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Carbon’s affinity for covalent bonding means that many distinct and relatively stable organic molecules nevertheless readily form larger, more complex molecules. Any large molecule is referred to as macromolecule    (macro- = “large”), and the organic compounds in this section all fit this description. However, some macromolecules are made up of several “copies” of single units called monomer (mono- = “one”; -mer = “part”). Like beads in a long necklace, these monomers link by covalent bonds to form long polymers (poly- = “many”). There are many examples of monomers and polymers among the organic compounds.

Monomers form polymers by engaging in dehydration synthesis (see [link] ). As was noted earlier, this reaction results in the release of a molecule of water. Each monomer contributes: One gives up a hydrogen atom and the other gives up a hydroxyl group. Polymers are split into monomers by hydrolysis (-lysis = “rupture”). The bonds between their monomers are broken, via the donation of a molecule of water, which contributes a hydrogen atom to one monomer and a hydroxyl group to the other.


The term carbohydrate means “hydrated carbon.” Recall that the root hydro- indicates water. A carbohydrate    is a molecule composed of carbon, hydrogen, and oxygen; in most carbohydrates, hydrogen and oxygen are found in the same two-to-one relative proportions they have in water. In fact, the chemical formula for a “generic” molecule of carbohydrate is (CH 2 O) n .

Carbohydrates are referred to as saccharides, a word meaning “sugars.” Three forms are important in the body. Monosaccharides are the monomers of carbohydrates. Disaccharides (di- = “two”) are made up of two monomers. Polysaccharides are the polymers, and can consist of hundreds to thousands of monomers.


A monosaccharide    is a monomer of carbohydrates. Five monosaccharides are important in the body. Three of these are the hexose sugars, so called because they each contain six atoms of carbon. These are glucose, fructose, and galactose, shown in [link] a . The remaining monosaccharides are the two pentose sugars, each of which contains five atoms of carbon. They are ribose and deoxyribose, shown in [link] b .

Five important monosaccharides

This figure shows the structure of glucose, fructose, galactose, deoxyribose, and ribose.


A disaccharide    is a pair of monosaccharides. Disaccharides are formed via dehydration synthesis, and the bond linking them is referred to as a glycosidic bond (glyco- = “sugar”). Three disaccharides (shown in [link] ) are important to humans. These are sucrose, commonly referred to as table sugar; lactose, or milk sugar; and maltose, or malt sugar. As you can tell from their common names, you consume these in your diet; however, your body cannot use them directly. Instead, in the digestive tract, they are split into their component monosaccharides via hydrolysis.

Three important disaccharides

This figure shows the structure of sucrose, lactose, and maltose.
All three important disaccharides form by dehydration synthesis.

Watch this video to observe the formation of a disaccharide. What happens when water encounters a glycosidic bond?

Questions & Answers

What is ELISA
difference between apocrine sweat glands and merocrine sweat glands
Binkheir Reply
I believe the apocrine sweat gland uses a sac under the hair follicle and the merocrine sweat gland releases directly on to the surface of the skin
normal blood volume in our body
pankaj Reply
Normal blood volume in adults is 6 litres
4.7 to 5ltr.. normal for adult
what are the advantages of the concave shape of red blood cells?
Amy Reply
This structure is VERY flexible. It can allow these cells to get into the most tiny places in our bodies. a VERY good design! The advantage of red blood cells' biconcave shape is that the surface area is increased to allow more haemoglobin to be stored in the cell.
They can stack so that they can move to capillaries
action of gluteus medius and minimus
Green Reply
Lateral rotation of the hip joint
Briefly explain location of ecg on a patient
Prince Reply
it is a machine that gives a graphical representation of heart beat
Briefly explain location of ecg leads on a patient?
in ecg we use electrical leads over the chest ,ancle and wrist
what is the anatomical and function difference between paravertebral and prevertebral ganglia ?
Rada Reply
types of tissue in human
Preety Reply
charactetistic Of cartilaginous tissue
what is theRecurrent infection?
pankaj Reply
what do you mean about recurrent infection
Recurrent or persistent infection is a manifestation of primary immuno deficiency
weakens the immune system, allowing infections and other health problems to occur more easily
lysis of RBC
What is barometric pressure
Kedha's Reply
what is the agglutination advantage
Gopal Reply
the functions of the liver
Nana Reply
it produces bile juice which is used to make the food smaller
it also plays an important role in conversion of amino acid into urea
it also has role in gluconeogenesis in which amino acids and lipids convert into glucose.
during fetal life it's a center for hemopoiesis (formation of blood cells)
it filters, or removes, harmful substances from the blood
It stores nutrients, such as vitamins and iron,for the body
what is the largest gland in human body
Shahid Reply
thyroid gland
thyroid is largest endocrine gland
describe microscopic structures of the kidney
Nana Reply
kidney is covered by fibrous capsule, consists of an outer cortex and inner medulla with medullary pyramids. The microscopic structure is seen as 1-2 millions of nephrons and collecting tubule.
identify the four major tissue types
Binkheir Reply
connective epithelial
two ramining
muscle nervous
epithelial, connective, muscle, and nervous tissue

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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