Biology

• Cell

  Fundamental unit of life
• Cell

  • Discovered by Robert Hooke in 1665
  • Box-like structures he observed under microscope
  • Hooke called them "cells"
• Cells are the building blocks of living things
• Types of organisms based on number of cells

  • Unicellular
  • Multicellular
• Unicellular organisms

  • Amoeba
  • Chlamydomonas
  • Paramecium
  • Bacteria
• Multicellular organisms are developed from a single cell
• Cells produce cells of their own kind by cell division
• Multicellular organisms are made up of different types of cells
• Different types of cells in the body

  • Muscle cells
  • Blood cells
  • Nerve cells
  • Bone cells
  • Ovum
  • Sperm cells
  • Fat cells
• Cell organelles

  Parts present inside the cell that perform specific functions
• Cell organelles

  • Cytoplasm
  • Smooth endoplasmic reticulum
  • Rough endoplasmic reticulum
  • Golgi apparatus
  • Lysosomes
  • Mitochondria
  • Vacuoles
  • Plastids
• Cytoplasm

  Semi-transparent jelly-like material inside the cell membrane, where many biochemical reactions take place
• Rough endoplasmic reticulum

  • Protein factory
  • Makes new proteins
• Smooth endoplasmic reticulum

  • Fat factory
  • Makes new fats
• Golgi apparatus

  • Dispatch center
  • Handles packaging and distribution of materials prepared by endoplasmic reticulum
• Mitochondria

  • Powerhouse of the cell
  • Produces energy from glucose
• Vacuoles

  • Storage bags
  • Store different materials
• Lysosomes

  • Suicide bags
  • Contain digestive enzymes and digest foreign materials and damaged cells
• Plastids

  • Pigment stores
  • Contain different pigments
  • Help in photosynthesis
• Cell organelles are membrane-bound and help keep chemical activities separate
• Cell organelles cannot be seen under a compound microscope, but can be seen under an electron microscope
• Plasma membrane

  • Protects inner components of the cell
  • Controls entry and exit of materials
• Diffusion


  Movement of gas molecules from high to low concentration
• Osmosis


  Movement of water molecules from high to low concentration through a semi-permeable membrane
• Active transport

  Transfer of other materials into the cell, requires energy
• Plasma membrane is made up of lipids and proteins, and can only be seen under an electron microscope
• Endocytosis

  Process by which amoeba engulfs food materials through its cell membrane
• Cell wall

  Rigid outer cover of plant cells, made of cellulose
• Plasmolysis

  Loss of water from plant cells, causing contents to shrink away from cell wall
• Nucleus

  • Covered by nuclear membrane with pores
  • Contains chromatin that becomes chromosomes during cell division
  • Contains DNA and proteins
• Nucleoid

  Nuclear region in prokaryotic cells without a nuclear membrane
• Differences between prokaryotic and eukaryotic cells

  • Prokaryotes lack nuclear membrane and membrane-bound organelles
  • Eukaryotes have nuclear membrane and membrane-bound organelles
• Proteins and fats

  Materials used by cells in different ways
• Cell membrane

  Made up of proteins and lipids
• For the formation of new cell membrane during cell division, proteins and fats are required
• Proteins and fats

  Can be converted to enzymes and hormones and secreted out of the cell to execute various functions
• Functions of endoplasmic reticulum

  • Facilitates transport of materials between various regions of cytoplasm
  • Provides surface for many important biochemical reactions
  • In vertebrates, smooth endoplasmic reticulum plays an important role in detoxifying toxins and drugs
• Golgi apparatus

  Flattened bags or vesicles arranged parallel to each other and forming stacks called cisterns
• Functions of Golgi apparatus

  1. Storage of materials

  2. Modification of materials

  3. Packaging and dispatch of materials
• Lysosomes

  Sac-like organelles covered by a membrane and filled with digestive enzymes