A level Biology: Post your doubts here!

[ShootingStar]

can someone please explain the pregnancy test kit?

 

[knowitall10]

Using examples outline the need for energy in living organisms.
I'm not sure what to write..

Examples of how energy is used in the transmission of nerve impulses- the activity of the sidium potassium pump


Read the first two pages of the respiration chapter

 

[sandrawrr]

Asalamulalikum can anyone explain that what is the role of Potassium channels and Calcium ions during the secretion of Insulin ?

So basically K+ channels in the plasma membrane of the beta cells first open causing K+ to diffuse out.
Which then causes the inside of the cell to be -70mV to compared to the outside.
If glucose levels are high, glucose enters the beta cells.
THe glucose is then phosphorylated then metabolised to produce ATP.
The presence of extra ATP causes K+ channels to close hence K+ cannot diffuse out of the membrane anymore making it -30mV.
Ca2+ channels are normally closed.
They open in response to the change in membrane potential.
Ca2+ move into the cell. Ca2+ then causes vesicles to release insulin by exocytosis

 

[Irfan1995]

CAN ANYONE EXPLAIN
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s12_qp_13.pdf Q2
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w11_qp_11.pdf Q14 Q24

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_qp_11.pdf Q5 Q6 Q14
THANK YOU

CAN ANYONE EXPLAIN
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s12_qp_13.pdf Q2
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w11_qp_11.pdf Q14 Q24

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_qp_11.pdf Q5 Q6 Q14
THANK YOU

1) We know that along food chains, the biomass decreases (roughly 10% is transferred to the next trophic level)
To find the total biomass of a population, multiply the number of individuals by the biomass of one individual
R: 10,000 x 0.1 = 1,000
S: 5 x 10.0 = 50
T: 500 x 0.002 = 1
U: 3 x 300,000 = 900,000
Just arrange them in decreasing order to get U --> R --> S --> T


2) If animal cells absorb too much water by osmisis, they will go through lysis (they will burst). Plants, on the other hand, have a cell wall which prevents lysis (bursting) and can allow the development of turgor pressures. Once a plant is turgid, no more water can get through.
Animals need the vacuole to remove water to prevent lysis.

3) It is the time between 1 and 2 plus the time between 3 and 4.

4) Goblet cells make a lot of vesicles which secrete mucus by exocytosis.

5) The first column shows how much reducing sugars are present.
After hydrolysis, you break down the non-reducing sugars into reducing sugars.
So the second column is the reducing sugars + non-reducing sugars
To find the amount of non-reducing sugars, subtract the corresponding values
A: 55 - 35 = 25
B: 55 - 55 = 0
C: 85 - 65 = 20
D: 80 - 70 = 10
So A has the most non-reducing sugars

6) When an inhibitor binds to the active site, this is known as competitive inhibition. The active site does not change shape, and the initial rate decreases
When an inhibit binds to a different site (allosteric site), then this is known as non-competitive inhibition.

 

[Zari]

So basically K+ channels in the plasma membrane of the beta cells first open causing K+ to diffuse out.
Which then causes the inside of the cell to be -70mV to compared to the outside.
If glucose levels are high, glucose enters the beta cells.
THe glucose is then phosphorylated then metabolised to produce ATP.
The presence of extra ATP causes K+ channels to close hence K+ cannot diffuse out of the membrane anymore making it -30mV.
Ca2+ channels are normally closed.
They open in response to the change in membrane potential.
Ca2+ move into the cell. Ca2+ then causes vesicles to release insulin by exocytosis

JazakAllah for the reply May Allah Bless you

 

[dragoninja98]

What the ETC does is that it splits hydrogen brought by the reduced NAD and FAD's into a proton (H+) and an electron. This electron has energy so it goes through an electron transfer chain all the way giving up energy. This energy is used to pump H+ into the intermembranal space of the mitochondrion. As the H+ concentration in the space increases it tends to flow out back into the mitochondrial matrix by diffusion. The H+ do so by passing through ATPase molecules. When H+ pass the ATPase molecules gain energy to combine ADP+P to form ATP. The H+ is then accepted by oxygen and thats why you need oxygen to respire and hence produce ATP and hence be able to eat, walk and talk.

Could anyone PLEASE give me an explanation or help me understand the electron transportchain in respiration?

 

[narutogirl]

I am very sorry to ask again, but can someone explain the null hypothesis, where we use the chi square test and if the value is less than the value of the critical value 0.05...
I don't understand how to correctly phrase that into an answer :/

 

[geek101]

Could anyone PLEASE give me an explanation or help me understand the electron transportchain in respiration?

Firstly the ETC chain takes place on the inner membranes of the mitochondria. here are a few steps:
1) at the beginning of the ETC the reduced NAD and reduced FAD (which are products of the previous stages of aerobic respiration) split, and give H+ ions and electrons. they are oxidized and regenerated for use in the other steps
2) The electrons are picked up by ELECTRON CARRIERS which are part of the electron transport chain (usually cytochrome molecules act as the electron carriers) these carriers pass the electrons down the chain
3) the electrons when split have high energies, as they pass down the chain they release some of their energy. This energy is used to pump out H+ ions from the mitochondrial matrix into the intermembrane space
4) These electrons are finally accepted by oxygen molecules. These oxygen molecules, along with H+ ions and the electrons from the chain combine to form a water molecule.
5) Now the concentration of H+ ions in the intermembrane space is higher than the matrix inside. So an electrochemical gradient is set up, H+ ions move down this concentration gradient via special transporter proteins on the inner membrane which have ATP synthase (enzyme) as part of their structure. 3 H+ ions produce one ATP molecule as they pass through this protein, this process is known as chemiosmosis...
hope that helps, good luck

 

[sandrawrr]

can someone please explain the pregnancy test kit?

Hormone HCG(Human chronic gonadotrophin) is produced by the chorion which is a layer of cells growing out from the embryo into the uterus wall (placenta)
It circulates in the mother's blood to reach ovaries by the time her period should normally start HCG has already built up to a high level which can be deteced in urine.
Because it is a glycoprotien, monoclonal antibodies can be produced against it.


(please look at the picture excuse my horrible drawing skills)

So we have
HCG: In red
Antibodies with granules: In blue with pink dots on top of them (which then act as antigens)
Antibody : In black which binds to the antibody with granules aswell as the HCG
Antibody: In yellow which is only there to show that the pregnancy kit worked.


Firstly the HCG (red) moves towards the granulated antibody( the blue one with pink dots). Notice how some of them do not have the HCG in them (2nd diagram).
But that doesnt matter because all of them ( the blue one with HCG and without HCG) move towards the 3rd part where the black and yellow antibody are present.
Only the one with the HCG will bind to the black antibody ( not really called black antibody) forming a colour band on the pregnancy kit.. The ones which do not have HCG molecules will still move towards the yellow antibody where they will both bind to form another colour band in the pregnancy test hence forming 2 lines showing that the patient is pregnant.
hope this helps..

 

[pearl angel]

What the ETC does is that it splits hydrogen brought by the reduced NAD and FAD's into a proton (H+) and an electron. This electron has energy so it goes through an electron transfer chain all the way giving up energy. This energy is used to pump H+ into the intermembranal space of the mitochondrion. As the H+ concentration in the space increases it tends to flow out back into the mitochondrial matrix by diffusion. The H+ do so by passing through ATPase molecules. When H+ pass the ATPase molecules gain energy to combine ADP+P to form ATP. The H+ is then accepted by oxygen and thats why you need oxygen to respire and hence produce ATP and hence be able to eat, walk and talk.

Firstly the ETC chain takes place on the inner membranes of the mitochondria. here are a few steps:
1) at the beginning of the ETC the reduced NAD and reduced FAD (which are products of the previous stages of aerobic respiration) split, and give H+ ions and electrons. they are oxidized and regenerated for use in the other steps
2) The electrons are picked up by ELECTRON CARRIERS which are part of the electron transport chain (usually cytochrome molecules act as the electron carriers) these carriers pass the electrons down the chain
3) the electrons when split have high energies, as they pass down the chain they release some of their energy. This energy is used to pump out H+ ions from the mitochondrial matrix into the intermembrane space
4) These electrons are finally accepted by oxygen molecules. These oxygen molecules, along with H+ ions and the electrons from the chain combine to form a water molecule.
5) Now the concentration of H+ ions in the intermembrane space is higher than the matrix inside. So an electrochemical gradient is set up, H+ ions move down this concentration gradient via special transporter proteins on the inner membrane which have ATP synthase (enzyme) as part of their structure. 3 H+ ions produce one ATP molecule as they pass through this protein, this process is known as chemiosmosis...
hope that helps, good luck

Jazak Allah thanku both so much for your help

 

[sandrawrr]

What do we need to know for bio tech? do we need to remember the fermeter ? like labelling aswell as functions?

 

[raamish]

hey guys what is the difference between embro, foetus, and zygote? And in section b where we have to answer 1 question. Whenever i answer those questions my answers are not very long but they do contain all the points in the markscheme. Like if they give a space of 3 pages my answer to a come in half page or a little more and the answer to b is also a half page or can be less. So, will my marks be deducted if i write short answers like this? plzz help ty

 

[externityxzx]

can anyone explain how does superovulation occur?? what hormones and drugs are used and what are their effects? how does it allow many follicles to form?

 

[comrade]

What do we need to know for bio tech? do we need to remember the fermeter ? like labelling aswell as functions?

Yes you should know about fermenter and how it works.

 

[comrade]

hey guys what is the difference between embro, foetus, and zygote? And in section b where we have to answer 1 question. Whenever i answer those questions my answers are not very long but they do contain all the points in the markscheme. Like if they give a space of 3 pages my answer to a come in half page or a little more and the answer to b is also a half page or can be less. So, will my marks be deducted if i write short answers like this? plzz help ty

They are similar. A zygote forms after fertilization. A zygote becomes an embryo which becomes a fetus.

An embryo is a multicellular diploid eukaryote in its earliest stage of development.

In organisms that reproduce sexually, once a sperm fertilizes an egg cell, the result is a cell called the zygote that has all the DNA of two parents.

A fetus (or foetus, or fœtus) is a developing mammal or other viviparous vertebrate, after the embryonic stage and before birth.

This is the very basic explanation.

 

[comrade]

can anyone explain how does superovulation occur?? what hormones and drugs are used and what are their effects? how does it allow many follicles to form?

Superovulation is a term used to describe the drug-induced production of multiple eggs for use during assisted reproductive technologies, such as IVF. Superovulation is also sometimes used during IUI treatment. Normally, a female ovulates just one or more egg per cycle. With the use of fertility drugs, she may be able to produce many eggs, which can then be retrieved from the ovaries prior to ovulation to be used for artificial semination of another female unable to produce eggs or that quality of egg.

FSH and LH hormones are used. Progesterone and oestrogen are also used. I'm can't recall the whole process as to when they are used.

 

[comrade]

Do have a look at the thread I've made. I've posted some links which may help you people out. It doesn't have everything but it helped me. Click on the (thread) and check the links.

 

[lionkill3r]

For electrophoresis in chem , PCR is used after restriction enzyme but in biology text book ( the green book)it is used before restriction enzyme.... what should i beleive ?

 

[raamish]

They are similar. A zygote forms after fertilization. A zygote becomes an embryo which becomes a fetus.

An embryo is a multicellular diploid eukaryote in its earliest stage of development.

In organisms that reproduce sexually, once a sperm fertilizes an egg cell, the result is a cell called the zygote that has all the DNA of two parents.

A fetus (or foetus, or fœtus) is a developing mammal or other viviparous vertebrate, after the embryonic stage and before birth.

This is the very basic explanation.

hey and what are difference between continous and discontinous variation . Can u explain this fully. And my other question: And in section b where we have to answer 1 question. Whenever i answer those questions my answers are not very long but they do contain all the points in the markscheme. Like if they give a space of 3 pages my answer to a come in half page or a little more and the answer to b is also a half page or can be less. So, will my marks be deducted if i write short answers like this?

 

[Soldier313]

For electrophoresis in chem , PCR is used after restriction enzyme but in biology text book ( the green book)it is used before restriction enzyme.... what should i beleive ?

As far as i know, it's the PCR first followed by the restriction enzyme.