Edexcel GCE Biology Unit 5 6BI05 June 2013

Reply 820

HQazi

9

Original post by jojo1995

what do we need to know about ECGs please >??

Yes you do.
The graph of pqrst
This links to heart activity and excitation too... so yh you need to :smile:

Reply 821

Sravya

Which bits are you struggling on? Id be happy to help anyone with specific questions

Reply 822

Sly1

6

Original post by bethanyfish

It's the muscle side i'm worried about :s-smilie:

and stuff about plants

I would say the transcription factors are a bit hard to grasp. But yeah we all have strong and weak points.

Reply 823

ViolentMind

10

Original post by Sravya

someone earlier posted this which i thought was very helpful

Thanks mate :smile:

Reply 824

InadequateJusticex

18

Original post by jojo1995

no i have a friend who is too ....

LOL yeah i am too DW ... it'll be over in 26 hours or so :redface:

haha i know, thank god! I wish it was in the morning so I can focus on C4 and Chem...

Original post by Zahra333

No don't worry, I'm right behind you.
But don't worry you'll do just fine.

I'm not too sure about that! article is a trek and the theory stuff is so boring I have no motivation to learn

Original post by bethanyfish

It's the muscle side i'm worried about :s-smilie:

and stuff about plants

aah same!

Reply 825

Sravya

Original post by InadequateJusticex

haha i know, thank god! I wish it was in the morning so I can focus on C4 and Chem...

I'm not too sure about that! article is a trek and the theory stuff is so boring I have no motivation to learn

aah same! :frown:

I agree with you! What do you need in nuit5? have you got c4 in the morning on Tuesday?that's my last exam

Reply 826

jojo1616

Why atp production decreases when oxygen is low in tissue?

Posted from TSR Mobile

Reply 827

jojo1995

2

Original post by InadequateJusticex

haha i know, thank god! I wish it was in the morning so I can focus on C4 and Chem...

ahh bless i feel your pain i have chem too .... you'll be fine with maths and everything... it should go well considering they messed up c3 (i dont know why i have concluded that but lol). i tend to do better when i have less time to revise lol good luck :smile:

.. you wont need it though

Reply 828

Sly1

6

Original post by InadequateJusticex

Am I the only one absolutely bricking it for this exam? :frown:

Watch this man to give you a pump
http://www.youtube.com/watch?v=oXJ1FZKwI7c

Reply 829

Mollymod

15

Original post by Sravya

Which bits are you struggling on? Id be happy to help anyone with specific questions

I'm really terrible with calculating bpm from looking at an ECG trace.

Reply 830

Sly1

6

For those that are lazy and don't work hard. Watch this http://www.youtube.com/watch?NR=1&v=8EGWEUf9Xr8&feature=endscreen

Reply 831

rudizzy123

5

Guys i need help with the core practicals that are NOT habituation. Could anybody tell me about them??!

Reply 832

TheNoobyPotato

The markschemes aren't clicking with me. For unit 1,2,4, I could write so much and hit almost all the marks on the markscheme but it's just not working..

Reply 833

Mjwilson1988

Original post by Sravya

can anyone explain the how plants detect light in 5/6 points..what you would write in an exam answer?

Also what are growth factors in plants...still a bit confused

I'll start with the easier question, Plant growth Factors, depending on what you're asking there are two answers: If you're asking what factors affect plant growth then you've got amount of light, temperature, soil type, nutrient availability, rate of respiration etc etc. However, I think you mean it in the other way, what are the chemicals produced by plants that affect their growth, the only one we need to know about is Auxins, particularly Indoleacetic Acid (IAA), there are others but we'll focus on Auxins.

Plants detect light using Photoreceptors, one particular type of photoreceptors are called Phytochromes, which have a pigment in them which can exist in two, interchangable, forms: Pr (Phytochrome Red) which absorbs Red Light and Pfr (Phytochrome far-red) which absorbs Dark Red (far red) light. These different forms of the Phytochrome pigments can act as transcription factors, or active transcription factors for different proteins, thus causing the plant to grow differently (examples below)

When RED light is shone onto a plant, Pr is converted into Pfr, and when FarRed light is shone onto it Pfr is converted into Pr. Pfr also converts slowly back into Pr in the dark. I'd also mention here that the amounts of Pfr and Pr alter how the plant is growing and flowering etc. Because natural sunlight contains more Red light than Far Red light, it is common that when the amount of Pr is greater than Pfr, the plant will behave as if it is in the dark, it will stop producing flowers, chloroplasts and side buds (leaves) and will quickly grow its stem, this is because the plant will be 'racing' to reach above whatever it is that is blocking out the sunlight (imagine the floor of the dense Rain forest, lots of little plants all blocking each other out, whoever grows the longest stem is more likely to live, or when a seen first sprouts and needs to get out of the soil into light). So in this case, the Pr is in abundance, acts as an excitory transcription factor (so promotes transcription) of the proteins which lead to stem growth, and it may act as an inhibitory transcription factor for leaf growth and flowering (No point growing leaves in the dark, so saves energy for stem growth).

Another way plants detect light is light with a different type of photoreceptor, and in this case it responds to blue light, this occurs in the tip of a stem, which then produces Auxins, these auxins diffuse down the stem and are broken down by sunlight, so they accumulate on the dark side of the stem (they are also actively transported to the dark side). Auxins then produce messenger molecules which act as transcription factors producing enzymes (They also alter the permeability of the membrane of a plant cell to H+ so the outside of the cell is more acidic), together these factors cause cellulose bonds to become altered, allowing the cellulose to expand, thus cell elongation occurs as more water moves in. As the cells on the shaded side are now longer, the stem will bend towards to light source. This is positive Phototropism

Reply 834

jojo1995

2

Hi guys does anyone know what we need to know about knee/ hip replacements ? i think its actually knee

Reply 835

iwantopas19

Original post by Sravya

Which bits are you struggling on? Id be happy to help anyone with specific questions

can u explain PFR ,PR convertion and all

Reply 836

Mjwilson1988

Original post by jojo1616

Why atp production decreases when oxygen is low in tissue?

Posted from TSR Mobile

When the amount of O2 is low in the tissues, the major type of respiration occurring is Anaerobic, anaerobic respiration is only Glycolysis and then reduction of Pyruvate to lactate (this happens so that the NADH produced during glycolysis can be converted back to NAD to be used again). Glycolysis only produces 2 molecules of ATP per glucose molecule, compared to the 36 produced by the whole of aerobic respiration.

Reply 837

Mjwilson1988

Original post by jojo1995

Hi guys does anyone know what we need to know about knee/ hip replacements ? i think its actually knee

We can repair some damage to the knee (typically the Cruciate ligaments) with Keyhole surgery, this is when one or two small incisions are made and the instruments are inserted and a repair can occur, remember that ligaments attach bone to bone and in the knee they prevent them knee from bending too far forward, backwards and side to side.

Knee replacement is when we use an artificial knee joint (prosthesis) to replace a joint which has been too badly damage, such as in the case of extreme wear and tear from professional athletes or by diseases such as arthritis. A large incision is made and the patella (knee cap) is moved out of the way, then the ends of the surrounding bones are shaved down (tibia and femur) and the replacement joint is inserted and cemented in with special glues and materials. The person should be able to walk normally after a few months, however the replacement joint isn't as good as the original so no heavy contact sports!

The keyhole surgery is a better choice if you can because it only requires local anesthetic, is much less invasive and has a much shorter recovery time (all of these things mean less likely to have complications etc)

Reply 838

Sravya

Original post by iwantopas19

can u explain PFR ,PR convertion and all

Original post by Mjwilson1988

I'll start with the easier question, Plant growth Factors, depending on what you're asking there are two answers: If you're asking what factors affect plant growth then you've got amount of light, temperature, soil type, nutrient availability, rate of respiration etc etc. However, I think you mean it in the other way, what are the chemicals produced by plants that affect their growth, the only one we need to know about is Auxins, particularly Indoleacetic Acid (IAA), there are others but we'll focus on Auxins.

Plants detect light using Photoreceptors, one particular type of photoreceptors are called Phytochromes, which have a pigment in them which can exist in two, interchangable, forms: Pr (Phytochrome Red) which absorbs Red Light and Pfr (Phytochrome far-red) which absorbs Dark Red (far red) light. These different forms of the Phytochrome pigments can act as transcription factors, or active transcription factors for different proteins, thus causing the plant to grow differently (examples below)

When RED light is shone onto a plant, Pr is converted into Pfr, and when FarRed light is shone onto it Pfr is converted into Pr. Pfr also converts slowly back into Pr in the dark. I'd also mention here that the amounts of Pfr and Pr alter how the plant is growing and flowering etc. Because natural sunlight contains more Red light than Far Red light, it is common that when the amount of Pr is greater than Pfr, the plant will behave as if it is in the dark, it will stop producing flowers, chloroplasts and side buds (leaves) and will quickly grow its stem, this is because the plant will be 'racing' to reach above whatever it is that is blocking out the sunlight (imagine the floor of the dense Rain forest, lots of little plants all blocking each other out, whoever grows the longest stem is more likely to live, or when a seen first sprouts and needs to get out of the soil into light). So in this case, the Pr is in abundance, acts as an excitory transcription factor (so promotes transcription) of the proteins which lead to stem growth, and it may act as an inhibitory transcription factor for leaf growth and flowering (No point growing leaves in the dark, so saves energy for stem growth).

Another way plants detect light is light with a different type of photoreceptor, and in this case it responds to blue light, this occurs in the tip of a stem, which then produces Auxins, these auxins diffuse down the stem and are broken down by sunlight, so they accumulate on the dark side of the stem (they are also actively transported to the dark side). Auxins then produce messenger molecules which act as transcription factors producing enzymes (They also alter the permeability of the membrane of a plant cell to H+ so the outside of the cell is more acidic), together these factors cause cellulose bonds to become altered, allowing the cellulose to expand, thus cell elongation occurs as more water moves in. As the cells on the shaded side are now longer, the stem will bend towards to light source. This is positive Phototropism