Edexcel A2 Biology Unit 4(6BIO4) 13/06/11 - OFFICIAL THREAD !

I hope TB case study dont come out, it was on the JAN 11 paper, I hope HIV comes out this time, its easier

Reply 281

Original post by InItToWinItGetIt?

I thought in active TB, the bacteria start destroying lung tissue. If they are dormant, how can they be active? :s-smilie:

Ok cool thank you. :smile:

EDIT: So if they ask you a question on how TB bacteria survive in the human body for a number of years, what would you say?

Page 8 near the bottom.

When TB bacteria enters the body it starts causing infection. This initiates an inflammatory response. Macrophages engulf the bacteria. However, these TB bacteria can survive once inside the macrophages as they have thick waxy cell walls , making them very difficult to break down. Hence, it can remain dormant for years.

Reply 282

Original post by idiotone

Competition between bracken and heather occurs mainly on moorland and heath, which exists as habitats because of sheep grazing.

Describe what you think might happen in areas of moorland and heath if sheep were removed. (4)

Increased temperature increases rate of decay of dead organic material. Explain why. (4)

Reply 283

Original post by idiotone

When TB bacteria enters the body it starts causing infection. This initiates an inflammatory response. Macrophages engulf the bacteria. However, these TB bacteria can survive once inside the macrophages as they have thick waxy cell walls , making them very difficult to break down. Hence, it can remain dormant for years.

That wwas were I was getting confused. But you kinda have explained it, thanks

Reply 284

InItToWinItGetIt?

11

Original post by idiotone

When TB bacteria enters the body it starts causing infection. This initiates an inflammatory response. Macrophages engulf the bacteria. However, these TB bacteria can survive once inside the macrophages as they have thick waxy cell walls , making them very difficult to break down. Hence, it can remain dormant for years.

So where does the formation of tubercles come into the scheme of things? I'm getting so confused by TB. Sorry for all these questions and thanks for answering them.

Reply 285

Maria1234

2

At a higher temperature rate of enzyme activities is fast,becuase at a higher temperature molecules have greater kinetic energy and move faster hence enzyme substrate molecules are formed. Enzymes are needed for growth and chemcal reaction ,fater decay is caused by enzymes

Original post by idiotone

Increased temperature increases rate of decay of dead organic material. Explain why. (4)

Reply 286

Original post by InItToWinItGetIt?

So where does the formation of tubercles come into the scheme of things? I'm getting so confused by TB. Sorry for all these questions and thanks for answering them.

When the bacteria is engulfed by macrophage, a mass of tissue forms to basically lock the "dormant" bacteria. The tissue mass are anaerobic and are called tubercules.

Reply 287

Original post by Maria1234

At a higher temperature rate of enzyme activities is fast,becuase at a higher temperature molecules have greater kinetic energy and move faster hence enzyme substrate molecules are formed. Enzymes are needed for growth and chemcal reaction ,fater decay is caused by enzymes

Yeah I get the enzyme part, but how do decomposer help decay the dead material..?

Reply 288

pearlover

could someone please go over how the changes in rainfall pattern and seasonal cycles will affect plants and animals and their distrubution and lifecycle?

Reply 289

InItToWinItGetIt?

11

Original post by idiotone

When the bacteria is engulfed by macrophage, a mass of tissue forms to basically lock the "dormant" bacteria. The tissue mass are anaerobic and are called tubercules.

Thank you so much. :smile:

Original post by idiotone

Yeah I get the enzyme part, but how do decomposer help decay the dead material..?

Enzymes in the decomposers break down carbon containing compounds so that they can be used as respiratory substrate in respiration. Nitrifying bacteria also break down nitrogen containing compounds to nitrates, which can then be used by plants.

Reply 290

Original post by idiotone

Yeah I get the enzyme part, but how do decomposer help decay the dead material..?

They break down the dead material by using enzyme :s-smilie:

Reply 291

imaam

Do we have to know about the humoral response (activation and effector stages) and cell mediated response? We learnt it in class, but its not in the spec or the CGP revision guide????? Thanks!

Reply 292

lw:)

2

What are the core pracs?

Reply 293

InItToWinItGetIt?

11

Original post by imaam

Do we have to know about the humoral response (activation and effector stages) and cell mediated response? We learnt it in class, but its not in the spec or the CGP revision guide????? Thanks!

I don't think they can specifically ask ''what is the humoral response and cell-medicated'' (as it's not on the spec), so I'm going to say no.

But in a nutshell:

humoural is the response that happens in the blood --> T-helper cells activate B-cells etc. etc.

cell-mediated is: T-killer cells killing infected body cells

Reply 294

LibbyU

Original post by imaam

Do we have to know about the humoral response (activation and effector stages) and cell mediated response? We learnt it in class, but its not in the spec or the CGP revision guide????? Thanks!

As far as im concerned we dont because 1) It's not in the specification 2) I've never heard of it, let alone been taught it so I hope not! and 3) "humoral" and "mediated" have never been mentioned in any of the previous 3 past papers :smile:

Reply 295

LibbyU

Original post by lw:)

What are the core pracs?

1) Study on the ecology of a habitat
2) Effects of temperature on the development of organisms
3) DNA amplification using PCR
4) Gel electrophoresis
5) Effect of different antibiotics on bacteria

Reply 296

Guys what did you get in the bloodty experiment, Practical the Unit 6 , Individual investigation? I dont know my mark because everyone studying A2 BIOLOGY had thier one marked by the exam board

Reply 297

LibbyU

Please could someone tell me how to calculate the efficiency of energy transfers between trophic levels?? the only thing I know is that energy entering a trophic level must equal energy lost by respiration, faeces etc. but this isn't calculating efficiency???

also what would they be likely to ask us about decomposition of a body? and do we need to know specific times e.g. if a body was found to be warm and not stiff would we need to be able to say how many hours it had been dead for?

Lastly, about insect evidence - I understand that the forensic entomologists know that different species of flies take different amounts of times to lay eggs on a body, so they can determine how long it took the flies to lay the eggs... then they can work out how long ago the eggs were laid by seeing what stage of development the insect is in. that's all I know :s-smilie:

is this correct? I still don't really understand it

Reply 298

doobucks

16

Original post by lw:)

[QUOTE=lw[excludedFace]smile[/excludedFace];32112041]What are the core pracs?

The hatching rate of shrimps/growth of seedlings,
The effectiveness of antibiotics (paper disc in agar)
Measuring abundance/distribution with a frame quadrat.

Reply 299