Biology Notes: Cells and Biomolecules
Structure of Cell (One-line Summary)
- Cell Membrane: Outer layer controlling substance movement and protecting the cell.
- Cell Wall: Rigid outer layer in plants providing shape and protection.
- Cytoplasm: Jelly-like fluid housing organelles and site for chemical reactions.
- Nucleus: Controls cell activities and stores genetic material (DNA).
- Nucleolus: Produces rRNA and ribosomes, inside the nucleus.
- Nuclear Membrane: Separates the nucleus from the cytoplasm.
- Chromosomes: DNA-containing structures responsible for heredity.
- Endoplasmic Reticulum: Transports substances and synthesizes lipids/proteins.
- Golgi Bodies: Modify, sort and package proteins for transport.
- Ribosomes: Sites of protein synthesis, free or attached to ER.
- Mitochondria: Powerhouse of the cell; produces ATP energy.
- Lysosomes: Digestive sacs destroying waste and foreign material.
- Chloroplast: Site of photosynthesis in plant cells; contains chlorophyll.
- Vacuoles: Storage sacs for food, water, and waste materials.
Functions of Cell
- Metabolism: Performs chemical reactions for life support.
- Protein synthesis: Produces proteins via transcription and translation.
- Support & Structure: Cell wall/membrane provide physical support.
- Growth (Mitosis): Cell division helps in organism growth.
- Transport: Moves nutrients and removes waste from the cell.
- Energy Production: Uses respiration/photosynthesis to create energy.
- Reproduction: Enables creation of new cells or organisms.
Types of Cells (Stem Cells)
- Totipotent: Can become any cell type.
- Pluripotent: Can become most cell types.
- Multipotent: Can become related cell types (e.g., blood cells).
- Oligopotent: Can form few cell types (e.g., lymphoid).
- Unipotent: Produces only one cell type (e.g., muscle stem cells).
- Adult Stem Cells: Found in organs; repair tissue (e.g., bone marrow).
- Induced Pluripotent: Lab-converted cells with embryonic traits.
- Mesenchymal: Form bone, cartilage, and fat from connective tissue.
Applications of Stem Cells
- Tissue Regeneration: Used in organ and skin repair.
- Cardiovascular Treatment: Form new blood vessels.
- Brain Disease Treatment: Replace damaged neurons (e.g., Parkinson's).
- Blood Diseases: Treats cancer and anaemia using bone marrow cells.
Properties of Proteins
- Water Solubility: Depends on hydrogen bonding and structure.
- Denaturation: Loss of structure by heat or chemicals.
- Coagulation: Heat-denatured proteins form clumps.
- Isoelectric Point: pH where protein has neutral charge.
- Molecular Weight: Depends on number and type of amino acids.
Functions of Proteins
- Digestion: Enzymes break down food.
- Movement: Myosin in muscles helps movement.
- Structure: Keratin forms hair, nails, etc.
- Communication: Receptors enable cell signaling.
- Messenger: Proteins act as hormones and messengers.
Properties of Nucleic Acids
- Chain of repeating nucleotide units.
- Each nucleotide has base, sugar, and phosphate.
- Contain A, T, G, C (DNA) or A, U, G, C (RNA).
- Purines: A, G; Pyrimidines: C, T, U.
- PNA: Synthetic alternative to DNA/RNA.
- T found in DNA, U found in RNA.
Functions of Nucleic Acids
- Stores genetic information.
- Protects genetic data.
- Carries hereditary traits.
- Used in DNA fingerprinting.
- Used in genetic and evolution research.
Prokaryotic vs Eukaryotic Cells
- Nucleus: Prokaryotes lack nucleus; eukaryotes have it.
- Size: Prokaryotes are smaller; eukaryotes larger.
- Organelles: Only eukaryotes have membrane-bound organelles.
- DNA: Prokaryotes have circular DNA; eukaryotes have linear DNA.
- Examples: Prokaryotes - Bacteria; Eukaryotes - Plants, Animals.
