The cell Common characteristics of cell – Typical cell under light microscope Cell organelles – 6 main types of organelles Mitochondria Endocytosis Receptor mediated endocytosis Phagocytosis Functional systems of the cell— Intercellular connections or junctions Basic mechanism of transport References

1. The
cell
Pandian M
Dept of Physiology
D.Y.Paril Medical College, KOP

2. SLO’s
• The cell
• Common characteristics of cell –
• Typical cell under light microscope
• Cell organelles –
• 6 main types of organelles
• Mitochondria
• Endocytosis
• Receptor mediated endocytosis
• Phagocytosis
• Functional systems of the cell—
• Intercellular connections or junctions
• Basic mechanism of transport
• References

3. The cell
The cell is bound by cell membrane which
also extends inside the cytoplasm to separate
various cell organelles.
The basic living unit of body.
Each organ is an aggregate of many different cells
held together by intercellular supporting
structures.
Each cell is adapted to perform specific functions.
Total 100 trillion cells in human
body

4. Common characteristics of cell –
- Release of energy required for various
activities of cell from O2 and breakdown
products of Carbohydrates, proteins & fats
- removal of waste products in surrounding fluid
- ability to reproduce to replace damaged cells

5. Protoplasm –
H2O, electrolytes, Pr., lipids, carbohydrates
- Water – 70-85 % ,
fluid medium for chemical reactions
- Electrolytes – K+, Mg++, PO4
---, SO4
--, HCO3
-
-Chemical reactions for cellular reactions
-Control of cellular functions
-Transmission of impulse

6. - Proteins – 10-20 %, 2 types
i) structural – filaments, cytoskeleton
ii) Globular – enzymes
- Lipids – 2 %
- Membrane barrier for h2o soluble substances
- Storehouse of energy
- Carbohydrates – 1%, energy substrate,
- ve charge on surface,
- attachment to other cells,
- act as receptors

7. Cell membrane /plasma membrane
Cytoplasm
Nucleolus
Nucleoplasm
Nuclear membrane
Nucleus
Typical cell under light microscope
Nuclear pores

8. elaborate protein
network
(cytoskeleton)
Cytoplasm
I Cytosol
Complex gel
like liquid
Site for compatible
chemical reactions
- gives shape
- Provides internal
organization
- Regulates its
movements
Organelles
Cytosol

10. Tail
(hydrophobic)
ECF
ICF
Glycolipid
Glycoprotein
Integral proteins
Intrinsic protein
Extrinsic protein
Lipidbilayer
Head
(hydrophilic)
cholesterol

11. Tail
(hydrophobic)
ECF
ICF
Glycolipid
Glycoprotein
Integral proteins
Intrinsic protein
Extrinsic protein
Lipidbilayer
Head
(hydrophilic)
cholesterol

12. Cell organelles –
highly organized physical
structures inside the cell membrane
which are very imp. for the cell.

13. Each organelle
II Organelles distinct,
highly organized,
membrane enclosed,
occupies about ½ of total
cell volume
‘Speciality shops’ in cell
Separate compartment
Separate contents

14. 6 main types of organelles
 Endoplasmic reticulum
 Rough ER
 Smooth ER
 Golgi complex
 Lysosomes
 Peroxysomes
 Mitochondria
 (Vaults)
- similar in all cells
- contain specific set
of chemicals
required for
particular cellular
function
- can carryout
incompatible
chemical reactions
simultaneously

15. Cell organelles
Membrane bound
-Mitochondria
-- E. R.
smooth
rough
- G. A.
- Lysosomes
- Peroxysomes
- Secretory
vesicles
- Nucleus
Filaments and
microtubules
-Actin filaments in
muscle, ectoplasm
– give elastic
support
--microtubules in
flagellum, cilium,
centriol & mitotic
spindles – give
stiffness
Inclusion
bodies
Fat
globules,
glycogen,
ribosomes

16. Mitochondria
Outer membrane
Crista
Matrix
Electron
transport
protein
Dissolved enzymes for citric acid
cycle Chemiosmotic
reactions

17. I. Mitochondria –
1) Final oxidation of fuel to release
energy
2) β- oxidation of fatty acids
3) Completion of the steroid synthesis

18. III. Smooth ER –
1) Intracellular transport
2) Synthesis of triglycerides
3) Synthesis of steroid hormones
4) Detoxification
5) Uptake of Calcium ions in skeletal
muscle
6) Formation of peroxisomes
II. Rough ER –
Synthesis and modification of proteins

19. IV.Golgi apparatus
1) Concentration of proteins
2) Synthesis of polysaccharides
3) Addition of carbohydrates in
glycoproteins
4) Cleavage of proteins
5) Formation of secretory vesicles
V. Secretory vesicles – contain proenzymes

20. IV. Lysosomes –
1) Storage of hydrolytic enzymes
2) Digestion of macromolecules
V. Peroxisomes
Destruction of H2O2
VII. Ribosomes –
Helps in protein synthesis
VIII. Centrioles –
Required for mitotic division

21. IX. Microtubules and microfilaments –
1) Give structural stability and shape
2) Transport system
3) Movement
X. Nucleus –
1) Store genetic material
2) Controls all activities of cell

22. Extracellular material to be tackled by
lysosome is brought into the cell by
endocytosis
3 types
pinocytosis
Receptor
mediated
endocytosis
phagocytosis

24. B. Receptor mediated endocytosis – highly selective process to
import imp. specific large molecules. Requires energy & Ca++
Coated pit
Clathrin, actin,
myosin

25. C. Phagocytosis
• Internalization of large
multimolecular particles by
specialized cells e.g. certain
types of WBCs ( Professional
phagocytes)

26. Pseudopodia
internalization
Fusion
digestion
absorption
Residual body
Phagoso-some
Phagocytosis
bactebactium

28. Functional systems of the cell—
i) Endocytosis – Pinocytosis, Phagocytosis
ii) Digestion of foreign substances –
Function of lysosomes
iii) Synthesis and formation of cellular structures –
ER and GA
iv) Extraction of energy from nutrients – mitochondria
v) Ameboid locomotion of the cell
vi) Cell reproduction – centriole, nucleus

29. Intercellular connections or junctions
Connections between cell membrane of
neighboring cells or cell to the basal lamina
1)Tight junctions – zona occludens
-fusion of outer layer of cell membranes
-forms barrier for ions & solutes from
one cell to other
-Examples – apical margins of cells of
intestinal mucosa & PCT
3 Types

30. 2) Adherens junctions – zona adherens
-cell membranes are seperated by 15-20 nm wide
space On the inner side of membrane –
- thickened plaque of protein.
-bundle of filaments in the space
2 types – desmosomes – thickening at both cells
hemidesmosomes – thickening at one cell
which is attached to basal lamina

31. 3) Gap junctions –
Channels connecting the lateral surfaces of
two neighboring cells through which organic
molecules, ions & chemicals are exchanged.
Channels are surrounded by channel proteins
Examples – cardiac muscle, basal part of
intestinal mucosa

32. hemidesmosomesDesmosomes
Intercellular connections or junctions
Tight junctions Adherens
junction
Gap junctions
Tight junctions / zonula occludens
Desmosome / zonule adherens
Gap junctions
Connexon
Hemidesmosomes

33. Tight junctions / zonula occludens
Desmosome / zonule adherens
Gap junctions
Connexon
hemidesmosomes

34. All the cells in the body must be supplied with essential
substances like nutrients, water, electrolytes, etc.
Cells also must get rid of many unwanted substances like
waste materials, carbon dioxide, etc.
The cells achieve these by means of transport mechanisms
across the cell membrane.

35. BASIC MECHANISM OF TRANSPORT
Two types of basic mechanisms are involved in the
transport of substances across the cell membrane:
1. Passive transport mechanism
2. Active transport mechanism.

36. PASSIVE TRANSPORT
Passive transport is the transport of substances along the
concentration gradient or electrical gradient or both
(electrochemical gradient). It is also known as diffusion or downhill
movement.
It does not need energy.
Passive transport is like swimming in the direction of water flow in a
river.

37. 1. Simple diffusion through lipid layer
(Lipid layer of the cell membrane is permeable only to lipid-soluble substances like
oxygen, carbon dioxide and alcohol.)
2. Simple diffusion through protein layer
(Protein layer of the cell membrane is permeable to water-soluble substances. Mainly,
electrolytes diffuse through the protein layer)
3. Facilitated or carrier-mediated diffusion.

38. ACTIVE TRANSPORT
• Active transport is the movement of substances against the
chemical or electrical or electrochemical gradient.
• It is like swimming against the water tide in a river.
• It is also called uphill transport.
• Active transport requires energy, which is obtained mainly by
breakdown of
• high energy compounds like adenosine triphosphate (ATP).

39. TYPES OF ACTIVE TRANSPORT
Active transport is of two types:
1. Primary active transport
2. Secondary active transport.

40. References
• Text book of Medical Physiology
– Guyton & Hall
• Human Physiology
–Vander
• Text book of Medical Physiology
–Indukurana, sembu
• Net source