Cell Biology and BiotechnologyClass 10 Science Part 2 Chapter 8 Notes – Maharashtra Board

Summary: Cell Biology and Biotechnology

Cell biology studies the structure and function of cells—the basic units of life. All living organisms consist of one or more cells. The cell theory states: all living things are made of cells; cells are the basic unit of life; all cells come from pre-existing cells. Prokaryotic cells (bacteria, archaea) lack a nucleus; eukaryotic cells (animals, plants, fungi) have a membrane-bound nucleus and organelles. Cell division occurs via mitosis (asexual reproduction, two identical daughter cells) or meiosis (sexual reproduction, four haploid cells). Understanding cells is fundamental to biotechnology applications.

Biotechnology uses living cells and organisms to develop products and solve problems. Fermentation (using bacteria/yeast) produces antibiotics, insulin, biofuels. Genetic engineering modifies organisms by adding foreign genes. Recombinant DNA technology cuts DNA from different species and joins them, creating new organisms with novel traits. CRISPR-Cas9 is a precise gene-editing tool. Applications include creating disease-resistant crops, producing human proteins (insulin) in bacteria, and developing cancer treatments. Stem cell research offers potential for regenerating damaged tissues.

Biotechnology has transformed medicine and agriculture. Insulin produced by genetically engineered bacteria eliminates animal-derived insulin. Gene therapy treats genetic diseases by replacing defective genes. Monoclonal antibodies target cancer cells specifically. However, ethical concerns include genetic privacy, equitable access to biotechnology, and long-term ecological impacts of genetically modified organisms. Balancing innovation with safety and ethics is crucial for responsible biotechnology development.

Key points to remember

• Cell theory: (1) All living things are made of cells, (2) cell is basic unit of life, (3) all cells come from pre-existing cells.
• Prokaryotic cell: bacteria/archaea. No nucleus, DNA in nucleoid. No membrane-bound organelles. Small (~0.5-5 μm).
• Eukaryotic cell: animals, plants, fungi. Nucleus with DNA, membrane-bound organelles. Large (~10-100 μm).
• Nucleus: contains DNA organized into chromosomes (DNA + proteins), surrounded by nuclear envelope.
• Mitochondria: powerhouse of cell. Site of aerobic respiration. Double membrane. Contains own DNA (evidence of endosymbiosis).
• Chloroplasts (plants): site of photosynthesis. Contains chlorophyll, double membrane, own DNA.
• Endoplasmic reticulum (ER): rough (attached ribosomes, protein synthesis), smooth (lipid synthesis, detoxification).
• Golgi apparatus: modifies and packages proteins and lipids from ER.
• Mitosis: cell division producing two identical diploid daughter cells. Stages: prophase, metaphase, anaphase, telophase.
• Meiosis: cell division producing four haploid cells (gametes). Two divisions (Meiosis I, II); crossing over increases genetic variation.
• Biotechnology: using cells/organisms to develop products. Applications: fermentation, genetic engineering, gene therapy, stem cells.
• Fermentation: anaerobic respiration by microorganisms to produce products. Alcoholic (yeast), lactic acid (bacteria).
• Genetic engineering: modifying organism's DNA by adding foreign genes. Tools: restriction enzymes (cut DNA), DNA ligase (join DNA), plasmids (vectors).
• Recombinant DNA: DNA from different species joined together; organism with recombinant DNA is transgenic.
• PCR (Polymerase Chain Reaction): amplifies specific DNA sequences; uses repeated cycles of heating (denature), cooling (annealing), and enzymatic synthesis.
• CRISPR-Cas9: gene-editing tool. Uses guide RNA to find target DNA; Cas9 cuts it; cell repairs the break, allowing precise editing.
• Insulin production: human insulin gene inserted into bacterial plasmid; bacteria produce insulin (cheaper, consistent than animal-derived insulin).
• Monoclonal antibodies: produced from single B cell clone; target specific antigens; used in cancer treatment and diagnostic tests.
• Stem cells: undifferentiated cells that can self-renew and differentiate into specialized cells. Embryonic (pluripotent) and adult (multipotent).
• Gene therapy: treating genetic disease by introducing functional gene to replace defective one. Somatic (body cells) vs. germline (heritable).

Cell Biology and Biotechnology – Notes

1. Cell structure and organelles

• Plasma membrane: phospholipid bilayer with embedded proteins. Selectively permeable—allows some substances through, blocks others.
• Cytoplasm: gel-like substance between plasma membrane and nucleus. Contains organelles and ribosomes.
• Nucleus: contains DNA organized into chromosomes (DNA + histones). Surrounded by nuclear envelope with pores for protein/RNA transport.
• Nucleolus: within nucleus; site of ribosomal RNA synthesis and ribosome assembly.
• Mitochondria: power of cell; aerobic respiration occurs in cristae (inner folds). ATP (energy currency) produced here. Own DNA—evidence of endosymbiotic origin.
• Chloroplasts (plant cells only): photosynthesis. Thylakoids (stacked into grana) contain chlorophyll. Own DNA.
• Ribosomes: site of protein synthesis. Free (in cytoplasm) or attached to ER (rough ER). Consist of rRNA and ribosomal proteins.
• ER: interconnected membrane network. Rough ER: ribosomes attached, synthesizes proteins. Smooth ER: lipid synthesis, detoxification, calcium storage.

2. Cell division: mitosis and meiosis

• Cell cycle: interphase (G1, S, G2) + mitosis. Interphase: cell grows, DNA replicates, prepares for division.
• Mitosis: produces two identical diploid daughter cells. Prophase (chromosomes visible, spindle forms), metaphase (chromosomes align), anaphase (sister chromatids separate), telophase (nuclear envelopes reform).
• Cytokinesis: cytoplasm divides. In animals: cleavage furrow. In plants: cell plate.
• Meiosis: produces four haploid cells. Meiosis I (reduction division): homologous chromosomes separate (n chromosomes); Meiosis II (like mitosis): sister chromatids separate.
• Crossing over (recombination): exchange of genetic material between homologous chromosomes during Prophase I. Increases genetic variation.
• Purpose of mitosis: growth, maintenance, asexual reproduction. Purpose of meiosis: sexual reproduction (gamete formation).

3. Genetic engineering and tools

• Restriction enzymes: endonucleases that cut DNA at specific recognition sequences. Leave sticky ends for joining.
• DNA ligase: enzyme that joins DNA fragments by forming phosphodiester bonds between sticky ends.
• Plasmids: small, circular DNA from bacteria; useful as vectors (carriers) for foreign DNA.
• Transformation: introduction of foreign DNA into cell. In bacteria: competent cells take up DNA. In plants: Agrobacterium tumefaciens transfers DNA.
• PCR: Polymerase Chain Reaction. Uses heat-stable DNA polymerase (Taq) and repeated cycles to amplify target DNA exponentially.
• Thermal cycles: 94°C (denature DNA), 50-65°C (primer annealing), 72°C (DNA synthesis). 30-40 cycles produces millions of copies.
• Gel electrophoresis: separates DNA fragments by size; fragments move through gel at rates proportional to size.

4. CRISPR and modern gene editing

• CRISPR: Clustered Regularly Interspaced Short Palindromic Repeats. Natural bacterial immune system against viruses.
• Cas9: endonuclease protein that cuts DNA. Guided by guide RNA that specifies target sequence.
• Advantages over older methods: precise (single base pair), efficient, fast, relatively cheap, applicable to many organisms.
• Applications: creating disease-resistant crops, disease-resistant animals, treating genetic disease, developing cancer treatments.
• Concerns: off-target cuts (guide RNA matches multiple sites), mosaicism (not all cells edited), ethical issues (designer babies, heritable changes).

5. Biotechnology applications and ethics

• Pharmaceutical applications: insulin production (bacteria genetically engineered with human insulin gene), growth hormone (hGH), clotting factors.
• Gene therapy: treat genetic disease by replacing defective gene. Somatic gene therapy: affects only treated cells. Germline therapy: heritable, more controversial.
• Cancer treatment: monoclonal antibodies (target tumor antigens), CAR-T cells (immune cells engineered to attack cancer).
• Agriculture: Bt crops (carry Bacillus thuringiensis toxin gene, insect-resistant), herbicide-resistant crops (e.g., Roundup Ready), disease-resistant crops.
• Environmental applications: bioremediation (microorganisms clean pollution), biofuels (algae, bacteria produce ethanol/methane).
• Ethical issues: genetic privacy, equity of access, unintended ecological consequences of GMOs, religious/cultural concerns about modifying life.
• Regulations: oversight by regulatory agencies; biosafety protocols; informed consent in gene therapy; public engagement in bioethics.

Formulas at a glance

Key terms

Cell Biology and Biotechnology – Flashcards

Read the question, answer it in your head, then tap the card to check. 20 cards.

Cell Biology and Biotechnology – MCQ Quiz

15 questions. Tap an option — you will see at once if it is right and why.

How to study Cell Biology and Biotechnology

⏱ About 5 hours

1. Day 1 — Cell and organelles
   Learn cell structure, organelles, metabolism.
2. Day 2 — Molecular and genetic
   Study DNA, genetic engineering tools and methods.
3. Day 3 — Applications
   Learn GMOs, gene therapy, biotechnology products.
4. Day 4 — Ethics and practice
   Study ethical issues, complete practice questions.

✍️ Diagrams to practise

• Cell structure diagram
• PCR amplification cycles
• CRISPR cutting mechanism
• Genetic engineering steps
• Fermentation bioreactor