1. What is the structural and functional unit of living organisms?
Cell is the structural and functional unit of living organisms.
2. What are the important postulates of cell theory? Who proposed?
The two important postulates of cell theory are
(i) All living organisms are made up of cells.
(2) New cells are formed only from pre- existing cells.
Theodor Schwann and Matthias Jacob Schleiden proposed the cell theory in 1839.
3. What is the shape and function of nerve cells?
Nerve cells are star shaped, and conduction of nerve impulses is its function.
4. What is the shape and function of Squamose epithelium?
Squamose epithelium is polygonal in shape. Protection and to give shape is the function of squamose epithelium.
5. What are endoplasmic reticulum?
Network of membranous system with vacuoles in the endoplasm is called endoplasmic reticulum.
6. What are the two types of endoplasmic reticulum?
They are rough ER and smooth ER. Rough ER is, with ribosomes on the surface and smooth ER is without ribosomes on the surface.
7. What are the functions of endoplasmic reticulum?
The functions of ER are,
a. Provide an ultra structural and skeletal frame work to the cell.
b. Smooth ER helps in the synthesis of lipids and rough ER helps in the synthesis of proteins.
c. During cell division, the endoplasmic reticulum membrane disappears and form new nuclear envelope after each nuclear division.
8. What are ribosomes? Where is it produced?
Small spherical structures attached with the membranes of endoplasmic reticulum or freely in the cytoplasm ribosomes. Ribosomes are produced in the nucleous.
9. What is the structure of ribosomes?
Ribosome is composed of two structural units, one smaller and the other a larger unit. The small sub-units occur on the larger unit and form a cup like structure.
10. What is the function of ribosomes?
Ribosomes are the sites of protein synthesis.
11. What are the components of Golgi apparatus?
It consists of three components, namely
i. Disc shaped group of flattened sacs or cisternae
ii. Small vesicles
iii. Large vacuoles
12. What are the functions of Golgi apparatus?
a. It produces secretory vesicles like zymogen granules that have enzymes inside.
b. It forms yolk substances in the developing oocytes.
c. It helps in the retinal pigment formation
d. It helps in the formation of acrosomes in sperm cells.
13. What are lysosomes?
Lysosomes are rounded structure in the cell originate either from Golgi apparatus or endoplasmic reticulum and is filled with dense material.
14. What are the functions of lysosomes?
a. Lysosomes help to keep the cell clean by digesting any foreign material as well as worn-out cell organelles.
b. When the cell gets damaged, lysosomes may burst and the enzymes digest their own cells.
15. Name the organelle called ‘Suicidal bags’ of a cell. Given reason.
Lysosomes are referred as ‘Suicidal bags’ of the cell. It is because when the cell gets damaged lysosomes may burst and enzymes digest their own cell.
16. What is the structure of mitochondria?
Mitochondria are double membranous structure, outer membrane and inner membrane. The outer membrane forms a bag like structure around the inner membrane and inner membrane produces finger like folds on the lumen of mitochondria. These folds are called cristae.
17. Which organelle referred as ‘power house of the cell? Why?
Mitochondria are considered to be the power house of the cell’ because they are the seat of cellular respiration. They also synthesise the energy rich compound ATP (Adenosine tri phosphate).
18. What are centrioles? What is its function?
Centrioles are microtubular structures found in rod shaped or as granules, located near the nucleus of the animal cell. During cell division centrioles produce spindle fibres and astral bodies.
19. Describe the structure of nucleus?
Nucleus consists of four parts.
1. Nuclear membrane: Outer covering of the nucleus. It contains pores for the transport of materials.
2. Nucleoplasm. Protoplasmic substance of the nucleus. It is also called nuclear sap.
3. Chromation reticulum: Network of elongated chromatin threads, overlap one another and are embedded in the nucleoplasm.
4. Nucleolus: Spherical structure present inside the nucleus. It is often called as cell organizer.
20. What are the functions of nucleus?
a. It controls all metabolic and hereditary processes of the cell.
b. Nuclear membrane allows exchange of ions between the nucleoplasm and the cytoplasm.
21. How are animal tissues classified?
Based on function animal tissues are classified into five categories. They are
a. Epithelial tissues
b. Vascular tissues
c. Connectives tissues
d. Nerve tissues
e. Muscular tissues.
22.What are epithelial tissues?
Epithelial tissues cover organs and cavities within the body. The absence of intercellular spaces is characteristic of epithelial tissues. These are attached to the basement membrane, that separates it from other tissues.
23. What are different types of epithelial tissues?
The seven types of epithelial tissues are (a) squamose epithelia (b) columnar epithelia c. cuboidal d. ciliated e. sensory f. glandular g. Germinal epithelia.