OCR A Level Biology Biological processes H420/01 - 9 Jun 2022 [Exam Chat]

hi guys! if u have any questions about bio content let me know and i'll try my best to explain :smile:

Reply 2

elin994

8

Original post by nanami8

hi guys! if u have any questions about bio content let me know and i'll try my best to explain :smile:

Hi! Please could you explain the role of cAMP??

Reply 3

nanami8

Original post by elin994

Hi! Please could you explain the role of cAMP??

cAMP is a secondary messenger which has a role in the model of hormone action:
1. hormone (primary messenger) binds to a receptor, activating an enzyme called adenyl cyclase
2. adenyl cyclase triggers the conversion of ATP to cAMP on the inner surface of the membrane
3. once cAMP levels inside the cell increase, protein kinase enzymes phosphorylate other enzymes to activate them

think of cAMP as a domino piece which falls onto another, protein kinase, which then makes loads of other enzymes activated in an enzyme cascade

Reply 4

nanami8

Original post by Zeke Yeager

can you please explain selective reabsorption ? thanks :smile:

urine formation occurs in 2 stages:
1. ultrafiltration
2. selective reabsorption

selective reabsorption happens in the PCT and its main importance is :
. during ultrafiltration lots of useful molecules are extracted from the blood since they can fit through podocytes in the basement membrane
. these need to be reabsorbed into the blood - this includes most of the water, all of the glucose (which is why having glucose in ur urine is a medical condition and suggests kidney damage), some of the inorganic ions

here is a useful extract outlining the process in detail:

Active transport is used to move Na+ out of the outer surface of a cell in the wall of the PCT into the blood.
This lowers the concentration of Na+ inside the cell, so that Na+ ions diffuse into the cell from the fluid inside the tubule. The Na+ ions diffuse through protein transporters in the cell surface membrane of the cell
As the Na+ions diffuse through these transporter proteins, they carry glucose molecules with them. This is called co-transport. The glucose molecules move through the cell and diffuse into the blood.
The movement of Na+ and glucose into the blood decreases the water potential in the blood. Water therefore moves by osmosis from the fluid inside the tubule, down a water potential gradient through the cells making up the wall of the tubule and into the blood.

Reply 5

Username33

6

hey! I haven't started revising for this yet and idek where to start. any ideas on what to do? im hearing some GCSE exams are being tested more on what isn't on the advanced information rather than what is so im worried it'll be the same for a levels. also, please can you explain photosynthesis?

(edited 1 year ago)

Reply 6

elin994

8

Original post by nanami8

cAMP is a secondary messenger which has a role in the model of hormone action:
1. hormone (primary messenger) binds to a receptor, activating an enzyme called adenyl cyclase
2. adenyl cyclase triggers the conversion of ATP to cAMP on the inner surface of the membrane
3. once cAMP levels inside the cell increase, protein kinase enzymes phosphorylate other enzymes to activate them

think of cAMP as a domino piece which falls onto another, protein kinase, which then makes loads of other enzymes activated in an enzyme cascade

Holy crap I totally forgot about this I'm so sorry 😅😅😅😅😅 that's really helpful thank you so much I'm literally revising this rn haha imma do some exam questions on this soon!

Reply 7

hey guys , how we feelings about paper 1 ????

Reply 8

Original post by 17177171Ammmmm

hey guys , how we feelings about paper 1 ????

so scared watch how topics not on the advanced info make a big fat appearance

Reply 9

Original post by lol2468

so scared watch how topics not on the advanced info make a big fat appearance

honestlyyyy biologly is so unpredictable. is there like a structure to the exam other than the multiple choice questions.

Reply 10

Original post by 17177171Ammmmm

honestlyyyy biologly is so unpredictable. is there like a structure to the exam other than the multiple choice questions.

wdym by structure?

Reply 11

pumpkinspice123

4

Hey could you help me understand the difference between permeable, semi-permeable, selectively permeable and partially permeable membranes. Which names classify as the same type of membrane and what do they mean? Whats the difference between them? Thanks

Reply 12

KHN123

5

hi,
Does anyone know or think that the info NOT in the advance info will make a massive appearance. Because I heard they will only be multiple choice question or 1 or 2 markers. Any thoughts?

Reply 13

Original post by KHN123

hi,
Does anyone know or think that the info NOT in the advance info will make a massive appearance. Because I heard they will only be multiple choice question or 1 or 2 markers. Any thoughts?

there deffo will be MCQ's but apparantly the OCR AS bio exam was last week and stuff not on the advanced info still a made up quite a bit of the marks so basically just revise everything and pray grade boundaries are low

Reply 14

Original post by lol2468

wdym by structure?

as in for my other exam it is like 8 10 12 20 marker ?

Reply 15

Original post by 17177171Ammmmm

as in for my other exam it is like 8 10 12 20 marker ?

there will deffo be at least one 6 marker in each paper if not 2 6 markers other than that there is really no structure

Reply 16

teeee7

12

the 2018 paper may be similar to what we will get for paper1
btw yes revise everything as mcq will be on anything

Reply 17

Original post by teeee7

the 2018 paper may be similar to what we will get for paper1
btw yes revise everything as mcq will be on anything

why do you think 2018 will be similar to paper 1?

Reply 18