone answer this one..
how companion cells load sucrose into phloem sieve tubes?

 

[arsimme]

Ok guys temme which year was the hardest


challenge

2005 and 2007

 

[Xthegreat]

- sucrose are loaded at the source into the companion cells.
- H+ ions are pumped out of the companion cells
- sucrose move into the companion cells through co-transporters
- sucrose move into the companion cells via active transport
- sucrose then move into the sieve tubes via the plasmodesmata between the sieve tubes and companion cells.
- sucrose diffuse down the concentration gradient into the sieve tubes.
- the low water potential in the sieve tubes then causes water to move by osmosis.
- the difference in hydrostatic pressure between source and sink causes mass flow to occur.
- sucrose is unloaded at the sink

so those are basically the points for the transport of sucrose. so from leaf ( source ) to companion cell, it is active transport, cause energy is needed to pump H+ ions out. then as the H+ ions have a higher concentration outside the companion cells, they then diffuses down the concentration gradient, back into the companion cells. AT THE SAME TIME, the sucrose move in together with the H+ ions into the companion cells. hence it is known as co-transport. then from companion cells to sieve tubes, is just diffusing across the plasmodesmata. simple

 

[arsimme]

guyz wot shud i study abt lipids ?

 

[nidzzz09]

im reading it almost gona finish!!!

also read the examiner report is a great help

 

[girlscampisra]

thanks a lot, Xthegreat!

 

[Xthegreat]

2 forms : triglyceride + phospholipids

triglyceride
- made up of glycerol + 3 fatty acids, form by condensation
- insoluble in water, but soluble in organic solvents
- non-polar, hydrophobic
- f(x) : storage for energy ( stores more energy than carbohydrate )
: as insulator against lost of heat
: to cushion organs

Phospholipids
- glycerol + phosphate + 2 fatty acids
- hydrophilic head, hydrophobic tails
- f(x) : forms the phospholipid bilayer of cell's plasma membrane

 

[girlscampisra]

oh so same process we have to write when asked about loading at source n unloading at sink?

 

[nidzzz09]

Phagocytosis is the process by which bacteria are ingested by cells.
Describe the role of the cell surface membrane during phagocytosis



hw do i write an accurate answer for this


this wats written in ms
bacteria / antigen / epitope( antigenic determinant), combine(s) with / attach to/ recognition by, receptor ;
antibody on bacteria combines with receptor ;
opsonisation / opsonisation described ; e.g. facilitates phagocytosis
ref. to constant region ;
membrane infolds / invaginates / envelops / engulfs / enclose / AW ;
accept answers without ‘membrane’ where implied previously / later
membrane fuses ;
to form, vacuole / vesicle / phagosome (enclosing bacteria) ;