This discussion is closed.
science-oliver
Badges: 11
Rep:
?
#221
Report 6 years ago
#221
(Original post by biology911)
As I said; it's a good start!
Right so could you tell me how that relates to cohesion tension theory and could you explain cohesion tension theory please? I get the cohesion part but what is the tension part of the theory?
0
Clare2012
Badges: 0
Rep:
?
#222
Report 6 years ago
#222
(Original post by Rumaanaa)
same,dont exactly understand the dissociation curve either.I get that for human haemoglobin it shifts to the right and for organisms that live in a o2 depleted enviroment it shifts to the left;but why?How do i interpret this graph?
Same applies to effetc of co2,enviroment and activity level of organism
someone please shed some light on this thankyou!
When i was revising I was stuck on this too but found out its to do with the PH.

- When O2 levels are high and CO2 levels lower, haemoglobin as a high affinity for oxygen (high affinity means easily loads but more difficult to unload) because the pH is higher (alkali as CO2 is acidic so less CO2 = more alkaline conditions). This changes the shape of the haemoglobin making it easier to load but hard to 'detatch'.

- Vice ser versa when there is more CO2 the heamaglobins shape is again changed due to the acidic conditions making it harder to load oxygen but easier to give it away therefore its got a low affinity for oxygen. It needs a low affinity for oxygen as in low concentration conditions the animal needs the O2 to be rapidly released into cells for respiration.

Different organisms have different shaped heamaglobin molecules which determine the strength of its oxygen affinity.

Organisms with low metabolism + low O2 supply = high O2 affinity
Organisms with high metabolism + high O2 supply = low O2 affinity

The Bohr effect is the shift. If theres not much oxygen, the polypeptides in haemoglobin are closely united making it difficult to load O2.

Hope this helps and doesn't confuse you further!
2
Rumaanaa
Badges: 2
Rep:
?
#223
Report 6 years ago
#223
(Original post by Clare2012)
When i was revising I was stuck on this too but found out its to do with the PH.

- When O2 levels are high and CO2 levels lower, haemoglobin as a high affinity for oxygen (high affinity means easily loads but more difficult to unload) because the pH is higher (alkali as CO2 is acidic so less CO2 = more alkaline conditions). This changes the shape of the haemoglobin making it easier to load but hard to 'detatch'.

- Vice ser versa when there is more CO2 the heamaglobins shape is again changed due to the acidic conditions making it harder to load oxygen but easier to give it away therefore its got a low affinity for oxygen. It needs a low affinity for oxygen as in low concentration conditions the animal needs the O2 to be rapidly released into cells for respiration.

Different organisms have different shaped heamaglobin molecules which determine the strength of its oxygen affinity.

Organisms with low metabolism + low O2 supply = high O2 affinity
Organisms with high metabolism + high O2 supply = low O2 affinity

The Bohr effect is the shift. If theres not much oxygen, the polypeptides in haemoglobin are closely united making it difficult to load O2.

Hope this helps and doesn't confuse you further!
thanks a bunch!makes things much clearer now
0
biology911
Badges: 0
Rep:
?
#224
Report 6 years ago
#224
(Original post by science-oliver)
Right so could you tell me how that relates to cohesion tension theory and could you explain cohesion tension theory please? I get the cohesion part but what is the tension part of the theory?
Well the video shows how the water molecules, being polar, are determined to hold on to each other. The δ+ (hydrogen) and δ- (oxygen) providing ideal conditions for hydrogen bonding. This is cohesion.

Now imagine the water as a long toy train with H2O ‘carriages’ and hydrogen bond couplings. Start to pull from the front and all the couplings become taut, introducing a tension in the entire train. Pull more and the train moves as a single entity.

The ‘pull’ comes from the leaves when they lose water by transpiration.
0
erp
Badges: 5
Rep:
?
#225
Report 6 years ago
#225
(Original post by TheAJK)
Biology unit 1 I scraped an A with 80/100 UMS, I just did this past questions book my teacher gave, revision cards for certain topics and just practiced exam technique a lot. My teacher was expecting me to get 90/100 UMS but I skipped a lot of biology revision to do chemistry instead.
Do you know what the grade boundaries were for Biol1? How did chem go?!
0
science-oliver
Badges: 11
Rep:
?
#226
Report 6 years ago
#226
(Original post by biology911)
Well the video shows how the water molecules, being polar, are determined to hold on to each other. The δ+ (hydrogen) and δ- (oxygen) providing ideal conditions for hydrogen bonding. This is cohesion.

Now imagine the water as a long toy train with H2O ‘carriages’ and hydrogen bond couplings. Start to pull from the front and all the couplings become taut, introducing a tension in the entire train. Pull more and the train moves as a single entity.

The ‘pull’ comes from the leaves when they lose water by transpiration.
ahhh so the tensions stems from the fact that water evaporates from the leaves meaning more water enters the air spaces which means more water then enters the mesophyll cells from the xylem and these water molecules that enter the mesophyll cells pull the water molecules in the xylem up and this pull creates the tension?
0
Locutus73
Badges: 2
Rep:
?
#227
Report 6 years ago
#227
(Original post by erp)
Do you know what the grade boundaries were for Biol1? How did chem go?!
Hmm, I'm not sure and Chem and Physics went well 98/100 in Chem and 118/120 in Physics.
0
biology911
Badges: 0
Rep:
?
#228
Report 6 years ago
#228
(Original post by science-oliver)
ahhh so the tensions stems from the fact that water evaporates from the leaves meaning more water enters the air spaces which means more water then enters the mesophyll cells from the xylem and these water molecules that enter the mesophyll cells pull the water molecules in the xylem up and this pull creates the tension?
Sounds good. I look forward to your book on the subject!
0
Ascience
Badges: 0
Rep:
?
#229
Report 6 years ago
#229
How far are people with their revision


Posted from TSR Mobile
0
Simran Mars Foster
Badges: 12
Rep:
?
#230
Report 6 years ago
#230
Do you have to understand cytokineses in terms of mitosis?
0
erp
Badges: 5
Rep:
?
#231
Report 6 years ago
#231
Do we have to recall the formula for standard deviation in the exam, or just know how to use it?
0
biology911
Badges: 0
Rep:
?
#232
Report 6 years ago
#232
(Original post by Simran Mars Foster)
Do you have to understand cytokineses in terms of mitosis?

Only in the sense of knowing that towards the end of telophase the actual cytoplasm of the dividing cell begins to separate. It does this in order to establish two diploid daughter cell.

Membrane ‘grows’ down between the newly established nuclei until they exist as two individual cells next to each other. You might have called it cytoplasmic cleavage in school.

Not having the actual term cytokinesis in your vocabulary is never going to lose you any marks.
0
science-oliver
Badges: 11
Rep:
?
#233
Report 6 years ago
#233
(Original post by biology911)
Only in the sense of knowing that towards the end of telophase the actual cytoplasm of the dividing cell begins to separate. It does this in order to establish two diploid daughter cell.

Membrane ‘grows’ down between the newly established nuclei until they exist as two individual cells next to each other. You might have called it cytoplasmic cleavage in school.

Not having the actual term cytokinesis in your vocabulary is never going to lose you any marks.
I was under the impression that when the cell pinches off at the equator, the membrane that divides the cytoplasm is not new membrane, but membrane which existed in the cell surface membrane, and that this membrane from either side of the cell joins at the middle of the equator? Or am I wrong? Is it new membrane?
0
biology911
Badges: 0
Rep:
?
#234
Report 6 years ago
#234
(Original post by erp)
Do we have to recall the formula for standard deviation in the exam, or just know how to use it?
In what the spec refers to as 'written papers' (so units 1, 2, 4 and 5) there is no requirement to calculate standard deviation. From this, it's probably safe to assume that you won't be expected to recall the formula either.
0
biology911
Badges: 0
Rep:
?
#235
Report 6 years ago
#235
(Original post by science-oliver)
I was under the impression that when the cell pinches off at the equator, the membrane that divides the cytoplasm is not new membrane, but membrane which existed in the cell surface membrane, and that this membrane from either side of the cell joins at the middle of the equator? Or am I wrong? Is it new membrane?
Yes, it is not new membrane, although one could argue that with such a dynamic interface, membrane is being created all the time.

I was careful to put 'grow' in inverted commas as in some mitosis illustrations or animations, it looks for all the world like membrane is growing down and up, and meeting in the middle.

Invagination is a more precise term although not everyone uses it. I think your "pinches off" is the best of all.
0
Scienceisgood
Badges: 21
Rep:
?
#236
Report 6 years ago
#236
Does anyone have the Jan 2013 paper?
0
dtin
Badges: 13
Rep:
?
#237
Report 6 years ago
#237
(Original post by Scienceisgood)
Does anyone have the Jan 2013 paper?
it will be on the web somewhere there are always people who will leak the latest papers on to the web try typing 'BIOL2 January 2013' in to the searchbar
0
Scienceisgood
Badges: 21
Rep:
?
#238
Report 6 years ago
#238
Guys, where did they get the answer 8 from for pt. 2 of this question?

Is it as simple as 2^3?

Name:  Capture.PNG
Views: 190
Size:  28.4 KB
0
biology911
Badges: 0
Rep:
?
#239
Report 6 years ago
#239
(Original post by Scienceisgood)
Guys, where did they get the answer 8 from for pt. 2 of this question?

Is it as simple as 2^3?

Name:  Capture.PNG
Views: 190
Size:  28.4 KB
Question shows three pairs of chromosomes, so in each case there's a maternal and paternal version of the chromosome.

Instead of long, short and hooked, lets use I, i and r and pink and blue for maternal and paternal respectively.

so in the original diploid cell we 've got

I I i i r r

only one of each pair can appear in a gamete, and whether it's maternal or paternal is of course random. So you could get:



Iir
Ii
r
I
ir
Iir
Iir
Ii
r
Iir
I
ir


and that's your total of 8 different ones


0
chelseafan
Badges: 21
Rep:
?
#240
Report 6 years ago
#240
I haven't started revising yet.
2
X
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

University open days

  • Cardiff Metropolitan University
    Undergraduate Open Day - Llandaff Campus Undergraduate
    Sat, 19 Oct '19
  • Coventry University
    Undergraduate Open Day Undergraduate
    Sat, 19 Oct '19
  • University of Birmingham
    Undergraduate Open Day Undergraduate
    Sat, 19 Oct '19

Why wouldn't you turn to teachers if you were being bullied?

They might tell my parents (12)
6.42%
They might tell the bully (19)
10.16%
I don't think they'd understand (32)
17.11%
It might lead to more bullying (70)
37.43%
There's nothing they could do (54)
28.88%

Watched Threads

View All