Immerse yourself in the intricate world of biology with my meticulously crafted handwritten notes on "Cell and Its Components" for the MCAT exam. Delve into the fundamental structures and functions that underpin life itself. Through concise explanations and vivid diagrams, grasp the intricacies of ...
● First discovered by Robert Hooke in 1665 in cork cells
● First living cell discovered by Anton van Leeuwenhoek.
● Cell is the basic structural and functional unit of all living organisms.
CELL THEORY
● Given by schleiden and Schwann.
● Described that all animals and plants are made of cells and their
products.
● Rudolf Virchow added by stating that all cells arise from pre-existing
cells (Omanis cellula e cellula)
● This theory is accepted widely with some exceptions like viruses, prions,
viroids etc.
FACT: the smallest living organism is PPLO or mycoplasma measuring
only 0.1micrometeres
CELL MEMBRANE
● It is the outermost layer in the animal cell and present inner to the cell
wall in bacteria, fungi, and plant cells.
● It is a living structure and absent in dead cells components of cell
membrane
a) Lipid-present in the form of phospholipid bilayer with a hydrophobic tail
and hydrophilic head b) Protein-can be fully embedded in the membrane or
peripheral.
c) Glycoprotein
d) Glycolipid
● The most widely accepted model of cell membrane is the fluid mosaic
model by Singer and Nicholson. It describes cell membrane as a quasi fluid
with an ocean of lipid and protein as icebergs.
, ● Transport across the membrane occurs through diffusion, active
transport or facilitated transport
● Active transport uses energy and protein channels to transport
substances from lower concentration to higher concentration.
● Facilitated transport occurs with the help of proteins but transport
substances from higher concentration to lower concentration.
CELL WALL
● Present in plant cell and fungi
● It is a dead structure
● It gives shape, rigidity, and protection from the environment
● The matrix of cell wall of bacteria is made up of galactan,
mannan and calcium carbonate.
● Cell wall is further divided into
a) Primary cell wall : made up of cellulose, hemicellulose,
pectin, and protein.
b) Secondary cell wall: present between plasma membrane
and primary cell wall. Made up of cellulose, pectin, and
lignin or subrein.
c) Middle lamellae: present between primary cell wall and
neighboring cell. Made up of calcium or magnesium
pectate.
ENDOMEMBRANE SYSTEM
● Consist of organelles with membrane that work in co-ordination
● Includes endoplasmic reticulum, Golgi bodies, vacuoles, and
lysosomes.
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