002 Cell physiology.pdf

Cell Physiology
Control of Cell Function
GAMBY, nursing
By Dessalegn D

Cell Physiology
 Cell is defined as the structural and functional
unit of the living body.
 The Cell is the Fundamental Unit of Life.
1)Because cells carry out and control the functional processes of
life.

1. Cell physiology
 What is the cell theory?
 The cell is the smallest (basic) unit of life.
 All organisms are composed one or more cells.
 New cells arise only from pre-existing cells.
Cell function and its basics
Human being have around 1013 to 1014 cells
Typical human cell 10-20 µm in diameter (µm = micrometer,
1/1000 mm, 1/1,000,000 m).
-Cell is the basic unit of living things
-humans are multicellular organisms

Cell Diversity
 Not all cells are alike.
 Even cells within the same organism show
enormous diversity in:
 Size
 Shape
 Internal Organization

Several basic functions of all cells
 Obtain nutrients and O2
 Make usable energy, Food + O2 ➝ CO2 + H2O + energy
 Eliminate wastes
 Synthesize needed molecules
 Respond to environmental changes
 Control exchange of materials with the environment
 Reproduction
Basic physiological function of cells
 Transport molecules across the cell membrane
 Bioelectrical phenomena of the cell.
 Contraction of muscle

 Human beings have around 1013 to 1014 cells
 Which we broadly categorized into 4 groups:
 Muscle cells
 Epithelial cells,
 Nerve cells and
 Connective tissue cells
** cells specialize to =>Tissues

 Organelle: a cell component that performs specific functions
in the cell.
 Protoplasm:
 Different substances that make up the cell are collectively called
as Protoplasm.
 It is the colorless material comprising the living part of a cell,
including the nucleus, cytoplasm, and other organelles.
 Cytoplasm:
 The material or protoplasm within a living cell, excluding the
nucleus.
• Cytosol:
• The aqueous component of the cytoplasm of a cell, within which
various organelles and particles are suspended.
• Semigelatinous intracellular fluid

Cytosol =55% of cell volume
 Cytosol functions (many in conjunction with other
processes) Cell signaling, Cytokinesis, Protein
synthesis, Glycolysis, gluconeogenesis
 -Composition varies in different areas of cell and
involved in several kinds of cell activities
1) Enzymatic regulation of intermediary metabolism
 Chemical reactions involving synthesizing and breaking down small
organic molecules
(e.g., sugars, amino acids, fatty acids)
 Provides raw material for structure and function

The Nature of Cells
 Plasma membrane (cell membrane) =Security gate
a. Defines inside/outside of cells
b. Intracellular fluid (ICF) - inside cell
c. Extracellular fluid (ECF) - outside cell
d. Selectively permeable - controls movement of molecules between ICF
and ECF
 Nucleus (Region containing DNA&RNA)=control center or , "genetic
blueprint,"
 Cytoplasm
a. Area between nucleus and plasma membrane
b. Cytosol is semiliquid, site of chemical reactions
c. Contains organelles (1) separation of chemical reactions (2) Specialized
for a particular function

Specialization of cellular function
and components of cell
Rough ER Smooth ER
Centrosome
CYTOSKELETON
Microfilaments
Microtubules
Microvilli
Peroxisome
Lysosome
Golgi apparatus
Ribosomes
In animal cells
Lysosomes
Centrioles
Flagella
Nucleolus
Chromatin
NUCLEUS
Flagelium
Intermediate filaments
ENDOPLASMIC RETICULUM (ER)
Mitochondrion
Nuclear envelope
Plasma membrane

Cell Membrane
 Cell membrane is a protective sheath, enveloping the cell body.
 It is also known as plasma membrane or plasmalemma.
 This membrane separates the fluid outside the cell called
extracellular fluid (ECF) and
 The fluid inside the cell called intracellular fluid (ICF).
 The cell membrane is a semipermeable membrane.
 Need to allow some materials; but not all to pass
through the membrane
What is being partitioned with the PM/ blood vessel wall??

Body fluid composition
All
compartments
have the same
osmolarity
at steady state.
*Transcellular fluid is part of the ECF and includes epithelial secretions
such as the cerebrospinal and extraocular fluids.

Total Body Water=70kg*0.6=42L
 ICF(interacellular fluid)
 2/3 total body water =28L
 ECF( Extracellular fluid
 1/3 of total body water =14L
 Interstitial fluid
 ¾ ECF=11L
 Plasma volume
 ¼ of ECF=3L
 Vascular compartment
 Blood volume: plasma + cellular element of blood
8/25/2022 BDU Renal -physiology BY Dessalegn.D 14

Composition of cell membrane
 Cell membrane are composed of three types of
substances with primarily of proteins and
phospholipids:
 Proteins (55%),
 Lipids (40%):
 Phospholipids 25%
 Cholesterol 13%
 Other lipids 4%.
 Carbohydrates (3-5%).

Fluid mosaic model of plasma membrane
Cholesterol - 13%
7.5- 10 nm
25%
Protein 55%
4%
Single transmembrane
Protein
Multiple
transmembrane
Protein
3
%
Lipid membrane form compartment inside the cell
 Proteins float in fluid lipid bilayer

Lipid bilayer: Phospholipids
 Most abundant lipid
 LIPID is Amphipathic
 Polar/hydrophilic head
(attracted to water)
 Pair of nonpolar
/hydrophobic tails (repelled
by water)

 Proteins (55%): Two types
 Peripheral proteins:
1) Are not imbedded in the cell membrane.
2) Cell surface identity marker (antigens)
 Integral proteins: Transmembrane protein
-Are anchored to or imbedded in the cell membrane through hydrophobic
interactions. Penetrate lipid bilayer
Membrane proteins:
Glycoprotein:
 The combination of Protein and sugar attached in one.
 Serves as specific biological marker  cell recognition

Functions of Integral proteins

Nucleus
 Nucleus is the most prominent and the largest cellular organelle.
 Nucleus is present in all the cells in the body except the red blood cells.
 The cells with nucleus are called eukaryotes.
 Most of the cells have only one nucleus (uninucleated cells).
 Few types of cells like skeletal muscle cells have many nuclei
(multinucleated cells).
 Contains DNA which directs the activity of
the cell – Blue print

Function of Nucleus
 Storage of hereditary information in genes (DNA)
Regulate and Control of all activities of the cell
 Synthesis of mRNA
 Sending genetic instruction to cytoplasm for protein
synthesis
 Control of cell division
 Formation of subunits of ribosomes

Ribosome=Workbenches
 Ribosomes are of two types:
 Some ribosomes that are attached to rough endoplasmic
reticulum
 Some free ribosomes that are distributed in the cytoplasm. free
ribosomes make enzymes for use in cytosol
 Function:
 Synthesis of proteins:
 Read instructions to build proteins from DNA.

Endoplasmic reticulum (ER) =Assembly
line
 is interconnected fluid-filled membranous system :two types
Smooth - interconnected tubules and rough - interconnected
flattened sacs has ribosomes which help in protein synthesis (cell
also has "free" ribosomes)
• There are two distinct ER:
a) The rough (Granular) ER is so named because the cytoplasmic
surface is covered with ribosomes.
b) The smooth (Agranular) ER appears smooth since its
cytoplasmic surface lacks ribosomes.

 Rough endoplasmic reticulum=
Synthesis of proteins
 The RER is where hydrolytic
enzymes are manufactured
before being transported to
the Golgi apparatus
 Smooth endoplasmic reticulum
 Lipid synthesis (steroid hormone
secreting cells)
 detoxify harmful substances (liver cells)
 store calcium (muscle cells)

Golgi apparatus=Distribution
center
 The GA is the distribution and shipping department for the cell's
chemical products.
 Golgi complex is a network of flattened smooth membranous sacs -
cisternae and vesicles.
 These are responsible for the secretion of proteins from the cells
(hormones, plasma proteins, and digestive enzymes).

lysosomes =Cleaning center
 "Lysosome" was the name given because of these enzymes' ability to "lyse" the
cell.
(1)membranous sacs containing hydrolytic enzymes
(2)digest cellular debris and other substances (old organelles, bacteria) or Degradation
of macromolecules.
 Initially referred to as "suicide bags”
 material from outside cell can be brought in to be digested by lysosome–
endocytosis (membrane surrounds substance and vesicle pinches off)
- Pinocytosis - fluids, "cell drinking"
-Phagocytosis - large particles, "cell eating"
*cell can use digested material

Peroxisomes=Detoxify various
wastes
 Peroxisome has oxidative enzymes that detoxify
various wastes.
 Breakdown of excess fatty acids
 Detoxification of hydrogen peroxide and other
metabolic products

Centrosome
 Centrosome is the membrane-bound cellular organelle
situated almost in the center of cell, close to nucleus.
 It consists of two cylindrical structures called centrioles which
are made up of proteins.
Centrioles are responsible for the movement of chromosomes
during cell division.

Mitochondria =Power house &
have double membrane
 It is the “Powerhouses” of the cell.
 Has its own DNA, Self-replicative.
 Mitochondrial DNA itself control the
replication itself.
 Based on the need of cell,
mitochondria may multiply.
 Oxidation of nutrients produce CO2 and
H2O.

 Inner membrane has folds called cristae (folds
increase surface area):-matrix is gel inside
 play a role in apoptosis (programmed cell death)
 converts energy from food into usable energy for
the cell - ATP (adenosine triphosphate)
 Energy in chemical bonds of food molecules can't be used
directly
 ATP ➝ ADP +Pi + useful energy

vaults
 Found associated with lipid rafts or
more cholesterol
1) non-membranous, octagonal organelle made of
protein
2) probably used to transport molecules from nucleus
to other cell locations (mRNA, ribosomes)

Cytoskeleton
 Cytoskeleton are Filaments &
fibers.
 It consists of three major protein
components:
a) Microfilaments
b) Microtubule
c) Intermediate filaments
 FUNCTION:
 Determination of shape of the cell
 Cellular movements of substances.

Special Structural Features of Cell Membranes
 Cilia:
 Tiny hair-like structures that project from the
surface of the cell.
1) Stroke in harmony, either up or down stroke, & forward or backward direction
 Respiratory tract, uterine tube.
 Flagella:
 Simple whip-like structure that propels sperm
through its environment.
 Microvilli:
 Numerous folds (finger-like projections) increase
surface area.
1) Aid absorption.

Cell junction
 is the connection between the neighboring
cells or the contact between the cell and extracellular matrix.
 It is also called membrane junction.
 Cell junctions are classified into three types:
 Occluding junctions,
 Communicating junctions,
 Anchoring junctions.

Tight junction
 Tight junction is the intercellular occluding
junction that prevents the passage of large
molecules.
 Function:
 Strength and stability to
tissues,
 Selective permeability,
 Fencing function,
 Maintenance of cell
polarity,
 Formation of blood
brain barrier.
 Present in the:
• Apical margins of Epithelial lining of intestinal
mucosa and wall of renal tubule.
• Endothelium in capillary wall and
choroid plexus.

Gap junction
 Gap junction is the intercellular junction
that allows passage of ions and smaller
molecules between the cells.
 It is also called nexus.
 Function:
 Allows passage of small
molecules, ions and
chemical messengers,
 Propagation of action
potential.
 Present in:
• Heart,
• Basal part of epithelial cells
of intestinal mucosa, etc.

Anchoring junctions
 Anchoring junctions are the junctions,
which provide strength to the cells by
acting like mechanical attachments.
 Function:
 It provides firm
structural attachment
between two cells or
between a cell and the
extracellular matrix.
 Cell to cell attachment  Present in :
• Epithelial lining
• Heart
• Epidermis

Cell Death
 Cell death occurs by two distinct processes:
 Apoptosis and
 Necrosis.
 Apoptosis is defined as the natural or programed death
of the cell under genetic control.
 Apoptosis usually does not produce inflammatory reactions in
the neighboring tissues.

1. Apoptosis
 Apoptosis can be defined as 'gene-directed cellular self-
destruction.
 It is often referred to as ‘programmed cell death’ or cell
suicide.
 Apoptosis is a peculiar well controlled individual cell death.
 In the human body About 10 million cells are produced
everyday in human body by mitosis and a similar number die
by apoptosis !!!

Functional Significance of Apoptosis:
 Plays a vital role in cellular homeostasis,
 Useful for removal of a cell that is damaged beyond
repair by a virus or a toxin,
 Crucial for embryonic development:
 Errors in Apoptosis can lead to Birth Defects
 An essential event during the development and in adult stage.

2. Necrosis
 Necrosis (means ‘dead’ in Greek) is the
uncontrolled and unprogramed death of cells
due to unexpected and accidental damage.
 It is also called ‘cell murder’ because the cell is
killed by extracellular or external events.
 After necrosis, the harmful chemical
substances released from the dead cells cause
damage and inflammation of neighboring
tissues.
Common causes of
necrosis are:
 Injury,
 Infection,
 Inflammation,
 Infarction and
 Cancer.

Cell Death
Change in
behaviors
Alteration of
physiological
response :major
organs
Environmental
stressor
Poor
mechanistic
understanding
cell
Death
less
descriptive
understanding
Less
cognitive
function
Alteration in
brain
physiology

Cell adaptation
 Cell adaptation refers to the changes taking place in a cell in
response to environmental changes.
 Cellular adaptation occurs by any of the following mechanisms.
 Atrophy means decrease in size of a cell.
 Atrophy of more number of cells results in decreased size or
wasting of the concerned tissue, organ or part of the body.

 Hypertrophy is the increase in the size of a cell.
 Hypertrophy of many cells results in enlargement or
overgrowth of an organ or a part of the body.
 Hyperplasia is the increase in number of cells due to
increased cell division (mitosis).
 It is also defined as abnormal or unusual proliferation
(multiplication) of cells due to constant cell division.

Cancer cell
 Immortality, as applied to cells, is the property of unlimited cell
proliferation.
 Normal (primary) cells, with the exception of stem cells, have a
limited lifetime.
 Cancer cells are of necessity, and by definition, immortal cells.
 Oncogenes are cancer-promoting genes that arise as the result of
a mutation in, or abnormal expression of a normal gene (“proto-
oncogene”).

 Cancers arise as the result of an interplay between your
 Genetic heritage,
 The environment,
 Luck, your choice of lifestyle and
 Occupation.
 Benign tumors do not spread : for example warts
 Malignant tumors (cancers) invade and spread throughout
the body (metastasis).

002 Cell physiology.pdf

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002 Cell physiology.pdf