ItZZ_ChAI
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Hi everyone,

I just did one of the essay style questions for the AQA A-Level Biology Paper 3 paper. I don't really trust myself to give an accurate mark so I was wondering if someone here would be kind enough to do so? Btw I kinda rushed the last point as my 45 mins were coming to an end. Some feedback for improvement would also be really helpful. Here's the question and answer:


The importance of nitrogen-containing substances in biological systems


Nitrogen-containing substance as very important in biological systems, one example of this is ATP, Adenosine tri phosphate, is an essential molecule in humans and many other organisms as it is one of the ways our body stores and transports chemical energy within cells. ATP contains adenine, which is one of the four nitrogenous bases. ATP can easily be transported and broken down via hydrolysis reaction into ADP where it can be remade back into ATP which is one of its key features which helps as it is a reliable source of energy for functions like active transport and protein synthesis.

In addition, without ATP Co-Transport and facilitated diffusion will not be able to happen, which is very essential for cells as this is the way many of them receive nutrients and essential substances for the survival of the cell, sodium ions require ATP to be hydrolysed to release energy so that it can be pumped in and out of cells which increases the concentration gradient, which also allows glucose to be transported with it (Co transport), This is important in the intestines where it needs to absorb the nutrients and transport it to the blood where it can be transported to organs and muscles, this happens via Na+ ions being pumped out of the epithelium tissue which creates a concentration gradient between the lumen of the ileum and the epithelium cells, this allows the Na+ ions to be diffused into the epithelium cells via co transporter proteins which allows glucose to be transported with the Na+ into the cell, this now creates another concentration gradient as there is more glucose in the epithelium cells than in the blood, thus the glucose diffuses out the epithelium cells into the blood.

Another example is the nitrogenous bases which were mentioned before. These bases are paramount for organisms as they are the main reason for the replication of DNA. The four bases (Adenine, Thymine, Cytosine, Guanine) form H bonds to their complementary bases (Adenine and Thymine, and Cytosine and Guanine) which is very important for semi-conservative replication as it makes sure the daughter copies are exactly the same, which stops mutations and ensure the genetic code is not changed or altered, thus another way nitrogen containing substances are indispensable for biological organisms.

Furthermore, another vital role nitrogen-containing substance play is in amino acids, these are the building blocks for proteins which are the fundamental substances for most organisms. Proteins are made via peptide bonds being made between amino acids which happens in the translation phase of protein synthesis. One-way proteins play an important role is in enzymes as they are proteins, enzymes reduce the activation energy for reactions by providing an alternative pathway which allows the reaction to take place. One important enzyme is DNA Helicase and Polymerase, Helicase allow DNA to “unzip” which then in turn allows free nitrogenous bases to bond with their complementary base via condensation reaction, which is catalysed by polymerase this is very important as this DNA replication allows the genetic code to stay intact and allow it to be passed down to offspring without any alteration.

Finally, another way nitrogen containing substance are of the essence is antibodies, antibodies bind onto pathogen which help phagocytes to engulf the pathogen via phagocytosis. Antibodies have an antibody-antigen complex which causes complementary antigens to bind to it.
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ItZZ_ChAI
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Report Thread starter 3 months ago
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(Original post by ItZZ_ChAI)
Hi everyone,

I just did one of the essay style questions for the AQA A-Level Biology Paper 3 paper. I don't really trust myself to give an accurate mark so I was wondering if someone here would be kind enough to do so? Btw I kinda rushed the last point as my 45 mins were coming to an end. Some feedback for improvement would also be really helpful. Here's the question and answer:


The importance of nitrogen-containing substances in biological systems


Nitrogen-containing substance as very important in biological systems, one example of this is ATP, Adenosine tri phosphate, is an essential molecule in humans and many other organisms as it is one of the ways our body stores and transports chemical energy within cells. ATP contains adenine, which is one of the four nitrogenous bases. ATP can easily be transported and broken down via hydrolysis reaction into ADP where it can be remade back into ATP which is one of its key features which helps as it is a reliable source of energy for functions like active transport and protein synthesis.

In addition, without ATP Co-Transport and facilitated diffusion will not be able to happen, which is very essential for cells as this is the way many of them receive nutrients and essential substances for the survival of the cell, sodium ions require ATP to be hydrolysed to release energy so that it can be pumped in and out of cells which increases the concentration gradient, which also allows glucose to be transported with it (Co transport), This is important in the intestines where it needs to absorb the nutrients and transport it to the blood where it can be transported to organs and muscles, this happens via Na+ ions being pumped out of the epithelium tissue which creates a concentration gradient between the lumen of the ileum and the epithelium cells, this allows the Na+ ions to be diffused into the epithelium cells via co transporter proteins which allows glucose to be transported with the Na+ into the cell, this now creates another concentration gradient as there is more glucose in the epithelium cells than in the blood, thus the glucose diffuses out the epithelium cells into the blood.

Another example is the nitrogenous bases which were mentioned before. These bases are paramount for organisms as they are the main reason for the replication of DNA. The four bases (Adenine, Thymine, Cytosine, Guanine) form H bonds to their complementary bases (Adenine and Thymine, and Cytosine and Guanine) which is very important for semi-conservative replication as it makes sure the daughter copies are exactly the same, which stops mutations and ensure the genetic code is not changed or altered, thus another way nitrogen containing substances are indispensable for biological organisms.

Furthermore, another vital role nitrogen-containing substance play is in amino acids, these are the building blocks for proteins which are the fundamental substances for most organisms. Proteins are made via peptide bonds being made between amino acids which happens in the translation phase of protein synthesis. One-way proteins play an important role is in enzymes as they are proteins, enzymes reduce the activation energy for reactions by providing an alternative pathway which allows the reaction to take place. One important enzyme is DNA Helicase and Polymerase, Helicase allow DNA to “unzip” which then in turn allows free nitrogenous bases to bond with their complementary base via condensation reaction, which is catalysed by polymerase this is very important as this DNA replication allows the genetic code to stay intact and allow it to be passed down to offspring without any alteration.

Finally, another way nitrogen containing substance are of the essence is antibodies, antibodies bind onto pathogen which help phagocytes to engulf the pathogen via phagocytosis. Antibodies have an antibody-antigen complex which causes complementary antigens to bind to it.
Btw i'm only in year 12 so i'm doing AS, sorry for any confusion.
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