Thank you again to my biology teacher for teaching me everything I know about biology (far too many repeated words in this sentence...).

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• DNA is made up of a series of nucleotides. Each nucleotide has a nitrogenous base attached to it, either adenine, guanine, thymine, or cytosine. 
• Different combinations of these nitrogenous bases code for different proteins
• The DNA is transcribed by RNA polymerase, into mRNA (messenger RNA) so it can leave the nucleus
• From there mRNA leaves the nucleus and makes it way to a ribosome which can then translate the mRNA strand into a protein 
• The ribosome "reads" the mRNA three nucleotides at a time, called codons, each codon codes for an amino acid, which is then attached to a growing chain of amino acids, which ultimately make a protein
• There are some cases where a codon can be altered due to a base substitution, whereby one of the bases is replaced by one that should not be there, this is the case in sickle-cell anaemia
• Usually the DNA codon is CTC, which then gets translated to the mRNA strand as GAG, this codon then codes for the amino acid glutamic acid in the ribosome, which ultimately leads to the formation of haemogloblin which carries oxygen on the red blood cells.
• If someone has sickle-cell anemia instead of the DNA codon CTC, it is CAC, which when translated to mRNA, results in a GUG codon. Unfortunately, this does not code for the same amino acid, so instead of glutamic acid, valine is attached.
• Because the wrong amino acid is placed haemoglobin is not formed properly, and cannot form its quaternary (globular) structure, this makes is significantly worse at carrying oxygen, and thus sufferers tend to get short-winded. It also results in the characteristic sickle shaped red blood cells, which are less efficient at carrying oxygen. 
• If two copies of the mutated gene are inherited then all of the red blood cells are sickle shaped
• If only one copy of the mutated gene is inherited half of the red blood cells will be sickle shaped, and the others will be normal. 
• The sickle shaped cells make sufferers resistant to malaria. 

Enzymes are proteins, which have the specific role of lowering the activation energy of reactions. A key fact about them, is that they are not used up during a reaction, and can thus be reused for multiple reactions. Enzymes have a Quaternary structure, making them globular in shape. Each of them has a so called active site, whereupon a substrate binds to it. The way the enzymes then lower the activation energy of a reaction is by stressing the bonds of the reactants (substrate), thus speeding up the process, and increasing rate of reaction. Though, it is important to note, that an enzyme will not increase the amount of product formed, merely the rate at which it is formed. 

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The lock and key model goes by the premise that there is a specific enzyme for each substrate. Which would mean there is an absurd amount of enzymes. Each of the active sites are perfectly shaped to fit the substrate, and thus there is only one enzyme that fits each substrate. It can thus perfectly stress the bonds of its particular substrate. However, the fact that so many enzymes would have to exist led to a revision of this particular model to the induced fit model.
This model takes more of a "glove and hand" approach, whereby the enzyme is roughly shaped like the substrate, and once one enters its active site it will shape itself around it. Making slight modifications in form until its active site fits the substrate. Once this has occurred it can once again stress the bonds of the substrate speeding up the reaction. With this model one enzyme can "fit" multiple substrates, thus reducing the number of enzymes needed. 

Thank you again to my biology teacher for teaching me everything I know about this!

On to the steps. Sigh.

1. The Krebs cycle follows the Link reaction and takes place in the matrix of the mitochondria 
2. One of the two, two-carbon Acetyl CoA molecules enter the Krebs cycle
3. Already in the Krebs cycle is a four carbon molecule called oxaloacetate 
4. One of the Acetyl CoA molecules will bind with oxaloacetate forming a six carbon compound, this compound is called citrate. The CoA (Co enzyme A) will recycled, and return to the link reaction. 
5. Citrate will be oxidized and decarboxylated (lose a carbon), this will result in a five carbon compound, a NADH molecule (which was reduced from NAD+), and one CO2 molecule. 
6. The five carbon compound will again be oxidized and decarboxylated, resulting in a four carbon compound, another NADH molecule, and another CO2 molecule
7. This four carbon compound will be oxidized again, and undergo further modification. Resulting in another NADH molecule, one FADH2 molecule (reduced FAD), and one ATP molecule. 
8. By the time all of this has occurred the four carbon compound is oxaloacetate again, and the cycle can begin again.
9. Keep in mind this cycle with occur twice for every molecule of glucose as two Acetyl CoA molecules are produced during the link reaction. 

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This is going to be the first post in a series of posts which answers (often short hand) several biology questions, that do well to summarize large sections of a high school level course. Again please be aware that I am no scientist, so take my words with a pinch of salt. Also, I won't be writing these rambling sort of introductions for the next posts, so there's that. Now on to the answer.

Thank you again to my biology teacher for teaching me everything I know about this!

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Cellular respiration is the process whereby glucose is converted into usable energy, in the form of ATP. The amount of ATP produced depends on the whether or not oxygen is present. If oxygen is present aerobic respiration is undertaken, if not then anaerobic respiration is undergone. In aerobic respiration a total of 36 ATP molecules are produced, whereas in aerobic respiration only 2 ATP molecules are produced.

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I'm actually serious. We are done. After this post, you will know the process of photosynthesis in its basics. Although, I might still write another couple, to sum it up a little more cohesively. Also if you can't learn in paragraph form, I sincerely apologize... On with the show! I should probably mention that the goal of photosynthesis is to make glucose... Yeah sorry about that.

We now move from the grana to the stroma of the chloroplast. Fun stuff. There we meet the Calvin Cycle. Not the Krebs Cycle. Don't get the two mixed up. I know I do. CALVIN CYCLE. Wonderful. Now we can move on. As we established with cellular respiration a cycle means it is continuous. This time, however, it is not oxaloacetate that we start off with, but a molecule called Ribulose Bisphosphate (RuBP). Unless unlike oxaloacetate it is a 5 carbon compound. Then in a process called carbon fixation, a CO2 molecule binds with RuBP. This reaction is catalyzed by enzyme RuBP carboxylase (Rubisco for short).

This creates a highly unstable 6 carbon molecule, which immediately splits into two 3 carbon molecules called glycerate-3 phosphate, GP (not G3P, which is glyceraldehyde 3 phosphate and what we made during glycolysis). GP is then reduced by NADPH and ATP (old friends from the light dependent reaction), which ultimately gives us a different 3 carbon molecule called TP (triose phosphate). TP now faces the most important decision of its life. To leave home (the cycle) and become a sugar phosphate (such as glucose), or follow in his father's footsteps and convert back to a RuBP molecule. Most TP molecules don't have the guts to leave the comfort of home and are thus converted back into TP with the help of ATP. And thus the cycle begins again.

Ta for now.

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As the name implies, in this stage of photosynthesis, light is needed. Duh.

Alrighty, well this process takes place in the chloroplasts of cells. You don't have chloroplasts, just a little by the way. Unless you're a plant... In which case, I guess I was under a rock when we figured out how to communicate with plants. Welcome fellow living things.

So this process takes places in the grana of the chloroplasts, which are stacks of thylakoids. These thylakoids have electron transport chains embedded into their membranes. The system gets kicked off in photosystem II of the electron transport chain. Yes. Photosystem II. Not one. It's not a typo. Photosystem II has two chlorophyll a molecules, which are a type of pigment. They also have a primary electron acceptor. Here's where the sun comes into play. A photon of light from the sun is captured by one of the pigment molecules inside Photosystem II, it is then passed along (like a hot potato) from one pigment molecule to the next, until it reaches one of the chlorophyll a molecules. The photon then proceeds to excite the electron of chlorophyll a to a higher energy level.

Backstep. The chlorophyll molecule's electron comes from a process called photolysis. Whereby water is split (using light), this results in two hydrogen ions and one oxygen atom. The two electrons on the hydrogen ions are handed over to two chlorophyll a molecules in photosystem II. The oxygen atom waits until this process happens one more time, bonds with the resulting oxygen, and leaves as a waste product.

Back to our negative friend the electron. This excited electron is captured by what is called the primary acceptor. From there it moves down the electron transport chain, first to a plastoquinone (PQ), then a cytochrome complex, and then another PQ. As the electron moves down the chain it loses energy, this energy is then used to undergo chemiosmosis. i.e. hydrogen ions are pumped into the thylakoid space, building up a high concentration of hydrogen ions in the thylakoid. These hydrogen ions then want to get out of the thylakoid to the lower concentration, they can only do this through the ATP synthase channel. Where they pass through and the energy released by them going through there is used to phosphorylate (photophosphorylate) ADP into ATP.

The electron then enters photosystem I, and is once again excited. It is once again captured by a primary electron acceptor. This electron is once again passed along another electron transport chain, and there ferrodoxin is used as the energy carrier. The energy created by passing along this electron is now used to reduce NADP+ to NADPH. An enzyme called NADP reductase catalyzes the movement of the electron from ferrodoxin to NADP.

Essentially, the whole point of this yet another lengthy process was to end up with ATP molecules and NADPH to be used in the light independent reaction.

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Hello again. Back to the world of biology. Whether or not that pleases you, I don't know. Anywho. My last post introduced you to the fine-art of glycolysis. If you still don't understand it, well, reread the blogpost? Otherwise Khan Academy is pretty darn amazing.

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Cellular Respiration. First things first, breathing is not cellular respiration. Drill that into your head. Please. If you start talking about lungs when referring to cellular respiration, you are wrong on so many different levels. Never ever ever think cellular respiration as breathing. If you do, mentally slap yourself in the face with a biology textbook. I hope I've made myself clear. I do believe I have.

I should probably give you a brief overview of the entire process of cellular respiration. Here you go: starts off with glycolysis, followed by the link reaction, then the Krebs Cycle, and finally the electron transport chain. Oh, please keep in mind only glycolysis will occur in a case of no oxygen.

Glycolysis reactants
1 glucose molecule
2 ATP molecules
4 ADP molecules

Glycolysis products
2 pyruvate molecules (pyruvic acid)
2 NADH (reduced NAD+ molecules)
Total ATP = 4
Net gain ATP = 2

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Yes. Indeed this is another post about science. Human anatomy to be specific. If you don't find it interesting, well there's an easy solution. I'm sure you can work it out. In any case, if you don't want to read this, I hope to see you soon!