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College of Health and medical Technology\Kufa
First year
Human Physiology Lectures
Lecture No. 1
Cell Structure & Function
Physiology –Is the science that describes how organisms f and survive in
continually changing environments that includes all chemical substances (atoms,
ions, & molecules) necessary for life .
Cells - cells are the basic structural and functional units of the human body &
there are many different types of cells (e.g., muscle, nerve, blood, and so on)
Tissue
- is a group of cells that perform a specific function and the basic types of tissues
in the human body include epithelial, muscle, nervous, and connective tissues
Organ - an organ consists of 2 or more tissues that perform a particular function
(e.g., heart, liver, stomach, and so on)
System - an association of organs that have a common function; there are 11
major systems in the human body, including digestive, nervous, endocrine,
circulatory, respiratory, urinary, reproductive, muscular, lymphatic, skeletal, and
integumentary.
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Structure of a typical cell
Cell, or Plasma, membrane
- encloses every human cell
Plasma membrane
1. Cell,
or Plasma, membrane:
Cell membrane is the primary building blocks include:Protein (about 60% of the membrane) and lipid, or fat (about 40% of the
membrane).
The primary lipid is called phospholipid, and molecules of phospholipid form a
'phospholipid bilayer' (two layers of phospholipid molecules). This bilayer
forms because the two 'ends' of phospholipid molecules have very different
characteristics: one end is polar (or hydrophilic) and one (the hydrocarbon tails
below) is non-polar (or hydrophobic):
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Cell membrane
Functions of cell membrane include:
1. Supporting and retaining the cytoplasm
2. Being a selective barrier
The cell is separated from its environment and needs to get nutrients in and waste
products out. Some molecules can cross the membrane without assistance, most
cannot. Water, non-polar molecules and some small polar molecules can cross.
Non-polar molecules penetrate by actually dissolving into the lipid bilayer. Most
polar compounds such as amino acids, organic acids and inorganic salts are not
allowed entry, but instead must be specifically transported across the membrane by
proteins.
3.transport
Many of the proteins in the membrane function to help carry out selective transport.
These proteins typically span the whole membrane, making contact with the
outside environment and the cytoplasm. They often require the expenditure of
energy to help compounds move across the membrane
At the heart of the immune response is the ability to distinguish between self and
nonself. Everybody cell carries distinctive molecules that distinguish it as "self."
Normally the body's defenses do not attack tissues that carry a self-marker; rather,
immune cells coexist peaceably with other body cells in a state known as selftolerance
2. Cells, cytoplasm, and organelles ( Cells Alive) :
I. Cytoplasm consists of a gelatinous solution and contains microtubules (which
serve as a cell's cytoskeleton) and organelles
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The cyotoskeleton represents the cell's skeleton. Like the bony skeletons that give
us stability, the cytoskeleton gives our cells shape, strength, and the ability to
move, but it does much more than that. The cytoskeleton is made up of three types
of fibers that constantly shrink and grow to meet the needs of the cell:
a. microtubules,
b. microfilaments, and
c. actin filaments.
Each type of fiber looks, feels, and functions differently.
a. Microtubules consists of a strong protein called tubulin and they are the 'heavy
lifters' of the cytoskeleton. They do the tough physical labor of separating duplicate
chromosomes when cells copy themselves. They also hold the ER and form the
main component of flagella and cilia.
Microtubules (blue)
intermediate filaments (red)
Actin (green)
The three fibers of the cytoskeleton play countless roles
in the cell
b. Microfilaments are unusual because they vary greatly according to their
location and function in the body. For example, some microfilaments form tough
coverings, such as in nails, hair, and the outer layer of skin (not to mention animal
claws and scales). Others are found in nerve cells, muscle cells, the heart, and
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internal organs. In each of these tissues, the filaments are made of different
proteins.
3. Actin filament: are made up of two chains of the protein actin twisted
together. Although actin filaments are the most brittle of the cytoskeletal fibers,
they are also the most versatile in terms of the shapes they can take. They can
gather together into bundles, or even three-dimensional gels. They shorten or
lengthen to allow cells to move and change shape.
In these cells, actin filaments appear light purple,
microtubules yellow, and nuclei greenish blue
.
II. Nucleus:Cells also contain a nucleus within which is found DNA (deoxyribonucleic acid) in
the form of chromatin (or chromosomes during cell division) plus nucleoli (within
which ribosomes are formed)
Chromatin & chromosomes
Organelles include:
1. - Endoplasmic reticulum
comes in 2 forms: smooth and rough; the surface of rough ER is coated with
ribosomes; the surface of smooth ER is not
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functions of endoplasmic reticulum include: mechanical support, synthesis
(especially proteins by rough ER), and transport
The endoplasmic reticulum (ER) is a special membrane structure found only in
eukaryotic cells. Some ER has ribosomes on the surface (rough endoplasmic
reticulum) --the cell's protein-making machinery. Proteins that require special
conditions or are destined to become part of the cell membrane are processed in the
ER and then handed off to another organelle called the Golgi apparatus.
Endoplasmic reticulum
2. Golgi complex
The Golgi complex consists of a series of flattened sacs (or cisternae).
Its functions as
a. cellular post office. Proteins that arrive there are sorted, packaged and
transported to various destinations in the cell.
b. synthesis (of substances likes phospholipids), and production of lysosomes
3. Lysosomes
membrane-enclosed spheres that contain powerful digestive enzymes
functions include destruction of damaged cells & digestion of phagocytosed
materials (such as bacteria)
4. Mitochondria :Mitochondria is energy producing organil have a double-membrane: outer membrane &
highly convoluted inner membrane .
inner membrane has folds or shelf-like structures called cristae that contain
elementary particles; these particles represent an enzyme important in ATP
production
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primary function is production of adenosine triphosphate (ATP)
Mitochondria are found exclusively in
eukaryotic cells. These organelles are often
called the "power plants" of the cell because
their main job is to make energy (ATP).
Mitochondria are highly unusual--they
contain their own genetic material and
protein-making machinery enwrapped in a
double membrane
5 - Ribosomes
composed of rRNA (ribosomal RNA) & protein may be dispersed randomly
throughout the cytoplasm or attached to surface of rough endoplasmic reticulum
(RNA) often linked together in chains called polyribosomes or polysomes primary
function is to produce proteins
6 - Centrioles
paired cylindrical structures located near the nucleus play an important role in cell
division
Flagella & cilia:- - hair-like projections from some human cells cilia are relatively
short & numerous (e.g., those lining trachea) , flagellum is relatively long and
there's typically just one (e.g., sperm)
Functions of cilia
- projections of cell membrane that serve to increase surface area of a cell Villi
(which is important, for example, for cells that line the intestine)
- controls cell function via transcription and DNA (Deoxyribonucleic acid)
translation ( by controlling protein synthesis in a cell).
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Components of the cellular environment
The cellular environment is composed of :1. Water comprises 60 - 90% of most living organisms (and cells)
important because it serves as an excellent solvent & enters into many
metabolic reactions
2. Ions : atoms or molecules with unequal numbers of electrons and
protons: found in both intra- & extracellular fluid .Examples of important
ions include sodium, potassium, calcium, and chloride
3. Carbohydrates: composed of carbon, hydrogen, & oxygen atoms
(e.g., glucose is C6H12O6) an important source of energy for cells.
Types include: 1. (e.g., glucose) - monosaccharaides :-most contain 5 or 6
carbon atoms.
2. disaccharides two monosaccharides linked together
Examples include:a. sucrose (a common plant disaccharide is
composed of the monosaccharide glucose
and fructose)
b. lactose (or milk sugar; a disaccharide
composed of glucose and the
monosaccharide galactose)
3. Polysaccharides
Several monosaccharaides linked together
Examples include starch (a common plant
polysaccharide made up of many glucose
molecules) and glycogen (commonly stored
in the liver)
4. Proteins: about 50 - 60% of the dry mass of a typical cell
subunit is the amino acid & amino acids are linked by peptide bonds
Two types of protein:a. functional categories = structural (proteins part of the structure of a
cell like those in the cell membrane)
b. enzymes :- Enzymes are catalysts to speed up the reactions.
5.Lipids: about 40% of the dry mass of a typical cell.
composed largely of carbon & hydrogen , generally insoluble in water.
Lipids functions:
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a. long-term energy storage
b. structural components (as in the case of phospholipids that are the
major building block in cell membranes)
c. "messengers" (hormones) that play roles in communications within
and between cells.
6. Nucleic Acids:
DNA
RNA (including mRNA, tRNA, & rRNA)
Movement Across Membranes
1 - Passive processes - require no expenditure of energy by a cell:
a. Simple diffusion= net movement of a substance from an area of high
concentration to an area of low .The rate of diffusion is influenced by:
- concentration gradient
- temperature of a substance
-
-molecular weight- distance through which diffusion occurs
b. Osmosis = diffusion of water across a semipermeable membrane
(like a cell membrane)
c. Facilitated diffusion = movement of a substance across a cell
membrane from an area of high concentration to an area of low
concentration. This process requires the use of 'carriers' (membrane
proteins). This causes an 'opening' in the protein through which a
substance (e.g., sodium ions) can pass.
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2 - Active processes - require the expenditure of energy by cells:
Active transport = movement of a substance across a cell membrane
from an area of low concentration to an area of high concentration using a
carrier molecule
Active Transport: The Sodium-Potassium
Pump
) ‫مصطلحات المحاضرة االولى ( فسلجة الخلية‬
actin filaments
‫شعيرات االكتين‬
Active transport
‫نقل فاعل‬
amino acids
‫احماض امينية‬
‫الجسيم المركزي‬
‫اهداب‬
‫صهاريج‬
Centrioles
cilia
cisternae
conformational
connective tissues
Convoluted
cyotoskeleton
‫متعلق بتكوين‬
‫األنسجة الضامة‬
disaccharides
‫ملتف‬
‫هيكل الخلية‬
‫السكريات الثنائية‬
Epithelial
‫ظهاري‬
ER
eukaryotic cell
expenditure
‫الشبكة الهيولية الباطنة‬
‫خلية حقيقية النواة‬
Facilitated diffusion
‫االنتشار بالمساعدة‬
‫اسواط‬
‫االنفاق‬
flagella
integumentary.
) ‫غالفي( جلدي‬
Lysosomes
microtubules
mitochondria
monosaccharides
organelles
‫الجسيمات الحالة‬
‫االنيبات الدقيقة‬
) ‫المتقدرات ( المايتوكوندريا‬
‫السكريات األحادية‬
‫العضيات‬
‫عملية سلبية‬
Passive processe
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‫‪phospholipids‬‬
‫‪polysaccharides‬‬
‫الدهون الفوسفاتية‬
‫عديد السكاريد‬
‫الحمض النووي الريبي‬
‫المنشطات‬
‫انتحار‬
‫األنسجة‬
‫‪RNA‬‬
‫‪steroids‬‬
‫‪suicide‬‬
‫‪tissue‬‬
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