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So far we've looked at the main bits of a cell and how things get into and out of the cell = structures and transport. But what about how it does what it does. We are going to look at the instructions for the cell - DNA and what the instructions make - Proteins. This is where biology and chemistry come together = Biochemistry.
Step 1 : Hopefully this should be reasonably familiar - as we are going to recap the structure of DNA. The shape - double helix, the basic building block - nucleotides, the bases - ATCG's.
Sparking memories??
Maybe you've seen these clips before - but they will help remind us about DNA. (Learn)
Mission 1 : Let make sure we've got all that - read and complete the questions as we recap our DNA knowledge. (Learn)
Done that? = Share with your teacher.
Yes = now its time for your next Step/Video clip/Challenge/Mission.
No = go back and complete the Step/Video clip/Challenge/Mission please.
Step 2 : We all started from a single cell ..... but by now you are made of several trillions of cells. Each has a copy of the instructions = DNA. So how do we get new cells? We are going to find out.
The journey from 1 cell to 2 cells starts with making a copy of the instructions - DNA replication. This is where biochemistry steps in as each of the key stages are controlled by special chemicals.
You need to be familiar with these chemicals and the stages - its both complex and simple at the same time.
Here is how its done ... (Learn)
Mission 2 : Told you it was both simple AND complex ..... How have you got on - what are the key stages? What are the key chemicals?
Read and complete the questions on DNA replication - don't forget you can "rewind" if you need to. (Learn)
Done that? = Share with your teacher.
Yes = now its time for your next Step/Video clip/Challenge/Mission.
No = go back and complete the Step/Video clip/Challenge/Mission please.
Step 3 : Life has phases/ages/events - its the same in the life of a cell. It goes through a cycle of life - you would have heard it mentioned in the clips above. You need to be familiar with the key stages and how long each lasts for.
What are your cells doing right now? Are they all doing the same thing?? (Learn)
Mission 3 : So what do you know now ... complete the section on the cell cycle. (Learn)
Done that? = Share with your teacher.
Yes = now its time for your next Step/Video clip/Challenge/Mission.
No = go back and complete the Step/Video clip/Challenge/Mission please.
Step 4 : So we've replicated our cells DNA = now what do we do with it - 2 copies of DNA need 2 cells to put it into. So how do cells actually divide .... Mitosis - a word you should have heard before - but what do you remember? Lets grow some knowledge and/or repair any gaps....
You need to remember not only Mitosis but also the key phases ..... have a look (Learn)
Mission 4 : So how do you remember the key phases and whats happening .... this is how I do it .....
Interphase = Inbetween divisions, Prophase = getting organised - going Professional, Metaphase = Meeting in the middle, Anaphase = Sister Anna with the Banner (silly song), Telophase = need to Telophone the new separate cell.
How did you get on - try t he questions on Mitosis. (Learn)
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Yes = now its time for your next Step/Video clip/Challenge/Mission.
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Step 5 : How fast does Mitosis happen - Think of when shops sell stuff off cheap = they have a SALE. But in this case its S.A.L.E. So what are these letters for?? (Learn)
Mission 5 : Read and complete the work on - factors affecting rates of mitosis. Did you get to the SALE?? (Learn)
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Yes = now its time for your next Step/Video clip/Challenge/Mission.
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So DNA is the instructions and Mitosis duplicates DNA and makes more cells .... we are made of all these cells and they follow the instructions to let us do what we do ..... we're about to find out how.
DNA carries the code - the code tells the ribosomes what to make - what they make are proteins. The exact way how is covered in more detail in the section of work we do later called "Gene Expression"
So what is it about proteins that is good for us = we are a biological protein machine - both the physical structures that make us are proteins and our physiological processes are controlled by special proteins.
Remember back in Yr 11 Chemistry we looked at the factors that influenced how fast reactions take place ...... temperature, concentration, surface area and catalysts effect reaction rates. Its easy to crank up the temperature in a beaker, or use super concentrated doses, or massive amounts - but do this inside of you or me = toxic to life as we know it.
So the processes happening inside of our cells at our normal operating temperature, at life friendly concentrations, in the amounts diet provides require help in the form of catalysts.
We are about to look at biochemical catalysts - called enzymes - made from (you guessed it) proteins, manufactured by ribosomes following the instructions given to them by DNA.
Step 6 : So what are proteins? What are they made of? what holds them together? How do they do what they do? What stops them from doing their "jobs"?
So much to find out .... they are really complex biochemical molecules - and we have so many.
Here is it explained to you - and a video game to challenge you too. (Learn)
Mission 6 : Now you can understand what you are reading when you answer the questions on protein structure and you should know what denaturation is and what can cause it. (Learn)
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Yes = now its time for your next Step/Video clip/Challenge/Mission.
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Challenge 1 : Ever cooked an egg? If yes then you have observed proteins denaturing = the egg white is only white after in has denatured. Ever tried to uncook an egg? Yes it can't be done - only some proteins undergo reversible denaturisation.
Have a go and observe carefully what happens - either in the lab or you can try this at home too. Heat = boil an egg, pH change = use bleach or vinegar, solvent = a little trickier but if you can find some methylated spirits try it out. (Learn) (Create) (Share)
Done that? = Share with your teacher.
Yes = now its time for your next Step/Video clip/Challenge/Mission.
No = go back and complete the Step/Video clip/Challenge/Mission please.
Step 7 : Let take a closer look at biochemical catalysts - called enzymes - if a word ends in -ase then it's most likely the name of an enzyme. Let find out more about these soluble globby blobs of protein - they are bit like puzzle pieces = have a particular shape and only fit one place.
Lets look at them in more detail.... (Learn)
Mission 7 : Using this information complete the questions on enzymes. (Learn)
Done that? = Share with your teacher.
Yes = now its time for your next Step/Video clip/Challenge/Mission.
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Step 8 : So what are enzymes actually doing to enable the reactions to happen inside our cells at "normal" body temperature. We know now that they are catalysts .... but how.
Here is part 1 of the how..... (Learn)
Mission 8 : Your turn .... or do you require a bit more activation energy to get started - what will catalysise you into action??? Have a go at the questions on activation energy - you're not over the hill yet! (Learn)
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Yes = now its time for your next Step/Video clip/Challenge/Mission.
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Step 9 : So Enzymes get things started easier - but how do they know what to work on? How do you know which key fits the lock?
There is one main theory - that has a modification made to it = enzymes are flexible.
Here is the main theory explained and some examples. (Learn)
Mission 9 : Have a go at what could be an end of year question .... stay flexible in your thinking.... (Learn)
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Yes = now its time for your next Step/Video clip/Challenge/Mission.
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Step 10 : Remember back in Yr 11 Chemistry we looked at the factors that influenced how fast reactions take place ...... temperature, concentration and surface area ...... Catalysts too .....
But we are looking at enzymes = they are the catalysts. But even they are affected by temperature, concentration and surface area.
We need to also go back to Yr 11 Chemistry and remind our selves about both Particle theory and Collision theory to help us visualise how enzymes are doing their thing.
So to help you remember here are these theories explained again. (Learn)
Step 10 : So now hopefully you remember ..... and now maybe you can see how enzymes are doing their thing = making sure that the particles collide with sufficient force and the correct orientation. The lock and key thing is what is helping with that. Sometimes I think of it as like using a funnel to help pour liquid from one container to another - you can do it without the funnel - but its a lot easier and quicker with it.
How much do you remember? Read and complete the questions on the nature of chemical reactions. (Learn)
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Yes = now its time for your next Step/Video clip/Challenge/Mission.
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Step 11(a) : Now we are going to be exploring some factors that affect enzyme performance. We'll be doing this by carrying out several practicals (hopefully) by making use of the fact that potatoes contain an enzyme called catalase (we are going to be modelling one of the things that happens in our liver)
The 2 main factors that mess with enzyme performance in us are temperature and pH. We'll also explore how surface area, substrate concentration and enzyme concentration affect performance too.
First we'll look at how catalase does its thing and what happens to it (Learn)
Step 11(b) : But the labs we'll be doing use potatoes (we'll crush ours) and we'll collect our results by measuring foam produced (easy way of collecting the gas)
Have a look - we'll be combining these 2 expts into 1 ...... (Learn)
Mission 11 : If we've been able to carry out these labs you'll have a bunch of results to use - if not you'll need to use the results you've seen in these videos to hypothesise what would have happened.
Now it time to read and complete all the work on the different investigations and factors affecting the performance of enzymes (Learn) (Create) (Share)
Done that? = Share with your teacher.
Yes = now its time for your next Step/Video clip/Challenge/Mission.
No = go back and complete the Step/Video clip/Challenge/Mission please.
So what is going on inside the enzyme so it works better (optimally) or not .... Going back to my funnel idea/analogy .....
Temperature - too cold enzymes go slow - try putting ice cubes through a funnel = they need to melt first = it works but a really slow rate - with enzymes to slow a rate to support life ie hypothermia kills as all our bodily reactions happen too slow to keep us alive. Too hot and we melt the funnel = shape changes and it no longer can do its job. We get too hot = run a high fever when sick - 40 degrees + and our bodily reactions stop = we die
pH - is like the too high a temperature = too high or low a pH and the funnel changes shape = stops working.
Substrate concentration - you can only pour so much through a funnel - keep tipping and the funnel backs up, even overflows. Enzymes have a maximum rate that they can function = they simply can't work any faster.
Enzyme concentration - get a bigger funnels = you can pour more and more stuff through. It will get to a point where you can't get enough substrate to the enzyme fast enough = lack of substrate becomes the limiting factor.
Here is are some clips that cover some of that too. (Learn)
Step 12 : Going back to my funnel analogy - it works best with a hand to steady it in the neck of the bottle - in "enzyme speak" we call this a "Co-factor" = something that many enzymes needs to work properly.
Ever had a funnel block up (it gets messy fast) - in "enzyme speak" we call this an "Inhibitor". Some inhibitors block permanently - many poisons are these type, others can "turn off" the enzyme and then later when the enzyme is needed can be unblocked so the enzyme is ready to be used again.
Lets look at this in "proper" science speak. (Learn)
Mission 12 : Hopefully you're not feeling inhibited by all of this = I'm hoping that this has be a co-factor that has helped you .... any way see how you get on with the questions on co-factors and inhibitors. (Learn)
Done that? = Share with your teacher.
Yes = now its time for your next Step/Video clip/Challenge/Mission.
No = go back and complete the Step/Video clip/Challenge/Mission please.
Mission 13 : At the end of this section of your workbook you'll find (maybe) a puzzle page or two, a review planning page then a practice copy of the end of topic test. Complete these pages plus don't forget the definition page found at the start of the topic = you'll be ready for the test. (Learn)
Included here is a power point that helps explain a lot about enzymes - along with quite a bit of other information that we'll meet later = have a look and you'll have a head start. (Learn)
Nature of Genes.pptDNA, Proteins and Enzymes review questions - you should have completed these by now = we'll go over the answers together. This should give you an idea of where you are at with your understanding of DNA, Proteins and Enzymes = let you know what you need to do the get ready for the practice exam at the end of the whole section on cell structures and functions.
Final Mission : At the end of this topic there is also a practice exam that puts problems from all the 3 topics (Cell Structures, Cell Transport, and DNA, Proteins and Enzymes) together in the form of the type of exam you'll be sitting at the end of the year. (we'll use for a trial run later in the year for the school practice exams) Do a bit more revision and give it a go. (Learn) (Share)
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