dasda
Badges: 15
Rep:
?
#1
Report Thread starter 6 months ago
#1
The importance of nitrogen-containing substances in biological systems.

answer
Dna replicates by semi-conservative replication. DNA helicase breaks the hydrogen bonds between base pairs. This allows the dna molecule to unwinds. Free nucleotides are activated. DNA polymerase joins the adjacent nucleotides together and forms the sugar phosphate backbone. Replicated DNA uses the strands as templates. Nucleotides contain bases which contain nitrogen. Bases are very important in DNA replication because without bases, DNA will not be able to divide. This means processes like mitosis will not occur which means we will be able to repair tissues and cells.
Proteins contain nitrogen in the NH2 group. Proteins are very important in biological systems especially enzymes. enzymes act as biological catalysts which speeds ups the rate of the rate of ther reaction. This is done when substrates bind to the active site. The induced fit model states that that the enzyme is not fully complementary to the substrate . when the substrate binds to the activate, it stresses the bonds on the enzyme. This causes an enzyme-substrate complex to be formed which lowers the activation energy. When the activation energy is lowered, this means that less energy is needed to start the reaction. This means that there will be more reactions occurring frequently because of the lower activation energy. Enzymes are therefore important because without enzymes, reactions would have a higher activation energy and would proceed more slowly. Certain examples of reactions which use enzymes is the hydrolysis of atp. Atp to adp and pi. This reaction is catalysed by ATP synthase. This reactions forms ADP quickly and can be used in processes like muscle contration and active transport
Haemoglobin is an important quaternary protein that has 4 binding sites for oxygen. When the first oxygen molecule binds. This slightly changes the quaternaty structure of haemoglibin and uncovers a new binding site. This allows the second oxygen molecule to bind. Oxyhaemoglobin disscoaites to oxgen and haemoglobin at low partial pressure for example in the muscle. The oxygen is used in respiration(oxidative phosphyrlation) which requires oxygen as a final terminal electron acceptor. If this process do not occur, oxygen cannot act as the terminal electron acceptor. This reduces the concentration gradient of protons. This means that less ATP is made. ATP is needed for muscle contraction. Without ATP, there will be no musce contration which means that the animal won’t be able to move. So they won’t be able to hunt for food since this requires muscle contration. There haemoglobin is an important quanternary protein which contains nitrogen because it provides the animal with oxygen which is used in respiration.
mRNA contains adenine,uracil,guanine,cytosine. mRNA is used in translation to produce a polypeptide. Mrna attaches to the ribosome and moves to the start codon. Complementary anticodon on trna binds to codon on mrna. different amino are binded to trna by atp. Amino acids from trna bind to each by peptide bonds. This process keeps repating until ribomose reaches stop codon. Polypeptide then floats away in the cytoplasm. As repeated, the bases of mRNA contain nitrogen. Due to their shape of the bases, they can bind to different bases with a complementary shape. This is important because it allows the condons to bind to the anticonds which leads to amino acids binding together by peptide bonds.
Nitrogen cycle shows how nitrogen is recycled through the food chain. Ammonia is nitrified to nitrite and then nitrified to nitrate. Decomposers break down the nitrogen compounds in dead animals by saprobioitic nutriotion into ammonia. This is then convented into nitrate by nitrifying bacteria. Nitrate also turns into nitrogen gas by denitrification. This happens in water logged soil in anaerobic conditions. Root modules in leguminous plants can convert nitrogen gas into ammonia. The nitrogen cycle shows the transferof nitrogen through the food web. This is important because it shows us that nitrogen is needed in ecosystems.
0
reply
username5064508
Badges: 16
Rep:
?
#2
Report 6 months ago
#2
I'm not an examiner, but ill try to apply the same logic using the mark scheme:

You've included around 5 distinct areas, all of which are relevant to the question.
You have also made an effort to explain why each use is important in the body, to justify your choices.
The only section which I think is not as clearly justified is the nitrogen cycle, but your other areas can compensate for that.
Each section seems to mostly flow quite well together, perhaps even better with some rearranging of certain sections.

However, as you have not included any beyond-spec material, it cannot score the top bracket of marks.

Therefore, I would probably estimate it to be in the region of 15-18 marks.

However, I'm not an examiner, I'm just going off of my experience with biology essays. If anyone else comes across this thread they are welcome to make their own decision of the mark.
1
reply
macpatgh-Sheldon
Badges: 20
Rep:
?
#3
Report 6 months ago
#3
Hi an opinion from me will hopefully help.

I think your answer has a large amount of correct and detailed information, and does display your knowledge well, in spite of a few errors e.g. module instead of nodule; ribomose instead of ribosome, etc.

The main criticism I have on immediate perusal of your answer is twofold:

Firstly, you have provided a lot of detail on a small number of points - although the detail might sound impressive, the mark schemes in biology "look for" a large variety of relevant ideas, concepts, factors, examples, etc.
Secondly, your reference to importance of nitrogen [which is after all the requirement of the Q] is limited.

I have not formally printed and marked your answer, but with a quick read and from extensive experience, I would say you would not score more than 10 out of 20 [sorry not meant to discourage you - carry on reading to learn how to improve ]. The reason is that each separate instance of ideas, concepts, factors, examples carries a mark, and in some cases further detail carries one more mark; however, by going into great detail on an individual point, YOU WILL EARN NO EXTRA MARKS.

Therefore, in an essay Q, the best way to earn "mark, mark, mark" [which is what counts in the end], is to delineate a large number of points [efficient use of the time available].

HOW TO IMPROVE YOUR ESSAY:

I) Firstly add the following [remember the Q is asking for IMPORTANCE]:-
1. A good short intro section outlining which molecules have nitrogen i.e. proteins, nucleic acids, creatinine, (urea), nitric oxide, with brief chemistry.
2. A lot more examples of functions of proteins:
a) importance in defence/protection i) antibodies - mention structure [Y-shaped with disulphide bonds] briefly. [IgA in secretions e.g. in tear fluid - outside syllabus as cited by HRobson]
ii) lysozyme + lactoferrin [enzymes in tears that kill bacteria]
iii) The CYP system (cytochrome oxidase) of enzymes break down toxins - importance in preventing chemical damage
iv) collagen in bone and cartilage/tendons/ligaments provide strength and stability - important in protection of internal organs against injury e.g. rib cage for heart + lungs, skull for brain.

b) importance in transport - proteins in blood carry e.g. iron [ferritin], copper [ceruloplasmin], and some drugs.
(your mention of haemoglobin appears here - MENTION IMPORTANCE OF THE TRANSPORT OF OXYGEN, for respiration ----> ATP..

c) importance in homeostasis: i): amino acids + proteins, being amphoteric (having both NH2 ANd COOH groups) are good pH buffers.
ii) some hormones are proteins e.g. insulin (56 amino acids) - importance in control of blood glucose; growth hormone.

d) importance in exchange/movement of materials across cells/membranes e.g. active transport in reabsorption of amino acids glucose in renal proximal tubule cells, active absorption of digested nutrients in small intestine [ileum]. [Outside syllabus: sodium-potassium pump (Na+,K+-ATPase)].

e) importance in movement e.g. to catch prey for predators or to escape for prey:- (i) myosin/actin filaments for muscle contraction [mention sarcomere and sliding filament theory briefly].
(ii) collagen in bone as muscles need to be attached to bone.

f) SIMILARLY a number of ideas for nucleic acids.
g) importance of the urea cycle [ornithine cycle] for excretion of excess nitrogen.

II) Add items outside syllabus for the last 2-3 marks.

III) Your quality of English is good by current standards, but try and avoid the typos.

Finally, if you would like to go through and apply my ten point article on exam technique published in a periodical, please feel free to PM me.

M (specialist biology tutor).
2
reply
dasda
Badges: 15
Rep:
?
#4
Report Thread starter 6 months ago
#4
(Original post by macpatgh-Sheldon)
Hi an opinion from me will hopefully help.

I think your answer has a large amount of correct and detailed information, and does display your knowledge well, in spite of a few errors e.g. module instead of nodule; ribomose instead of ribosome, etc.

The main criticism I have on immediate perusal of your answer is twofold:

Firstly, you have provided a lot of detail on a small number of points - although the detail might sound impressive, the mark schemes in biology "look for" a large variety of relevant ideas, concepts, factors, examples, etc.
Secondly, your reference to importance of nitrogen [which is after all the requirement of the Q] is limited.

I have not formally printed and marked your answer, but with a quick read and from extensive experience, I would say you would not score more than 10 out of 20 [sorry not meant to discourage you - carry on reading to learn how to improve ]. The reason is that each separate instance of ideas, concepts, factors, examples carries a mark, and in some cases further detail carries one more mark; however, by going into great detail on an individual point, YOU WILL EARN NO EXTRA MARKS.

Therefore, in an essay Q, the best way to earn "mark, mark, mark" [which is what counts in the end], is to delineate a large number of points [efficient use of the time available].

HOW TO IMPROVE YOUR ESSAY:

I) Firstly add the following [remember the Q is asking for IMPORTANCE]:-
1. A good short intro section outlining which molecules have nitrogen i.e. proteins, nucleic acids, creatinine, (urea), nitric oxide, with brief chemistry.
2. A lot more examples of functions of proteins:
a) importance in defence/protection i) antibodies - mention structure [Y-shaped with disulphide bonds] briefly. [IgA in secretions e.g. in tear fluid - outside syllabus as cited by HRobson]
ii) lysozyme + lactoferrin [enzymes in tears that kill bacteria]
iii) The CYP system (cytochrome oxidase) of enzymes break down toxins - importance in preventing chemical damage
iv) collagen in bone and cartilage/tendons/ligaments provide strength and stability - important in protection of internal organs against injury e.g. rib cage for heart + lungs, skull for brain.

b) importance in transport - proteins in blood carry e.g. iron [ferritin], copper [ceruloplasmin], and some drugs.
(your mention of haemoglobin appears here - MENTION IMPORTANCE OF THE TRANSPORT OF OXYGEN, for respiration ----> ATP..

c) importance in homeostasis: i): amino acids + proteins, being amphoteric (having both NH2 ANd COOH groups) are good pH buffers.
ii) some hormones are proteins e.g. insulin (56 amino acids) - importance in control of blood glucose; growth hormone.

d) importance in exchange/movement of materials across cells/membranes e.g. active transport in reabsorption of amino acids glucose in renal proximal tubule cells, active absorption of digested nutrients in small intestine [ileum]. [Outside syllabus: sodium-potassium pump (Na+,K+-ATPase)].

e) importance in movement e.g. to catch prey for predators or to escape for prey:- (i) myosin/actin filaments for muscle contraction [mention sarcomere and sliding filament theory briefly].
(ii) collagen in bone as muscles need to be attached to bone.

f) SIMILARLY a number of ideas for nucleic acids.
g) importance of the urea cycle [ornithine cycle] for excretion of excess nitrogen.

II) Add items outside syllabus for the last 2-3 marks.

III) Your quality of English is good by current standards, but try and avoid the typos.

Finally, if you would like to go through and apply my ten point article on exam technique published in a periodical, please feel free to PM me.

M (specialist biology tutor).
Thank you. I will use those points to try to improve further essays.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Do you have the space and resources you need to succeed in home learning?

Yes I have everything I need (398)
56.37%
I don't have everything I need (308)
43.63%

Watched Threads

View All