December 22, 2014

10th Class Physical Sciences - Imp Questions from Acids and Bases

The students should think creatively and write answers which are quite different from those given in the text book. Keeping this in view the following questions and answers are given.

Q: How do you appreciate the role of Toothpaste in preventing the tooth decay. (1 Mark)

A: 1) Bacteria present in the mouth produce acids by degradation of sugar and food particles remaining in the mouth.
2) Using tooth pastes, which are generally basic neutralize the excess acid and prevent tooth decay.

Q: Why does water kept in a clay pot remain cool? (1 Mark)
A: 1) A clay pot is porus.
2) Water in the pot comes out of the pot through pores and stay on the outer surface of the pot.
3) The necessary heat to evaporate for these water particles is taken from the water inside the pot.
4) The water on the outer surface of the pot thus evaporates cooling the water inside the pot.

Q: Name the mirror used in car headlights? How is it arranged in the car headlight? (1 Mark)

A: 1) A concave mirror is used in car headlights.
2) When a source of light is placed at the principal focus of a concave mirror, it produces a strong parallel beam of light.
3) Thus concave mirror is used as a reflector in car (automobile) headlights.

Q: Sri Lakshmi inserted two nails in a beaker which are connected to two wires with A.C. small bulb. She has taken different solutions like Sodium hydroxide, Potassium hydroxide, Alcohol, Glucose, Hydrochloric acid and Sulphuric acid in the beaker one after another. Answer the following questions: a) Which solutions can make the bulb glow? Why? b) Categorize these as acids, bases and neutral? c) Mention what is common in acids and bases? (4 Marks)

A: a) 1) Hydrochloric acid, Sulphuric acid, Sodium hydroxide and Potassium hydroxide solutions can make the bulb glow.
2) These solutions have ions and the moment of these ions in solution helps for flow of electricity through the solution.
b) 1) Hydrochloric acid, Sulphuric acid are acids.
2) Sodium hydroxide, Potassium hydroxide are bases.
3) Glucose and alcohol are neutral substances.
c) 1) Acids produce H+ ions in solutions
2) Bases produce OH− ions in solutions.

Jr Inter Botany SAQ Important Questions - Cells

Q: Which division is necessary to maintain constant chromosome number in all body cells of φ multicellular organisms and why?
A: Mitotic cell division is necessary to maintain the chromosome number in all the cells of an organism. The mother cell in mitotic cell division produces 2 daughter cells which are equal to their mother cell both in quantity and quality of chromosomes.

Every sexually reproducing diploid organism starts its life with a single cell called Zygote. It under goes numerous mitotic divisions and forms an organism which consists the same chromosome number in all its cells.

The spore also produces a gametophyte by mitotic divisions due to which multicellular the chromosome number is maintained constant in all the cells.

Q: Though redundantly described as a resting phase, interphase does not really involve rest. Comment.

A: Interphase represents the phase between two successive M phases. Interphase lasts more than 95% of duration of cycle. Thus it is the largest stage. It is a preparatory stage or resting phase. It is also called phase of non-apparent division. Though it is called resting phase, it is actually the most active phase as it involves the following activities.

It has 3 phases.
1) G1 (G = Gap): Cytokinesis is followed by G1
The cell is active and shows normal metabolism. Organelle duplication occurs. The amount of DNA in the cell is 2C.

2) S (S = Synthesis):
It is between G1 and G2. It is the largest phase of Interphase. DNA synthesis (replication) occurs in the nucleus 2C DNA becomes 4C. But there is no increase in chromosome number. Parallel to this in animal cells centriole duplicales in cytoplasm.
3) G2 (G = Gap)
Cytoplasm increases. The amount of DNA is 4C. Protein synthesis, ATP synthesis occurs. The cells are ready to participate in Prophase.

Junior Inter Botany - Cells - Important Questions for AP and Telangana Students

Q: Explain Prophase I of Meiosis.
A: It is more complex and divided into 5 phases based on chromosomal behaviour.

1) Leptotene: Chromosomes appear like long, thread like structures (say for example Maize microspore mother cells 2n = 20).

2) Zygotene: Homologous Chromosomes pair with each other under the influence of a protein called synaptinemal complex.
Pairing is called synapsis. Each pair thus formed is called bivalent (Maize: 10 bivalents).

3) Pachylenes: Each chromosome has 2 chromatids. Thus a bivalent is now called tetrad of chromatids (Maize 10 tetrads). Exchange of genetic material occurs between non sister chromatids of homologous chromosomes.
It is enzyme (Recombinase) mediated process. Chiasmata (X-Shape) are formed at the place of recombination nodule (Where non-sister chromatids meet).
Quality of the chromosomes changes. Recombinants are formed.

4) Diplotene: Synaptonemal complex dissolves. Chromosomes of the bivalents repel or separate except in the region of X-ma. It lasts long time in oocytes of vertebrates.

5) Diakinesis: Chromosomes become more distinct. Chiasmata show terminalisation. Nuclear membrane and necleolus dissolve. Spindle apparatus begins to form.

Q: Mention the key features of Meiosis.
A: Meiosis, a reductional cell division occurs in diploid cells (Concerned with reproduction) only.
Ex: Zygote in Algae and Fungi; Spore mother cells (of anther and ovule in angiosperms.) In higher plants the meiocyte (2n) divides by Meiosis to form 4 haploid of cells (n), which in turn produce gametes by mitosis. It is divided into 2 parts.
Meiosis I (Hetero type division): Meiocyte divides into 2 haploid daughter cells.
Quality of chromosomes changes in Pachentene of Prophase I due to crossing over. Recombinants are formed.
Quantity of chromosomes is reduced to half in Anaphase I where centromeres separate and disjunction of homologous chromosomes occurs.
Inter Kinesis: 2 daughter cells (n) enter into short Interphase where S-stage is absent.
Meiosis II (Homotype division): The 2 daughter cells (n) participate in it. Each one produces 2 daughter cells similar to their immediate mother cell.

Key features:
1. Number of chromosomes is reduced to half.
2. Recombinants are formed due to crossing over in Pachytene. It helps in evolution.
3. It is essential to keep the chromosome number constant for any number of generations.