OBJECTIVES

Multiple Choice Questions MCQs

1. Four options are given at the end of each statement. You should
   encircle one option from them.
2. The number of electrons present in nature are:

(a) 57               (b) 87                           (c) 92                           (d) 97

2. Carbon, hydrogen, oxygen, and nitrogen forms:

(a) 72%           (b) 87%                       (c) 92%                       (d) 97%

3. Which of the following is trace element?

(a) Oxygen (b) Iron                             (c) Hydrogen               (d) Carbon

4. The smallest part of an element that can enter into a chemical reaction is called:

(a) Mass          (b) Atom                      (c) matter                    (d) Compound

5. The amount of matter in an object is called:

(a) Mass          (b) Atom                      (c) matter                    (d) Compound

6. A substance that conducts electricity in solution form is called

(a) Mass          (b) electrolytes            (c) matter                    (d) Compound

7. A substance that releases hydrogen ions (1-1^–) when dissolved in
   water.

(a) Mass          (b) electrolytes            (c) Acid                       (d) Compound

8. Polyhydroxy aldehyde and ketones are:

(a) Proteins (b) Carbohydrates (c) Nucleic acid                    (d) Fats

9. Nitrogen is present in:

(a) Proteins (b) Carbohydrates (c) Nucleic acid                    (d) Fats

1. Which of the followings is a monosaccharides?

(a) Glucose (b) Sucrose                     (b) Lactose                  (d) Maltose

• Which of the followings is a polysaccharide?

(a) Glucose (b) Cellulose                    (b) Lactose                  (d) Maltose

• Chitin is a:

(a) Proteins (b) Carbohydrates (c) Nucleic acid                    (d) Fats

ns:

. (c) 2. (d) 3. (b) 4. (b) 5. (a) 6. (b) 7. (c) 8. (b) 9 (a) 10. (a)11. (b) 2. (b)

Fill in the blanks

Anything that occupies space and has mass is called _________________

The amount of matter in an object is called __________________

The chemical substances that in ordinary chemical reactions cannot break

down into simpler units are called ________________

The different forms with the same atomic number but different atomic

masses are____________

The electrons of an atom are distributed around its nucleus in orbital called

energy level or________________ or clouds of electrons.

A _________________________ is composed of atoms of two or more elements
chemically united in fixed proportions.

The chemical bond formed by the sharing of electrons is called

____________ bond.

The electrostatic force of attraction between electronegative atom and

partially positively charged hydrogen atom is called _______________________
boding.

A substance that conducts electricity in solution form is called _______________________

• An ____________ is a substance that releases hydrogen ions (H^–) when
  dissolved in water.
• The negative log (antilog) of hydrogen ion concentration is called _______________________ .
• • The substance which resists change in pH is called __________________
  • The organic molecules containing only carbon and •hydrogen are called __________________

  The reactive groups of the organic molecules are called

  .     Fats are esters of fatty acids and _____________

  6. A liquid fat is called __________
  7.                      is a chemical messenger.
     Ans:

  1. Matter                    2. Mass                      3. element                  4. isotopes

  5.shells                     6. compound            7. covalent                 8B. hydrogen

  9. electrolytes           10. acid                      11. pH                         12. buffer

13. hydrocarbons 14. functional                 15. glycerol               lb. oil

17. cAMP

Short Questions

1. What are major elements?

Ans: These are six elements. The carbon, hydrogen, oxygen, and nitrogen majority (97%) of an animal’s body weight. The remaining 3% of an animal’s weight consists primarily of calcium, phosphorus, and potassium

2. What are trace elements?

Ans: Elements present in trace amounts include sodium, sulfur, manganese, magnesium, copper, iodine, iron, and chlorine.

3. What are isotopes?

Ans: The different forms with the same atomic number but different atomic masses are isotopes. All atoms of a given element have the same number of pr6tons in the nucleus. But some have different numbers of neutrons. So they have different atomic masses.

4. What are radioisotopes?

Ans: The unstable isotopes are radioisotopes (radioactive isotopes). Oxygen. iron, cobalt, iodine, and phosphorus are examples of elements have radioactive isotopes.

5. What are compounds?

Ans: A compound is composed of atoms of two or more elements chemically united in fixedproportions. For examOle, water has two Hydrogen atoms and one Oxygen atom. This composition does not change.

6. What is nonpolar covalent bond?

Ans: The electrons spend same time orbiting both nuclei in a molecule like H2 Therefore, the distribution of charges is symmetrical. So the bond is called a nonpolar covalent bond.

7. What is polar covalent bond?

Ans: The electrons spend more time orbiting the oxygen nucleus than the hydrogen nuclei in water molecule. Therefore, the electrical charge is asymmetrical. Such bond is called a polar covalent bond.

8. What is hydrogen bonding?

Ans: The electrostatic’ force of attraction between electronegative atom and partially positively charged hydrogen atom is called hydrogen boding.

9. What are cations?

Ans: A positive ion is knoWn as a cation. An atom loses one or more electrons. Thus it becomes positively charged. Now it has more positively charged protons in the nucleus. This positive charge is shown as one or more “plus” signs. Examples of cations are sodium (Na^t), potassium (KS), hydrogen (H⁴).

1. What are anions? Give example.

Ans: A negative ion is known as an anion. An atom gains one or more electrons. Thus it becomes negatively charged. This negative charge is shown as one or more “minus” signs. Some anions are chloride (CI), hydroxyl (OH), bicarbonate (HCO₃).

1. Differentiate between acid and base.

Ans: An acid is a substance that releases hydrogen ions (H) when dissolved in water. A substance that releases hydroxyl ions (OH) when dissolved in water is called base.

2. Why does is it necessary to maintain pH in the body?

Ans: Stable internal environment is maintained in animals. It requires a relatively constant pH of the body fluids. A strong acid or base can destroy cell stability. Similarly sudden charges attract each other and form the ionic bond.

3. What are functional groups? What is . their importance for compounds?

Ans: The reactive groups of the organic molecules are called functional groups. The carbon chain or ring of many organic molecules forms inactive molecular “backbone”. Many reactive groups or atoms are attached with this backbone. The unique chemical properties and behavior of molecules are due to these functional groups.

4. What are carbohydrates?

Ans: Polyhydroxy aldehyde or ketones are called carbohydrate. Carbohydrates are major source of energy for animals.

5. What are lipids?          .

Ans: Lipids are nonpolar organic molecules that are insoluble in polar water but soluble in nonpolar organic solvents like ether, alcohol, and chloroform.

6. What is the importance of phospholipids?

Ans: Phospholipids have double tendency. They are soluble at one end and insoluble at the other end. So they are the major structural components of cell membranes.

7. Give two importance of protein.

Ans: Proteins are structural material. They act as energy sources.

True/ False                   (For Punjab University only)

Marks are True or False statement. Give correct statement if false Statement

1. The electrostatic force of attraction between electronegative atom and

partially positively charged hydrogen atom is called hydrogen boding.

.       Base is a substance that releases hydrogen ions (H)
Lipids are structural material.

The reactive groups of the organic molecules are called functional groups.

5. A negative ion is known as cations.
6. Polyhydroxy aldehyde or ketones are called carbohydrate. Carbohydrates are major source of energy for animals.
7. Lipids are nonpolar organic molecules that are insoluble in polar water.
8. The substance which resists change in pH is called buffer.
9. Fats are esters of fatty acids and glycerol.
10. The different forms with the same atomic number but different atomic masses are isotopes.

Ans:

Statement	T/F	Correct Statement
The electrostatic force of attraction between electronegative atom and partially positively charged hydrogen atom is called hydrogen boding.	T
Base is a substance that releaes hydrogen ions (ft)	F	An acid is a substance that releases hydrogen ions (H–)
Lipids are structural material.	F	Proteins are structural material.
The   reactive    groups    of the     organic molecules are called functional groups.	T
A negative ion is known as cations.	F	A negative ion is known as an anion.
Polyhydroxy aldehyde or ketones are called     carbohydrate.        Carbohydrates are    major     source     of     energy     for animals.	T
Lipids are nonpolar organic molecules that are insoluble in polar water.	T
The substance which resists change in pH is called buffer.             .	T
Fats    are   esters     of   fatty    acids    and glycerol.	T
10.The    different     forms   with    the    same atomic     number     but   different    atomic masses are isotopes.	T

 

 

 

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