by pillai aswathy viswanath

1. Cell biology
Pillai Aswathy Viswanath
Dept. of Botany
Assumption College
Chenganacherry

2. Indroduction
• The study of cells is called cell biology, cellular
biology, or cytology.
• The cell is the basic structural, functional, and
biological unit of all known organisms.
• A cell is the smallest unit of life. Cells are often
called the "building blocks of life".
• Discovered by robert hooke in 1665,

3. • A single cell is often a complete organism in
itself, such as a bacterium or yeast.
• Other cells acquire specialized functions as
they mature.
• These cells cooperate with other specialized
cells and become the building blocks of large
multicellular organisms, such as humans and
other animals.

5. CELL THEORY
• Cell theory is the historic scientific theory,
now universally accepted, that living
organisms are made up of cells,
• All living organisms are composed of one or
more cells.
• Cells come from pre-existing cells.
• Cells are the basic unit of structure in all
organisms and also the basic unit of
reproduction.

6. PROTOPLASAM THEORY
• Protoplasm is the living part of a cell that is
surrounded by a plasma membrane.
• "Protoplasmic Theory" which states that all living
matter, of which animals and plants are formed,
is protoplasm.
• Protoplasm (Gr. Protos = first, plasma = form) is
the general term used for the living substance of
cells which is enclosed by the plasma membrane.
• In some definitions, it is a general term for the
cytoplasm, but for others, it also includes the
nucleoplasm. (Except plasma membrane)

8. Plasma membrane or Cell membrane
• An outermost envelope surrounding the cell
that separates and protects the cell from the
external environment and provides a
connecting system B/w the cell and its
environment is called plasma membrane.

9. • Outermost layer (animal)
• Thickness is 5-8 nm
• Serve as outer boundary
• Also called cell membrane
• Selectively permeable
• Selectively controls the movement of
materials into and out of the cell

10. Structure of the Plasma Membrane
• The plasma membrane is composed of two
layers of phospholipids back-to-back.
• Phospholipidsare lipids with a phosphate
attached to them.

11. Phospholipids
• Fatty acid tails (hydrophobic)
• Phosphate group head (hydrophilic)
• Arranged as a bilayer

12. Fluid mosaic model
• Fluid
Individual phospholipids and some proteins can
move sideways(laterally) in each layer-therefore
FLUID . Capable of rotating and moving.
• Mosaic
Range of different proteins resting on the surface or
through the phospholipid layer gives it a mosaic
appearance

13. • Fluid mosaic model describes the plasma
membrane as a flexible boundary of a cell.
• “Cell membrane is lipid bilayer in which
proteins are partially embeded like Floating
iceburgs in sea”

15. Chemical composition
• Composed of Lipids, Proteins and Carbohydrates.
• Actual components differs from tissue to tissue.
• Lipids of cell membrane are :
Phospholipids
Glycolipids
Sterol
Cholesterol

16. Membrane proteins
• Membrane proteins are categorized into two
groups:
1- Extrinsic (peripheral) membrane proteins
2- Intrinsic (integral) membrane proteins

17. Extrinsic membrane protein
• Proteins loosely associated with membrane
surface
• Located entirely outside of the lipid bilayer
• Either on the extracellular or cytoplasmic surface
• Also called Peripheral membraneproteins:
• Example:
Cytochrome C of Mitochondria
Cell surface identity marker (antigens)

18. Intrinsic membrane proteins
• Directly incorporated within the lipid bilayer
• Tightly bound to lipid bilayer
• Provides channel for the water-soluble
substances
• Also called Integral membrane proteins
• Example:
Transmembrane protein
Transport proteins
Channels,
pumps

19. Plasma Membrane
• Located:
Surrounds the cell forming a boundary
between the cell contents and the
extracellular environment.
• Structure:
Semi-fluid phospholipid bilayer in which
proteins are embedded. Some of the proteins
fully span the membrane.

20. • Function:
• As the barrier between the internal environment
of a cell and the external medium
• By acting as the boundary that separates
the Protoplasm from the extracellular
environment
• Transport is one of the main functions of the
plasma membrane.
• The plasma membrane helps to regulate
substances that enter or leave the cell

21. • Endocytosis:
Infolding of plasma membrane help in the
intake of solid and liquid materials
• exocytosis:
It permits exit of secreations and wastes

22. Cytoplasm
• Cytoplasm is a gel like fluid present between
the plasma membrane and the nucleus
• Cytoplasm is the semi-fluid substance of a cell
that is present within the cellular membrane
and surrounds the nuclear membrane
• It is sometimes described as the non nuclear
content of the protoplasm

23. • All the cellular contents in a prokaryote
organisms are contained within cell's
cytoplasm
• In eukaryote organisms, the nucleus of the
cell is separated from the cytoplasm
• Cytoplasm is a thick and semitransparent fluid
• The cytoplasm was discovered in the year
1835 by Robert Brown

24. • The cytoplasm is made of 70% - 90% water
and is colorless usually. Most of the cellular
activities occurs in the cytoplasm

25. There are three main
component of cytoplasm;
(a) Inclusion
• Cytoplasmic inclusions are small particles seen
temporarily in the cytoplasm
• They may are may not be membrane bound,and
are metabolicaly inactive for example
lipid,droplet,glycogen granules and pigment
grales
(b) Organalelles
• are small organs within the cell which are
involved in metabolism for example mitochondria
and endoplasmic reticulum

26. (C) Cytosol
• It is the fluid portion.
• Itis about 55% 0f the total cell volume.
• It various for composition in different cells.
• It is 75%- 90% of water plus various dissolved
and suspended ions and molecules
• It contains different types of ions,molecules
like glucose,amino asids, fatty acids, ATP etc

27. Cytoplasm Function
• Cytoplasm is the site of many biochemical
reactions that are vital and crucial for
maintaining life
• The cytoplasm is the place where the cell
expands and growth of the cell takes place
• The cytoplasm provides a medium for the
organelles to remain suspended
• It also aids in the movement of the different
cellular elements

28. • The enzymes in the cytoplasm metabolize the
macromolecules into small parts, so that it can
be easily available for the other cellular
organelles like mitochondria
• The cytoplasm is a means of transport for
genetic material
• It also transports the products of cellular
respiration

29. • The cytoplasmic organelles are specialized
structures that haves its own functions like
cellular respiration, protein synthesis,etc