The document provides an overview of the structure and function of eukaryotic cells. It discusses the key parts of the cell including the plasma membrane, cytoplasm, organelles like the nucleus, mitochondria and Golgi apparatus. It also describes cellular transport mechanisms like passive diffusion and active transport. The summary is as follows: The document discusses the basic structure and functions of eukaryotic cells. It describes the key parts of the cell including the plasma membrane, cytoplasm and organelles. It also explains cellular transport mechanisms such as passive and active transport that allow movement of substances into and out of cells.

1. Unit:-I, Chapter:-2
Cellular level of organization
Represented By,
Mr. Audumbar Mali.
(Assistant Professor)
Sahyadri College of Pharmacy Methwade
BP101T. Human Anatomy And Physiology-I (Theory)

2. CELL
•A cell is the basic, living, structural and functional unit of
living organisms.
•There are about 200 different types of cells in our body.
•All cells produced by the process of cell division.
•Cell biology is the study of cellular structure and function.
•Structure of the cell is intimately related to its function.

3. PARTS OF ACELL
1. Plasma membrane
2. Cytoplasm
a) Cytosol
b) Organelles
3) Nucleus

4. The plasma membrane
•Structure:
• The membrane is composed of proteins and lipids
(phospholipids).
• It bind together by non covalent forces
• The phospholipid molecules have head which is electrically
charged and hydrophilic in nature. A tail which has nocharge
and hydrophobic in nature.
• In this layer the sugar molecule is embedded in between
them.

5. Functions
• Protection
• Barrier
• Shape of the cell
• Cell junction
• Cell movement
• Selective permeability
• Impulse transmission

6. Cytoplasm
• The cytoplasm has two components
a) Cytosol:
• It is the fluid portion of cytoplasm that contains water (75-90 %), ions,
amino acids, proteins, lipids, ATPand waste products.
b) Organelles:
1. Ribosomes
2. Endoplasmic reticulum (smooth & rough)
3. Golgi complex
4. Mitochondria
5. Nucleus

7. 1. Ribosomes
• These are tiny granules composed of RNA & protein.
• They synthesize protein from amino acids using RNA.
• When this is present in free units in the cytoplasm, the ribosomes
make proteins for use within the cell.
• Ribosomes are also found on the outer surface of the nuclear envelope
and rough endoplasmic reticulum where they manufacture proteins for
export from the cell.

8. 2. Endoplasmic Reticulum
•It is the series of interconnecting membranous canals in the cytoplasm.
There are 2 types of endoplasmic reticulum
1. Smooth endoplasmic reticulum:
• Here is lack of ribosomes
2. Rough endoplasmic reticulum:
• This is studded with ribosomes that synthesize proteins.

9. 3. Golgi apparatus
• It consist of stack of closely folded flattened membranous sac.
• It present in all cells but is larger in those cells that synthesize and
export proteins.
• The proteins move from ER to golgi apparatus where they are
‘packaged’ into membrane bound vesical called secretory granules.
• The vesicles are stored and when needed more to plasma membrane,
through which the proteins are exported.

10. 4. Nucleus
• Every cell in the body has nucleus, with exception of mature RBC.
• Skeletal muscle and some other cell contain several nuclei.
• It is the larger organelle of the cell and is contained within the nuclear
envelope.
• The nucleus contains body’s genetic
material which directs all metabolic
activities of the cell.
•This consist of 46 chromosomes,
which are made from DNA.

11. 5. Mitochondria
• This is also called ‘Power House’of
cell.
• They are involved in the aerobic
respiration. The process by which
chemical energy is made available in
the cell.
• This energy is in the form of ATP
which release energy when the cell
break it down.
• Synthesis of ATP is most efficient in
the final stage of aerobic respiration.
A process requiring oxygen.

12. TRANSPORT OF MATERIAL ACROSS THE CELL
•Motion of substances in and out of the cell
•Cell membranes are Selectively permeable
•Two Types of Transport Mechanisms:
1. Passive Transport
2. Active Transport

13. Membrane transport
•Passive transport is movement of molecules
through the membrane in which no energy is
required from the cell
•Active transport requires energy expenditure by
the cell

14. 1. Passive Transport
•Passive transport is movement of molecules through the
membrane in which no energy is required from the cell.
• Molecules move in response to a concentration gradient.
- A concentration gradient is a difference between the
concentration on one side of the membrane and that on the
other side.
•Passive transport mechanisms only movement substances
along the concentration gradient.

15. 1. Passive Transport
•Passive transport mechanisms only movement
substances along the concentration gradient:
- Substances move from an area of high
concentration to an area of low concentration

16. 1. Passive Transport
•Mechanisms of Passive Transport:
1. Diffusion
-movement of solute molecules from high solute
concentration to low solute concentration
2. Osmosis
-movement of solvent water from high solvent
concentration to low solvent concentration

17. Diffusion
• Diffusion is movement of solute molecules from high
concentration to low concentration.

18. Diffusion
•There are two types of diffusion
I. Simple Diffusion
II. Facilitated Diffusion

19. I. Simple Diffusion
•Substances pass directly through the cell
membrane
•The cell membrane has limited permeability
to small polar molecules, water, and ions
•The motion of water across the membrane is
known as osmosis

20. diffusion depends on the
•The rate (molecules/s) of simple
degree of
concentration gradient
•As the gradient reaches equilibrium,
diffusion slows
•At equilibrium, substances pass in and
out of the membrane at equal rates

21. II. Facilitated Diffusion
•Substances must pass through
transported proteins to get through the
cell membrane.
•The cell membrane is selectively
permeable.
•Carrier proteins bind to the molecule
that they transport across the
membrane.

22. II. Facilitated Diffusion
•Selective permeability: integral membrane
proteins
allow the cell to be selective about what passes
through the membrane.
-Channel proteins have a polar interior
allowing polar molecules to pass through.
-Carrier proteins bind to a specific
molecule to facilitate its passage.

23. Ion Channels

24. Carrier
Proteins
Carrier proteins bind to a specific
molecule to facilitate its passage.

25. Osmosis
•Osmotic concentration is
determined by the
concentration of all solutes in
solution.

26. 16
2. Active Transport
Active transport
• Requires energy – ATP is used directly or
indirectly to fuel active transport
• Able to moves substances against the
concentration gradient - from low to high
concentration
- allows cells to store concentrated substances
•Requires the use of carrier proteins

27. Active transport

30. 20
Bulk Transport
Bulk transport of substances is
accomplished by
1.Endocytosis – movement of
substances into the cell
2.Exocytosis – movement of
materials out of the cell

31. 21
Bulk Transport
•Endocytosis occurs when the plasma membrane
envelops food particles and liquids.
1. phagocytosis – the cell takes in particulate
matter
2.pinocytosis – the cell takes in only fluid
3. receptor-mediated endocytosis – specific
molecules are taken in after they bind to a receptor

32. 22

33. 23

34.  Intercellular space in closely packed tissue is about 20nm. The cells
are bound together by the specific adhesive glycoprotein.
 Epithelial cells adhere to each other through glycoproteins
called Cadherins
 Modified cell membranes contributing in cohesion and
communication are called Cell junctions
Cell Junctions


35.  There are three types of Cell Junctions
1. Tight Junctions or Occluding Junctions
2. Adhering Junctions
3. Communicating Junctions
Types of Cell Junctions


36.  Found in epithelial tissues
 Also known as “Tight Junctions”
 Do not allow passage of small molecules form impermiable
membrane.
Types:
 Zonula Occludens
 Fascia Occludens
1. Tight Junctions 

37.  Encircles the entire cell perimeter
 Occludes the intercellular space
 Series of focal fusions
 The adjacent cell membranes approach each other, outer leaflets
fuse, diverge again then fuse again
 At fusions sites specific trans membranous proteins named
(Occludins, and Claudins) perform the binding function
 Less in PCT and more in the intestinal mucosa
Zonula Occludens


38. 

39.  A strip like tight junction of limited extent
 Found between the endothelial cells of the blood
vessels
Fascia Occludens


40.  Anchoring junctions
 Provide cell-cell or cell to basal lamina adherence
Types:
 Zonula adherens
 Fascia adherencs
 Macula adherens (Desmosomes)
 Hemidesmosomes
Adhering Junctions


41.  A belt like junction
 No fusion of cell membranes
 Trans membranous glycoprotein “E-cadherin” occupies
intercellular gap
 E-cadherin links to adherent proteins in cytoplasm which are:
 Catenin
 Vinculin
Zonula Adherens


42.  Structurally it is similar to Zonula adherence
 But its cell junction is strip-like and (not ring-like or belt-like)
 i.e. Cardiac muscle cells.
Fascia Adherens


43.  Macula adherins are commonly known as desmosomes
 “Spot-weld” like junctions
 Randomly distributed along lateral plasma membranes of the cells in
simple epithelium
 In stratified epithelium it is distributed throughout the plasma
membrane
 It is also found in cardiac muscle cells
2. Desmosomes


44.  Cell membrane in the region of junctions are seen further apart
(30mm) than the usual gap
 Electron dense attachment plaques are located opposite to each
other on the cytoplasmic aspects
 Intermediate filaments of the cytoskeleton are anchored to the
attachment plaques
 Two types of transmembranes glycoproteins named
Desmocolins and Desmogleins provide adherence
Desmosomes


45. 

46. These junctions serve to anchor the epithelial cells to the basal
lamina
A hemidesmosome is a spot like adhering junction which
gives appearance of a half desmosome
In hemidesmosome transmembrane linker proteins are
integrins
The cytoplasmic intermediate filaments of keratin are
inserted in to the attachment plaque
Hemidesmosomes


47. 

48. Characterized by presence of minute
tubular passageways
Provide direct cell to cell communication
Tubular passages allow movement of
ions and other small molecules between
adjacent cells
Communicating Junctions

49.  Gap junction also called the “Nexus” which are
communication junctions, occur frequently between the
epithelial cells
 Also found in cardiac muscle cells, smooth muscles,
neurons, astrocytes, and osteocytes
 Plasma membrane of the adjoining cells are closely
opposed with a gap of only 2nm
 The gap junction contains closely packed numerous
tubular intercommunicating channels
3. Gap Junction


50. The lumens of the channels of gap junction have an
average diameter of 1.5nm
These channels permit free passage of ions, sugar and
amino acids
In cardiac and smooth muscles the gap junction
provides electrical coupling of the adjacent cells
Gap junctions are frequently found in embryonic cells
Gap Junctions


51. 

52. 

53. Cells belonging to renewing population undergoes a sequence of events
which are repeated over and over again
The cycle is divided in to two parts
M PHASE: in which mitosis occurs (30 to 60 minutes)
INTERPHASE: it is intervening period between two cell divisions
consist of three sub phases
1 The G1 Phase
-During this phase synthesis of RNA and proteins occur s
-Cell size is restored to normal
-The duration of G1 is about 8 hours
Cell Cycle


54. 2 The S-Phase:
-During this synthesis of DNA takes place
-It results in preparation of exact replica of genetic material
and duplication of centrioles
-Duration is 8 hours
2 G2 Phase:
- It is period between the end of S phase and beginning of
mitosis
-During this process production and accumulation of energy for mitosis
takes place
-Duration is 2 to 4 hours
Cell Cycle


55. 

57. Mitosis

• The process of cell division which results in the
production of two daughter cells from a single
parent cell.
• The daughter cells are identical to one another and
to the original parent cell.

58. Mitosis can be divided into stages

1. Interphase
2.Prophase
3. Metaphase
4.Anaphase
5. Telophase

59. Interphase
The cell prepares for division

 DNA replicated
 Organelles replicated
 Cell increases in size

60.  Chromosomes become visible under LM
 Threads become shorter and thicker consist of two
chromatids joined by centromere
 Nucleoli disappears
 Centrioles separates and migrate to each pole and
starts giving out mitotic spindle
Prophase
The cell prepares for nuclear division


61.  Chromosomes line up at the center of the cell
 Spindle fibers attach from daughter cells to
chromosomes at the centromere
 Equatorial plate is formed
 Microtubules of mitotic spindle are attached at
centromere
 Microtubules exert pull on chromosomes
Metaphase
The cell prepares chromosomes for division


62.  Spindle fibers pull chromosomes apart
 ½ of each chromosome (called chromatid) moves to
each daughter cell
 Chromatids separate and move to respective poles as an independent
chromosome
 In human cell two identical sets of 46 chromosomes
move to the opposite poles
Anaphase
The chromosomes divide


63.  A constriction called cleavage furrow appears in the middle of
elongated cell
 Nuclear envelop is formed enclosing chromosomes
 2 nuclei form
 Cell wall pinches in to form the
2 new daughter cells
Telophase
The cytoplasm divides


64. 

65. Mitosis -- Review
Interphase Prophase
Metaphase Anaphase
Telophase Interphase

67. • Meiosis is the type of cell division by which
germ cells (eggs and sperm) are produced.
• One parent cell produces four daughter cells.
• Daughter cells have half the number of
chromosomes
found in the original parent cell
Meiosis


68. During meiosis, DNA replicates once, but
the nucleus divides twice.
Four stages can be described for each division
of the nucleus.
Meiosis


69.  Prophase is much longer consisting of five stages
1. Leptotene: Chromosomes becomes visible in the nucleus
2. Zygotene: Homologus chromosomes come together along their entire length
and synapses are formed
3. Pachytene: Chromosomes become thicker and shorter Each chromosome
pair is called bivalent
4. Diplotene: Chromosomes began to separate along their
length. Each bivalent consists of four chromatids
5. Diakinesis: Separation of chromosomes continue. Nucleolus and the
nuclear envelop disappears
Prophase


70. A spindle of microtubules is produced
by centrioles
Equatorial plate is formed
The bivalent chromosome pairs align
in the centre of the spindle
Metaphase


71. Chromosomes of homologous pairs
completely separates and move to the
opposite poles
No division of centromere occurs and the
whole chromosomes move to opposite
poles
Anaphase


72.  Nuclei are reconstructed
The parent cell is divided in to two daughter
cells
Each daughter cell contains haploid
(23) chromosomes
Each chromosome is double structured
consisting of two sister chromatids
Telophase


73. Meiosis II


74. Differences in Mitosis & Meiosis

 Mitosis
 Asexual
 Cell divides once
 Two daughter cells
 Genetic information is identical
 Meiosis
 Sexual
 Cell divides twice
 Four haploid daughter
cells
 Genetic information is different

75. General principles of cell communication
•Cell signaling is part of a complex system of communication that governs basic
activities of cells and coordinates cell actions.
•The ability of cells to perceive and correctly respond to their microenvironment is
the basis of development, tissue repair, and immunity as well as normal tissue
homeostasis.
Classification
These signals can be categorized based on the distance between signaling and
responder cells. Signaling within, between, and among cells is subdivided into the
following classifications:
1. lntracrine signals are produced by the target cell that stays within the target cell.
2. Autocrine signals are produced by the target cell, are secreted, and affect the target
cell itself via receptors. Sometimes autocrine cells can target cells close by if they are
the same type of cell as the emitting cell. An example of this is immune cells.

76. 3. Juxtacrine signals target adjacent (touching) cells. These
signals are transmitted along cell membranes via protein or lipid
components integral to the membrane and are capable of
affecting either the emitting cell or cells immediately adjacent.
4. Paracrine signals target cells in the vicinity of the emitting
cell. Neurotransmitters represent an example.
5. Endocrine signals target distant cells. Endocrine cells produce
hormones that travel through the blood to reach all parts of the
body.
6. Some cell-cell communication requires direct cell-cell
contact. Some cells can form gap junctions that connect their
cytoplasm to the cytoplasm of adjacent cells.

77. (a) Contact-dependent signaling: In which two
adjacent cells must make physical contact in order to
communicate. This requirement for direct contact allows for
very precise control of cell differentiation during embryonic
development. In the worm Caenorhabditis elegans, two cells
of the developing gonad each have an equal chance of
terminally differentiating or becoming a uterine precursor cell
that continues to divide. The choice of which cell continues to
divide is controlled by competition of cell surface signals. One
cell will happen to produce more of a cell surface protein that
activates the Notch receptor on the adjacent cell.

78. (b) Endocrine signaling: Many cell signals are carried by molecules
that are released by one cell and move to make contact with another cell.
Endocrine signals are called hormones. Hormones are produced by
endocrine cells and they travel through the blood to reach all parts of the
body. Specificity of signaling can be controlled if only some cells can
respond to a Particular hormone.
(c) Paracrine signaling: Paracrine signals such as retinoic acid target
only cells in the vicinity of the emitting Cell. Neurotransmitters
represent another example of a paracrine signal. Some signaling
molecules can function as both a hormone and a neurotransmitter. For
example, epinephrine and norepinephrine can function as hormones
when released from the adrenal gland and are transported to the heart by
way of the blood stream.

79. (d) Synaptic signaling: Synaptic signaling is a special case
of paracrine signaling (for chemical synapses) or juxtacrine
signaling (for electrical synapses) between neurons and target
cells. Signaling molecules interact with a target cell as a
ligand to cell surface receptors, and/or by entering into the cell
through its membrane or endocytosis for intracrine signaling.
This generally results in the activation of second messengers,
leading to various physiological effects.

80. References:
1. Presentation on Introduction To Human Anatomy &
Physiology, By Mr. Abhay Shripad Joshi.
2. Human Anatomy and Physiology-I,
By Dr. Mahesh Prasad, Dr. Antesh Kumar Jha, Mr.
Ritesh Kumar Srivastav, Nirali Prakashan, As per PCI
Syllabus. Page No. 1.7 to 1.22.
3. www.google.com.

81. THANK YOU