The document discusses the structural and functional organization of cells, including their compartmentalization into organelles. It describes the main organelles found in cells and their functions. The key organelles discussed are the nucleus, which controls cell activities; mitochondria, which generate energy; the endoplasmic reticulum and Golgi apparatus, which help synthesize and transport molecules; lysosomes and peroxisomes, which digest and break down waste; and plastids like chloroplasts, which facilitate photosynthesis in plant cells. The document contrasts the structures of typical animal and plant cells.

1. •Structural and Functional Organization
•Compartmentalization
•Cell organelles

2. The discovery of cells
followed form the invention
of the microscope by Robert
Hooke, and its refinement by
Anton Leewenhoek.

3.  Was articulated in the mid-1800s by
Schleiden, Schwann and Virchow.
 All organisms are composed or one or more cell.
 The cell is the basic organizational unit of life.
 Cells arise from pre-existing cells by division.

4. 1. Cells Are Highly Complex and Organized
2. Cells Posses a Genetic Program and the Means to Use It
3. Cells Are Capable of Producing More of Themselves
4. Cells Acquire and Utilize Energy
5. Cells Carry Out a Variety of Bio-Chemical Reactions
6. Cells Engage in Mechanical Activities
7. Cells Are Able to Respond to Stimuli
8. Cells Are Capable of Self-Regulation
9. Cells Evolve

7.  Compartmentalization: Membranes form continuous sheets that
enclose intracellular compartments
 Scaffold for biochemical activities: Biomembranes provide a
framework that organizes enzymes for effective interaction
 Selectively permeable barrier: Plasmamembranes allow
regulated exchange of substances between compartments
 Transporting solutes: Membrane proteins facilitate the
movement of substances between compartments
 Responding to external signals: Receptors on the
plasmamembrane transduce signals from outside the cell in response
to specific ligands, hormones, growth factors etc.
 Intracellular interaction: Membranes mediate recognition and
interaction between adjacent cells
 Energy transduction: Membranes transduce photosynthetic
energy, convert chemical energy to ATP, and store energy

10.  Endoplasmic Reticulum (ER)
 A complex network of tubes
 Lumen is filled with fluid
 Two types of ER are seen:
 Tubes with a smooth surface are called smooth
endoplasmic reticula. They secrete lipids
 Tubes with spherical bodies (ribosomes) attached are
known as rough endoplasmic reticula
 Functions of the endoplasmic reticulum:
 To form the skeletal framework of the cell
 To provide a pathway for the distribution of nuclear
material from one cell to the other
 To synthesize fats, steroids and cholesterol with the help
of enzymes secreted by the cell.

11.  Golgi Apparatus
 Also known as Golgi Complex or Golgi Bodies,
 Consist of tiny, elongated, flattened sacs (cisternae), which are
stacked parallel to one another along with some vacuoles and clusters
of vesicles
 The Golgi body is usually found close to the nucleus
 Function of the Golgi Body
 To secrete certain hormones and enzymes.
 It also forms lysosomes and peroxisomes.
 Lysosomes
 Tiny, spherical, sac-like structures scattered all over the cytoplasm
 Main function is digestion:
 Contain powerful destructive enzymes capable of digesting
all organic material, and hence called “digestive bags”
 Lysosomes present in WBCs are
capable of digesting bacteria and viruses
 During starvation, lysosomes digest proteins, fats and glycogen in the
cytoplasm, and supply energy to the cell
 Also capable of digesting worn out cell organelles, or even digesting
the entire damaged cell containing them
 Hence, “suicide bag” is a sobriquet that is often used for Lysosomes.

12.  Peroxisomes
 Found in the liver and kidney cells
 They are small, membrane-bound sacs
 Contain powerful oxidative enzymes.
 Chief function is to remove toxic substances.
 Ribosomes
 These are spherical, granular particles which occur
freely in the matrix or remain attached to the
rough endoplasmic reticulum
 Ribosomes contain RNA (ribonucleic acid) and
proteins
 Provide the surface for protein synthesis
 Provides protection to the mRNA and the nascent
polypeptide
 Centrosome
 This is found in the cytoplasm near the outer
surface of the nucleus and contains two cylinders
called centrioles
 The centrosome is found only in the animal cell
 The centrosome and the centrioles play an
important role by forming the poles of the spindle
during cell division

13.  Mitochondria
 Cylindrical or rod-shaped or spherical
 Distributed in the cytoplasm
 Each mitochondrion is bound by a double membrane
 The inner membrane is folded into ridges called cristae, which
increase the surface area of the membrane
 It is in the mitochondria that the sugar is finally burnt during cellular
respiration
 The energy thus released is stored as high-energy chemicals called
ATP (adenosine triphosphate)
 Hence, mitochondria are termed as the “power house” or of the
cell
 The body cells use the energy stored in ATP for synthesis of new
chemical compounds, the transport of these compounds and for
mechanical work
 Structure of mitochondria

14.  Plastids
 These organelles are found only in plant cells.
 Plastids are of three types
 Chloroplasts
 They are green and found in leaves.
 The green colour is due to the presence of
chlorophyll.
 Chromoplasts
 They are yellow, orange and red, and found in flowers
and fruits.
 Leucoplasts
 They are colourless and found in roots, seeds and
underground stems.
 The function of the chloroplast is to trap solar energy
for photosynthesis.
 Chromoplasts impart colour to flowers to attract
insects for pollination.
 Leucoplasts store food in the form of carbohydrates,
fats and proteins.

15.  Nucleus
 This is a prominent, spherical or oval structure found at the
centre of the cell
 It is the controlling centre of all cell activities and has been
described as the brain of the cell
 It regulates all metabolic and hereditary activities of the cell
 The nucleus is composed of the following structures:

16.  Nuclear Membrane
 This is a double-layered membrane which separates the nucleoplasm from
the cytoplasm.
 The nuclear membrane has minute pores which allow the selective transfer
of material between the nucleoplasm and the cytoplasm
 Nucleoplasm
 Within the nuclear membrane, completely filling up the space, is a clear,
semi-solid, granular substance or matrix called the nucleoplasm
 The nucleolus and the chromatin network lie suspended in the nucleoplasm
 Nucleolus
 This dense, spherical granule found in the nucleus contains RNA (ribonucleic
acid) which is responsible for protein synthesis in the cytoplasm
 Chromatin network
 These are very fine thread-like, coiled filaments uniformly distributed in the
nucleoplasm.
 At the time of cell division, the chromatin becomes thick and ribbon like and
are known as chromosomes
 The chromosomes contain genes, which are composed of DNA (deoxy-
ribonucleic acid)
 Genes are responsible for storing and transmitting hereditary characteristics
from one generation to another
 A gene is the functional unit of a chromosome
 Genes are arranged in single linear order along the chromosome
 One gene may be responsible for a single characteristic, or a single
characteristic may be transmitted by a set of genes

18. Animal Cell Plant Cell
Usually smaller in size Usually larger in size
Cell wall absent. Cellulose in any
form is absent
Cell wall made up of cellulose is
present.
Cytoplasm is denser, more granular
and occupies most of the space in
the cell
Cytoplasm is pushed to the
periphery and forms a thin lining
against the cell wall
Vacuoles absent. If present, they are
small, temporary and concerned
with excretion or secretion
Vacuoles are large and prominent.
May be one or more. The central
space in the cell may be occupied by
a large, single vacuole
Plastids are absent Plastids are usually present
Centrosome is present Centrosome is absent. Instead two
small clear areas called polar caps
are present
Prominent and highly complex Golgi
bodies present near nucleus
Contain several sub units of Golgi
aparatus called dictyosomes