Q. Why is the cell known the 'fundamental and structural unit of life '
Ans:
ell is called as the structural and functional unit of the living
organism because it the smallest living entity that is capable of an
independent existence. Separated cell organelles cannot be said to be
living and are not capable of independent existence. Q,
what is a semi permeable membrane? what are the differences between
semi permeable membrane and selectively permeable membrane? Ans:
a semi permeable membrane is a membrane that allows only the entry of
substances that are helpful for the body. a semi permeable membrane is
also called a selectively permeable membrane. Q. Which cell in the human body does not have the mitochondria? Ans: Mature erythrocytes don't have mitochondria Q.What are plastids? Write their functions? Plastids are double membrane organelles which are found in plant cells only. Functions: 1. By trapping solar energy, green plastids manufacture food through photosynthesis 2. Chloroplasts provide colored to various flowering parts. 3. Leucoplasts help in storage of protein, starch and oil Q. which structure of animal cells forms the asters of spindle ? Ans: Centrioles. Q. Name two semi- autonomous organelles? Ans: Chloroplast and mitochondria Q. Which cell organelle is rich in acid hydrolases? Ans: Lysomes are loaded with acid hydrolases Q. Which cell organelles are called ribonucleoprotine particle? Ans: Ribosome. Q. Differentiate between SER and RER Ans:
Rough endoplasmic reticulum[RER] has ribosomes attached to it giving a
rough appearance thereby deriving its name. RER- involved in protein
synthesis as ribosomes are concerned with protein synthesis. Smooth
endoplasmic reticulum [SER] is devoid of ribosomes. SER-concerned
with lipid synthesis in intestinal cells and with steroid formation in
adrenals Q. what is the difference between eukaryotes and prokaryotes? Ans:
| Prokaryotes | Eukaryotes |
| They are mainly unicellular | They are mainly multicellular except for protista |
| They have only a few organelles | Many organelles |
| DNA is circular | DNA is linear |
| DNA lies in the cytoplasm (Nucleus absent) | DNA is inside the nucleus |
| Cell division occurs mostly through binary fission | Mitosis, meiosis or both take place. |
Q .What is the difference between osmosis and diffusion. Ans:
| Osmosis | Diffusion |
| It is the movement of water. | It is the movement of solute particle. |
| Membrane is required | Membrane is not required. |
| Movement from low concentration to high concentration of solute. | Movement from high concentration to low concentration of solute. |
| It is associated with liquids. | It is associated with both liquid and gases |
Q. Differentiate Between : Plant cell and animal cell Ans: Plant cell a) have chloroplasts and use photosynthesis to produce food. b) have cell wall made of cellulose. c) A plant cell has plasmodesmata - microscopic channels which traverse the cell walls of the cells. d) one very large vacuole in the center. e) are rectangular in shape. Animal cell a) don 't have chloroplast. b) no cell wall (only cell membrane). c) No plasmodesmata. d) one small vacuole. e) either circular, irregular or defined shapes depending on the type of cell. Q. Where are peroxisomes found ? Ans:
Peroxisomes are small, living, membrane bound, sac like cell organelle
found in photosynthetically active cells of plants, liver and kidneys.
These are meant for removing toxic substances from the cell by oxidative
reactions. These are also involved in photorespiration in plants. Q. what are the chemical reactions take place in cytoplasm, nucleoplasm, and in mitochondria? Ans: 1. Cytoplasm- Reactions of glycolysis. 2. Mitochondria- Reactions of Kreb's cycle. 3. Nucleoplasm- Reactions involving formation of RNA. Q. what is Diffusion? Ans:
Diffusion is a spontaneous movement in which a substance moves from its
region of higher concentration to the region of lower concentration.
For example, in the case of a perfume, it moves from the region of
higher concentration to lower concentration. So, it is a type of
diffusion. Q . What is dictyosomes ? Ans:
Dictyosomes are membranous or vesicular structures making up the Golgi
apparatus. They together with golgi vesicles form the golgi apparatus .
(b)
Movement of water molecules from their higher concentration to their
lower concentration through a semi- permeable membrane is called
Osmosis.
(c) The functional components of cell are plasma membrane, cytoplasm & nucleus.
(d) Protoplasm has two parts- cytoplasm & nucleoplasm.
(e) Nucleus, mitochondria & plastids have their own DNA & ribosomes.
(f) The shrinkage or contraction of the contents of the cell away from the cell wall is known as plasmolysis.
(g) The process by which Amoeba can engulf a food particle is endocytosis.
(h) Biogenesis is the manufacture of lipids required for making cell membrane.
(i) A cell that lacks nuclear membrane is called a prokaryotic cell & the nuclear region is called nucleoid.
(j) Movement of materials in & out of the cell takes place by diffusion & osmosis.
2. What is the advantage of multicellularity over unicellularity?
Ans- Division of labour.
3. What are the chromosomes made up of?
Ans- DNA & proteins
4. A cell placed in a solution swells up. What kind of solution is it? Why does it happen?
Ans- It is a hypotonic sol ution & water enters the cell by endosmosis causing the cell to swell up.
5. Why are lysosomes known as "suicidal bags”?
Ans- They secrete powerful digestive enzymes to digest the worn out and damaged cell
organelles as well as the cell itself when it loses its functional ability.
6.Why is the nucleus so significant in a cell?
Ans- Nucleus has the following important functions-
(i) It controls all cell activities
(ii) It contains hereditary material that transmits hereditary information from one
generation to the next(iii) It helps in cell division7. Differentiate between plant and animal cells. 1.PLANT CELL 1- Surrounded by two membranes- cell wall & cell membrane.2- Possess three types of plastids chloroplasts, chromoplasts, leucoplasts.
3- Do not possess lysosomes.
4- Nucleus is towards the periphery.
5- Centrioles are absent
ANIMAL CELL
1- Surrounded only by cell / plasma membrane.2-Do not possess plastids.3-Possess lysosomes4-Nucleus is in the center .. 5-Centrioles present & help in cell division.8. Give the major functions of the following cell organelles-(a)
Endoplasmic reticulum RER-- Synthesis of proteins as it has ribosomes
attached to itSER- Synthesis of lipids required for making cell membrane(b) Golgi apparatus-----------Storage & packaging of various products.(c) Mitochondria------Production of ATP(Adenosine Triphosphate) which is a source of energy.(d) Ribosomes ---Protein synthesis(e) Golgi ApparatusStorage & packaging of various products.(f) LysosomesDigestion of worn out & damaged organelles
| 
