What are Carbohydrates????


They are made up of carbon and water and have the formula (CH2O)n

The functions  of carbohydrates are

Energy source–  Monosaccharides and disaccharides are broken down to form glucose and sucrose

Storage–  Starch and glycogen are the main storage polysaccharide

Remember — Starch is used by plants while Glygogen is used by animals.

When glucose concentration in the body is high the pancreas produces insulin. This converts the glucose into glycogen and it is then stored in the liver and muscle. The secretion of insulin is VERY IMPORTANT  as it is the only hormone that lowers the blood glucose level. When insulin production is low  this result in diabetes mellitus .

When the glucose concentration is low  the hormone glucogon is produced. This converts the glycogen into glucose.

Structure-  The most significant component of the cell wall in plants is cellulose.  It is a polymer of β-D- glucose. Approximately 50% of  the carbon found in plants is in cellulose.  It has tremendous tensile  strength.  This protects the cell and prevents it from bursting when osmosis occur and water enters.

Chitin  -This is found is some fungi  and animals , the arthropods. It is made up of bundles of long parallel chains similar to cellulose.

Precursor molecule–  It is involved in the making of other biomolecules.

Carbohydrate metabolism:  Glycolysis


Monosaccharide these are simple sugars that contain  many OH groups.  Monosaccharide with three carbons are called triose, with four tetrose , with five pentose, with six hexose.


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Disaccharides is formed when two monosaccharide  combine through condensation.

Oligosaccharide contains a few monosaccharide that are linked covalently 

Polysaccharide – This is polymers made up of chains of monosaccharide units.


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There are two types of monosaccharide

Aldose and Ketose…

Aldose  contains an aldhyde group at one end CHO

Ketose contains a keto group C=O


Chiral compound- is where there are  four different groups attached to a carbon. There are mirror images of each other.



D AND L designations???

This  refers to the arrangement about the single asymmetric carbon in glyceraldehyde, where the asymmetric carbon had four different group attached to it. The OH group can be present on two different sides of the asymmetric carbon. If on the right hand side , it is called a D isomer , if it is on the Left hand side it is called a L isomer.



Whenever you have sugars that contain more than one chiral carbon the D or L configuration is usually the chiral carbon, that is the furthest from the aldehyde or ketone group.

D and L are mirror images of each other

Points to note: When aldehyde reatcs with alcohol it forms hemiacetal

                         When a ketone reacts with an alcohol is forms hemiketal






What is it?  It is a disease where person has high blood glucose due to low insulin production or as a result of the body cells not responding to insulin.

There are three types

  1. Type 1  – There is no production of insulin in the body.
  2. Type 2- Insufficient amounts of insulin is being produced in the body for normal functioning.
  3. Gestational Diabetes- This occurs during pregnancy.  In some women glucose levels are very high and adequate amounts of insulin is not produced to carry all the glucose into their cells, this leads to high glucose levels.

Do you have it?

 Frequently urinating?

Always thirsty?

Always hungry?

Feeling tired?

Seeing blurry?

Long healing cuts or bruises?

Are you losing weight even though you are consuming more food?

 Is there a tingling, a pain or are you getting a numbness in your hand or feet?





When you hear the word carbs, what comes to mind????????

Looks good doesn’t it, but looks can be very deceiving sometimes. Because too much of this and no exercise can lead to…………………….



They are good for you to a certain extent, that is in the right amounts at the right times but i like to call them “THE DELICIOUS DEVILS”.

  Let’s dig deeper to find out more about carbohydrates……….   


  A glycosidic bond is formed when two monosaccharides join together using condensation. The two OH or hydroxyl groups line up side by side, where one combines with a hydrogen atom from the other and form a water molecule. An “oxygen bridge” is formed joining the two molecules together forming a disaccharide.  In alpha glucose the OH group is always below.


  “Di” here, meaning two, so a disaccharide is two monosaccharides joined together by a glycosidic bond. The three main dissaccharides that we should know are: maltose, lactose and sucrose.


 Maltose is formed by the joining of two glucose molecules. (Maltose = glucose + glucose). It is a disaccharide with 1-4 glycosidic bonds. That is the glycosidic bond is formed between the 1st carbon on one glucose molecule and the 2nd carbon on the other.



Here, you can see that the oxygen bridge forms perfectly between the two glucose molecules, since their OH group is at the bottom.


Or what we know as “table sugar”


Sucrose is a combination of glucose and fructose. Glucose which is an example of an aldose, that is it has an aldehyde group has an anomeric, carbon 1, while fructose, which is a ketose, meaning it contains a ketone group, has an anomeric carbon 2. So the glcosidic bond is formed on carbon 1on glucose and carbon 2 on fructose.

  This causes sucrose, to be a non- reducing sugar, since both anomeric carbons are involved in the glycosidic bond, or in other words, there are no free anomeric carbons. It looks like this………………



Lactose is what we call “milk sugar”

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Lactose is a combination of glucose and galactose, it is formed by a beta 1-4 linkage. Glucose has its OH group below while galactose has its OH group above, so for them to come together, the galactose has to be flipped upside down.

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The “z” formation shows that the galactose is being flipped. Lactose is the main energy source that is found in nearly all mammalian milk, so it is the also the major food and energy source for growing and developing babies.

 Staying on the topic of lactose. Let’s talk about Lactose intolerance.



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Lactose intolerance is “serious business”, might be a bit nasty but it’s serious.

 We all vary in the amount of enzymes we have in our stomach that digests dairy products. This enzyme, known as lactase, lessens as we age, however one out of two things causes lactose intolerance:

  • The body is producing less lactase enzymes
  • The enzymes, lactase, are not working properly

If this is happening in your stomach, then the lactose in the dairy you consume, is not being broken down. When this happens, the lactose stores water causing bloating, then all this water wants to come out immediately so you get diarrhoea. In addition to that, bacteria love to respire on lactose so the result of that is gas. Not the useful ones, the ones to make you feel to………………………….


                                              funny people running

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So what to do if you know that you cannot consume dairy, the safest thing to do is to stay away from it although it might be very difficult since not everything you eat will say whether or not it is lactose free.

  When that happens walk with your resources…………………………………………


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These are polymers (a larger molecule composed of smaller ones, that are chemically bonded together), made up of many monosaccharides formed by condensation reactions and glycosidic bond formation. The three main polysaccharides are:

  • Starch
  • Glycogen
  • Cellulose


This is the glucose storage unit specific to plants only. It is made up of amylose (a spiral shaped polysaccharide made up of D glucose with no branches and a 1-4 alpha linkage) and amylopectin ( a polymer  of glucose with a lot of 1-6  branching).

   The types of starches vary according to the proportion of amylose and amylopectin that it contains.


This is the where glucose is stored in animals only and is relatively similar to amylopectin, however, glycogen has more alpha 1-6 branches, that is , every 10 glycosyl residue (every 10 units). This allows the quick release of glucose from glycogen stores in times of need. Animals, require much more energy output than plants, thus, the ability to move glucose to the areas of need from the glycogen stores is of major importance.


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This requires a lot of energy, so bring on the glucose.


This is what makes up the cell walls of plants. It is made up of long, linear chains of glucose that has beta 1-4 linkages. As compared to starch and glycogen, it plays a structural role and not a storage role. In cellulose, every other glucose is flipped, this is because of the beta linkage (the OH group being above).

   There are a lot of hydrogen bonds within cellulose which helps it to be straight and rigid and filled with crystalline structures in thick bundles, which we call micro fibrils. This provides it with high tensile strength, meaning, they can stretch without tearing or bursting. Perfect for plant cell wall which has to undergo hydrostatic conditions (water coming into the cell).

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References for pictures