Hey guys, this is Hazel-Ann and Aaliyah and we’ll be taking over this week. We’re so excited to talk about the TCA and ETC! Week 8 has truly been interesting since we had only quizzes during our lecture time…YIKES!!!!!

Okay so back to the topic….TCA: have you ever wondered why it’s called TCA instead of TAC? I mean after all it stands for Tricarboxylic Acid Cycle right??

Baffled yet??…wait there’s more: this cycle actually has two other names: Citric Acid Cycle and Krebs Cycle!

The Citric Acid Cycle is a sequence of enzyme-catalyzed chemical reactions which are imperative in aerobic respiration in cells.

  • The cycle begins with the end product of glycolysis (the first step of cell respiration), pyruvate.
  • In glycolysis, glucose is decomposed into pyruvate.
  • A two carbon fragment of pyruvate is used to form acetyl coenzyme A. The acetyl-CoA enters the Krebs cycle which occurs in the mitochondria.
  • In the process of converting pyruvate to acetyl-CoA, carbon dioxide is produced and a molecule of NADH is formed.

Step 1:

A molecule of citrate is formed by the joining of the Acetic acid subunit of acetyl CoA with oxaloacetate.  The function of acetyl coenzyme A is to transport acetic acid from one enzyme to another. After this, the Krebs Cycle is restarted when hydrolysis releases the coenzyme so it may combine with another acetic acid molecule.

Step 2:

Then, citric acid molecule goes through an isomerization.  Water is removed from the citrate structure but a double bond forms between the 2 carbons and the water molecule is reintroduced. However, unlike the first citrate molecule structure, the hydroxyl group and hydrogen molecule are transposed. Hence, Isocitrate is forms.

Step 3:

Oxidization of the isocitrate molecule occurs by a NAD molecule that is reduced by the H atom and the OH group. NAD binds with a hydrogen atom and carries off the other hydrogen atom leaving a carbonyl group.  Due to the instability of structure a CO2 molecule is released forming alpha-ketoglutarate.

Step 4:

Here, coenzyme A, reappears and oxidizes alpha-ketoglutarate.  NAD reduction occurs again producing NADH and another H atom remains. Again, a carbonyl group is released as carbon dioxide and is replaced by a thioester bond between the previous alpha-ketoglutarate and coenzyme A while a molecule of succinyl-coenzyme A complex is produced.

Step 5:

Hydrogen atoms from a water molecule are attached to coenzyme A. Coenzyme A is then displaced by a free phosphate group which transfers to a GDP molecule to yield a GTP energy molecule. A succinate molecule remains.

Step 6:

Flavin adenine dinucleotide (FAD) oxidizes succinate removing two H atoms from it and forms a double bond in between the two C atoms, making fumarate.

Step 7:

Malate is formed by the addition of water to the fumarate by an enzyme.

Step 8:

An NAD molecule oxidizes the malate molecule. The OH carrying carbon is transformed into a carbonyl group.  Oxaloacetate is the end product. It can then join acetyl-coenzyme A and resart the Krebs cycle.


In summary, Krebs cycle involves 3 major activities.

1)      Production of 1 GTP (guanosine triphosphate) which eventually donates a phosphate group to ADP to form 1 ATP;

2)      Reduction of 3 NAD molecules;

3)      Reduction of 1 FAD molecule.

In the cell’s energy-generating process, formation of reduced NAD and FAD are more imperative than 1 molecule of GTP producing 1 ATP because NADH and FADH2 give their electrons to the electron transport chain (ETC) that creates a lot of energy by making a lot of molecules of ATP.

If it’s too much to digest right now how about this?


So let’s move on!


Now, the electron transport or respiratory chain is where electrons are transported to join oxygen from respiration at the end of the chain. The overall ETC reaction is:

2 H+ + 2 e+ + 1/2 O2 —> H2O + energy

Pre-Initiation of Electron Transport Chain:

Figure 3: simplified illustration of ETC

ETC is started by oxidation reaction of an organic metabolite with the coenzyme NAD+ (nicotinamide adenine dinucleotide). 2 hydrogen atoms are removed from the organic metabolite which is usually from the citric acid cycle and fatty acids oxidation:

MH2 + NAD+ —–> NADH + H+ + M: + energy, where M= any metabolite (usually an alcohol oxidized to a ketone).

Removal of one hydrogen with 2 electrons as a hydride ion (H) and another as the positive ion (H+) occurs.

NAD+ is a coenzyme containing the B-vitamin, nicotinamide.

The other steps in the ETC are:
1) to pass along 2H+ ions and 2e to eventually react with oxygen;
2) to save energy by forming 3 ATPs; and
3) to restore the coenzymes back to their original form as oxidizing agents.

Initiation of Electron Transport Chain:

  • NADH interacts with the first complex 1 enzyme, known as NADH reductase. Complex 1 contains a coenzyme flavin mononucleotide (FMN), similar to FAD.
  • The NADH, and another hydrogen ion then enter the enzyme complex and pass along the 2 hydrogen ions into the mitochondrial interspace. Acting as a pump, these H atoms are used by ATP synthetase to form an ATP for every two hydrogen ions produced.
  • Performing similar to this, three complexes (1, 3, and 4) produce 2 hydrogen ions each, therefore 3 ATP are produced for every use of the complete ETC.
  • NADH passes along 2 electrons to FMN, iron-sulfur protein (FeS), and lastly to coenzyme Q. These reactions restore coenzyme NAD+ and create a cycling effect. The NAD+ is then ready to react further with metabolites in the TCA cycle.
  • Coenzyme Q makes CoQH2 by joining 2 H ions and is soluble in the lipid membrane and moves through the membrane to encounter enzyme complex 3.
  • Enzyme complex 1 of the ETC is combined with the formation of ATP:

a) MH2 + NAD+ —> NADH + H+ + M + energy

b) ADP + P + energy —> ATP + H2O


Figure 4: Illustration of ETC in mitochondria and the association with TCA Cycle.


Enzyme Complex 3:

  • Cytochrome reductase bc is a series of activities through enzyme complex 3 that begins when CoQH2 carries 2 extra electrons and 2 extra hydrogen ions.
  • Cytochromes are similar in structure to myoglobin or hemoglobin. The heme structure containing the iron ions, initially in the +3 state and changed to the +2 state by the addition of an electron is significant. The CoQH2 passes along the 2 electrons first to cytochrome b1 heme to b2 heme, to an iron-sulfur protein, then to cytochrome c1, and finally to cytochrome c.
  • The 2 hydrogen ions are directed to the inside of the mitochondria for conversion into ATP.


Figure 5: Illustration of cytochrome b, c complex 3.

Complex 4:

  • Cytochrome c is a small molecule able to travel in the lipid membrane layer and diffuses toward cytochrome a complex 4.
  • The transport of the electrons continues, and this is the third and last time that 2 hydrogen ions are directed to the inside of the mitochondria for ATP conversion.
  • ATP synthetase is found throughout the bilayer membrane of the mitochondria. The pumping of the re-entry of the hydrogen ions through the ATP synthetase produces 3 ATP.
  • Finally, diffusion of oxygen into the cell and mitochondria occurs for the last metabolic reaction. A water molecule is produced by reaction of oxygen atom with the 2 electrons and 2 hydrogens.


  • The tricarboxylic acid cycle got the common name “Krebs’ cycle” after the biochemist Hans Adolph Krebs when he discovered the steps of the cycle through a series of experiments, in 1937.
  • This cycle is the second of three parts in the process of breaking down glucose into energy that the body can use, in the form of ATP. The stage before TCA is glycolysis and the stage after is oxidative phosphorylation.
  • The Electron Transport Chain (ETC), while it is the last step of the three in gaining energy from the foods we eat, it is actually THE most important step since most of the ATP is produced here.
  • In glycolysis, the final net production of ATP molecules is 2, in the citric acid cycle, it is 2 and in the electron transport chain, the net production of ATP is 32 ATP molecules. In total, 36 ATP molecules are formed from the entire process during aerobic respiration per pyruvate molecule.
  • In ETC electrons move from high energy to low energy making a proton gradient that then pushes the production of ATP.
  • Altogether TCA and ETC are ESSENTIAL for human survival, since these stages to produce ATP give us energy to carry out our daily activities. ATP is also important in synthesizing RNA and DNA.

So that’s all for this week peeps…thanks for tuning in, hope that this was helpful! Don’t forget to check us for our next post, next week same time.




Hey guys this Kim and Kevin here to bring to you part of glycolysis.

I essentially wanted to show you how biochemistry can tie in with real life problems that many people especially children suffer with. OBESITY!



Obesity contributes to all these factors, not just being obese.

<<<< SAY U LOVE ME LIKE A FAT KID LOVES CAKE! Ok that was a little humour but seriously this is an important issue that is threatening kids’ lives today!

So just to juggle your mind fructose is one of the monosaccharide polymer of the disaccharide sucrose ( table sugar). It is wayyyy sweeter, more soluble than sucrose and inexpensive to produce in the form of high fructose corn syrup. Well you know this just entices manufacturers of sodas and processed foods. However those of you chefs out there that like to sweeten with this and even those who consume these foods concentrated with it, there are many dangers of high fructose corn syrup which are listed below:


 Alright let’s try to link it to obesity

Obesity is a very serious epidemic. One of the factors that may be contributing to this epidemic is consuming way too much high fructose foods and drinks. So guys you see all those Coca- cola drinks and canned syrups and fruits THOSE ARE A BIG NO-NO! This is essentially what is in 20 ounce glass of coca cola.

Image Image

Let me show you why through the explanation of the metabolism of fructose.

There are 2 ways fructose can be metabolised in the body: (which parts of the body do you think these occur?)

  • Adipose tissue, muscle and kidney- the enzyme hexokinase phosphorylates or converts fructose into fructose- 6-phosphate and then enters glycolysis. Below shows the what happens in equation form:

Fructose + ATP ——-à Mg2+  fructose-6-phosphate + ADP

  • Liver- this is the pathway that fructose is primarily metabolised since hexokinase is not present but the enzyme glucokinase. Glucokinase has a low affinity for fructose or basically hates and avoids fructose. Therefore fructose goes through the fructose-1-phospate pathway. Below shows the summary of fructose metabolism in the liver:
  • Image


Reasons for high fat storage:

1)      – Fructose is phosphorylated to give fructose- 1 – phosphate by enzyme fructokinase. It’s that easy just remember 1 goes in between fructose and phosphate.

–          Then the fructose- 1- phosphate is then split up by the enzyme fructose-1 – phosphate aldolase into two, 3C molecules ( glyceraldehyde and dihydroxyacetone phosphate) Gosh I know right those words are so long to remember so here’s an acronym for the 2nd one (DHAP)

–          Only one the 3C molecules actually move on to the 2nd stage of glycolysis. Which one do you think it is? Don’t worry if you got it wrong, this question is tricky! It’s DHAP! It can be converted by the enzyme triose phosphate isomerase to glyceraldehyde-3-phosphate and then it continues into glycolysis.

–          However the glyceraldehyde is converted into glyceraldehyde-3-phosphate which is then converted to glycerol- 3- phosphate. And why do you think this latter conversion is bad? Ok let’s try to break it down where have you seen the word glycerol already, not in triglycerides which are mainly lipids(fats). However in this case it contributes to triacylglycerols. This can cause more fat being stored thus more fat + no exercise———à OBESITY

2)      The second reason for the contribution of the obesity epidemic is that:

–          There is a step that fructose metabolism completely bypasses in glycolysis which is the phosphofructokinase-catalyzed step and thus it avoids a major regulatory point.

–          Therefore disruption of the metabolism occurs and there is a greater lipid production or more fat is produced than in glucose metabolism.

–          This is why eating too many high fructose foods result in obesity due to fat storage.

Below shows a summary of the metabolism of fructose as well as glucose which has been discussed before:


Here is a simpler diagram to follow from:


So next time you want to pick up that can of coke or partake of  a McFlurry or even Grandma’s sweet homemade cookies just think again before it leads to this:


Alright see you next time guys, talking to you about this topic has been informative and fun for both you and I. Take care, see you next time!




Pratt, Charlotte W., and Kathleen Cornely. Essential biochemistry. Hoboken, NJ: J. Wiley, 2004.


Glycolysis, Parts 1 and 2


Hey guys, Kimberly and Kevin are here with you this week and the topic of discussion is Glycolysis. For those of you who may consider this topic as equally horrendous as calculus, it truly isn’t because I too, was under that impression and you will soon realize the simplicity once you complete our fun and interactive blog on Glycolysis. Enjoy!!

Before we can truly learn about Glycolysis, we must understand the basics:

  • Glycolysis can be described as the oldest of all metabolic pathways.
  • It takes place in ALL life.
  • It occurs in the cytoplasm of the cell.
  • It forms 2 pyruvate molecules from the breakdown of a glucose molecule.
  • It is NOT oxygen dependant, that is, it can occur in an anaerobic environment.
  • It produces a net gain of 2 NADH molecules AND 2 ATP molecules per glucose molecule.


Lysis means “to split.” Therefore, Glycolysis can be easily remembered as the splitting of glucose which is a 6 carbon structure into two pyruvates which are 3 carbon structures.


The Glycolysis process above can be divided in TWO phases:

1.) The Energy Investment Stage (Preparatory Stage) in which 2 ATP forms 2 ADP and occurs from step 1 to 5.

2.) The Energy Generation Stage (Payoff Stage) in which 4 ADP forms 4 ATP, 2 NAD+ forms 2 NADH and occurs from step 6 to 10.


If this is your reaction at the moment, then DO NOT PANIC! It gets easier after the following diagrams and explanations, so keep calm and LEARN GLYCOLYSIS! 😀

1.) Preparatory Stage – conversion of glucose to glyceraldehyde 3 – phosphate via phosphorylation.

  • Image

The numbers 1 to 5 represent the specific enzymes present as illustrated in the diagram above:

  • Enzyme 1 = Hexokinase; phosphorylates the glucose molecule to form glucose 6 – phosphate.
  • Enzyme 2 = Phosphohexose Isomerase; helps convert glucose 6 – phosphate to fructose 6 – phosphate.
  • Enzyme 3 = Phospho – fructokinase – 1; most important enzyme in terms of regulation.
  • Enzyme 4 = Aldolase; helps split the 6 carbon sugar phosphate to form the 3 carbon sugar phosphates.
  • Enzyme 5 = Triose Phosphate Isomerase; converts DHAP molecule into G3P molecule.

2.) Payoff Stage – conversion of G3P to pyruvate via oxidation and the formation of both ATP and NADH


The numbers 6 to 10 represent the specific enzymes present as illustrated in the diagram above:

  • Enzyme 6 = Glyceraldehyde 3 – phosphate dehydrgenase; catalyzes the oxidation of the aldehyde group to a carboxylic group and phosphorylates the G3P to 1,3 – BPG
  • Enzyme 7 = Phosphogylcerate kinase; 1,3 BPG loses a phosphate group which is transferred to an ADP molecule to form ATP
  • Enzyme 8 = Phosphoglycerate mutase; phosphate group on carbon 3 is removed and the one on carbon 2 remains.
  • Enzyme 9 = Enolase; dehydrogenation occurs.
  • Enzyme 10 = Pyruvate kinase; form ATP when converting PEP to pyruvic acid.


Have no fear my viewers because we’re almost at the end!! Let us move on to the Fates of Pyruvate. The following diagram is a simple illustration showing the different fates of pyruvate.


The following table represents the same concept as the previous diagram, however the structural formulas of the various conversion reactions of pyruvate are illustrated in this table.


1.) Aerobic Conditions – Entry into TCA cycle.

  • The pyruvate is converted to Acetyl – Co A via an oxidative decarboxylation reaction.
  • The enzyme that catalyses this reaction is pyruvate dehydrogenase.
  • This reaction can only occur if mitochondria are present.
  • This reaction is referred to as a link reaction because it links pyruvate to the TCA cycle.

2.) Anaerobic Conditions – Lactic acid Fermentation

  • The pyruvate is converted to lactate.
  • The enzyme that catalyses this reaction is lactate dehydrogenase.
  • Lactic acid fermentation regenerates NADwhich allows glycolysis to be completed as there are limited NAD+ molecules within a cell and is important for the erythrocyte.
  •  No ATP is generated when pyruvate is converted to lactate.

3.) Anaerobic Conditions – Alcoholic Fermentation

  • This is a 2 step reaction that first converts pyruvate to acetaldehyde and then to ethanol.
  •  The two enzymes that catalyse these reactions are pyruvate decarboxylase and alcohol dehydrgenase.
  • Pyruvate decarboxylase requires TPP as a cofactor for the enzyme to work.
  • Alcholic fermentation regenerates NADwhich allows glycolysis to be completed as there are limited NAD+ molecules within a cell.


AND THAT’S IT FOR MY PART GUYS!!!! Until next time.



Avril Chew. 2003. GCE ‘A’ Level Biology @ Your Fingertips. Singapore : Redspot Publishing. (accessed March 9th, 2014)

CJ Clegg with DG Mackean. 1994, 2003. Advanced Biology Principles and Applications. 2nd edition. London : Hudder Education. (accessed March,9th,2014)

BiochemJM You Tube Page. Glycolysis Parts 1 and 2. (accessed March 9th, 2014)

All Things Enzymes

All Things Enzymes

Using a lock and key as my word cloud from the Lock and Key Hypothesis! I thought it was pretty cool anyway lol..hope you enjoy! ~Aaliyah



E– Enzymes are very specific. Some enzymes only catalyze one specific reaction, while others only act on a particular functional group, chemical bond or optical isomer.

N Not all enzymes are proteins. Shocking, I know! Some RNA molecules actually act as enzymes and these are called ribozymes, and also, some antibodies have catalytic properties, and these are called abzymes.

Z(I couldn’t think of anything with Z so an exclamation from Shaggy in Scooby Doo will have to suffice lol) Did you know that all metabolic reactions in the cell are catalyzed by enzymes? The reactions are too slow to occur on their own, so we would all be dead if there weren’t enzymes in our body!

Y-Yeast enzymes are used in fermentation. These enzymes break down disaccharides to simple sugars, and in the process, alcohol and carbon dioxide is produced. This fermentation process is what allows us to get wine from fruit juices and beer from wort. So for all of you wine and beer lovers out there know that you get your favourite drinks via the actions of enzymes.

M-Meeting of enzymes and substrates occur at a point on the enzyme called the active site. The enzyme gets near the substrate and is all like   (lol) and since enzymes are proteins, the amino acid residues of the active site binds with the substrate through interactions like hydrophobic interactions, electrostatic interactions, hydrogen bonding and Van der Waals interactions.

E– Every woman takes a pregnancy test at least once in her life, I assume. But did you know that pregnancy tests work via the action of enzymes as well? The hormone human chorionic gonadotropin (HCG) is produced after a woman becomes pregnant. The HCG in her urine, reacts with an antibody-enzyme complex, forming an HCG-antibody enzyme complex confirming her pregnancy.

And just for a little enzyme joke : 


Worthington Biochemical Corporation. “Introduction to Enzymes.” Specificity of Enzymes. (accessed March 2, 2014).

“ELISA for Home Pregnancy Test.” (accessed March 2, 2014). “Yeast.” HowStuffWorks. (accessed March 3, 2014).


Hey guys, Aaliyah here and this week we’re talking about enzymes. 🙂 Now, I particularly love this topic so I hope you guys enjoy learning new things about enzymes with me.

Spongebob - ENZYMES

Most enzymes are proteins . Enzymes are biological catalysts that speed up the rate of a chemical reaction but remain unchanged during the reaction.

The way enzymes work is by lowering the activation energy of a reaction so the reaction occurs more easily and faster. The activation energy is simply the minimum energy required for a reaction to occur, either substances reacting together, or a substance being broken down. The graph below shows how this happens.

To help understand, you can imagine that a car going over a hill is the reaction you want to occur. The uncatalyzed reaction requires a lot of energy from the car, since the hill is high. You’re going to be mashing X like crazy! The enzyme steps in and cuts down the hill for you, making it a shorter hill to go over. This would be the enzyme lowering the activation energy, and the car can go over the hill while using less energy and power. The car both starts and ends at the same places in both “reactions”, but the energy required to get the car over the tall hill is much more than the energy required going over the short hill.

Now, one thing that I surely didn’t know before was that enzymes are classified into six groups. It’s preferred that you learn them in a specific order so I’ve come up with this to help me remember and I hope it helps you too-using the first letters of these words Only The Happy Life Is Lovely. Corny, I know lol…but it helps! These stand for Oxidoreductases, Transferases, Hydrolases, Lyases , Isomerases and Ligases, all of which catalyze different types of reactions.

There are two theories as to how enzymes work- The Lock and Key Theory and The Induced Fit Theory.

In the lock and key theory, the shape of the active site is complementary to the shape of the substrate.  The lock is analogous to the enzyme and the key is analogous to the substrate. The correct key would fit into the key hole of the lock, just like the correct substrate would fit into the correct active site of the enzyme, as shown in the illustration below.

In the Induced Fit Theory the substrate can slightly alter the shape of the active site in the enzyme so that it can fit, as shown in the illustration below.

Now there are many more things I can say about enzymes, but I don’t want to keep rambling for too long, so the last thing I’ll leave you with is a basic summary on how enzymes work in a reaction.

Enzyme + Substrate ==> enzyme-substrate complex ==> Enzyme + Products

And there you have it! Hope you guys enjoyed this post, and I hope you learnt at LEAST one thing. Be sure to check out the following post for some interesting facts about enzymes and look out for a cool word cloud on all things enzymes! 🙂 Now, if only there was an enzyme to help us study faster, like Studyase…sighhh!

Until next time!    


Nelson, David L., and Michael M. Cox. 2008. Lenhinger Principles of Biochemistry. 5th edition. New York: W.H Freeman and Company.

“Mechanism of Enzyme Action.” Enzymes. (accessed March 2, 2014).

Amino-Acids and Proteins

Hi guys BrandnB is here to share some info on amino-acids. Hope you pay attention.

meme 2

So We know that Amino-acids are generally important but do you know the formula. In class, I was like it has nitrogen, hydrogen, carbon and oxygen. These are some of the important atoms that exist in our biochemical reactions.

Amino-acids have a general structure that consists of an amino group, alpha carbon, carboxyl group and R’ chain( hydrocarbon attachment).


The amino-acids exist as a charged species in ionic form or neutral species ( non-ionic). This depends on ?????, the charges present on the terminal ends of course. Compare these forms, the one above and the one below. Which is the ionic species?


If you chose the first one then you won a prize of………..knowing the difference of a charge.

Wait there’s more…..

Amino acids have certain categories that exist in terms of its structure and their interacts with water and even themselves.

Amino-acids are unique in their structure but there exists various forms like polar uncharged R groups, non-polar  groups, positively charged, negatively charged and aromatic.

amino grps

Polarity and non-polarity are important in amino-acid structure and reactivity with each other.  Polar groups can interact with each other to form connective structures that leads the formation of hydrogen bonds with the amide group and carbonyl group.

More importantly amino-acids bond together to create peptide bonds or petide linkages to create a chain of amino-acids. That reaction is fueled by a condesation reaction. Note the positioning of the amino group and the carbonyl group.


Indeed Patrick, this helps in adding amino-acids to the peptide chain as more amino acids add to it. The carboxyl group must be exposed in order to react with the amino end of the adjacent amino-acid.


It’s a condensation reaction due to the fact water was lost from both structures combining. The important linkage is the bond of the carbonyl carbon of the carboxyl group to the nitrogen on the amino group. Hence the link is quite mutual in forming a polypetide chain.

Since on the topic of bond formation, other bonds do exist in the bonding of amino-acids. The disulphide bridge/linkage between two amino-acids call cysteine. The oxidation of two molecules allows for cystine to be formed and ” bridge” the gap. The reaction is reversible by reduction of the cystine to two individual cysteine molecules. This type of bonding is present in the structures of tertiary proteins in which we will see in oncoming posts.


A dipetide is a chain formed between two amino acids and polypetide is between two or twenty amino acids long. Upon mentioning the number twenty there exists 20 esstential amino acids that you must obtain through dietary means.


To answer your question and that strange figure above amino acids can be obtained through everyday diet.  Meats and eggs are primary sources of amino-acids which are building blocks of proteins. For some of us that are a little reluctant of consuming meat,  beans and peas are alternative sources of amino acids. Plants which are our meatless……fat less…and minimal amino providing selection allow for creatine deficiency in our muscles. Creatine is an amino-acid that is a storage molecule for energy in our muscles and brains. Ever wonder about plants versus zombies, zombies eats plants to get to what?  the BRAINS of course. For that much needed creatine to keep those dead bodies moving.



Bear Grylls understands too much about proteins in his daring adventures, we know how he washes all of that down….. Since he resides in nature for all of us to experience the wild to our comfort with our cable television, air conditioning, lighting, bathrooms, internet and other household essentials he knows the natural proteins are the best.

Wait a hint has appeared remember for glucose that the D isomer is the most useful and exists commonly compared to the L isomer.

L isomers of amino acids are the common form compared to the D isomer. So the more natural the better. Won’t you say Bear….


Back to the Isomerism of the amino acids.


The identification of the L isomer is determined by the placement of the atoms around the alpha carbon. The structures are arranged into the Fischer projections. The carbon molecules align themselves and the amino group assumes on the left or right of the chiral carbon. If the group is found on the left of the asymmetric carbon it is named L-isomer. So D isomer exists as the right…..

Functions Of Proteins.

They can acts as biological catalysts, storage molecules( ferritin), transport molecules of Oxygen and Carbon dioxide (hemoglobin), Protein pumps and protein channels and they assist in muscle growth. Due to different functional roles of proteins their structure differ from task to task.


There exist the primary(1) structure: that is in a linear arrangement and the amino-acids can be identified in a  particular order due the peptide bonds through out.

The secondary(2) structure consists of habitual folding patterns or an individual strain being warped around. They are the beta pleated sheet and the alpha helix. the beat pleated sheet can be represented by a pleated skirt or something like that and the alpha helix is like a telephone cord if got one that curls,  just so you know cordless phones have none.  The alpha helix contort to adjust themselves every 4th  amino acid to create a hydrogen bond of the electronegative oxygen on the carbonyl group with the hydrogen of amino group. These structures in alpha helices  can be disrupted by large hydrocarbon chains and other amino-acids.

phone card

The tertiary ( 3) structure of proteins are a little more complex with more bonding attributes like hydrogen bonding, salt bridges and disulphide bridges. This is essential for the tertiary  structures because various combinations allow for variety.

Structural proteins like Collagen:  Note the triple helix.


Example myoglobin for oxygen storage:


The Quaternary structure is a  much more complex arrangement. In these structures subunits can combine to form structures like haemoglobin with side chains and iron groups:


As I come to a close I can share some interesting things I learnt in my lecture about Arginine, this amino-acid is responsible for the expansion of blood vessels. So it can assist for heart defects and help in blood pressure regulation. Gym buffs can utilize this for max reps.!!! .

meme5So certain amino-acids can be determined by the Ninhydrin test which produces a purple color.


Proteins can be determine by the biuret test that involves the reduction of copper(II) ions due to linking with the nitrogen. The basic solution of copper sulphate allows the hydrogen attached to the nitrogen to be removed.

In closing I leave this with you,


Elkaradagi S,Protein Structure and Structural Bioinformatics,,16,2014).

S. F. Betz,Disulfide bonds and the stability of globular proteins.,,16,2014)

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