Proteins and Protein synthesis (A.S. 91159 (Bio 2.7 Ext ) Gene Expression )

Now its time to look closer at DNA - how does a chunk of DNA (a Gene) actually create the trait that we see? The blood type, the eye colour, the ability to roll your tongue etc. We need to go back to the molecule itself and look at how it is made and how the code is turned into reality.

Step 1 : Lets remind ourselves about the basic building blocks of DNA - nucleotides and introduce its close relative RNA. Remember the 4 bases of DNA - ATGC, well with RNA there is 1 more U (where DNA has T's, RNA has U's) 

Replay the clip to rewind your memories. (Learn)

Mission 1 : Okay using that refreshed memory and after reading the information - complete the nucleic acids recap questions. (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 : So why do A's and T's join up or C's and G's? Its to do with the shape of the molecule that is the base - its also key to how the DNA molecule gets its shape. 

Here are a couple of explanations - they are pretty full on and also go over stuff you should know = skip through to the important bits if you wish. (Learn)

Mission 2 : Using what you now know from these clips plus what you can read in your workbook - you need to be able to explain the bases pair up in the way they do. (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 : Okay we should have DNA/RNA sorted - so we will take a step away from them (we'll come back to them soonish) and have another look at proteins and their building blocks amino acids.

We've met them before when looking at enzymes - you can reply that video = I'll put it here too. but we are now needing to know more about their structure.

Here is how amino acids make proteins .... (Learn)

Mission 3 : After watching the "Structure of Protein" clip and reading the information make sure you can answer the questions on Proteins and Amino acids. (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 : Ever watched someone weaving a kete? From a simple strand of flax a complex shape is formed = something that can be far more useful than the strand alone was.

Its the same with polypeptide chains - the chain isn't the same as the finished protein. Proteins are formed from one or more polypeptide chains folded/woven together into a specific shape. Its not until the polypeptide chain/s form this final shape that we have a functional protein .

There are 4 levels of shape/protein structure. Shapes are easier to see than read about .... have a look (Learn)

Mission 4 : What level of understanding have you got to? Ready to weave some answers? Have a go at the advanced protein structure questions. (Learn)

Done that? = Share with your teacher.

Yes = now its time for your next Step/Video clip/Challenge/Mission.

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Step 5 : So why are proteins so important ...... I've said it before - we are a biochemical "machine" made from proteins. 

We have 2 main groups (a) insoluble, fibrous structural proteins. (b) soluble, globular biochemical proteins. 

So whats the big difference and why - have a look. I've also included as an interesting aside a clip on eating proteins - what happens then = do protein powders grow muscle? (Learn)

Mission 5 : So while you slurp back that protein shake (If exercise grows muscle - does thinking grow brain?) Test out that theory as you take on the questions about the significance of proteins. (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 6 : Now comes the full on bit - turning the code on the DNA into the sequence of amino acids that will become the functional protein. AKA Protein Synthesis.

There are 3 "easy" steps to a functional protein - you've all ready met the 3rd step = the folding of the polypeptide chain/s into a functional protein. Here are the steps .....

(1) Transcription = copying the code from the DNA (which never leaves the nucleus) to make RNA - specifically mRNA = messenger RNA that takes the code out into the cytoplasam where it gets .....

(2) Translation = taking the code from the mRNA and letting the ribosome turn the code into a polypeptide chain (this involves tRNA = transfer RNA)

(3) = the folding of the polypeptide chain/s into a functional protein. 

There is also an rRNA = ribosomal RNA = RNA is as quite important to life as DNA is

Its quite hard to separate steps 1 and 2 = we'll need to look at them all together. Take your time - this is important = often in exams.  (Learn)

Sometimes its good to see what it really looks like = here a couple to 3-D animations of protein synthesis (start the second one about 3 minutes in to skip stuff we've all ready covered) (Learn)

Mission 6(a) : Read and complete the genes to proteins questions - Important key point is mRNA is coded from the DNA template strand = then it has the same code as the DNA coding strand. Remember the base difference DNA base T = RNA base U. (Learn)

Mission 6 (b) : Read and complete the work on protein synthesis - transcription. Take note of the enzymes involved - how are they made? (Learn)

Mission 6 (c) : Now read and complete the work on protein synthesis - translation. Notice the tRNA's - how many different amino acids do we use to make proteins? = how many  different tRNA's are there? (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.

Challenge 1 : Have a go at making proteins yourself - use the following PHET link. (Learn) (Create) (Share)

Step 7 : During the videos for Step 6 you would have seen a chart of all the 64 codons that are used to decide which amino acid is used to synthesise the polypeptide chain. 

So how do you read this table - Left side, then top side, then right side. 

Just like in English grammar where a sentence starts with a capital letter and ends with a full stop, exclamation mark or question mark - a polypeptide chain needs a start codon and finishes with one of the 3 stop codons.

Here is a demonstration video ..... (Learn)

Mission 007 : Your turn to use the codon chart to "break" the code and sequence the amino acids.... (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 8 : Can you really crack the code? tRNA or transfer RNA - actually looks like a little letter t - how does it connect with the correct amino acid and match it to the correct codon on mRNA? 

Have a look (Learn)

Mission 8 : Prove that you can crack the code by completing transcribing and translating DNA, then show us what you've learned in a closer look at tRNA. (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 9 : So how do 4 bases ATCG code for 20 amino acids - by arranging the bases into 3's = triplets. This gives us 64 possible combinations or codons. 

1 of the 64 is the start codon, 3 of the 64 are stop codons.

 This leaves 60 codons to code for 20 amino acids. We have amino acids being coded for by multiple codons (= redundancy in the system)  ie some code words have the same meaning (= degenerate)

Why is this important ..... aircraft have redundant control systems/computers = if one breaks down - we have spares to stop disaster. its the same in the DNA code - mutations have less effect with the degenerate/redundant systems in place.

Have this explained using the codon chart. (Learn)

Mission 9 : Have ago and see how redundancy works  as you create more DNA codes. Read and complete the work on the redundant code. (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 10 : 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) 

Here is a power point that reviews many of the key points covered in this topic ..... plus recaps information found in previous topics too. (Learn)

Protein and Protein Synthesis 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 Protein and Protein Synthesis = let you know what you need to do the get ready for the practice exam at the end of the whole section on Gene Expression.