biological molecule Flashcards
cohesion and adhesion
- COHESION: is the attraction among water molecules
ADHESION: is the attraction among water molecules and polar surface
Biochemistry
- Biochemistry is a branch of biology which deals with the study of chemical
components and the chemical processes in living organisms. - All living organisms are made of organic and inorganic compounds.
- Inorganic substances in living organisms are water, carbon dioxide, acids, bases, and
salts etc.
Some Basics Of Biochemistry
- Living organisms contain macromolecules formed from a small number of simple
molecules. - These simple molecules suggest that all life had a common origin.
- The characteristics of an organism are determined by the information contained in its
DN. - The DNA contains information that the cell can use to make proteins. Many proteins
are enzymes, which control the physical and chemical activities of an organism. - The chemical activities that go on inside an organism can organism can be given the
general term metabolism. - Metabolic reactions can be divided into two general categories: anabolic and
catabolic. Anabolic reactions build up large molecules from smaller ones. While:
catabolic reactions do the reverse, breaking down larger molecules. - Anabolic reactions usually involve condensation reactions ill which building-block
molecules are joined together and a water molecule is released. - Catabolic reactions, such as those that occur during digestion, usually involve
hydrolysis reactions in which larger molecules are split as they react with water. - In photosynthesis, plants use the energy from sunlight to build up organic molecules
such as sugars from simple ones such as carbon dioxide and water. - All organisms need a supply of energy, which they obtain via respiration. In respiration
organic molecules are oxidized into simpler molecules, usually carbon dioxide and
water. The resulting energy is used to fuel many energy-requiring processes within the
organism.
Water Importance
§ Water is the medium of life.
§ It is the most abundant compound in all organisms. It
varies from 65 to 89 percent in different organisms.
§ Human tissues contain about 20 per cent water in bone
cells and 85 per cent in brain cells.
§ Almost all reactions of a cell occur in the presence of
water. It also takes part in many biochemical reactions
such as hydrolysis of macromolecules.
§ It is also used as a raw material in photosynthesis.
* Ionic substances when dissolved in water, dissociate into
positive and negative ions.
* Non-ionic substances having charged groups in their
molecules are dispersed in water.
* When in solution, ions and molecules move randomly and are in a more favorable state
to react with other molecules and ions. It is because of this property of water that almost
all reactions in cells occur in aqueous media. In cells all chemical reactions are catalyze by
enzymes which work in aqueous environment.
* Non-polar organic molecules, such as fats, are insoluble in water and help to maintain
membranes, which make compartments in the cell.
* Water has great ability of absorbing heat with minimum of change in its own temperature.
* The specific heat capacity of water – the number of calories required to raise the
temperature of 1g of water from 15 to 16°C is 1.0. This is because much of the energy is
used to break hydrogen bonds. Water thus works as temperature stabilizer for organisms
in the environment. Protects living material against sudden thermal changes.
* Water absorbs much heat as it changes from liquid to gas. “Heat of vaporization is
expressed as calories absorbed per gram vaporized.” The specific heat of vaporization of
water is 574 Kcal/kg, which plays an important role in the regulation of heat produced by
oxidation.
* It also provides cooling effect to plants when water is transpired.
imp points 1
To animals when water is perspired. Evaporation of only two ml out of one liter of water,
lowers the temperature of the remaining 998 ml by 1°C.
H2O H+ + OH-
* The water molecules ionize to form H+ and OH- ions:
* This reaction is reversible but an equilibrium is maintained. At 25°C the concentration
of each of H+ and OH- ions in pure water is about 10-7 mole/litre.
* The H+ and OH- ions affect, and take part in many of the reactions that occur in cells
* Water is effective lubricant that provides protection against damage resulting from
friction.
* Tears protect the surface of eye from the rubbing of eyelids.
* Water also forms a fluid cushion around organs that helps to protect them from
trauma.
Carbohydrates
- Carbohydrates are polyhydroxy aldehydes or ketones, or complex substances which
on hydrolysis produce polyhydroxy aldehyde or ketone subunits. - Three major groups of Carbohydrates are: Monosaccharides, Oligosaccharides &
Polysaccharides. - General formula for Carbohydrates is Cx(H2Q)y. General formula for monosaccharides
is (CH2O)n. General formula of oligosaccharides is Cx(H2O)y – General formula of
polysaccharides is Cx(H2O)y –. - Monosaccharides: These are generally Trioses, Tetroses, Pentoses. Hexoses &
Heptoses. Examples of trioses are dihydroxy acetone and glyceraldehyde’s. These are
also intermediates in respiration and photosynthesis. Examples of Hexose”, Glucose,
Galactose, Fructose etc. - Oligosaccharides: These have 2 – 10 Monosaccharides. If two Monosaccharides then
it is a Disaccharide. Examples of Disaccharides are: Maltose, Lactose and Sucrose etc. - Polysaccharides: These have more than ten Monosaccharides. Examples are
Cellulose. Starches and Glycogen etc. Most abundant polysaccharide is Cellulose. - Polysaccharides are usually branched.
- Cellulose present in wood, cotton and paper.
- Starches present in cereals and root tubers etc.
- In biology the most important hexose is glucose. Our blood normally contains 10.08 %
glucose. - For the synthesis of 10 g of glucose 717.6 Kcal of solar energy is used.
*Glucose is aldose sugar. Fructose is ketose sugar. Fructose is sweeter as compared to glucose.
Monosaccharide
Types: Glucose, fructose, Galactose
sources: fruits and Vegetable
Function: Provide energy converted to glycogen
for storage
Disaccharide (double/complete sugar)
Types: Sucrose, Maltose, Lactose
sources: Sugar cane,Beat root, Milk
Function: Excess is stored as fat
Polysaccharide
Types: Starch,Cellulose,Glycogen
sources: Rice, Cereal, Bread
Function: Used in synthesis of many complex molecules
Starch
- Starch is compact, insoluble and IS a mixture of two compounds, amylase and
amlyopectin. - Amylose is an un-branched polymer in which glucose monomers are joined by α-1 4-
glycosidic linkages. They are soluble in hot-water. - Amylopectin molecule α-1, 4-glycosidic linkages and α-1, 6-glycosidic linkages. This
allows branching. They arc “Insoluble in hot or cold water.
Glycogen
- In humans, glycogen is the main storage carbohydrate. Its structure is similar to
amylopectin, but it is even more frequently branched. - In humans, glycogen is stored in large amounts in the liver and the muscles. During
prolonged exercise, when the immediate supply of glucose is used up, the body
restores its supplies by breaking down glycogen. - If an average person goes without food, his or her glycogen stores last for about a day.
When glycogen runs out, the body turns to using its lipid store. This is why eating less
while taking more exercise is the quicker way to lose weight. - One of the major changes associated with improving fitness is an increase in the
amount of the enzyme glycogen synthetase in the muscles. This allows glycogen to be
built up faster after it has been used.
Cellulose
- Cellulose is a structural polysaccharide. It gives strength and rigidity to plant cell walls.
- Individual cellulose molecules are long un-branched chains containing many β-1, 4-
glycosidic linkage. The molecules are straight, side by side and are called microfibrils. - Cellulose is probably the most abundant structural chemical on Earth but few animals
can digest it because they do not make the necessary enzyme, cellulose. Herbivorous
animals, whose diet contains large amounts of cellulose, can deal with it because they
have cellulose-producing microorganisms in their digestive system.
Lipids
§ Lipids are heterogeneous group
of compounds that include fats
and oils.
§ As they are non-polar molecules,
most lipids are insoluble in
water but soluble in nonpolar
solvents such as alcohol and
ether. Important exceptions are
phospholipids, which have polar
heads,
§ Lipids contain the elements
carbon, hydrogen, oxygen and sometimes phosphorus and nitrogen.
§ They are intermediate-sized molecules that do not achieve the giant sizes of the
polysaccharides, proteins and nucleic acids.
Lipid Structure And Function
- The triglycerides, which act mainly as energy stores in animals and plants, are a large
important group of lipids. - Triglycerides consist of one molecule of glycerol and three fatty acids.
- The glycerol molecule is common to all triglycerides and so the properties of different
triglycerides depend on the nature of the fatty acids. Monounsaturated fatty acids
possess one C=C bond and polyunsaturated contain more than one.
Phospholipids
- Phospholipids are derivatives of phosphatidic acid. The phosphatidic acid is composed
of glycerol, fatty acids and phosphoric acid. - Phosphatidylcholine is one of the common phospholipids.
- Phospholipids have a similar structure to triglycerides but one of the fatty acids is
replaced by polar phosphoric acid. - This gives the molecule a polar head and a non-polar tail. When placed in water,
phospholipids arrange themselves with their hydrophobic (water-hating) tails pointing
inwards and their hydrophilic (water-loving) heads pointing outwards. This is very
important because it results in double layers called bilayers. Phospholipid bilayers
form the basis of all biological membranes.