Tag Archives: amino acids

It’s….Quiz Time!!! :D


Test your knowledge on amino acids and proteins


1)      Which of the following amino acids is the smallest amino acid possible?

 A. Valine

B. Proline

C. Glycine

D. Leucine

E. Serine

2) Which three amino acids are essential amino acids?

A. Arginine, Leucine, Alanine

B. Histidine, Lysine, Valine

C. Cysteine, Proline, Tryptophan

D. Methionine, Phenylalanine, Asparagine

E. Serine, Isoleucine, Threonine

3)      Which test is used to test for amino acids?

A.  Benedict’s Test

B. Biuret Test

C. Iodine Test

D.  Ninhydrin Test

E.  Molisch’s Test

4)      By what process is Cystine formed as shown in the diagram?


A. reduction

B. condensation

C. hydrolysis

D. hydration

E. oxidation

5)      What kind of bond is shown in the red circle on the diagram?


A. covalent bond

B. disulphide bond

C. ionic bond

D. polar covalent bond

E. metallic bond

6)      What is the name of the bond highlighted in blue in the diagram?


A. disulphide bond

B. peptide bond

C. metallic bond

D. ionic bond

E. hydrogen bond

7)      What is the name given to a molecule containing three amino acids joined by peptide bonds?

A. tripeptide

B. protein

C. polypeptide

D. dipeptide

E. peptide

8)      The primary level of structure in a protein is:

A. the regular folding of regions of the polypeptide chain.

B. the spatial arrangement of amino acids that are far apart in the linear sequence.

C. the composition and linear sequence of amino acids as joined together by peptide bonds.

D. the first level of the proteins structure

E. the alpha and beta folding of the protein structure

9)      What bonds are involved in stabilizing the tertiary structure of a protein?

A. Hydrogen bonds and covalent disulphide bonds

B. Hydrogen bonds, hydrophobic forces, electrostatic forces, covalent disulphide bonds

C.  Hydrogen bonds

D. Ionic bonds and covalent disulphide bonds

E. Hydrogen bonds, ionic bonds and electrostatic forces

10)   Name the chaotrope in the experiment below and state the role of the chaotrope.


A. Mercaptoethanol; disrupts the hydrogen bonds in the protein structure

B. Urea; disrupts the hydrogen bonds in the protein structure

C. Mercaptoethanol; disrupts the hydrophobic interactions in the protein structure

D. Urea; disrupts the hydrophobic interaction in the protein structure

E. Mercaptoethanol; reduces the disulphide bond in the protein structure


Test your knowledge on Glycolysis

Select the correct multiple answer using ONE of the keys A, B, C, D or E as follows:

A. 1, 2 and 3 are correct

B. 1 and 3 are correct

C. 2 and 4 are correct

D. only 4 is correct

E. all are correct

Question 1: In the energy investment phase of glycolysis:

  1. There are 2 irreversible reactions
  2. There are 3 reversible reactions
  3. Phosphorylation of glucose occurs
  4. 4 ATP is used

Question 2: The purpose of converting pyruvate to lactate is:

  1. To regenerate ATP
  2. To regenerate ATP and NAD+
  3. To regenerate NADH
  4. To regenerate NAD+

Question 3: In the conversion of pyruvate to lactate:

  1. NADH is a cofactor
  2. The enzyme used in the reaction is lactate decarboxylase
  3. The reaction is reversible
  4. ATP is a cofactor

Question 4: In the conversion of pyruvate to Acetyl-CoA:

  1. TPP is a cofactor
  2. Lipoate is a cofactor
  3. FAD is a cofactor
  4. FADH is a cofactor

Question 5: In the energy generation phase of glycolysis:

  1. There are 2 irreversible reactions
  2. Therese are 4 reversible reactions
  3. 4 ATP used
  4. 2 NAD+ used


Question 6: In the payoff phase of glycolysis, which 5 enzymes catalyse the 5 reactions?

  1. Glyceraldehyde 3-phos[ate dehydrogenase
  2. Pyruvate kinase
  3. Phosphoglycerate mutase
  4. Enolase
  5. Phosphoglycerate kinase

Question 7:  Which enzyme(s) catalyses the conversion of acetaldehyde to ethanol?

  1. Pruvate decarboxylase
  2. Alcohol decarboxylase
  3. Pyruvate dehydrogenase
  4. Alcohol dehydrogenase

Question 8:  For every glucose molecule entering glycolysis:

  1. 2 ATP are used
  2. 4 NAD+ used
  3. 4 ATP generated
  4. 4 NADH generated

Question 9:  The net gain of glycolysis is:

  1. 2 ATP
  2. 4 NADH
  3. 2 NAD+
  4. 2 NADH

Question 10: The two ATP forming reactions (substrate level phosphorylation) are:

  1. Glucose>Glucose-6-phosphate
  2. Glyceraldehyde-3-phosphate> 1,3-Bisphosphoglycerate
  3. 3-phosphoglycerate> 2-phosphoglycerate
  4. Phosphoenolpyruvate> pyruvate


Ninhydrin Starring in CSI!



Every family has their own special traditions. For my mummy and I, we enjoy curling up on the couch on a Friday evening to watch marathons of our favourite TV-shows. One such show is CSI, specifically CSI Miami. I love Horatio’s character the most! He’s just so badass.


If you’re an avid CSI fan such as me, you may have noticed that in the field of forensics, fingerprint work makes an appearance in every episode. Have you ever wondered what they use in forensics to develop fingerprints?






Ninhydrin has become the most common method used to reveal prints on porous surfaces. Nearly all forensics labs use ninhydrin for this purpose, and some seldom use anything other than ninhydrin. Ninhydrin is cheap, sensitive, and commercially available in disposable spray cans. The developed prints are a high-contrast purple that’s readily visible on most paper backgrounds.



Ok, so how does the ninhydrin work exactly?

Dusting the crime scene is the commonest, simplest and oldest latent print developing technique. A white powder composed of the chemical ninhydrin is used to develop latent prints (prints invisible to the eye). Latent prints are formed by sweat, either from the hands themselves or by unconscious contact between the fingers and the face or other parts of the body. Even the swiftest of criminals find it difficult to escape without leaving behind the trace of a single fingerprint. The traces of amino acids present in perspiration bind with the ninhydrin and the prints begin to appear in about an hour. In the pH range of 4-8, all α- amino acids react with ninhydrin; a powerful oxidizing agent to give a purple colored product (diketohydrin) termed Rhuemann’s purple.




Ninhydrin degrades amino acids into aldehydes, ammonia, and CO2 through a series of reactions; the net result is ninhydrin in a partially reduced form hydrindantin. Ninhydrin then condenses with ammonia and hydrindantin to produce an intensely blue or purple pigment, sometimes called Ruhemann’s purple.

ninhydrin reaction

In our last lecture, we made a clear distinction between the two tests : Biuret test and Ninhydrin test. Mr. Matthew (my lecturer) made a video that clearly differentiates between the two tests in a clear understandable manner so if you are having trouble understanding their differences, I urge you to watch the vid! It’s really helpful and not too long.

Apparently students mix up their uses all the time, and if my lecturer didn’t stress on this I’m 99.9% sure I would’ve been one of those careless students as well.The Biuret test is used to test for proteins while the Ninhydrin test is used to test for amino acids.  Don’t forget!!!!

Mr. Matthew also posed a question to us. Do all amino acids give that lovely purple colour when the ninhydrin test is performed? From his tone I knew there had to be some exception.

Here’s what I found:

The color produced when the ninhydrin test is performed varies slightly from amino acid to amino acid, probably because the unreacted acids complex with the pigment.

Proline and hydroxyproline give a yellow color.  Proline has aliphatic side chains with a distinctive cyclic sturcture. The secondary amino (imino) group of proline  residues is held in a rigid conformation that reduces the structural flexibility of polypeptide regions containing proline. Proline does not give the ninhydrin reaction as this reagent requires free alpha amino group (-NH2) but proline has an imino group (-NH).  For the amino acids which have a free -NH2 (amino) group, ninnydrin test is positive but is negative for proline because it only has -NH (imino) group.

I hope this post was helpful! Can you find any more amino acids that don’t give the purple colour when the ninhydrin test is performed?


















Did You Know…?



Now that we are onto the topic of amino acids and proteins in my biochemistry course, I found it only appropriate to share some interesting facts about protein that I discovered . I’m sure at least one will interest you!

  • Proteins can have really weird names. For example, the protein Pikachurin is a retinal protein that was named after a Pokémon character Pikachu and the protein Sonic Hedgehog was named after Sonic the Hedgehog. There is also a blue protein that is named Ranasmurfin, after the Smurfs.

pikachu2 images images (1)

  • Protein is found in each of the trillions of cells in the human body. Life would not be possible without proteins. Water is the only other substance which is as abundant in the body. Approximately 18-20% of the body is protein by weight.

Inside Outside Puzzle Human Body inside

  • In 2010, 20-year-old athlete Ben Pearson tried to increase his protein intake to boost muscle development. However, no one knew he had a rare genetic disorder that prevented his body from breaking down protein.

AthlteThe increased protein intake increased ammonia levels in his blood that caused brain swelling and death. (Read more of his story here: http://abcnews.go.com/Health/w_DietAndFitness/high-protein-diet-linked-hockey-players-death/story?id=11815908)

  • Hair is made up of a protein called keratin, which forms a helical shape. This protein has sulfur bonds, and the more sulfur links it has, the curlier a person’s hair will be. I guess my hair has A LOT of sulfur links!curly_by_jessicaxyl-d4q8gau
  • One of the smallest countries in the world, Luxembourg, is per capita the biggest meat eater. Luxembourgers eat on average about 300 pounds of meat annually per person. The U.S. comes in second with about 276 pounds of meat—mostly beef—per year. Austria is third with about 267 pounds of animal protein per person.


  • Cow used to be the global leader in meat eaten. The pig is now the most popular.


  • Without a protein called Albumin, the entire human body would swell.


  • Cataracts are caused by the denaturation of proteins in the lenses of the eyes.


  • Insects are more nutritious than many other common forms of protein. For example, 100 grams of top sirloin beef contain 29 grams of protein and 21 grams of fat. However, 100 grams of grasshopper contain 20 grams of protein and just 6 grams of fat.


  • A protein in semen acts on the female brain to prompt ovulation.


  • The human body has about 100,000 different types of protein. The body needs protein to grow, heal, and carry about nearly every chemical reaction in the body.


  • Protein deficiency can cause serious health problems. For example, children with a protein deficiency could develop a condition known as Kwashiorkor. The symptoms include a protruding belly, thin hair, overall weight loss, and discolored skin and hair. Left untreated, it can lead to stunted growth, mental impairments, and death


  • Middle- aged and elderly people have more extensive body breakdown than a younger person, which means they need more protein. However, as people enter middle age, hydrochloric acid, which helps digest protein in the stomach, drops to half its regular level. Because protein is crucial in cell regeneration, some researchers suggest that most of aging is due to this drop alone.


  • Eating too much protein can be dangerous for the body. For example, high levels of protein can stress the livers and kidneys because they have to work extra hard to dismantle and dispose of the extra protein. Excess protein can result in weight gain.


  • Proteins in the human body have many jobs. For example, a protein called rhodopsin in our eyes helps us see light. Hemoglobin in red cells carries oxygen from the lungs to the body’s cells and takes away their harmful waste product, carbon dioxide. A series of chemical reactions involving proteins makes the blood clot. Additionally, proteins give the body structure, help regulate body processes, defend against disease, maintain the body’s internal environment, and give us energy


  • While human meat is a good source of high-quality protein, cannibalism was not historically motivated by diet or starvation. Rather it was a symbolic gesture, usually as a way to commune with the gods.


Well, if you didn’t know any of these things..