Summary of Cellular Respiration

[happyhappyland]

Here is a short summary I did based upon my own knowledge and my MCAT book... Ill be giving it to my students but thought I might as well share it to everyone else.

Some of it is beyond VCE but I still reckon you should know it (sometimes in VCAA questions they give you information for you to familiarise during the exam, but if you are already familiar with it, it becomes much easier to answer the questions.

Also feel free to point out any mistakes on there! Im 99% sure I made atleast one on it.


Couldnt shove all the pictures onto one post :@

[happyhappyland]

Glycolysis

[happyhappyland]

Kreb's Cycle

[happyhappyland]

Electron Transport Chain

[mrc93]

i made my version in yr 11 and plan on using it this year tell me what you think

What is cellular respiration?

Cellular respiration is the process in which a cell converts glucose and Oxygen via chemical processes to produce Water and energy in the form of ATP which is also known as adenosine triphosphate. The cellular respiration process takes place firstly within the cytosol as well as in many different places within the mitochondria.

Process of cellular respiration:
 In simple terms the process of cellular respiration converts glucose and oxygen to produce carbon dioxide, water and ATP, this can also be expressed as Glucose + oxygen → carbon dioxide + water +  ATP
Glycolysis:
 Glycolysis takes place in the cell’s cytosol and involves the breaking down of glucose molecules from carbohydrates into molecules of pyruvate during this process the energy released during Glycolysis is used to produce ATP. In the first stage of glycolysis, ATP is used to phosphorylate the 6-carbon glucose molecule. This means that a phosphate is taken from the ATP molecule (which then becomes ADP also known as adenosine diphosphate) and added to the glucose molecule to form a 6-carbon sugar diphosphate molecule. The 6-carbon sugar molecule is then split by an enzyme to form two 3-carbon glucose molecules which are then converted by a number of enzymes to form pyruvate. During the process of converting 3-carbon glucose two pyruvate electrons are transferred to the coenzyme (A small molecule not a protein but sometimes a vitamin) essential for the activity of some enzymes) NAD+ to form NADH also known as nicotinamide adenine dinucleotide and is also another source of energy. As well as NADH two ATP molecules and two water molecules are produced per one pyruvate molecule.
The Krebs Cycle:
The Krebs Cycle is a series of steps, catalyzed by enzymes, which completely oxidize the Aceytl CoA molecule which forms as follows. As pyruvate is being shuttled from the cytosol to the interior of the mitochondrion, a microenzyme removes one carbon and two oxygens from each pyruvatemolecule, producing Aceytl CoA, one NADH molecule and emitting one carbon dioxide molecule. The 2 carbon Aceytl CoA molecule is transferred to a 4 carbon molecule to produce a 6 carbon compound. In the next step a carbon dioxide molecule is released from the 6 carbon molecule to form a 5 carbon compound. During this step, hydrogen is removed and transferred to NAD+ to produce another NADH molecule. Next, a second oxidation and decarboxylation (a chemical reaction in which CO2 is released) occurs. This again produces another NADH molecule and carbon dioxide molecule. In addition one molecule of ATP is produced. As a result of these reactions, a 4-carbon molecule is formed. In the final step the 4 carbon molecule is oxidised and the removed hydrogens are used to from another NADH molecule and one FADH2 molecule, also known as flavin adenine dinucleotide. These reactions then bring us back to the original 4-carbon molecule the initially reacts with acetyl-CoA. These steps are known collectively as the Krebs cycle. Two circuits of the Krebs cycle must be completed to completely break down one glucose molecule which is in the form of two pyruvate molecules.
Electron Transport Chain:
 Very little energy has been produced during glycolysis and the Krebs cycle. Most of the energy locked in the original glucose molecule will be released by the electron transport chain. The electron transport chain is a network of electron-carrying proteins located in the inner membrane of the mitochondrion. Involved in the electron transport chain are four protein complexes and two carriers. The four protein complexes are NADH dehydrogenase, Cytochrome b-c1, Cytochrome Oxydase, and ATP synthase and the two carriers are called ubiquinone and cytochrome c. Also during the electron transport chain hydrogen ions are pumped across the inner membrane. The gradient created by the pumping of hydrogen ions is used by the ATP synthase complex to synthesise ATP. At the start of the electron transport chain two electrons from NADH are passed into the NADH complex, coupled with this transfer is the pumping of one hydrogen ion for each electron. The two electrons are then passed via the mobile transfer molecule, ubiquinone into the cytochrome b-c1 complex. Each electron is then passed to cytochome C one at a time and as each leaves another hydrogen ion passes the membrane. The next step occurs at the cytochrome oxidase complex and requires four electrons. These four electrons react with one oxygen molecule and eight hydrogen molecules. The four electrons, four hydrogen ions and the molecular oxygen are used to form two water molecules. The other four hydrogen ions are pumped through the membrane. The pumping of hydrogen ions has created a concentration gradient with high concentration outside the membrane and low concentration within the membrane. This gradient has potential energy which is used by the ATP synthase complex to synthesise ATP from ADP and Pi (inorganic (means it does not have a carbon bases) phosphate).
During the synthesis of ATP from ADP and Pi one hydrogen ion enters the ATP synthase on the intermembrane space and one hydrogen leaves it on the matrix space. Each time this happens the upper part of the ATP synthase complex rotates. Once three hydrogen ions have entered the matrix space there is now enough energy to synthesise one molecule of ATP.

[happyhappyland]

Thats really detailed for a year 11 student!

At VCE level you dont need to know all those specific, infact it will be detrimental during the exam because in my Unit 3 biology I had to describe the process of photosynthesis and it was only worth 3 marks! Ofcourse cellular respiration is a bit more complex but if you were given 4 marks to "Name and give a brief description of the stages of photosynthesis" you must make a condense, yet sufficient, description of the process.

Concerning the first stage of glycolysis... you must keep in mind that there are many enzymes and many steps become it becomes that 6 carbon and phosphate molecule, but you seem to have understood that concept in the later stages.

I would really try and simplify the whole process because even those molecule names is in the ETC is worthless to memorise. Its good to read about the whole process, but its better to understand the whole concept why the important stages occur.
Such as, you can scrap out that whole bit about cytochrome b-c1 complex and etc etc and explain WHY the hydrogen is accepted by oxygen to form water rather than just accept that these things happen.