Edexcel GCE Biology Unit 4 6BI04 June 2013

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Reply 20

shumen9523

Hey guys,

How about we do a group revision for unit 4 together ??
You know, ask each other questions or something like that ...

Reply 21

Obtas

Original post by shumen9523

Hey guys,

How about we do a group revision for unit 4 together ??
You know, ask each other questions or something like that ...

Yeah why not?! I need help with Unit 4 as well! :smile:

Lets do it!

Reply 22

nukethemaly

Original post by Satta101

Yeah why not?! I need help with Unit 4 as well! :smile:

Lets do it!

I have a chemistry exam tomorrow, but I will partake in this after wednesday!

Reply 23

Obtas

Original post by nukethemaly

I have a chemistry exam tomorrow, but I will partake in this after wednesday!

Same! Are you on OCR by any chance?

Reply 24

username1054067

I'll join you guys too after Chemistry tomorrow :P, final week before Unit 4! :eek:

Reply 25

nukethemaly

Original post by Satta101

Same! Are you on OCR by any chance?

Yep Salters OCR. How are you feeling about it?

Reply 26

shumen9523

Original post by Satta101

Yeah why not?! I need help with Unit 4 as well! :smile:

Lets do it!

Great !!

I'll start if nobody minds ....
Q: Compare between the structural features of bacteria and viruses.

Reply 27

username1054067

Original post by shumen9523

Great !!

I'll start if nobody minds ....
Q: Compare between the structural features of bacteria and viruses.

Urgh fml

Why is bio so hard lmao

Reply 28

shumen9523

Original post by yarshad

Urgh fml

Why is bio so hard lmao

I know what you mean ..
The questions in the exam require thinking and analysis but there is so little time !!
If you have any questions, post them here so that we can keep this thread alive. :smile:

(hey that kinda rhymes :P )

(edited 10 years ago)

Reply 29

username1054067

Original post by shumen9523

I know what you mean ..
The questions in the exam require thinking and analysis but there is so little time !!
If you have any questions don't hesitate to post them here so that we can keep this thread alive. :smile:

After my two exams tomorrow I promise I'll ragg out this thread :P

Reply 30

shumen9523

Original post by yarshad

After my two exams tomorrow I promise I'll ragg out this thread :P

Good luck

Reply 31

itsjordan

Original post by shumen9523

Great !!

I'll start if nobody minds ....
Q: Compare between the structural features of bacteria and viruses.

BACTERIA:
- cell surface membrane, cytoplasm, cell wall, ribosomes, plasmids and sometimes pilli, mesosomes and flagellum
- circular strand of DNA
- can live independently
- average diameter 0.5 to 5 um
- mucus based out capsule (slime capsule) protecting bacteria from attack (not all bacteria)

VIRUSES:
- no cell surface membrane, no cytoplasm, no cell wall and no organelles. Nucleic acid (DNA/RNA) enclosed in protein coat (capsid)
- DNA/RNA = genetic material
- must have living organism as host
- variety of shapes and sizes
- may have outer membrane (envelope) stolen from the hosts cell membrane. It contains glycoproteins from the virus

Q: Why is only 2-10% of energy transferred from producers to primary consumers?

(edited 10 years ago)

Reply 32

Taylor Swift

2 questions would really appreciate someones help:

Can someone give me a CLEAR and CONSISE answers please :smile:

(b) (i) Name two types of cell that HIV enters in the immune system.
(ii) Explain how HIV is able to enter these cells.
(iii) Describe the sequence of events following infection of these cells by HIV, that
may lead to the death of the patient.

Reply 33

shumen9523

Original post by itsjordan

Nice !!
A/-Not all of the parts of the producers are eaten
-Not all of the food that is eaten by the primary consumers is digested
-Some energy is lost by respiration in the plants
Q/ Suggest how the interspecific competition might affect the abundance and distribution of a certain population (give examples to clarify your answer if you wish)

Reply 34

Obtas

Original post by nukethemaly

Yep Salters OCR. How are you feeling about it?

I do OCR Chemistry A, so I don't know if we sit the same paper? :confused:

Reply 35

username1054067

Original post by shumen9523

Good luck

Fankzzz

Reply 36

shumen9523

Original post by Taylor Swift

2 questions would really appreciate someones help:

Can someone give me a CLEAR and CONSISE answers please :smile:

b) i) Macrophages + T-helper cells
ii) T-helper cells:
- HIV binds to specific receptors on a T-helper cell
- The lipid envelope around the HIV fuses with the cell membrane of the T-helper cell allowing the HIV to enter into it
Macrophages:
- They engulf the HIV
- They take it in by endocytosis
- The HIV would be incorporated into a vacuole
iii) - The viral RNA would be converted into viral DNA by the enzyme reverse transcriptase
- Viral DNA enters into the nucleus of the cell by the enzyme Integrase
- It controls the cell's metabolism causing more viruses to be produced
- These escape from the T helper cell causing the T helper cell to burst
- The viruses infect other T helper cells
- This causes the number of T helper cells to fall
- which causes the immune system to weaken which exposes the body to opportunistic infections such as Tuberculosis

-

Reply 37

nukethemaly

Original post by Satta101

I do OCR Chemistry A, so I don't know if we sit the same paper? :confused:

We're both doing unit 2 :smile:

Reply 38

Taylor Swift

Describe the role of micro-organisms in the decomposition of organic matter and the recycling of carbon.

Explain how bacterial and viral infectious diseases have a sequence of symptoms that may result in death, including the diseases caused by Mycobacterium tuberculosis (TB) and Human Immunodeficiency Virus (HIV).

Explain the roles of antigens and antibodies in the body’s immune response including the involvement of plasma cells, macrophages and antigen-presenting cells.

Distinguish between the roles of B cells (including B memory and B effector cells) and T cells (T helper, T killer and T memory cells) in the body’s immune response.

Good replies to this would be great thanks!

Reply 39

SKK94

Original post by Taylor Swift

Explain the roles of antigens and antibodies in the body’s immune response including the involvement of plasma cells, macrophages and antigen-presenting cells.

- Antigens are mainly proteins on the surface of pathogens (they can also be the actual pathogen themselves)
- They help cells in the immune system identify pathogens. Specific antibodies can recognise antigens of a specific pathogen.
- When a pathogen enters the body, macrophages can engulf and digest them (non-specific response). The antigens which were in the pathogen are then presenting on major histocompatability complexes (MHCs).
- The macrophage is now an antigen-presenting cell.
- T helper cells (with receptor sites specific to the particular antigen) bind to the APC and are stimulated to form T memory cells and active T helper cells
- Active T helper cells produce cytokines which then stimulate B cells to produce B memory and B effector cells
- B effector cells differentiate into Plasma cells
- Tthese plasma cells produce antibodies that identify the specific antigen originally engulfed by the macrophage.
- Antibodies can then bind to the specific pathogens and work different ways (eg cause clumping, help phagocytes indentify pathogens, destruct cell membrane etc)

Sorry this is really long.
Hope it helps though :smile: