Cell Structure & Function : 12th Class Biology Question Answer Lesson 4 – NIOS
INTEXT QUESTIONS 4.1
- From where do new cells arise ? – Pre-existing cells
- Name the scientists who proposed the ‘cell theory’. – Schleiden and Schwann
- Name an organelle which a plant cell has but an animal cell does not. – Chloroplast / plastid
- 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
INTEXT QUESTIONS 4.2
- 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.
- What does active transport mean?
Ans. Movement of molecules against concentration gradient that is region oflower to higher concentration by expending energy.
- Give one point of difference between phagocytosis and pinocytosis.
Ans. Intake of solid particles (phagocytosis)
Intake of fluid droplets (pinocytosis)
- 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
- Give two functions of the plant cell wall.
(i) Protection / shape
(ii) Provide communication between cells through plasmodesmata
INTEXT QUESTIONS 4.3
- What is a cell organelle?
Ans. Membrane bound bodies in the cytoplasm
- Name the chemical which provides energy trapped in its bonds to the cell. – ATP
- Which part of the chloroplasts is the site of light reaction? – Grana
- Name the sac like–structure which form the grana? – Thylakoids
- Why is mitochondrion called the “power house” of the cell?
Ans. Because energy as ATP is generated and stored in mitochondria
- Which organelle contains enzymes for cellular respiration? – Mitochondria
- State two similarities between mitochondria and chloroplasts.
Ans. (i) both are semiautonomous of Life
(ii) both contain DNA or both contain ribosomes
- Which plastid imparts colour to flower petals? – Chromoplasts
- Which plastid is green in colour? – Chloroplast
- 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
- 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
- Name the equivalent structure of Golgi body in plants. Mention two differences between their structures.
Ans. refer text
- Mention any two advantages of the extensive network of endoplasmic reticulum.
Ans. (i) internal framework, (ii) transport of cellular substances
- What are the three places where ribosomes occur in a cell?
Ans. cytoplasm, ER, Nucleolus; chloroplasts, mitochondria
- Name the membrane system that connects the nuclear membrane with the cell membrane?
INTEXT QUESTIONS 4.5
- Why are lysosomes called suicidal bags?
Ans. Because the lysosome can devour organelles of the same cell
- List the usefulness of intracellular digestion by lysosomes
Ans. They help in cleaning up the cell by digesting useless matter
- What is the function of peroxisomes in plant cells
Ans. Fat metabolism
INTEXT QUESTIONS 4.6
- Why cannot the cell survive without the nucleus?
Ans. Nucleus controls all the functions of the cell as it has the hereditary information
- 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
(b) chromosomes – Bearers of hereditary information as genes on them
- What is the function of the nucleolus in the cell?
Ans. Site of RNA synthesis
INTEXT QUESTIONS 4.7
- 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
- Which is the basic molecule in starch?
- What is a peptide bond and where will you find it?
Ans. –NHCO–, between amino acids in a polypeptide, found in proteins
- Which is the most energy rich biomolecule in living organisms?
- What are nucleotides?
Ans. building blocks of nucleic acids, each containing a pentose sugar,
nitrogenous base and phosphate
INTEXT QUESTIONS 4.8
- 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
- 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
- Name the stage of cell cycle during which chromatin material is duplicated.
Ans. S-shape of Interphase
- Is the number of chromosomes reduced in the daughter cells during mitosis? yes/no? – No
- 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
- 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
- Sites of meiosis in flowering plants, are : Microspore / pollen mother cell in anthers and megaspore mother cell in the ovule.
- 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,
- 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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