Cell - The Unit of Life 09 Class Notes PDF - Yakeen NEET 3.0 2025

# YAKEEN NEET 3.0 2025 ## Botany Lecture: 09 ### Cell: The Unit of Life By: Vipin Sharma Sir ## Topics to be Covered: 1. Nucleus 2. Chromosome 3. Microbodies 4. PUNCHayat ## Nucleus: - Discovered by: Robert Brown in 1831 - Its material is called: Chromatin which can be stained by Basic-dye. -...

# YAKEEN NEET 3.0 2025 ## Botany Lecture: 09 ### Cell: The Unit of Life By: Vipin Sharma Sir ## Topics to be Covered: 1. Nucleus 2. Chromosome 3. Microbodies 4. PUNCHayat ## Nucleus: - Discovered by: Robert Brown in 1831 - Its material is called: Chromatin which can be stained by Basic-dye. - Term given by Flemming. ### Number of Nucleus is various cells: 1. Usually it is ‘one’ per cell 2. It can be Ont: - Matured mammalian RBC - Sieve tube - Tracheid, vessel 3. Nucleus can be Ant: - Phycomycetes Fungus - Paramecium ## Structure of Nucleus - Nucleoplasm - Chromatin - Cell is(not dividing.. at Rest: Interphase) - Extended, DNA - RNA - Protein - Outer nuclear membrane - Inner nucleaн тетьнапе - Intermembrane space/Perinuclear space: 10-50nm - NUCLEOLUS - Membraneless (continuous with nucleoplasm) - Nuclear-porе (zenvelope fused) - rRNA की Factory - If a cell contain bigger & more nucleolus; - rRNA↑ - Ribosome↑ - Protein↑ - Send material from nucleus to cytoplasm & Vice-versa - 2 way transport ## Chromosomes: - Satellite - Chromosomes in which satellite is found are called SAT-Chromosomes - 2°constriction (only in few chromosomes) - centromere (1°constriction) - Kinetochore - Proteinaceous disc like str. that surround centromere - 1st chromatid and chromatid - SISTER CHROMATIDS - Spindle fiber attach to Kinetoc-hore NOT centro-мене - Non-staining region - Small region - Location is also constant= Terminus (end) - It contains repetitive DNA. ## Types of Chromosomes: - Metacentic - Centromere@Center - Both arms equal - V-shape - Sub-Metacentric - Centromene slightly away from centre - L-Shape - Acrocentric - Centromere is Sub-terminal - -Shape - Telocentric - Centromere at end/terminus - I-Shape ## Microbodies: - Small organelle - Unit-membrane one - Body - Peroxisome - Peroxidase - Plasma Enzymes Ant - Peroxide metabolism - In plants - In animals - 2 H2O2 Dangerous - → 2H2O+02 Harmless ## NCERT Maiyaaaa Ki Reading: ### 8.5.10 Nucleus: Nucleus as a cell organelle was first described by Robert Brown as early as 1831. Later the material of the nucleus stained by the basic dyes was given the name Chromatin by Flemming. The interphase nucleus (nucleus of a cell when it is not dividing) has highly extended and elaborate nucleoprotein fibres called chromatin, nuclear matrix and one or more spherical bodies called nucleoli (sing.: nucleolus) (Figure 8.11). Electron microscopy has revealed that the nuclear envelope, which consists of two parallel membranes with a space between (10 to 50 nm) called the perinuclear space. forms a barrier between the materials present inside the nucleus and that of the cytoplasm. The outer membrane usually remains continuous with the endoplasmic reticulum and also bears ribosomes on it. At a number of places the nuclear envelope is interrupted by minute pores, which are formed by the fusion of its two membranes. These nuclear pores are the passages through which movement of RNA and protein molecules takes place in both directions between the nucleus and the cytoplasm. Normally, there is only one nucleus per cell, variations in the number of nuclei are also frequently observed. Can you recollect names of organisms that have more than one nucleus per cell? Some mature cells even lack nucleus, e.g., erythrocytes of many mammals and sieve tube cells of vascular plants. Would you consider these cells as 'living'? The nuclear matrix or the nucleoplasm contains nucleolus and chromatin. The nucleoli are spherical structures present in the nucleoplasm. The content of nucleolus is continuous with the rest of the nucleoplasm as it is not a membrane bound structure. It is a site for active ribosomal RNA synthesis. Larger and more numerous nucleoli are present in cells actively carrying out protein synthesis. You may recall that the interphase nucleus has a loose and indistinct network of nucleoprotein fibres called chromatin. But during different stages of cell division, cells show structured chromosomes in place of the nucleus. Chromatin contains DNA and some basic proteins called histones, some non-histone proteins and also RNA. A single human cell has approximately two metre long thread of DNA distributed among its forty six (twenty three pairs) chromosomes. You will study the details of DNA packaging in the form of a chromosome in class XII. Every chromosome (visible only in dividing cells) essentially has a primary constriction or the centromere on the sides of which disc shaped structures called kinetochores are present (Figure 8.12). Centromere holds two chromatids of a chromosome. Based on the position of the centromere, the chromosomes can be classified into four types (Figure 8.13). The metacentric chromosome has middle centromere forming two equal arms of the chromosome. The sub-metacentric chromosome has centromere slightly away from the middle of the chromosome resulting into one shorter arm and one longer arm. In case of acrocentric chromosome the centromere is situated close to its end forming one extremely short and one very long arm, whereas the telocentric chromosome has a terminal centromere. Sometimes a few chromosomes have non-staining secondary constrictions at a constant location. This gives the appearance of a small fragment called the satellite. ### 8.5.11 Microbodies: Many membrane bound minute vesicles called microbodies that contain various enzymes, are present in both plant and animal cells. ## NCERT PUNCH Objective questions: ### Question 1: Which of the following organelles is directly connected to the outer membrane of the nucleus in a eukaryotic cell? (1) Mitochondrion (3) Golgi apparatus (2) Lysosome (4)Endoplasmic reticulum **Answer: (4) Endoplasmic reticulum** ### Question 2: A chromosome having terminal centromere is called (1) Telocentric (3) Metacentric (2) Acrocentic (4) Sub-metacentric **Answer: (1) Telocentric** ### Question 3: Chromosome having centromere in its middle is: (1) Acrocentric (2) Telocentric (3) Metacentric (4) Sub-metacentric **Answer: (3) Metacentric** ### Question 4: The function of nucleous is the synthesis of: (1) DNA (2) m-RNA (3) r-RNA (4) t-RNA **Answer: (3) r-RNA** ### Question 5: In which type of chromosome, one arm is very long and one arm is very short? (1) Acrocentric (3) Sub-metacentric (2) Metacentric (4) Telocentric **Answer: (1) Acrocentric** ### QUESTION 6: Satellite means: (1) terminal part of the chromosome beyond secondary constriction. (2) terminal part of the chromosome beyond primary constriction. (3) terminal part of chromosome beyond terary constriction. (4) none of these **Answer: (1) terminal part of the chromosome beyond secondary constriction.** ### Question 7: Find out the correct option on the basis of following diagrams. [The picture shows various parts of a chromosome, each labeled with a letter: A, B, C, D. The letters correspond to the following parts of a chromosome: A - Satellite, B - Centromere, C - Short arm, D - Long arm.] **Answer: (2) A - A satellite, B - Centromere, C - Short arm, D - Long arm** ### Question 8: Read the following statements carefully and mark them as true (T) or false (F). A. The content of nucleolus is continuous with the rest of the nucleoplasm. B. In the chromoplast, water soluble carotenoid pigments like carotene and xanthophyll are present. C. Basal body of bacterial flagellum has 9+2 arrangement of microtubules. (1) T, F, F (2) F, T, T (3) T, F, T (4) T, T, F **Answer: (1) T, F, F** # Home Work: - Read NCERT or NOTES for Today’s Topic. - Solve OBJECTIVE NCERT PUNCH TOPIC WISE QUESTIONS. - Exercise-1: 99, 100, 101, 102, 103, 104, 105, 106, 107, 108 - Exercise-2: 27, 29 # Active Recall [Image of a man with a brain holding a dumbbell, suggesting active recall is like strength training for the brain.] # Thank You [Image with a stethoscope on a blue background.] # BOTANY Med Easy - Handwritten Notes of Dr. Vipin Sharma - Updated as per latest NMC NTA Syllabus - Loaded with Row Charts and Mindmaps | Special Mreumonics of Vain Sir - Highlighted Points and Sticky Notes | Visual Memory Based Notes | 100% Errorless - 100% NCERT Based Content for NEET & Board Exams # OBJECTIVE NCERT PUNCH BIOLOGY - MCQs Extracted from NCERT Line by Line - NEET 2024 Solved Paper Included - Rationalised as Per Latest NMC-NEET Syllabus - Updated With New Pattern Questions As Per 2024 NEET Paper - Dr. Vipin Kumar Sharma - Edition 3