Edexcel GCE Biology Unit 5 6BI05 June 2013

Can someone explain what is transcription factor??

It's basically a protein that binds to DNA to switch certain genes on or off for transcription - if it switches genes on then it's called an activator, if it switches genes off then it's a repressor. I think at our level that's all we really need to know :P

EDIT : factors that switch on genes are activators, my bad.

(edited 10 years ago)

Reply 721

joan2468

1

Original post by TheNoobyPotato

Do you guys think we need to know the structure of the eye?

Is chemiosmosis basically just oxidative phosphorylation/ETC or is it more?

I don't remember the eye structure being part of the spec...and it's never been asked before o_O

There's a bit more to chemiosmosis. Basically the NADH and FADH release hydrogen atoms, they split into H+ (protons) and electrons. The electrons enter the electron transport chain and as they are passed from one carrier to another energy is released which is used to actively transport the protons into the intermembrane space.

So there's more H+ in that space than there is in the matrix. H+ will tend to want to leave this space due to concentration and electrochemical gradient - they can only leave through the ATP synthase molecule. As they go through ATP synthase, this enzyme synthesises new ATP molecules. H+ then combines with electron and oxygen to form water.

So the ETC is one part but the proton gradient is pretty important too.

Reply 722

nomrota95

Original post by joan2468

Habituation is when you stop responding to a neutral stimulus. The response is lost for a long period of time (sometimes even permanently) unless you are specifically sensitised to it because the calcium ion channels in your pre-synaptic membrane have become less responsive.

Adaptation is (or at least I think it is) linked with accommodation of the synapses, when your receptor cells adapt to a stimulus they stop sensing it because the neurotransmitters at the synapses need time to be re-synthesised, but if you remove the stimulus for a while then bring it back the neurotransmitters are replaced so you can sense it again.

I look at the difference as habituation being long-term loss of response and adaptation as short-term loss of response.

all clear! thanks alot! :smile:

)

Reply 723

bubblegummer

Can someone explain why opsin causes the sodium channel to close? And what does the retinal do?

One more thing... why is it when no neurotransmitter is released at the synapse the bipolar cell stimulates action potential?

Reply 724

iwantopas19

Original post by TheNoobyPotato

Do you guys think we need to know the structure of the eye?

Is chemiosmosis basically just oxidative phosphorylation/ETC or is it more?

NO, u dont need to know the structure, its not in the spec.. but if u have free time :tongue:

no harm in learning

Guys im still worried aboout the scientific article. What do you think the main points are for it

Reply 726

iwantopas19

Original post by TheNoobyPotato

Nope, just 7 papers from june 10-now + a specimen.

Posted from TSR Mobile

where can i get the specimen ? :/

Reply 727

joan2468

1

Original post by bubblegummer

Can someone explain why opsin causes the sodium channel to close? And what does the retinal do?

One more thing... why is it when no neurotransmitter is released at the synapse the bipolar cell stimulates action potential?

Rhodopsin bleaching stimulates a cascade reaction that closes the channels, the more rhodopsin that is bleached the more sodium channels close and the greater the hyperpolarisation of the rod cells.

I'd just think of opsin and retinal as two components of the rhodopsin, really.

And if you're referring to the CGP Revision Guide explanation, it's referring to inhibitory neurotransmitters. When a large enough generator potential is created in the rod cell inhibitory neurotransmitters are not released so this allows an action potential to be generated in the bipolar cell.

Reply 728

jojo1995

2

could someone define both negative feedback and homeostasis for me PLEASE :smile:

?

Reply 729

jojo1616

Anyone can upload the specimen papers both ques and ans ?thx

Posted from TSR Mobile

Reply 730

nomrota95

in glycolysis, "a small amount of ATP is also made available directly from the energy transfer when the 3C sugar is converted to pyruvate. the phosphorylation of the sugar at the beginning of the glycolyisis is reversed when the final intermediate compound is converted to pyruvate. the phosphate group released is used to convert ADP to ATP" - do we need to remember this part as answers to questions relating gycolysis, aerobic respiration, etc? :/ or just the part with hydrogen removed from the 3C, which taken up by NAD to reduce it and pass on to the elctron carrier system, where the energy made available is used to phosphorylate ADP into ATP is enough?

Reply 731

nomrota95

the spec doesnt mention cytochromes or cytochrome oxidase in the electron transport chain, do we have to know about them?

Reply 732

Mjwilson1988

Original post by jojo1995

could someone define both negative feedback and homeostasis for me PLEASE :smile:

?

Homeostasis is the maintenance of a constant internal environment by an organism or cell etc. It is achieved, in humans, by a series of feedback loops.

A Negative feedback loop is when an input causes a reduction of output by a system. A little simpler, it is when a stimulus causes a system to act against that stimulus and try to counteract whatever it is.

Example: As you exercise, you muscles cells are respiring more, this produces heat as a waste product (not all the energy for Respiratory substrates is converted to ATP remember!) and uses up glucose, so your body begins to heat up and blood glucose levels drop (These are changes are detected by Sensory Neurons or Receptors). The sensory receptors, such as thermoreceptors on the skin, send signals to a control centre (for temperature it is the Hypothalamus in the brain), the control centre then activates Motor neurons to cause effectors to take action to lower the body temp and increase blood glucose concentration so that the Body temp remains constant and glucose levels are returned to normal. In the case of body temp things that might happen to reduce temp are: -Increased Vasodilation of the capillaries near the skin to allow heat to radiate to surroundings, -arrector Pili muscles relax, lowering body hair to reduce air-insulation, -Metabolic processes in organs which aren't vital to movement are slowed down (reducing heat production), -Sweat glands are activated to produce sweat which cools the skin as sweat evaporates.

So as you can see, a change (increase in body temp) causes a response which acts to reduce the change (to decrease body temp).

Reply 733

Helena Kennedy

Does anyone have a specific definition of the word 'endemic'? Like one from the mark scheme ? :smile:

In the cgp book all it says is that an organism is unique to an area

Reply 734

Mjwilson1988

Original post by nomrota95

the spec doesnt mention cytochromes or cytochrome oxidase in the electron transport chain, do we have to know about them?

From what I know for further reading those are the Electron Transport Enzymes on the membrane of the Mitochondria which are responsible for the transport electrons, thus movement of H+ ions into the Inter-membrane space, I wouldn't think you need to know the actual names of them (Go for it if you can remember it though, no harm in that), Cytochrome Oxidase is the enzyme on the membrane that is responsible for transporting the electrons to their final electron acceptor (Which is Oxygen, to make water). To be honest, I'd just probably call them the 'Series of electron transport molecules/proteins between the Inter-membrane space and the matrix of the mitochondria' and even that might be over doing it!

Reply 735

Mjwilson1988

Original post by Helena Kennedy

Does anyone have a specific definition of the word 'endemic'? Like one from the mark scheme ? :smile:

In the cgp book all it says is that an organism is unique to an area

I took this one from the Jan 2013 Mark Scheme:

"idea that the ( species / eq ) is restricted in its distribution / species only found in one specific { location / area / eq } ;"

So you can say anything so long as you get across the idea that a species is only found in one place and nowhere else (Such as Madagascar has many species which are endemic to it because it is an Isolated Island).

Reply 736

Lujain Al Omari

Original post by Helena Kennedy

Does anyone have a specific definition of the word 'endemic'? Like one from the mark scheme ? :smile:

In the cgp book all it says is that an organism is unique to an area

Original post by Mjwilson1988

I took this one from the Jan 2013 Mark Scheme:

"idea that the ( species / eq ) is restricted in its distribution / species only found in one specific { location / area / eq } ;"

So you can say anything so long as you get across the idea that a species is only found in one place and nowhere else (Such as Madagascar has many species which are endemic to it because it is an Isolated Island).

If there are more marks to the question, then you can see that endemism is a result of geographical isolation.

Reply 737

jojo1995

2

Original post by Mjwilson1988

Homeostasis is the maintenance of a constant internal environment by an organism or cell etc. It is achieved, in humans, by a series of feedback loops.

A Negative feedback loop is when an input causes a reduction of output by a system. A little simpler, it is when a stimulus causes a system to act against that stimulus and try to counteract whatever it is.

Example: As you exercise, you muscles cells are respiring more, this produces heat as a waste product (not all the energy for Respiratory substrates is converted to ATP remember!) and uses up glucose, so your body begins to heat up and blood glucose levels drop (These are changes are detected by Sensory Neurons or Receptors). The sensory receptors, such as thermoreceptors on the skin, send signals to a control centre (for temperature it is the Hypothalamus in the brain), the control centre then activates Motor neurons to cause effectors to take action to lower the body temp and increase blood glucose concentration so that the Body temp remains constant and glucose levels are returned to normal. In the case of body temp things that might happen to reduce temp are: -Increased Vasodilation of the capillaries near the skin to allow heat to radiate to surroundings, -arrector Pili muscles relax, lowering body hair to reduce air-insulation, -Metabolic processes in organs which aren't vital to movement are slowed down (reducing heat production), -Sweat glands are activated to produce sweat which cools the skin as sweat evaporates.

So as you can see, a change (increase in body temp) causes a response which acts to reduce the change (to decrease body temp).

I can't stress to you how much this helped ... Thank you so much :smile:

!

Reply 738

tabz18

Original post by Hdizzle

Hey if you inbox me your email address I can send you a fully annotated article
File is too big to upload

hi could you send it to me too plz...would really appreciate it :smile:

Reply 739

Lujain Al Omari

Original post by RnTf

Can someone explain what is transcription factor??

Transcription factors are proteins coded for by other parts of the chromosomes. They are required to be present for transcription to be initiated.
Transcription factors are activated my signal proteins (hormones, regulatory proteins)
Active transcription factors can be: hormone/receptor complexes in the case of anabolic steroids, and the final product of the cascade where several proteins are activated in the case of peptide hormones.
The active transcription factors bind to the promoter region, allowing RNA polymerase to start transcription

Edexcel GCE Biology Unit 5 6BI05 June 2013

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