A level Biology: Post your doubts here!

[strangerss]

If the air inhaled is less than the air exhaled, then you will exhale more than you inhale, so eventually, you should completely run out of air, right?
In order to maintain a constant lung volume, the air inhaled must equal the air exhaled.

Oops my bad I meant shouldn't be More , but I think I got it , so the volume remains equal but the composition of air changes right?

 

[lee mee..]

Hey... can someone please explain me Bohr shift . Please .....

 

[knowitall10]

Hey... can someone please explain me Bohr shift . Please .....

In the cytoplasm, there's an enzyme called Carbonic Anhydrase right? what does it do? it catalyses the reaction of CO2 with water to form H2CO3, carbonic acid. this furthur dessociates-breaks down- to form a hydron ion and a hydrogen carbonate ion, HCO3-.
Heamoglobin readily combines with the H+ ions released forming haemoglobinic acid,HHb.
This in turn, makes the haemoglobin release the O2 it is carrying
The net effect of the reaction is two-fold (basically it has plays two important roles)
1) The Haemoglobin "mops up" the H+ ions which are formed when CO2 dissolves and breaks down. why is this an advantage? because a high H+ conc lowers blood pH; if they were left in the blood, it would become acidic. therefore: Haemoglobin acts as a buffer since it maintains the blood's pH by removing these ions. it keeps the pH maintained close to normal.
2) Bohr effect: this is when the presence of a high partial pressure of CO2 causes the release of O2 from the haemoglobin-the reaction i described up there-. and it's important because there are especially high concentrations of CO2 in actively respiring cells, so O2 would be released more readily in these cells because they are respiring.
I hope i cleared your doubt

 

[strangerss]

Hey... can someone please explain me Bohr shift . Please .....

It occurs during high partial pressure of carbon dioxide during muscle activity , which reduces the percentage saturation of hemoglobin because , the carbon dioxide diffuses into the red cells and with the aid of the enzyme carbonic anhydrase it reacts with water forming carbonic acid , the carbonic acid dissociates into a hydrogen ion and hydrogen carbonate ion , now the hydrogen ion combines with haemoglobin forming haemoglobinic acid , as it does so it releases the oxygen so , carbon dioxide reduces the haemoglobins affinity to oxygen . some of the carbon dioxide diffuses into the red cells but instead of forming carbonic acide it reacts with the terminal amino groups of some of the haemoglobon molecules forming carbamino-haemoglobin , and I think this also makes it release it's oxygen but I'm not sure , any one can help? ..so eventually that's the reason why the sigmoid curve shifts to the right because for the same partial pressures of oxygen but with carbon dioxides presence the percentage saturation of haemoglobin is lower to relaes more oxygen for the respiring muscles who are releasing carbon dioxide. I hope you understood from me

 

[strangerss]

In the cytoplasm, there's an enzyme called Carbonic Anhydrase right? what does it do? it catalyses the reaction of CO2 with water to form H2CO3, carbonic acid. this furthur dessociates-breaks down- to form a hydron ion and a hydrogen carbonate ion, HCO3-.
Heamoglobin readily combines with the H+ ions released forming haemoglobinic acid,HHb.
This in turn, makes the haemoglobin release the O2 it is carrying
The net effect of the reaction is two-fold (basically it has plays two important roles)
1) The Haemoglobin "mops up" the H+ ions which are formed when CO2 dissolves and breaks down. why is this an advantage? because a high H+ conc lowers blood pH; if they were left in the blood, it would become acidic. therefore: Haemoglobin acts as a buffer since it maintains the blood's pH by removing these ions. it keeps the pH maintained close to normal.
2) Bohr effect: this is when the presence of a high partial pressure of CO2 causes the release of O2 from the haemoglobin-the reaction i described up there-. and it's important because there are especially high concentrations of CO2 in actively respiring cells, so O2 would be released more readily in these cells because they are respiring.
I hope i cleared your doubt

OH my GOD we wrote at the same time XD

 

[lee mee..]

In the cytoplasm, there's an enzyme called Carbonic Anhydrase right? what does it do? it catalyses the reaction of CO2 with water to form H2CO3, carbonic acid. this furthur dessociates-breaks down- to form a hydron ion and a hydrogen carbonate ion, HCO3-.
Heamoglobin readily combines with the H+ ions released forming haemoglobinic acid,HHb.
This in turn, makes the haemoglobin release the O2 it is carrying
The net effect of the reaction is two-fold (basically it has plays two important roles)
1) The Haemoglobin "mops up" the H+ ions which are formed when CO2 dissolves and breaks down. why is this an advantage? because a high H+ conc lowers blood pH; if they were left in the blood, it would become acidic. therefore: Haemoglobin acts as a buffer since it maintains the blood's pH by removing these ions. it keeps the pH maintained close to normal.
2) Bohr effect: this is when the presence of a high partial pressure of CO2 causes the release of O2 from the haemoglobin-the reaction i described up there-. and it's important because there are especially high concentrations of CO2 in actively respiring cells, so O2 would be released more readily in these cells because they are respiring.
I hope i cleared your doubt

It occurs during high partial pressure of carbon dioxide during muscle activity , which reduces the percentage saturation of hemoglobin because , the carbon dioxide diffuses into the red cells and with the aid of the enzyme carbonic anhydrase it reacts with water forming carbonic acid , the carbonic acid dissociates into a hydrogen ion and hydrogen carbonate ion , now the hydrogen ion combines with haemoglobin forming haemoglobinic acid , as it does so it releases the oxygen so , carbon dioxide reduces the haemoglobins affinity to oxygen . some of the carbon dioxide diffuses into the red cells but instead of forming carbonic acide it reacts with the terminal amino groups of some of the haemoglobon molecules forming carbamino-haemoglobin , and I think this also makes it release it's oxygen but I'm not sure , any one can help? ..so eventually that's the reason why the sigmoid curve shifts to the right because for the same partial pressures of oxygen but with carbon dioxides presence the percentage saturation of haemoglobin is lower to relaes more oxygen for the respiring muscles who are releasing carbon dioxide. I hope you understood from me

Thaaank you sooo much guys

 

[knowitall10]

OH my GOD we wrote at the same time XD

LOL!! SubhanAllah!

 

[strangerss]

Thaaank you sooo much guys

any time

 

[Irfan1995]

Outline the ways in which the endocrine and nervous systems carryout teir roles in control and co ordination in animals..
Can anyone write the full answer? the marks scheme is given below..
endocrine
1. hormones ;
2. chemical messengers ; A chemicals that transfer information
3. ductless glands / (released) into blood ;
4. target, organs / cells ;
5. ref. receptors on cell membranes ;
6. example of named hormone and effect ;
nervous
7. impulses/ action potentials ; R electrical, signals / current
8. along, axon / neurones / nerve fibres ; R nerves R across
9. synapse (with target) / neuromuscular junction ;
10. ref. receptor / sensory neurones ;
11. ref. effector / motor neurones ;
differences – endocrine
12. slow effect / ora ;
13. long lasting effect / ora ;
14. widespread effect / ora ;
15. AVP ; e.g. extra detail of synapse / hormone changes triggered within cells [8 max]

• In the endocrine system, the messengers are hormones (chemical messengers) while in the nervous system, the stimulus is transferred as impulses.
• Hormones reach their target organs (where it binds to the receptors on the cell membranes) by being circulated around the blood while the impulses travel from a sensory neuron, along axons, towards the synapse where it will meet with the motor neurone which delivers the impulse to an effector.
• As a result, hormones achieve their effect much slower than nervous impulses.
• However, nervous impulses target a very specific region of the brain (whereas hormonal effects are widespread) and the effect only lasts for a short period of time relative to hormonal effect.

I think I just mentioned the first 14 points. You don't have to say them in order, but the order you mention your points must be clear and logical.

 

[HorsePower]

Thanks for the help , I didn't even figure out it's a RBC , I know a rbc is biconcave , but it looks to me like a triangle more than anything XS

i got this question in my mocks... and even i culdnt tell
plus the image was in black and white, which made it more difficult

 

[MÁťT PŭמҚ]

can sm1 plz tell me tht y there is a need for transport systems in multi cellular plants and animal in terms of size and surface area to volume ratio...

 

[Irfan1995]

can sm1 plz tell me tht y there is a need for transport systems in multi cellular plants and animal in terms of size and surface area to volume ratio...

Okay, if we look at cnidarians, we can easily see that they don't need a transport system.
Cnidarians are organisms that live underwater and are only two cells thick (hence very high surface area to volume ratio). This means that any required nutrients or any wastes can easily pass in or out through simple diffusion.

Plants, however, are much larger and more complex. They continuously photosynthesize, so they need a constant supply of water (which can only be achieved through a transport system). Since plants can grow quite large (low surface area to volume ratio), the transport system must also branch and reach many cells. Since the requirements are not extremely demanding, a simple transport system (made up of vascular bundles - xylem and phloem vessels) is enough to provide the plant with all its needs.

Animals (like humans) have an even greater need for energy. Humans constantly move, breathe, and talk, so our energy demands are very high. Also, we produce a lot of wastes too. Diffusion would be too slow to provide all the cells with enough sugar for energy. Also, some cells (like liver and heart cells) require much more energy than others (like epidermal cells). The transport system in animals is much more complex; it involves many aspects like a pump (the heart).

 

[MÁťT PŭמҚ]

Okay, if we look at cnidarians, we can easily see that they don't need a transport system.
Cnidarians are organisms that live underwater and are only two cells thick (hence very high surface area to volume ratio). This means that any required nutrients or any wastes can easily pass in or out through simple diffusion.

Plants, however, are much larger and more complex. They continuously photosynthesize, so they need a constant supply of water (which can only be achieved through a transport system). Since plants can grow quite large (low surface area to volume ratio), the transport system must also branch and reach many cells. Since the requirements are not extremely demanding, a simple transport system (made up of vascular bundles - xylem and phloem vessels) is enough to provide the plant with all its needs.

Animals (like humans) have an even greater need for energy. Humans constantly move, breathe, and talk, so our energy demands are very high. Also, we produce a lot of wastes too. Diffusion would be too slow to provide all the cells with enough sugar for energy. Also, some cells (like liver and heart cells) require much more energy than others (like epidermal cells). The transport system in animals is much more complex; it involves many aspects like a pump (the heart).

thnkx alot.. ^_^

 

[falcon678]

guyss! advantages of double circulation system over single circulation? n vice versa.....thanks in advance!

 

[Student12]

guyss! advantages of double circulation system over single circulation? n vice versa.....thanks in advance!

Double circulatory system has 2 main advantage: - ability to create more pressure to pump blood around the system and the seperation of oxygenated and deoxygenated.

 

[railey]

Salaam Alaykum guys,
can someone please explain or send me some notes on the Kidneys, i don't get it at all. Please anyone. Thanks in advance.
Ali Railey

 

[falcon678]

n wat bout sinlge circulatory's advantages...?

 

[railey]

Can someone please help me with the reabsorption into the proximal convoluted tubule
So i got two sources of information which i summarized but i dunno which one is the right one. Please anyone doing A2, please help me, am really confused.

first one:
'Sodium ions and glucose molecules are transported from the filtrate into the proximal convoluted tubule cells by active transport. Specialised carrier protein molecules called symports transport glucose and sodium at the same time.
Glucose is then transported out of the PCT and into the blood by facilitated diffusion (the carrier protein is glucose permease), while the sodium ions are transported via the sodium pump into the blood.'

Second one:
'The basal membranes (the one nearest to the blood and away from the lumen) of the walls lining the proximal convoluted tubule actively transport sodium ions out of the cell.
(Energy for active transport comes from the mitochondria in the form of ATP) The sodium ions are carried away in the blood. This lowers the concentration of sodium ions present inside the proximal convoluted tubule. This causes them to be passively diffused into the bloodby specialised carrier protein molecules called symports transport not only the sodium leaves the PTC but also glucose molecules. There are several kinds of these carrier proteins in the membrane.
In order to avoid decreasing the solute concentration of the filtrate, water is also moved freely by osmosis into blood through the walls of the tubule, not changing the filtrate concentration.
A lot of urea is also reabsorbed in this way as it is a small molecule which can easily pass through to the blood as there is a high amount In the filtrate. More than half of the urea is reabsorbed.
(The other 2 forms of excretory products, the creatine and the uric acid aren’t able to do this)
A lot of reabsorption takes place in this stage.'
anyone please help me.

 

[Irfan1995]

Can someone please help me with the reabsorption into the proximal convoluted tubule
So i got two sources of information which i summarized but i dunno which one is the right one. Please anyone doing A2, please help me, am really confused.

first one:
'Sodium ions and glucose molecules are transported from the filtrate into the proximal convoluted tubule cells by active transport. Specialised carrier protein molecules called symports transport glucose and sodium at the same time.
Glucose is then transported out of the PCT and into the blood by facilitated diffusion (the carrier protein is glucose permease), while the sodium ions are transported via the sodium pump into the blood.'

Second one:
'The basal membranes (the one nearest to the blood and away from the lumen) of the walls lining the proximal convoluted tubule actively transport sodium ions out of the cell.
(Energy for active transport comes from the mitochondria in the form of ATP) The sodium ions are carried away in the blood. This lowers the concentration of sodium ions present inside the proximal convoluted tubule. This causes them to be passively diffused into the bloodby specialised carrier protein molecules called symports transport not only the sodium leaves the PTC but also glucose molecules. There are several kinds of these carrier proteins in the membrane.
In order to avoid decreasing the solute concentration of the filtrate, water is also moved freely by osmosis into blood through the walls of the tubule, not changing the filtrate concentration.
A lot of urea is also reabsorbed in this way as it is a small molecule which can easily pass through to the blood as there is a high amount In the filtrate. More than half of the urea is reabsorbed.
(The other 2 forms of excretory products, the creatine and the uric acid aren’t able to do this)
A lot of reabsorption takes place in this stage.'
anyone please help me.

Both are correct; I don't see any contradiction between the two explanations.

 

[Irfan1995]

n wat bout sinlge circulatory's advantages...?

I wouldn't say exactly that they have an advantage, but some organisms (like fish and earthworms) don't need the complexity of a double-circulation system. This is because their volumes are very small hence their energy requirements are low. Such requirements can be easily fulfilled by a single-circulation system.
In birds and other mammals, however, the energy demands are very high, so they need to circulate their blood as quickly as possible to maximize the rate of oxygen delivery. Such rates can only be achieved through a double-circulation method.