Basic biochemistry on carbohydrates

  • Carbohydrate is a biological molecule consisting of carbon (C), hydrogen (H) and oxygen (O) atom, with a hydrogen: oxygen atom ratio of 2:1 (as in water) and an empirical formula of Cm(H2O)n. Carbohydrates can be viewed as hydrates of carbon, hence their name. Structurally however, it is more accurate to view them as polyhydroxy aldehydes and ketones. Historically nutritionists have classified carbohydrates as either simple or complex; however, the exact delineation of these categories is ambiguous. Today, the term simple carbohydrate typically refers to monosaccharide and disaccharides, and complex carbohydrate means polysaccharides (and oligosaccharides).

    Classification of Carbohydrates

    1. Monosaccharide’s

    Monosaccharides (from Greek word mono; means single, sacchar; means sugar).Monosaccharide’s are the most basic units of biologically important carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose (dextrose), fructose (levulose), galactose, xylose and ribose. Monosaccharides are the building blocks of disaccharides such as sucrose and polysaccharides (such as cellulose and starch).

    2. Disaccharides

    A disaccharide is the carbohydrate formed when two monosaccharide’s undergo a condensation reaction which involves the elimination of a small molecule, such as water, from the functional groups only. Like monosaccharide, disaccharides also dissolve in water, taste sweet and are called sugars. The glycosidic bond can be formed between any hydroxyl groups on the component monosaccharide. So, even if both component sugars are the same (e.g., glucose), different bond combinations and stereochemistry (alpha- or beta-) result in disaccharides with different chemical and physical properties. Depending on the monosaccharide constituents, disaccharides are sometimes crystalline, sometimes water-soluble, and sometimes sweet-tasting and sticky-feeling.

    Example of a disaccharide:

    i. Sucrose (table sugar, cane sugar, beet sugar) sucrose is the combination of glucose and fructose joined by a gycosidic bond α(1→2),
    ii. Lactose (milk sugar), a combination of galactose and glucose β(1→4)
    iii. Maltose, having two glucose unit joined by a glycosidic bond α(1→4)
    iv. Cellobiose, two glucose unit joined by a glycosidic linkeage β(1→4)

    3. Oligosaccharides

    An oligosaccharide (from the Greek word oligos, means a few, and sacchar, means sugar) is a saccharide polymer containing typically three to ten component sugars, also known as simple sugars, or monosaccharide’s. Oligosaccharides can have many functions; for example, they are commonly found on the plasma membrane of animal cells where they can play a role in cell-cell recognition. In general, they are found either O- or N-linked to compatible amino acid side-chains in proteins or to lipid moieties. Example fructo-oligosaccharides (FOS), which are found in many vegetables, consist of short chains of fructose molecules. (Inulin has a much higher degree of polymerization than FOS and is a polysaccharide.) Galactooligosaccharides (GOS), which also occur naturally, consist of short chains of galactose molecules. These compounds can be only partially digested by humans.

    4. Polysaccharides

    Polysaccharides are polymeric carbohydrate structures, formed by repeating units of (either mono- or disaccharides) joined together by glycosidic bonds. These structures are often linear, but may contain various degrees of branching. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure, these macromolecules can have distinct properties from their monosaccharide building blocks. They may be amorphous or even insoluble in water.

    Carbohydrate metabolism

    Carbohydrate metabolism denotes the various biochemical processes responsible for the formation, breakdown and inter conversion of carbohydrates in living organisms.

    The carbohydrate metabolism process is as follows:

    1. Food (a carbohydrate diet) is first consumed, the mouth being the first contact point.
    2. The Carbohydrates are broken down into glucose - by saliva and the gut.
    3. Glucose enters the bloodstream
    4. Pancreas responds to the presence of food by releasing stored insulin (phase 1 insulin response)
    5. Insulin allows glucose from the blood to enter into the body’s cells - where the glucose can be used for fuel.
    6. Insulin also allows glucose to be stored by muscles and the liver as glycogen
    7. If needed, the stored glycogen can later by returned to the blood as glucose
    8. If there is glucose remaining in the blood, insulin turns this glucose into saturated body fat.
    9. Proteins in the meal also get broken down into glucose to some degree; however, this is a much slower process than it is with carbohydrates.
    10. After the body’s initial release of insulin, the beta cells in the pancreas start to develop new insulin which can be released as well. This is known as the phase 2 insulin response.
    11. As mentioned above, if glucose is taken from the blood to the point where blood sugar levels start to approach a low level, the body releases glucagon.
    12. Glucagon works to change the stored glycogen into glucose which is released into the blood stream.
      Note that the stored glycogen in the muscle cannot be broken down to glucose for the purpose of buffering blood glucose levels, only liver glycogen can because of the phosphatase in d hepatocytes.

No Stickers to Show


Recent Articles

  • vvhg

    Posted 4 hours ago


  • Nostalgia, flaw and fear: Recognizing red flags in a relationship

    Posted Jul 30

    Jenny met Hassan at a party, they clicked instantly, and before they knew it, their friendship blossomed into something else. After much persuasion from Hassan, Jenny finally agreed to move in with him. Everything was all roses and rainbows until it started; Hassan didn...

  • Domestic violence: Why the victims stay

    Posted Jul 29

    To what can we liken domestic violence? An insidious virus or a fast-acting poison? Either way, domestic violence has far-reaching, and often, fatal effects. This is why society always condemns it and also why we ask the obvious question every time, “Why does she...

  • Two souls in a single body: A journey into the mind of a solo writer

    Posted Jul 25

    The writer and I are two souls sharing a single body, and I can safely say it is the most confusing relationship I have ever been in my entire life; the same thing that gives me life seems to have a way of taking a little from everything it has given me. As writers, we ...

View All

Random Articles

  • Top eleven resourceful websites for literary students

    Posted January 9, 2017

    Students in the current age have got no excuse for failure. Technology has radically removed all the barriers hitherto encountered in the academic world. Students are no longer limited to their classroom notes and outdated/ancient textbooks imposingly piled up in their...

  • Young African writers: Breaking barriers and shifting paradigms

    Posted July 23, 2018

    Don't you want to pick up a novel and read the words Wi-fi, Chanel, iPhone, Slayage, Egusi and Africa all in the same line? Don't you want to write your language without explaining what it means, be African in your writing without apologising for it? I bet you won't min...

  • Alzheimer’s disease and prevention

    Posted September 11, 2018

    Alzheimer’s is the leading cause of dementia and is the most frequent neurodegenerative disorders. More than 5 million Americans are living with Alzheimer’s. Although, in most cases, it is diagnosed somewhere in the mid-60s, in a small number of cases it may...

  • Past, present, future: How mobile applications shape Nigerian lives

    Posted Feb 19

    “Mobile apps are shaping the future” – Oluwatobi Akinpelu You might not realize it, but our lives are more or less governed by mobile applications. Perhaps this is an oversimplified perspective but analyze it: if you learn that money problems are loom...

View All