Cell Structure & Function : 12th Class Biology Question Answer Lesson 4 – NIOS

Cell Structure & Function : 12th Class Biology Question Answer Lesson 4 – NIOS

INTEXT QUESTIONS 4.1

1. From where do new cells arise ? – Pre-existing cells
   
2. Name the scientists who proposed the ‘cell theory’. – Schleiden and Schwann
   
3. Name an organelle which a plant cell has but an animal cell does not. – Chloroplast / plastid
   
4. Give two points of difference between a prokaryotic cell and a eukaryotic cell
   Ans. Prokaryote – naked nucleus, no membrane bound cell organelles
   Eukaryote – distinct nucleus with a cell membrane, membrane bound cell
   organelles present

INTEXT QUESTIONS 4.2

1. Define diffusion and osmosis.
   Ans. Diffusion : Movement of molecules from region of their higher concentrationto region of their lower concentration.
   Osmosis : Movement of water molecules across a semipermeable membranefrom region of their higher concentration to the region of their lowerconcentration.
   
2. What does active transport mean?
   Ans. Movement of molecules against concentration gradient that is region oflower to higher concentration by expending energy.
   
3. Give one point of difference between phagocytosis and pinocytosis.
   Ans. Intake of solid particles (phagocytosis)
   Intake of fluid droplets (pinocytosis)
   
4. Match the following :
   (i) hydrophilic end (a) cell wall
   (ii) microfibrils (b) inner ends of lipids
   (iii) fluid-mosaic model (c) fluid droplets
   (iv) hydrophobic end (d) outer ends of lipids
   (v) pinocytosis (e) Nicholson and Singer
   Ans. (i) – d (ii) – a (iii) – e (iv)– b (v) – c
   
5. Give two functions of the plant cell wall.
   (i) Protection / shape
   (ii) Provide communication between cells through plasmodesmata

INTEXT QUESTIONS 4.3

1. What is a cell organelle?
   Ans. Membrane bound bodies in the cytoplasm
   
2. Name the chemical which provides energy trapped in its bonds to the cell. – ATP
   
3. Which part of the chloroplasts is the site of light reaction? – Grana
   
4. Name the sac like–structure which form the grana? – Thylakoids
   
5. Why is mitochondrion called the “power house” of the cell?
   Ans. Because energy as ATP is generated and stored in mitochondria
   
6. Which organelle contains enzymes for cellular respiration? – Mitochondria
   
7. State two similarities between mitochondria and chloroplasts.
   Ans. (i) both are semiautonomous of Life
   (ii) both contain DNA or both contain ribosomes
   
8. Which plastid imparts colour to flower petals? – Chromoplasts
   
9. Which plastid is green in colour? – Chloroplast
   
10. Why are mitochondria and chloroplast called semi-autonomous?
    Ans.They have their own DNA for production of more copies of themselves by self duplication but cannot lead independent life, outside the cell / cytoplasm.

INTEXT QUESTIONS 4.4

1. Given below is a list of functions, relate them to their respective organelles :
   (a) synthesis of some enzymes – Golgi Body
   (b) synthesis of steroids – ER
   (c) storage of carbohydrates – amyloplasts
   (d) Intracellular transport – ER
   (e) Synthesis of proteins – Ribosomes
   
2. Name the equivalent structure of Golgi body in plants. Mention two differences between their structures.
   Ans. refer text
   
3. Mention any two advantages of the extensive network of endoplasmic reticulum.
   Ans. (i) internal framework, (ii) transport of cellular substances
   
4. What are the three places where ribosomes occur in a cell?
   Ans. cytoplasm, ER, Nucleolus; chloroplasts, mitochondria
   
5. Name the membrane system that connects the nuclear membrane with the cell membrane?
   Ans. ER

INTEXT QUESTIONS 4.5

1. Why are lysosomes called suicidal bags?
   Ans. Because the lysosome can devour organelles of the same cell
   
2. List the usefulness of intracellular digestion by lysosomes
   Ans. They help in cleaning up the cell by digesting useless matter
   
3. What is the function of peroxisomes in plant cells
   Ans. Fat metabolism

INTEXT QUESTIONS 4.6

1. Why cannot the cell survive without the nucleus?
   Ans. Nucleus controls all the functions of the cell as it has the hereditary information
   
2. Explain the following terms:
   (a) chromatin network – Chromosomes are present as a network when not dividing, that is,at early interphase or Go-stage (Differentiation stage during
   development)
   (b) chromosomes – Bearers of hereditary information as genes on them
   
3. What is the function of the nucleolus in the cell?
   Ans. Site of RNA synthesis

INTEXT QUESTIONS 4.7

1. What is the importance of water in a living cell.
   Ans. (i) It is a universal solvent and most chemical reactions of the cell occurin aqueous medium
   (ii) It is a constituent of protoplasm
   
2. Which is the basic molecule in starch?
   Ans. Glucose
   
3. What is a peptide bond and where will you find it?
   Ans. –NHCO–, between amino acids in a polypeptide, found in proteins
   
4. Which is the most energy rich biomolecule in living organisms?
   Ans. ATP
   
5. What are nucleotides?
   Ans. building blocks of nucleic acids, each containing a pentose sugar,
   nitrogenous base and phosphate

INTEXT QUESTIONS 4.8

1. Explain in one sentence
   (i) Interphase – stage between two successive cell divisions;
   (ii) Synthetic-phase – DNA is synthesised
   (iii) Dividing-phase – Mitosis in somatic cells or meiosis in the germ cells take place
   
2. What is the full form of the following in the cell cycle?
   (i) Gl – First growth phase;
   (ii) S – Synthetic phase
   (iii) G2 – Second Growth phase
   (iv) M-Phase – Mitosis / meiotic phase.

INTEXT QUESTIONS 4.9

1. Name the stage of cell cycle during which chromatin material is duplicated.
   Ans. S-shape of Interphase
   
2. Is the number of chromosomes reduced in the daughter cells during mitosis? yes/no? – No
   
3. Name the stage in nuclear division described by each of the following sentences:
   (i) disappearance of the nuclear membrane – Late Prophase
   (ii) The nuclear membrane and nucleolus reappear – Late Telophase
   (iii) The centromere divides and the chromatids move to opposite poles due to the shortening of spindle fibres – Anaphase
   (iv) The chromosomes arrange themselves at the equatorial plane of the spindle with the spindle fibres attached to the centromeres. – Metaphase

INTEXT QUESTIONS 4.10

1. Name the sub-stage of meiosis-I in which the :
   (i) Homologous chromosomes pair – zygotene (prophase I)
   (ii) Tetrads are formed – Pachytene
   (iii) Homologous chromosomes begin to move away from each other – Diplotene
   
2. Sites of meiosis in flowering plants, are : Microspore / pollen mother cell in anthers and megaspore mother cell in the ovule.
   
3. Rearrange the following stages of meiosis I in their proper sequence :
   zygotene, pachytene, leptotene, metaphase-I diakinesis, anaphase-I, telophase-I.
   Ans. Leptotene, zygotene, pachytene, diplotene, diakinesis, metaphase I,
   telophase I.
   
4. Mention two major points in which meiosis I differs from meiosis II
   Ans. Reduction in chromosome number to half in Meiosis-II; exchange ofgenetic material in meiosis I.

NIOS 12th class biology Q Ans

• Origin and Evolution of Life & Classification : 12th Class Biology Notes – NIOS
• The Kingdoms Monera, Protista & Fungi : 12th Class Biology Notes – NIOS
• Kingdoms Plantae & Animalia : 12th Class Biology Question Answer Lesson 3 – NIOS

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