Photosynthesis

• During carbon fixation, carbon dioxide from the air is converted into bicarbonate (HCO3−) inside the chloroplast.
• The Theory of Spontaneous Generation stated that living organisms could arise from nonliving matter and that such a process was regular in nature
• Aristotle proposed that life arose from nonliving material if the material contained pneuma ("vital heat")
• Francesco Redi's experiment in 1668 refuted the idea that maggots spontaneously generate on meat left out in the open air
• John Needham observed that broth became cloudy and contained microscopic creatures after briefly boiling broth infused with plant or animal matter
• Lazzaro Spallanzani's experiments contradicted Needham's findings, showing that heated but sealed flasks remained clear without signs of spontaneous growth
• Louis Pasteur's experiments with filtered air through a gun-cotton filter disproved the theory of spontaneous generation, leading to the conclusion "Omne Vivum Ex Vivo" ("life only comes from life")
• Robert Hooke observed cells in cork in 1665, naming the compartments "cells"
• Antonie van Leeuwenhoek observed red blood cells, sperms, and single-celled organisms in pond water in 1674
• Robert Brown discovered the nucleus in 1831 and theorized it as a fundamental component of the cell
• Felix Dujardin found that living cells contained an internal substance named "sarcode" in 1835
• Jan Evangelista Purkinje named the colloidal substance in the cell "protoplasm" in 1839
• Matthias Schleiden stated in 1838 that all plants are composed of cells
• Theodore Schwann concluded in 1839 that all animals are composed of cells
• Rudolph Virchow theorized in 1858 that all living cells come from pre-existing living cells
• The cell theory states that:

  • All living cells come from other living cells by the process of cell division
  • Cells are the basic units of structure and function in organisms
  • All living things are composed of one or more cells and cell products
• Processes of cell division in higher organisms

  • Mitosis
  • Meiosis
• Meiosis

  In this type of cell division, sperm or egg cells are produced with a haploid set of chromosomes instead of identical daughter cells as in mitosis
• Interphase is actually a non-dividing state. In this state, the cell grows in size, organelles are replicated, replication of DNA, synthesis of proteins associated with DNA, synthesis of proteins associated with mitosis
• Cells divide for three reasons: For the growth & development of our body, to repair the dead and damaged tissues, for reproduction
• During the cell cycle, the cell grows, DNA is replicated, mitotic cell division produces daughter cells identical to the parent. There are two primary phases in the cell cycle: Interphase and M Phase (Mitosis phase). There are two key steps in this phase, namely cytokinesis and karyokinesis
• Phases of interphase

  • G0 Phase (Resting Phase)
  • G1 Phase (Gap 1)
  • S Phase (Synthesis)
  • G2 Phase (Gap 2)
  • Quiescent Stage (G0)
• Cell division


  Process by which a parent cell divides into two or more daughter cells. Cell division usually occurs as part of a larger cell cycle. In cell division, the cell that is dividing is called the "parent" cell. The parent cell divides into two "daughter" cells and the process then repeats in what is called the cell cycle
• Division of somatic cells in eukaryotic organisms is called mitosis. In this process, a single cell divides into two identical daughter cells. Daughter cells have the same set of chromosomes as does the parent cell
• The cells that do not undergo further division exit the G1 phase and enter an inactive stage. This stage is known as the quiescent stage (G0) of the cell cycle
• Mitosis


  The process that cells use to make exact replicas of themselves. Mitosis is observed in almost all the body’s cells, including eyes, skin, hair, and muscle cells
• Telophase

  In the telophase stage, the spindle fibers between the poles disintegrate. The nuclear envelopes start reforming around both the groups of chromosomes at the poles. Chromosomes revert to their extended state by absorbing water from the cytoplasm. There appears a constriction in the cytoplasm between the two groups of dividing chromosomes. Cytokinesis completes the enclosing of each daughter nucleus into a separate cell
• Prophase


  3 Major Events take place: Chromosomes condense, Spindle fibers form (spindle fibers are specialized microtubules radiating out from centrioles), Chromosomes are captured by spindle
• Anaphase


  In anaphase stage the sister chromatids separate from each other. Spindle fibers attached to kinetochores shorten and pull the chromatids towards the opposite poles. The cell appears almost oval in shape as it starts becoming longer
• Mitosis Cell Division
• Division of somatic cells in eukaryotic organisms is called as mitosis
• Cytokinesis in Animal Cell


  Cytokinesis is the last phase of the normal cell cycle. In this phase the cell physically divides into two identical daughter cells. In animal cells, the cell membrane pinches together and the membrane breaks apart where it was pinched and now it is two daughter cells. In both new cells the DNA is identical
• Mitosis


  It has 4 sub-phases: 1st – Prophase, 2nd – Metaphase, 3rd – Anaphase, 4th – Telophase followed by Cytokinesis
• Reduction Cell Division


  Meiosis is a process where a single cell divides twice to produce four daughter cells containing half the original amount of genetic information. These cells are called as gametes - sperm in males, eggs in females
• Mitosis

  1. Cell grows in size

  2. Organelles replicated

  3. Replication of DNA

  4. Synthesis of proteins associated with DNA

  5. Synthesis of proteins associated with mitosis
• In mitosis, a single cell divides into two identical daughter cells. Daughter cells have the same set of chromosomes as does the parent cell
• Diploid organisms receive one of each type of chromosome from female parent and one of each type of chromosome from male
• Haploid


  Contains only one copy of chromosome, designated as "n"
• Ploidy


  Refers to the number of sets of chromosomes in cells
• Zygotene

  Homologous chromosomes begin to pair, known as synapsis