BATs!!!!!

Cannon Barbara, Nedergaard Jan. ‘Brown Adipose Tissue: Function and Physiological Significance’.Psychological Reviews.Web.April 13,2013.<http://physrev.physiology.org/content/84/1/277.full>

 

Bearing in mind that I have a ridiculous fascination with anything to do with food and now food and biochemistry, it comes as a surprise that when I learnt about brown adipose tissues, I was fascinated enough to leave it alone. Its functions and physiology contributes to and important aspect of nature and calls for a sense of wonder in what has been achieved through evolution.   So the article I decided to review talks about everything to know about adipose tissue.

The first thing to understand is the role of brown adipose tissue; brown adipose tissue functions as a heat generator. Controlled by the hypothalamus, used in times of need for extra heat and coupled with an ‘uncoupler protein’ (UCP-1), this tissue proves to have a fundamental role in nature as it was necessary for the evolutionary success of mammals. Its main purpose is to enhance neonatal survival and allow active life in an arctic environment.

BROWN ADIPOSE TISSUE ACTIVITY:

Information regarding bodily function (temperature, energy reserves and feeding status) is observed in the ventromedial hypothalamic nucleus (VMN).  When there is a decrease in metabolic efficiency or increase in temperature, the VMN signals the brown adipose tissue via the nervous system.  Norepinephrine (a transmitter) is released and initiates the breakdown of triglycerides found in the tissue.  Triglycerides functions as the acute substrate for thermogenesis and as a regulator to the activity og UCP-1. Combustion of the fatty acids in the respiratory chain leads to extrusion of H+, and UCP1 which allows for mitochondrial combustion of substrates, uncoupled from the production of ATP, by functioning as a H+ transporter. This results in an increase of available food and oxygen in the blood to be combusted by the tissue, which in turn results in an increased production of heat.

The article does more than just explain the reaction; it also goes in-depth on each of the reactants and products mention. It also refers the importance of brown adipose tissue in humans aside from neonatal care; it recommends it as a cure for obesity. Well worth the read and sure to grasp your attention (if you’re into this sorta thing), it’s really no wonder that I didn’t bother comparing it to food.

Advertisements

SWEET and SOUR and SALTY and BITTER and UMAMI, OH MY!!!!

DuBois Grant E. ‘Unraveling the biochemistry of sweet and umami tastes’. PNAS. Web. April 13, 2013. <http://www.pnas.org/content/101/39/13972.full>

Millions of miniature papillae litters a tongue and holds a lot of responsibility, they ensure that for everything that is placed in the mouth an intriguing sensation is acquired, whether sweet, salty, umami, bitter or sour. These tiny hard workers are referred to as taste buds, on which are found taste receptors; which is where the magic, or more likely the science happens. ‘Taste’ allows us to maintain nutrition and identify some toxins, and as one of the main senses, sends information to the brain to allow prompt and proper responses. The ability to taste is attributed to the ability to perceive chemically, as taste depends on chemical stimuli. Taste sensations are elicited by flavor molecules, which are found in amino acids and peptides. Each new taste we experience is a result of the action of ion channels and G protein-couple taste receptors.

G-protein-coupled receptors form a modular system that allows transmission of a wide variety of signals over the cell membrane, between cells and over long distances in the body (Kungl. Vetenskaps-Akademien.2012).   

The article focuses mainly on the biochemistry of sweet and umami tastes and the progress made with regards to the discoveries pertaining to the biochemical pathways that mediates sweet and umami tastes.Sweet and umami tastes serve to classify compounds as either nutritive or beneficial. Umami taste is evoked by glutamate and aspartate, in contrast to sweet tastes which are evoked by a diverse range molecules including carbohydrates such as glucose and sucrose.

Considering my fondness of desserts I thought that this article was sweet in all the right places. I had to do some extra research to understand some of the terms and concepts used, but the article still proved to be very interesting and informative. Though the article raises more questions than it answers, I learnt a fair bit about what happens when something sweet and delicious hits your tongue, which made it all the more worthy of reading.

MULTIPLE CHOICE QUESTION TIME…

Image

1. What hormone is derived from tyrosine

  • A. Adrenaline
  • B. Progesterone
  • C. Glucagon
  • D. Insulin
  • E. Renin

 

2. 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

Which of the following step/s of glycolysis are irreversible reactions

  1. Glucose to Glucose 6 phosphate
  2. Fructose 6 phosphate to fructose 1,6-bis phosphate
  3. Phosphoenolpyruvate to pyruvate
  4. Glyceraldehyde 3 phosphate to 1,3- bisphosphoglycerate 

Any educated guesses, comments or queries?…leave a comment and let me know what you think the answers are.

GLYCOLYSIS RAP

Glycolysis…glycolysis, come on sugar, come on sugar for the breakdown…for the breakdown. This video had me rotfl, its an interesting and catchy rap on glycolysis that will have you laughing and learning at the same time.

So, food and glycolysis….whats the link?
Well…whats the main purpose of food…besides amazing tastes, smells and getting people fat? Energy, and unless you’ve turned into a plant, food is your main source of energy. The action of converting food into useful products for the body is known as glycolysis, the splitting of one glucose molecule (obtained from food intake) into 2 pyruvate molecules through a series of ten enzyme catalysed reactions.

It is the oldest metabolic pathway and the sole energy provider for erythrocytes (red blood cells). So take a look at this amazing life sustaining reaction and enjoy.

Happy eatings 😀

MAILLARD REACTION: THE MOST FLAVORED CHEMISTRY

Okay so i learnt something new today about a guy named Maillard and the major role he played in terms of understanding flavur in food. This is more chemistry of food than biochemistry but i thought it was very interesting and definitely worth mentioning. So i summarized an article on the reaction…i really enjoyed reading about it, so here goes…

Melted chocolate, grilled steak, baked bread and beer on tap have many things in common as they are prime examples of flavours, amazing textures, mouthwatering tastes and enticing smells of foods. All of which is owed to a series of chemical reactions triggered by the interaction of reducing sugars and proteins in food. Chemical reactions which can be considered the most practiced experiment as it occurs in just about every household; an experiment more commonly referred to as the Maillard reaction.

Maillard’s reaction was first published in 1912 and can be considered one of the more delectable aspects of chemistry history. His work was the cornerstone for a new branch of science; food science. Though a cornerstone, it was not fully recognized until World War II, where there was much interest in palatable food with a long shelf life. However it wasn’t until 1953, a chemist John E. Hodge was able to explain the complicated mechanism of a reaction of simple products.

According to Hodge, the Maillard reaction occurs in three stages.

  1. A carbonyl group of a sugar and an amino group on the protein to produce water and an unstable glycosylamine.
  2. The glycosylaminethen undergoes Amadori rearrangements to produce aminoketose compounds.
  3. Lastly, molecules of flavor, aroma and colour are created when the aminoketose compounds undergo further rearrangements, conversions, additions and polymerization.

Few of the thousands of compounds that compose the end products of the reaction contribute to the aroma and flavor. The majority consists of unwanted products which prove to be harmful.

The Maillard reaction has its bitter moments, as the same chemical reaction which produces popcorn and caramel is also responsible for the formation of acrylamide. Acrylamide is a toxic chemical that is considered carcinogenic and is found in highly processed or burnt meats. However, processed food is not the only source of distress from the Maillard reaction.

While food scientists have shown increased concern in the unwanted byproducts of the Maillard reaction in processed foods, medical researchers are more concerned with how it will stand to affect the human body, which contains enough of the necessary reactants for the reaction to occur. Medical research shows that the Millard reaction can occur spontaneously in human tissue and its products may be responsible for a variety of diseases including diabetes.

The Maillard reaction could be referred to as a paradox as it continues to be responsible for fantastic foods and harmful threats.

Article link:Chemical and Engineering News.2012. ‘The Millard Reaction turns 100’. October 1, 2012http://cen.acs.org/articles/90/i40/Maillard-Reaction-Turns-100.html(Accessed April 07, 2013)

Chicken and chick?

Got me thinking and just wanted to share

So how do you feel about enzymes in food…more specifically enzymes and bread?

So how do you feel about enzymes in food…more specifically enzymes and bread?

When you think about the science behind bread making…some questions you should ask yourself how fermentation occurs? is the sugar for fermentation part of flour? how do you get sugar from yeast? where does the flavor come from… the ethanol evolved during fermentation?

Understanding the incredible actions of enzymes and its involvement in dough making can help answer these questions and maybe make you ask a few more.

So what happens when you make bread….first thing you want to concern yourself with is the ‘rising of the dough’

This occurs via the action of fermentation which produces a gas CO2 which allows the dough to expand or rise. The longer the dough is left alone, in optimum conditions…the higher the concentration of CO2 evolved and the greater the expansion.

So what, when, where, how and why does fermentation happen in bread making?

When ‘proofed’ yeast is added to flour, sugar and salt

Where…in the dough which is hopefully in a bowl or the kitchen counter?

How? well here’s where it gets interesting…. Fermentation is a metabolic process in which an organism converts a carbohydrate, such as starch or a sugar, into an alcohol or an acid. Yeast ferments to obtain energy by converting sugar into alcohol; pyruvate (from glucose) is broken into ethanol and carbon dioxide. The net chemical equation for the production of ethanol from glucose is:

C6H12O6 (glucose) → 2 C2H5OH (ethanol) + 2 CO2 (carbon dioxide)

So how does that tie in with bread and enzymes for that matter? Well the first thing to note is that although flour contains just about 1 to 2% sugar…we can’t forget that the primary component of flour is starch. Starch which is a protein that can be broken down into sugars…glucose sugars to be specific. The breakdown of the starch is a result of the work of …u guessed it…enzymes.

AN ENZYME IS A GLOBULAR PROTEIN THAT CATALYZES A BIOLOGICAL REACTION. Enzymes speeds up reactions by reducing the activation energy needed for a reaction to occur.

Side Note: Most important biological reactions take millions of years to occur without enzymes. Enzymes are extremely important molecules as it allows the existence of life.

The activation energy is the energy barrier of a reaction. It is the energy that reactants must be given, in excess of the energy they normally possess, in order to start forming products. A catalyst affects the rate of a reaction by affecting the activation energy. Enzymes are catalysts because they reduce the activation energy which results in more successful collisions and a faster rate of reaction.

In bread making the enzymes catalyzes three major reactions; starch to maltose; complex sugars to simple sugars; and breaking protein chains.

ENZYMES ARE SPECIFIC

EACH ENZYME HAS A SPECIFIC JOB TO DO AND IT ONLY INTERACTS WITH MOLECULES FOR WHICH IT WAS DESIGNED TO INTERACT WITH.  THEY REACT WITH THE SUBSTRATE TO FORM AN ENZYME SUBSTRATE COMPLEX WHICH RESULTS IN THE FORMATION OF THE PRODUCT AND AN UNCHANGED ENZYME MOLECULE. THE ENZYME IS NOT CONSUMED OR CHANGED WITHIN THE REACTION THEREBY ALLOWING CONTINUOUS CATALYSIS.

To understand the specificity of enzymes, you have to understand the ‘Fischer’s lock and key hypothesis’.

The basis of the lock and key hypothesis;

Just like each lock is specific to a certain key and can only be opened by that key…. An enzyme would only bind with a certain substrate. The enzyme acts as the lock and the substrate acts as the key. The substrate binds to the enzyme via its active site, which has a shape similar to that of the substrate. The bond formed between the active site and the substrate is weak, i.e. hydrophobic bonds, and alters the substrate to allow a favorable reaction. When the reaction occurs, the enzyme releases the products and moves on.

Lock and key

 

 

The first enzyme to take action in bread dough is amylase. Amylase reacts with starch (either amylose or amylopectin), and breaks the chain between adjacent sugar rings. There are two kinds of amylase: α-amylase randomly breaks the chain into smaller pieces while β-amylase breaks maltose units off the end of the chain.

Flour is made up of wheat kernels which contains amylase. Wheat kernels contain amylase because they need to break starch down into sugar to use for energy when the kernels germinate.

Amylase is a large molecule with hundreds of amino acids and is activated when water is added to the flour.  Many different groups contribute to the bonding between the amylase and the starch substrate.

Because of amylase, some of the starch in bread dough is broken into maltose, a double-ring sugar composed of two glucose molecules; but fermentation reactions require single glucose rings. Simple sugars like glucose also provide flavor to the bread and participate in browning reactions that occur at the crust during baking.

This is where the yeast used in bread-making comes into play as yeast contains the enzyme maltase, which breaks maltose into glucose. Yeast absorbs a maltose molecule and the maltase binds to the maltose and breaks it into two glucose molecules.

Yeast cells also contain invertase, another enzyme that can break sucrose. This enzyme works on the small percentage of sucrose found in the flour. These two enzymes are responsible for producing much of the glucose needed by the yeast for fermentation.

The other major enzyme at work in bread dough is protease. Protease acts on protein chains, breaking the peptide bonds between amino acids. There are hundreds of proteases, but only a few are found in bread dough, where they chop the gluten into pieces. Proteases occur naturally in flour, yeast cells, and malt.

Gluten is a combination of proteins that forms a large network during dough formation. This network holds the gas in during dough proofing and baking. The strength of this gluten network is therefore extremely important for the quality of all bread raised using yeast. This is why only a little bit of protease is required, as it would soften the dough making it more workable and too much protease activity would break up the gluten, destroying the network that forms during kneading. If the dough is allowed to rest, proteases have time to work before kneading, making the dough easier to knead.

In addition to affecting the consistency of the dough, proteases affect its flavor. Proteases result in single amino acids when they break the last peptide bond of the protein chain. These amino acids can participate in the flavor and browning reactions that occur at the crust during baking.

So these magnificent  enzymes help to make amazing things in the kitchen like:

this focaccia and ciabatta bread;

Foccacia Bread         IMG00636-20120829-2116

 

The crust for this pizza;

IMG00520-20120613-1934

 

 

and the ‘carrier’ for these sandwiches

IMG00651-20120921-1514

 

IMG00530-20120622-1215

IMG00452-20120327-1741

Without enzymes, bread-making would not be possible. Then again, neither would we.

Happy eatings to all 😀

ALTON BROWN; PROTEINS IN EGGS

Okay so my second post mentioned something about the proteins which make up eggs; specifically albumin in egg whites, which can be used to make meringue.
So here’s a video from one of my all time favourite chefs- Alton Brown- with an albeit cooler explanation. He seamlessly blends science and food which results in brilliance.
In this video he discusses egg whites and its versatility… so for a mouth watering and brain stimulating take on egg whites and its proteins which result in amazing desserts…just click that little button that says play. Trust me it’ll be worth it. 😀

Stay Hungry 🙂