Chemical basis of life.
The bodies of all organisms are composed of a variety of chemical compounds. These are formed by the bonding of naturally existing elements in different ways. There are 25 elements found in the living body out of 92 elements found in nature. Out of those elements, the most common four elements are C, H, O, and N. Other essential elements are S, P, Na, K, Ca, Mg, Fe, and Cl.
The percentages of
O- 65%,
C – 18% ,
H – 10%.
C, H, O, N S, P, Na, K, Ca, Mg, are known as macro elements. (Need in relatively large amount)
Cl, Fe, and I are microelements. (Need in small amount)
Q.1. Write the most common four elements found in living bodies.
Carbon (C), Hydrogen (H), Oxygen (O), and Nitrogen (N)
2. What are the other essential elements of living bodies?
Sulphur (S), Phosphorous (P), Sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe) and chlorine.
3. What are the micro elements of living bodies?
Chlorine (Cl), Iron (Fe), Iodine (I)
4. What is the ascending order of percentages of four elements found in living bodies?
N, H, C, O
Chemical compounds found in living bodies can be divided into two groups as organic and inorganic according to the presence or absence of carbon in them. Compounds with carbon are known as organic compounds. (But some inorganic compounds like carbonic acid and salts of it, carbon disulphides are also contained carbon)
Compounds without carbon are known as inorganic compounds.
Organic compounds which build up the living bodies are known as biological molecules.
· Main four biological molecules are namely,
carbohydrates, Proteins, Lipids, and Nucleic acids.
Q 5. (a) What are the biological molecules found in living organisms?
Carbohydrates, Proteins, Lipids, and Nucleic acids.
(b) Name the elements found in them.
Carbohydrates – C, H, O
Proteins- C, H, O, N
Lipids- C, H, O
Nucleic acids- C, H, O, N, S, P
(c) Among the elements you have written above, which elements are most common?
C, H, O, N,
6. (a) Name the two types of chemical compounds found in living beings?
Organic compounds and inorganic compounds
(b)What is the main difference between organic compounds and inorganic compounds?
All the organic compounds contain C atoms in their structure. Most of the inorganic compounds do not have Carbon atoms in their structure. But some inorganic compounds like carbonates and carbon dioxide (CO2) contain carbon. Some carbonates. e.g K2 CO3, CaCO3 Na2CO3
(c) Categorize the following compounds into the above two groups.
Sucrose, water, protein, glucose, mineral salts, lipids, starch
Organic compounds: protein, glucose, Sucrose, lipids, starch
Inorganic compounds: mineral salts( NaCl, KCl, K2 CO3, CaCO3,
mineral acids: H2SO4 , HCl, water
Carbohydrates
The most abundant organic compound in the earth Glucose, one of the carbohydrates produced in the photosynthesis of green plants. This is converted into other types of carbohydrates. Excess carbohydrates will be stored as starch in plants and as glycogen in animals. The main elements present in carbohydrates are C, H, and O. The ratio of H: O = 2:1 The common molecular formula of carbohydrates is C x ( H2O)y
If x=6 and y= 6 the formula will be. C 6 H 12 O6 ie glucose
Carbohydrates can be categorized into three groups according to their complexity monosaccharides, disaccharides, and polysaccharides.
Monosaccharides are with only one monomer so these are the most simple sugars.
Disaccharides are with only two monomers.
Polysaccharides are with many monomers
7. (a) What is the most abundant organic compound on the earth?
Carbohydrates
(b) Green plants produce a form of this compound (glucose) by photosynthesis
(c) What happens to the excess food produced by green plants?
Store in various plant parts like roots, stems, and fruits
8. Fill the blanks in the given table showing the plant parts with stored carbohydrates
Name of the plant | Part of the plant |
Cane sugar | Stem |
Carrot, beet root | Root |
Wheat, Paddy | seeds |
Bread fruits, Ash plantains |
| Fruits |
9. There are 3 types of carbohydrates as monosaccharides, disaccharides and polysaccharides. Where do you find these three types of monosaccharides in nature?
Type of monosaccharide | Location of it |
Glucose | Ripen fruits, Bees' honey |
Fructose | Ripen fruits, Bees'honey |
Galactose | Dairy products, |
Disaccharides
Two monosaccharides join to form a disaccharide.
· During this process a water molecule is released.
· Two glucose molecules bonded together by releasing one water molecule.
· Chemical equation is as follows,
· 2 C6H12O6 à C12H22O6 + H 2O
· Maltose, sucrose, lactose are examples of disaccharides.
· Two glucose molecules bonded together and form maltose and water.
· Maltose is an intermediate product of starch digestion.
· Glucose molecule and Fructose molecule bonded together and form sucrose molecule and water.
· Galactose and glucose molecules bonded together and form lactose and water.
· Lactose is not found in plants.
· Not sweet as sucrose.
· Cow’s milk contains 4%- 6% of lactose.
· Human milk contains 6% - 7% of lactose
10. Write the location of Maltose, Sucrose, and Lactose.
Disaccharide Location
Maltose germinating seeds Sucrose sugar cane Lactose dairy products
11. What is the function of salivary amylase?
Digesting starch into maltose
12. Glucose is given to the athletes when they are participating in running events. But they are not given sugar or sucrose. What is the reason?
Glucose is directly absorbed into the bloodstream without digesting. B sucrose has to be digested before absorbing into the blood.
Glucose is a monosaccharide, so, a simple, water-soluble, and small molecule when compared to sucrose, which is a disaccharide.
13. What is the only sugar which is absent in plants?
Lactose
14. Sucrose is obtained by the stem of sugar cane. Name other roots used for sugar production.
Beetroot.
15. What is the main function of Glucose in our bodies?
Glucose is the main energy source. It acts as a substrate for respiration. Glucose is broken down into carbon dioxide and water (gaseous)in the presence of oxygen in cellular respiration and energy is released, which is needed for us to use in our day-to-day life.
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