The Cell, Physiology, Introductory level

Basic functions of the human physiology at the cellular level, discussing the cell and its organelles and the role of each one alone.

1. The Cell and General
Physiology
Dr. Fuad Al-Ameer
Introduction to Physiology

2. WHAT IS PHYSIOLOGY?
•Physiology is the study of life, specifically, how cells,
tissues, and organisms function.
•Physiology studies the normal function within living
organisms.

3. LEVELS OF ORGANIZATION:
Chemicals→cells→tissues→organs→systems→organisms
Each level is associated with a proceeding level.

4. •Cell: The structural and functional unit of the living
body.
•Tissue: The group of cells having similar function.
•Organ: The structure that is formed by two or more
primary types of tissues.
•System: Group of organs that work together to
carry out specific functions of the body.

5. STRUCTURE OF THE CELL
The structure of the cell is studied
under three headings:
1. Cell membrane
2. Cytoplasm
3. Nucleus.

6. 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).

7. Lipid Layers of the Cell Membrane:
Major lipids are:
1. Phospholipids
2. Cholesterol
Protein Layers of the Cell Membrane
1. Integral proteins or transmembrane
proteins.
2. Peripheral proteins or peripheral
membrane proteins.
COMPOSITION OF CELL MEMBRANE
Cell membrane is composed of three
types of substances:
1. Proteins (55%)
2. Lipids (40%)
3. Carbohydrates (5%).

8. LIPID LAYERS OF THE CELL MEMBRANE
•Phospholipids: The lipid substances containing
phosphorus and fatty acids. Phospholipids are soft
and oily structures.
Phospholipid molecules are arranged in two layers.
The outer part of the phospholipid molecule is called
the head portion (hydrophilic).and the inner portion
is called the tail portion (hydrophobic).
Hydrophilic soluble in water and has strong
affinity for water.
Hydrophobicinsoluble in water and repelled by
water.
•Cholesterol: is responsible for the
structural integrity of lipid layer of
the cell membrane.

9. PROTEIN LAYERS OF THE CELL MEMBRANE
•Integral proteins: proteins that pass
through entire thickness of cell
membrane from one side to the other
side.
•Peripheral proteins: proteins which are
partially embedded in the outer and
inner surfaces of the cell membrane and
do not penetrate the cell membrane.

10. FUNCTIONS OF CELL MEMBRANE
1. Protective function: Cell membrane
protects the cytoplasm and the
organelles present in the cytoplasm
2. Selective permeability: Cell membrane
acts as a semipermeable membrane,
which allows only some substances to
pass through it and acts as a barrier for
other substances
3. Exchange of gases: Oxygen enters
the cell from the blood and carbon
dioxide leaves the cell and enters the
blood through the cell membrane
4. Maintenance of shape and size of the
cell: Cell membrane is responsible for
the maintenance of shape and size of
the cell.

11. CYTOPLASM
Organelles with limiting membrane:
1. Endoplasmic reticulum 2. Golgi apparatus
3. Lysosome 4. Peroxisome
5. Centrosome and centrioles6. Secretory vesicles
7. Mitochondria 8. Nucleus
Organelles without limiting membrane:
1. Ribosomes 2. Cytoskeleton
Jellylike material formed by 80%
of water. It contains a clear liquid
called cytosol and various
particles of different shape and
size.
ORGANELLES IN CYTOPLASM :
The cellular structures embedded in
the cytoplasm. Organelles are
considered as small organs of the
cell.

12. Organelles Functions
Rough endoplasmic reticulum 1. Synthesis of proteins
2. Degradation of wornout organelles
Smooth endoplasmic reticulum 1. Synthesis of lipids and steroids
2. Role in cellular metabolism
3. Storage and metabolism of calcium
4. Catabolism and detoxification of toxic substances
Golgi apparatus 1. Processing, packaging, labeling and delivery of proteins and lipids
Lysosomes 1. Degradation of macromolecules
2. Degradation of wornout
organelles
3. Removal of excess of secretory products
4. Secretion of perforin, granzymes, melanin and serotonin
Mitochondria 1. Production of energy
2. Synthesis of ATP
3. Initiation of apoptosis
Functions of cytoplasmic organelles

13. Organelles Functions
Peroxisomes 1. Breakdown of excess fatty acids
2. Detoxification of hydrogen peroxide and other metabolic products
3. Oxygen utilization
4. Acceleration of gluconeogenesis
5. Degradation of purine to uric acid
6. Role in the formation of myelin
7. Role in the formation of bile acids
Centrosome 1. Movement of chromosomes during cell division
Ribosomes 1. Synthesis of proteins
Cytoskeleton 1. Determination of shape of the cell
2. Stability of cell shape
3. Cellular movements
Nucleus 1. Control of all activities of the cell
2. Synthesis of RNA
3. Sending genetic instruction to cytoplasm for protein synthesis
4. Formation of subunits of ribosomes
5. Control of cell division
6. Storage of hereditary information in genes (DNA)

14. 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.
Eukaryotescells with nucleus
Prokaryotescells without nucleus
•Types of cells:
Uninucleated cells: only one nucleus (Most of
the cells)
Multinucleated cells: many nuclei (Few types of
cells like skeletal muscle cells)
•Nucleosome: packing unit of chromatin.
Nucleosomes are packed together tightly
with the help of a histone molecule to
form a chromatin fiber. Just before cell
division, the chromatin condenses to form
chromosome.

15. CHROMOSOMES
Chromosome is the rod-shaped nuclear
structure that carries a complete
blueprint of all the hereditary
characteristics of species.
A chromosome is formed from a single
DNA molecule coiled around histone
molecules. Each DNA contains many
genes.
Only during cell division, the
chromosomes are visible under
microscope.
All the dividing cells of the body except
reproductive cells contain 23 pairs of
chromosomes. Each pair consists of one
chromosome inherited from mother and
one from father.
reproductive cells contain only 23 single
chromosomes.
Diploid cells:cells with 23 pairs of
chromosomes
Haploid cells. The reproductive cells
called gametes or sex cells, contain only
23 single chromosomes.

16. NUCLEOLUS
•Nucleolus is a small, round granular
structure of the nucleus.
•The nucleolus contains RNA and some
proteins.
•The RNA is synthesized by five different
pairs of chromosomes and stored in the
nucleolus.
•Later, it is condensed to form the subunits
of ribosomes.
•All the subunits formed in the nucleolus are
transported to cytoplasm through the
pores of nuclear membrane.
•In the cytoplasm, these subunits fuse to
form ribosomes, which play an essential
role in the formation of proteins.

17. DEOXYRIBONUCLEIC ACID (DNA)
•DNA is a nucleic acid that carries the
genetic information to the offspring
of an organism.
•DNA forms the chemical basis of
hereditary characters. It contains the
instruction for the synthesis of proteins
in the ribosomes.
•Gene is a part of a DNA molecule.
•DNA is present in:
Nucleus (chromosome)
Mitochondria of the cell.
•DNA in the nucleus is responsible for the
formation of RNA. RNA regulates the
synthesis of proteins by ribosomes.
•DNA in mitochondria is called non-
chromosomal DNA.

18. STRUCTURE OF DNA
•DNA is a double stranded complex nucleic acid.
•Each chain of DNA molecule consists of many
nucleotides. Each nucleotide is formed by:
1. Deoxyribose –sugar
2. Phosphate
3. One of the following organic (nitrogenous)
bases:
Purines: –Adenine (A)
–Guanine (G)
Pyrimidines: –Thymine (T)
–Cytosine (C)
•The strands of DNA are arranged in such a
way that both are bound by specific pairs
of bases.
Adeninewith Thymine (2 hydrogen bonds)
Guaninewith Cytosine(3 hydrogen bonds)
•The hereditary information that is encoded
in DNA is called genome. Each DNA
molecule is divided into discrete units
called genes.

19. GENE
•Gene is a portion of DNA molecule that
contains the message or code for the
synthesis of a specific protein from amino
acids.
•Gene is considered as the basic
hereditary unit of the cell.
•In the nucleotide of DNA, three of the
successive base pairs are together called
a triplet or a codon.
•For example, the triplet CCA is the code
for glycine and GGC is the code for
proline.

20. GENETIC DISORDERS
•A genetic disorder is a disorder that occurs
because of the abnormalities in an
individual’s genetic material (genome).
Genetic disorders are either hereditary
disorders or due to defect in genes.
•Causes of Gene Disorders:
1. Genetic variation
2. Genetic mutation
•Classification of Genetic Disorders:
Genetic disorders are classified into
four types:
1. Single gene disorders
2. Multifactorial genetic disorders
3. Chromosomal disorders
4. Mitochondrial DNA disorders.

21. RIBONUCLEIC ACID (RNA)
•RNA is a nucleic acid that contains a
long chain of nucleotide units. It is
similar to DNA but contains ribose
instead of deoxyribose.
•RNA is formed from DNA.
•Each RNA molecule consists of a single
strand of polynucleotide unlike the
doublestranded DNA.
Each nucleotide in RNA is formed by:
1. Ribose –sugar.
2. Phosphate.
3. One of the following organic bases:
Purines: –Adenine (A)
–Guanine (G)
Pyrimidines: –Uracil (U)
–Cytosine (C).
Uracil replaces the thymine of DNA and
it has similar structure of thymine.

22. TYPES OF RNA:
1. Messenger RNA (mRNA):
Messenger RNA carries the genetic code
of the amino acid sequence for synthesis
of protein from the DNA to the cytoplasm.
2. Transfer RNA (tRNA):
Transfer RNA is responsible for decoding
the genetic message present in mRNA.
3. Ribosomal RNA (rRNA):
Ribosomal RNA is present within the
ribosome and forms a part of the structure
of ribosome. It is responsible for the
assembly of protein from amino acids in
the ribosome.

23. CELL DEATH
APOPTOSIS:
•Apoptosis is the natural or programed
death of the cell under genetic control.
•This type of programmed cell death is a
normal phenomenon and it is essential
for normal development of the body.
•The purpose of apoptosis is to remove
unwanted cells without causing any stress
or damage to the neighboring cells.
NECROSIS:
Necrosis is the uncontrolled and unprogramed
death of cells due to unexpected and accidental
damage.
Common causes of necrosis are injury, infection,
inflammation, infarction and cancer.
Necrosis is induced by both physical and
chemical events such as heat, radiation, trauma,
hypoxia due to lack of blood flow and
exposure to toxins.

24. 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.
1. Atrophy: decrease in size of a cell.
2. Hypertrophy: increase in the size of a cell.
3. Hyperplasia: increase in number of cells
due to increased cell division (mitosis).
4. Dysplasia: the condition characterized by
the abnormal change in size, shape and
organization of the cell.
5. Metaplasia: the condition that involves
replacement of one type of cell with another
type of cell.

25. CELL DEGENERATION
•Cell degeneration is a process
characterized by damage of the cells at
cytoplasmic level, without affecting the
nucleus.
•Degeneration may result in functional
impairment of a tissue or an organ.
•It is common in metabolically active
organ like liver, heart and kidney.
•Causes for Cell Degeneration:
1. Atrophy, hypertrophy, hyperplasia
and/or dysplasia of cell
2. Fluid accumulation in the cell
3. Fat infiltration into the cell
4. Calcification of cellular organelles.

26. CELL AGING AND STEM CELLS
CELL AGING:
Cell aging is the gradual structural and
functional changes in the cells that occur
over the passage of time.
STEM CELLS:
Stem cells are the primary cells capable
of reforming themselves through mitotic
division and differentiating into
specialized cells.
TYPES OF STEM CELLS
Stem cells are of two types:
1. Embryonic stem cells derived from
embryo
2. Adult stem cells derived from adults.
ADVANTAGES OF STEM CELLS
Adult stem cells from bone marrow are
used in bone marrow transplant to treat
leukemia and other blood disorders.

27. THE END
Done by:
Dr. Fuad Al-Ameer