Cell the basic unit of all living organisms; it is surrounded by a cell surface membrane (also known as the plasma membrane) and contains cytoplasm and organelles.
Short Q/A:
1. What is a cell?
Ans: Cell the basic unit of all living organisms; it is surrounded by a cell surface membrane (also known as the plasma membrane) and contains cytoplasm and organelles.
2. What are the functions of plastids?
Ans: the main functions of a plastid are to produce and store food, and cause the appealing and colourful appearance of flowers, fruits and leaves of a plant. Flowers with appealing colours helps pollinate plant.
3. What is the relation between tissue and organ?
Ans: Cells that do the same job group together to form tissues. Different tissues combine to make organs.
4. What is the importance of endocrine glands?
Ans: There are a few ductless or endocrine glands within the bodies of animals. These produce hormones and have no ducts for transportation. Blood carries the hormones from one place to another. The endocrine system is made up of endocrine glands such as Pituitary, Thyroid, Parathyroid, Islets of Langerhans of Pancreas, Suprarenal etc.
5. Which part of cell is called the 'Power house ' of the cell?
Ans: The main function of mitochondria is to help the organism in cellular respiration. Maximum energy is produced in Kreb's cycle. This is why a mitochondrion is called 'the power house' of a cell.
6. What are the functions of blood?
Ans: The function of blood are- a) Haemoglobin easily mixes with oxygen to form the oxyhaemoglobin compound, which carries oxygen to the different parts of the body. b) Leucocytes destroy harmful microorganisms and protects the body against diseases. c) There are various kinds of white blood cells in the human body Thrombocytes take part in blood coagulation or blood clotting.
Easy type Questions:
1. Describe the structure of a mitochondrion with a labeled diagram.
Ans: Mitochondria are surrounded by a double -layered membrane which is composed of phospholipid and protein. The inner membrane has enfoldings called cristae. These folding are studded with small round bodies known as oxysomes. The oxysomes contain enzymes. The space enclosed by the inner membrane is the matrix.
2. Compare the structures and functions of different types of simple tissue.
Ans: The tissue which contains cells of the same shape, size and structure, is called simple tissue. On the basis of the nature of cell, simple tissues are divided into three types:
I) Parenchyma: Parenchyma cells are seen in almost every part of a plant. Cells of this type are living, isodiametric, thin walled and turgid with protoplasm.
Function: The main functions of parenchyma cells are to organise the body or body parts of plants to produce, transport and stone food.
Collenchyma: Collenchyma tissues are a special type of cell. The walls of the cells become thick with the compilation of cellulose and pectin. These walls are irregularly thickened with thicker corners.
Function: Their main functions are to produce food and provide the plant with mechanical support and rigidity.
Sclerenchyma:
Tissue composed of cells with the thickening of walls with lignin for providing mechanical support is called sclerenchyma. While in early stage of their development, sclerenchyma cells are alive, losing the living protoplasm when they become mature.
Function: The main functions of sclerenchyma tissue are to provide mechanical support and rigidity and to conduct water and minerals.
3. Discuss the structures and functions of animal tissue.
Ans:
On the basis of nature and number of cells, and the presence or absence of the intercellular materials or matrix secreted by cells, tissue is divided into four main categories.
i) Epithelial Tissue:
The cells of the epithelial tissue lie closely or side by side on a base membrane. The function of this tissue is not only to provide cover to the organs.
ii) Connective Tissue:
Connective tissue has more matrix compared to the number of cells is comparatively less.
iii) Muscular Tissue:
Growing from the mesoderm of the embryo, the particular type of tissue capable of contracting and expanding to affect movement and tissue forming the muscles of vertebrate animals is called Muscular tissue.
iv) Nerve tissue:
The particular type of tissue which forms the nervous system is called nervous tissue. It consists of numerous neurons.
Nerve tissue receives stimulus and transmits it to the brain, and the brain responds to it. In higher animals, nerve tissue store memory and controls the work of the different organs of the body and coordination among them.
Multiple choice questions:
1. Which is the function of lysosome?
a) to produce food b) to produce energy c) to engulf microorganisms d) to synthesize protein
2. Amobea is an animal cell, because it has-
i) well formed nucleus ii) pigments iii) cell membrane Which one is correct? a) i & ii b) i & iii c) ii & iii d) i , ii & iii Read the following stem and answer the questions 3 and 4. On the way to his village house, Ruhit saw a man extracting fibers from a jute plant.
3. What kind of tissue is being collected?
a) Parenchyma b) Collenchyma c) Chlorenchyma d) Sclerenchyma
4. The characteristics of the tissue mentioned are
I) cell wall is lignified ii) cell wall is irregualerly thickened iii) protoplasm is absent in the cell Which one of the following answers is correct? a) i & ii b) ii & iii c) i & iii d) i, ii & iii
Creative Questions:
1. a) What is plasmalemma?
Ans: The double layered membrane around the protoplasm of a cell is called cell membrane or plasmalemma.
b) Why are plastids called colour forming organs?
Ans:
The colour organelles present within the cytoplasm of plant cells are known as plastids. They are responsible for the formation of colour of any plant part like leaves, flower and fruits. In absence of light plastids become colourless. The colourless plastids are known as leucoplasts generally present in the cell of root and context where light is not available. In presence of light, colourless plastids may develop colour. So the plastids are known as the colour forming organelles.
c) Why is the organelle marked with N important for the living world?
Ans:
The N marked organelles in the diagram of the stem is the chloroplast or green plastid. Plants trap light energy coming from the sun by the chloroplast to manufacture carbohydrate food by combining water absorbed by the roots and CO2 absorbed from the air. In this process O2 is evolved as a by product. The carbohydrate produced in the process of photosynthesis act as intermediate substance of various substance constituting the living body. It also acts as the source of energy required by the living cells to their metabolic activities and also existence. O2 produced in this process is utilized by living organisms for their respiration. Thus the organ maintains continuous supply of O2 to the living world and establishes balance of O2 and C)2 in the environment.
d) What types of problem will appear in living bodies if the part marked M is absent?
Ans:
The M- marked part of the diagram in the stem is the centriole. Centrosome is generally present in animal cells though some plants of lower group may have centrosome. The two centriole present in the centrosome move to two opposite poles during cell division and asternays develop from the cenrioles from the srindle apparatus. aster rays help to pull the two chromatids of a chromosome to opposite poles during mitosis and help cell division. If active centrosome is absent, animals can not divide. So in absence of the organ, number of cells will not increase and growth and development of organism will be stopped.
2. a) What is muscle tissue?
Ans:
The tissue having the capacity of contraction and expansion is known as muscle tissue. It originates from the mesoderm of the embryo and regulates the movement of the organs and the organism. The cells of muscle tissue are elongated and myofibrils are present in them. Matrix generally remains absent in this tissue.
b) How does skeletal tissue protects the brain?
Ans:
Skeletal tissue constitutes the structural framework of animal body, holds the muscles and protects the internal organs from injury. Brian is the most sensitive and important part of the body of vertebrate animals. So its protection demands highest importance. There is a cover made up of hard bones around the brain known as skull. In the vicinity of the skull brain remain situated and its safety is maintained and protected from external injury.
c) Explain the cause of the location of part marked Q?
Ans: The Q marked part of the diagram in the stem is the companion cell. It remains attached to the sieve tube of phloem through which food manufactured in gree seive tube and the companion cells originate from the same mother cell by unequal division. The larger cell attached to it develop into the companion cell. Paranchyma cells generally store excess food from the sieve tube and supply them when a shortage of food in seive tube takes place.
d) Between Figure A and B, which one plays an important role in physiological activities besides conduction? Explain your answer with logic.
Ans: The A-marked part of the stem is the phloem of the plant which conducts food from the leaves to the different parts of the plant body and figure -B indicates the different types of blood cells of the mammals which also carry digested food particles and other things like hormones, vitamins to the cell and excretory materials from the cell to the excretory organs. Except transportation of materials blood also performs some other functions such as blood plasma participates in maintaining the ionic balance of the body and produces antibodies which give body resistance against disease and prevents bleeding from the wounded part. Blood also maintains the body temperature constant. Phloem of plant body performs some special functions like protection of the body and healing the wounds and giving strength to the plant organs.
