Monthly Archives: March 2013

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My examination for the nation!!!

You have exactly 2 minutes to answer the following questions. Please ensure that you read the questions properly and post your answers in the comment slot provided!! You may begin!!

Question 1

Lysosomes and Proteasomes both degrade intracellular debris. Lysosomes contains enzymes to degrade Proteins, Nucleic acids and Lipids. However, Proteasomes contains enzymes to degrade:

1. Lipids

2.Nucleic acids

3.Proteins

4. Carbohydrates

Choose the correct answer from the options below:

A. 1 and 2

B. 4 only

C. 3 only

D. 1, 2 and 3

E. the answer is not an option.

 

Question 2

Which bonds are responsible for the stability of the 3-D structure of the Protein:

A. Covalent Bonds

B. Hydrogen Bonds

C. Electrostatic forces

D. Hydrophobic Interactions

E. Peptide Bonds

 

Time up!! Hope you guys did well!!  😀

 

Be the change you want to see in the world!
He who changes one person, changes the world entire!
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So last time i was here, we were discussing the bio-signifance of Carbohydrates. 

On tonight’s Biochem broadcast; we will be covering the following top stories:

  • Monosaccharides
  • Disaccharides
  • Polysaccharides

I am your presenter for this evening; my name is Shan Fred.

I  was informed earlier today that the famous family “Monosaccharide” is indeed the simplest sugar unit of a Carbohydrates. 

To cover this story in depth we shall go over to Stacii Fred, who will present to us from a Biochemist perspective. 

The family Monosaccharide can be further classified into two groups: Aldehydes and Ketones; more specifically aldoses and ketoses. 

For those who are not doing chemistry, i will explain what a carbonyl group is, since it is necessary to understand the classification of aldose sugars and ketose sugars.

  • Carbonyl group: it is a functional group that is recognized by a carbon atom being doubly bonded to an oxygen atom.

We will use the carbonyl group to differentiate between an Adlose sugar and a Ketose sugar:

  • Aldose Sugar: the carbonyl group is at the end of the Monosaccharide chain (last member of the family): Example:the most famous daughter GLUCOSE:

Note the position of hydroxyl group (OH) on the 5th Carbon atom; which is the chiral carbon furthest away from the carbonyl group. Glucose has 4 chiral carbons. Based on the report in front me, a Chiral carbon (asymmetric carbon) is defined as a compound which has four different groups bonded to it, therefore the atoms are arranged differently in space thus resulting in optically active isomeric forms called Enantiomers. When the OH group is on the left this is L-designation, therefore L-Glucose and when its on the right it is D-Designation therefore D-glucose.

  • Ketose Sugar: the carbonyl group is within the chain structure. i.e. any other carbon that is not at the end. However it is usually at carbon 2. An example would be Fructose the jealous sister:

Notice the position of the carbonyl group(C-2); and also the position of the chiral carbon furthest away from the carbonyl group(C-5).
All the structures above for glucose and fructose are in the Fischer projection form.

Now we are going to focus on the Haworth Projections:

These structures are derived from the cyclization of the Monosaccharides, which is as a result of a reaction between the aldehyde or ketone group and an alcohol group. The structures formed are either:

  • Hemiacetal——–> if the reaction is between an aldehyde and alcohol
  • Hemiketal———> if the reaction is between a ketone and alcohol.

Since we have been looking at glucose and fructose; They will be the candidates for cyclization.

The Cyclization of Glucose occurs between the aldehyde group on C1 and the OH group on C5. Glucose forms a 6 member ring hence it is referred to as pyranose ring. A new asymmetric carbon is formed at C1 due to the cyclization, thus 2 new stereo-isomers called anomers are formed: α and ÎČ. 

cyclization of glucose

(Moran et al 2012, 232).

The structure is deemed α or ÎČ based on the position of the OH group which is attached to the anomeric carbon. If the OH group is above the plane of the ring, it is ÎČ; if the OH group is below the plane of the ring it is α.

NB: the anomeric carbon for cyclized glucose is C1

The cyclization of fructose occurs between the ketone group at C2 and the OH group at C5, which produces a 5 member ring called furanose. A new asymmetric carbon is formed at C2 thus resulting in the formation of α and ÎČ structures. The same theory applies for the identification of the alpha or beta structure of fructose.

 

NB: the anomeric carbon for cyclized fructose is at C2

Disaccharides:

They are produced via a condensation reaction, which occurs between two monosaccharides. The OH group of one monosaccharide combines with the Hydrogen group of another, producing a water molecule. The two monosaccharides are now covalently bonded by an oxygen bridge called a Glycosidic Bond.

The 3 major disaccharides we should be aware of are:

  • Maltose: formed via a condensation reaction between two α Glucose monosaccharides.

The Glycosidic bond formed: α (1-4) .

As you can see from the diagram, the bond is formed between the OH group on C1 of one Glucose molecule and C4 of the other.

  • Lactose: formed via a condensation reaction between ÎČ Glucose and  ÎČ Galactose.

Glycosidic bond formed: ÎČ(1-4)

  • Sucrose: formed via a condensation reaction between ÎČ Fructose and α Glucose.

Glycosidic Bond formed: (α1-2ÎČ)

As you can see from the diagram the bond formed is between C1 of Glucose and C2 of Fructose.

Polysaccharides: 

These are polymers of monosaccharides. The 3 major structures we should be aware of are ALL polymers of Glucose:

  • Starch: contains two types of Glucose polymers: Amylose and Amylopectin;

amylose

(Moran et al 2012, 241).

Amylose is unbranched, with α(1-4) linkages between Glucose molecules.

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(Moran et al 2012, 242).

Amylopectin is branched with α(1-4) and α(1-6) linkages between the Glucose molecules

  • Glycogen: the structure resembles that of Amylopectin, however there are more α(1-6) branches present in glycogen.This is a branched structure with α(1-4) and α(1-6) linkages between the Glucose molecules.
  •  Cellulose: is composed of  ÎČ(1-4) linkages. In this structure every other glucose molecule is flipped over to accommodate the ÎČ linkages. 

This is an unbranched structure.

As we come to the end of our broadcast I would like to thank our sponsors:

Google Images: all diagrams were obtained from Google Images unless otherwise stated.

Moran, Laurence A, H. Robert Horton, K. Grey Scrimgeour, Marc D. Perry. 2012. Principles of Biochemistry. 5th ed

Cox, Michael, and David L. Nelson. 2008. Lehninger Principles of Biochemistry. 5th ed. New York

That will be all for the night! Hope my presentation was informative. Back to you Shan Fred. Goodnight!

Be the change you want to see in the world!
He who changes one person, changes the world entire!

 

Carbohydrates

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Peak Down

Good day bloggers!!!

How are you guys doing? panicking yet? Well i am! we are currently in the “peak down” for semester 2. A semester that supposedly is long, but feels quite short. I went to bed just a few hours ago to rest my worry eyes, with hopes of rising refreshed and ready to tango. BUT then, a tentative timetable was just posted!! yup!! im betting you guys heard me screaming! i would not normally go into panic mode for week 9, but it just feels like time is going by so quickly and i am not ON TOP my game.

Blogging is some thing that is quite new to me. First off i am not one to be into all the “features” of the internet. I am a simple girl, living in a simple world. ITS FANTASTIC!!! ………sorry…..yes i was saying, its a learning time consuming process. I am not OMG super excited about it; but the point of the matter it has to be done!! SO i have decided to use my saturday night to get in touch with my blogging and my “creative” side. Well its almost sunday morning!!!

Wish me luck as burn the midnight oil trying to get back on top my game.

Dont know what it is, but this semester just seems soooooo argh!! i really dont know what that means, but i think you do understand my pain. Cheers to the……i don’t know! cheers to something! 

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Thanks to Photosynthesis!!

Hey there guys!!!!

Its been awhile!!!! Im not gonna waste anymore time with small talk, but just get straight into the meet of the matter!

Thanks to the never ending photosynthetic process, Carbohydrates are the most abundant bio-molecules on earth.  Image

We all know from primary school photosynthesis equation is as follows:

CO2 + H2O—–light—-> O2 + (CH2O)

Now this is an oxidation-reduction reaction, where water donates its electrons to reduce carbon dioxide to form the carbohydrate and oxygen. As you can see from the equation this process occurs in the presence of sunlight; it is the light energy from the sun that is converted to chemical energy, which then becomes trapped in the bonds of the carbohydrate!

Now that i have explained how a carbohydrate is formed, you can understand why it has that name: they are hydrates of carbon.

Since carbohydrates is a very broad topic, we will take it step by step. I will 1st introduce the bio-significance and functions of carbohydrates; then i will later blog about its different classes.

Now please don’t get bored!! We can do this yes!!!

Bio-significance and Functions:

Have you ever been to a children’s party? It is actually most parents nightmare!! Have you ever noticed that at the end of the party, when parents seem to be oooh so tired, the children have this energy kick and they can’t seem to sit or lie down? Well it has to do with all the carbohydrates the children consumed during the course of the party!  Which brings us to the first bio-significance and its function:

1.Energy Source: 

Recall, that the light energy from the sun is trapped in the bonds of the carbohydrate-glucose. Therefore if we were to reverse photosynthesis and conduct respiration, this light energy will be released. Therefore, during metabolism we humans, as well as other animals oxidize glucose to produce water and carbon dioxide, hence releasing the energy. This obviously will occur in various steps, which are not relevant to us RIGHT NOW!! 

2.Storage

Now although we have not reached the different classes of carbohydrates, we need to mention the group polysaccharides. Starch: storage product for plants and glycogen:storage product for animals are the main storage polysaccharides. Now if we consume too many carbohydrates (like children do at parties), we would have a high concentration of blood glucose. A high concentration of blood glucose can be very fatal, therefore once our pancreas is working efficiently, it releases the hormone insulin. Insulin will work its magic by converting the excess glucose to the main storage product glycogen, which is then stored in the muscle and liver for later use. Now if you pancreas is NOT working efficiently, it will not be able to release insulin, hence it would have to be administered. 

The “later use” period comes into play when our blood glucose level is too low. This is once again a battle for our pancreas. The pancreas releases a different hormone called glucagon. Glucagon have similar powers like insulin; but instead converts the stored glycogen in the liver and muscles to glucose. 

3. Structure

The structural carbohydrates are Cellulose and Chitin. Recall from the blog on Cells: “what makes you you and me, me!” that Plant cells possess a cellulose cell wall, a structure that Human cells lack. Cellulose is a very strong fibre made of ÎČ-D-glucose (will be explained in later blogs) that provides structure as well as protection for plant cells. Chitin however, is found in the exoskeleton of insects. It is because of the chitinous exoskeleton, insects are so adaptive and diverse. Chitin is very strong and flexible and gives insects such a great advantage, therefore humans use it for medical purposes, example sutures. Please note cellulose and chitin are both polysaccharides.

4. Precursor Molecules:

There is so much of it, why not use it in the synthesis of other bio-molecules? Carbohydrates are used to synthesis other products.

Examples:

  • Glucose is synthesized to produce Vitamin C.
  • Ribose forms part of the skeleton of the nucleic acids: RNA (ribose nucleic acid) and DNA (deoxyribose nucleic acid)
  • The carbon skeletons of carbohydrates is the basis for the synthesis of organic molecules such as amino acids and fatty acids.

Theses are the 4 main functions of carbohydrates! Please read to understand. If you do have any questions feel free to post them under my blog!!! Happy Biochemistry!

Im out!

Be the change you want to see in the world!

He who changes one person, changes the world entire!