m_ew
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Hi,
I'm an Access to HE student that's struggling with the following questions that will be on my exams in mid-January. I'd really appreciate any help/ideas or just a point in the right sort of direction.

1. Explain why tissues are regarded aggregations of similar cells

Is this just because tissues are made up of cells performing similar functions?

2. Explain how the sequence of nucleotides within a gene is used to construct a polypeptide/protein

3. Explain how the structure of a biological macromolecule is related to its properties and influences its functions
I understand the structure and functions of, e.g. carbohydrates and proteins but I don't know how to explain why the structure influences what it does.
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Dynamo123
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(Original post by m_ew)
Hi,
I'm an Access to HE student that's struggling with the following questions that will be on my exams in mid-January. I'd really appreciate any help/ideas or just a point in the right sort of direction.

1. Explain why tissues are regarded aggregations of similar cells

Is this just because tissues are made up of cells performing similar functions?

2. Explain how the sequence of nucleotides within a gene is used to construct a polypeptide/protein

3. Explain how the structure of a biological macromolecule is related to its properties and influences its functions
I understand the structure and functions of, e.g. carbohydrates and proteins but I don't know how to explain why the structure influences what it does.
1. Yes and no. Tissues are formed by cells aggregating together through a LOT of adhesions (like cell-cell and cell matrix and others). I once wrote a treatise on it, which you can find here, but don't study it in detail unless you really want to understand how cells are integrated into tissues.
2. Now this is defined by the central dogma of molecular biology. DNA makes RNA makes protein. So the genes are first transcribed to mRNA, and are then translated into proteins. This process is not as simple as it seems, and is actually quite complex. If you want to understand it, see this.
3. Structure influences function. Imagine an enzyme. The structure of an enzyme must be specific so that the active site is available for substrate binding. If the structure is disrupted (as during noncompetitive inhibition and enzyme denaturation), the function of binding to the substrate and catalyzing a chemical reaction will not be performed.
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m_ew
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(Original post by Dynamo123)
1. Yes and no. Tissues are formed by cells aggregating together through a LOT of adhesions (like cell-cell and cell matrix and others). I once wrote a treatise on it, which you can find here, but don't study it in detail unless you really want to understand how cells are integrated into tissues.
2. Now this is defined by the central dogma of molecular biology. DNA makes RNA makes protein. So the genes are first transcribed to mRNA, and are then translated into proteins. This process is not as simple as it seems, and is actually quite complex. If you want to understand it, see this.
3. Structure influences function. Imagine an enzyme. The structure of an enzyme must be specific so that the active site is available for substrate binding. If the structure is disrupted (as during noncompetitive inhibition and enzyme denaturation), the function of binding to the substrate and catalyzing a chemical reaction will not be performed.
Thank you, I really appreciate the help.

For question 3, I still don't understand exactly HOW structure influences function. E.g. I can say for lipids that the lack of -OH groups make them largely insoluble, and the amount of C-H bonds make them very energy rich (with the "branches" or chains also making them very compact therefore making them good at storing a lot of energy in a small space), but I'm not sure about carbohydrates and I'm also not sure how to go into enough detail for proteins. I know their function depends on their structure and that their structure is so important that if a protein unfolds it stops working, but I'm just worried that isn't enough information.
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Dynamo123
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(Original post by m_ew)
Thank you, I really appreciate the help.

For question 3, I still don't understand exactly HOW structure influences function. E.g. I can say for lipids that the lack of -OH groups make them largely insoluble, and the amount of C-H bonds make them very energy rich (with the "branches" or chains also making them very compact therefore making them good at storing a lot of energy in a small space), but I'm not sure about carbohydrates and I'm also not sure how to go into enough detail for proteins. I know their function depends on their structure and that their structure is so important that if a protein unfolds it stops working, but I'm just worried that isn't enough information.
Don't be worried: it's enough for an A Level student (I'm assuming you are one). Protein structure is vital for function. I think you haven't studied proteins in that much detail, otherwise it would be quite easy to grasp the concept. I'll show by an example what I mean.

You know that hormones travel through blood, and when they reach a target cell, they bind to specific receptor on the surface of the cell, and initiate the response. Now this receptor on the cell is a protein. You must be wondering why the receptor does not respond all the time even in the absence of the hormone. This is because the receptor has a specific structure. Its structure normally blocks certain events from happening that lead to response. When a hormone binds to it, the receptor changes its shape, and stops blocking the events that lead to the response. This is called a conformational shape change. So you see, the structure is vital to the function of the receptor protein. Structural changes drastically affect the function of the protein. See this animation. Notice the shrinking in the size of the protein as a specific molecule binds to it and allows it to perform a function.

For carbs, simply think about how their structure affects their function. Glucose and fructose are two ideal examples. Both have the same no of C atoms. A few changes in their structure mean that their chemical reactions, and their properties and everything differs quite a lot. For instance, see their structures:
Image
the one on the left is fructose. On the right is glucose. These structures are almost similar, but if you consider the ring forms of both these molecules, fructose forms a 5 membered ring, while glucose forms a 6 member ring.

Image
So you see, structure largely affects function.
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