brief description of cytology

2. Presented By:
Ayaz Ahmed
BS-MT (DOW), MPH (Fellow)
Dow University of Health Sciences, Karachi.
E-mail: aalksite@gmail.com
Dated: 06-11-2017

3.  Cell Biology
 Cell
 The cell theory
 Features of cell
 Types of cell
 Levels of organization
 Anatomy of cell and,
 Physiology of cell.

4.  The study of cell, molecules and chemical
processes in metabolism called cell biology.
 Often called cytology.

5.  The cell (from Latin cella, meaning "small room“ or “Hollow
Space”) is the basic structural, functional, and biological unit of all
known living organisms.
 The cell is the lowest level of structure capable of performing all
the activities of life.
 The first cell was observed and named by Robert Hooke in 1665
from slice of cork.
 Every living thing has cells: bacteria, protozoans, fungi, plants, and
animals are the main groups (Kingdoms) of living things.

7.  Robert Hooke - 1665 - using
an early microscope viewed
cork and saw many repeating
box-like structures and called
them “cells.”
 What he saw were spaces
surrounded by walls that once
contained living cells.
 Since Hooke’s first
observations what is known
about cells has increased
greatly.

8.  The cell theories were proposed by Matthais
Schleiden andTheodor Schwann in 1839:
 All living things are made up of cells.
 Cells are the smallest working unit of all living
things.
 All cells come from preexisting cells through
cells division.

9.  Cells are 90% fluid (called cytoplasm) which
consists of free amino acids, proteins,
carbohydrates, fats, and numerous other
molecules.
 The cell environment (i.e., the contents of the
cytoplasm and the nucleus, as well as the way
the DNA is packed) affect gene
expression/regulation, and thus are VERY
important aspects of inheritance.

10.  There are two most important type of cell.
 Prokaryotic Cells ( Bacteria, Cyanobacteria)
 Eukaryotic cells (Fungi, Protozoa, Animals
and Plants).
 According to human physiology, there are two
major types of cells
 Somatic Cells (soma=body; body cells)
 Sex Cells ( for differentiation of gender)

11. Prokaryotic cell (Bacteria) Eukaryotic cell

12.  There are specialized cells - both in structure
and function - within the body, all cells have
similarities in their structural organization
and metabolic needs (such as maintaining
energy levels via conversion of carbohydrate
to ATP and using genes to create and
maintain proteins).

13. Here are some of the different types of specialized cells within the
human body.
Nerve Cells: Also called Neurons, these cells are in the nervous
system and function to process and transmit information (it is
hypothesized).They are the core components of the brain, spinal
Cord and peripheral nerves.They use chemical and electrical
synapses to relay signals throughout the body.
Epithelial cells: Functions of epithelial cells include secretion,
absorption, protection, transcellular transport, sensation detection,
and selective permeability. Epithelium lines both the outside (skin)
and the inside cavities and lumen of bodies.

14. Exocrine cells: These cells secrete products through ducts, such as
mucus, sweat, or digestive enzymes. The products of these cells
go directly to the target organ through the ducts. For example, the
bile from the gall bladder is carried directly into the duodenum via
the bile duct.
Endocrine cells: These cells are similar to exocrine cells, but
secrete their products directly into the bloodstream instead of
through a duct. Endocrine cells are found throughout the body but
are concentrated in hormone-secreting glands such as the
pituitary. The products of the endocrine cells go throughout the
body in the blood stream but act on specific organs by receptors
on the cells of the target organs. For example, the hormone
estrogen acts specifically on the uterus and breasts of females
because there are estrogen receptors in the cells of these target
organs.

15. Blood Cells: The most common types of blood cells are:
Red blood cells (erythrocytes). The main function of red blood
cells is to collect oxygen in the lungs and deliver it through the
blood to the body tissues. Gas exchange is carried out by simple
diffusion (To see this in action please click here [1]).
White blood cells (leukocytes). They are produced in the bone
marrow and help the body to fight infectious disease and foreign
objects in the immune system. White cells are found in the
circulatory system, lymphatic system, spleen, and other body
tissues.
Platelets (Thrombocytes). Helps in blood clotting.

16.  Oocytes
 Sperm cells

18.  A cell is the smallest unit of life that can replicate
independently, and cells are often called the "building blocks
of life".The study of structure of cell is called anatomy of cell.

19.  Controls the cell; houses the genetic material (DNA). The nucleus
is the largest of the cells organelles. Cells can have more than one
nucleus or lack a nucleus all together. Skeletal muscle cells contain
more than one nucleus whereas red blood cells do not contain a
nucleus at all. The nucleus is bounded by the nuclear envelope, a
phospholipid bilayer similar to the plasma membrane. The space
between these two layers is the nucleolemma Cisterna.
 The nucleus contains the DNA, as mentioned above, the
hereditary information in the cell. Normally the DNA is spread out
within the nucleus as a threadlike matrix called chromatin. When
the cell begins to divide, the chromatin condenses into rod-shaped
bodies called chromosomes, each of which, before dividing, is
made up of two long DNA molecules and various histone
molecules. The histones serve to organize the lengthy DNA,
coiling it into bundles called nucleosomes.

21.  The gel-like material within the cell membrane is referred to
as the cytoplasm. It is a fluid matrix, the cytosol, which
consists of 80% to 90% water, salts, organic molecules and
many enzymes that catalyze reactions, along with dissolved
substances such as proteins and nutrients.
 The cytoplasm plays an important role in a cell, serving as a
"molecular soup" in which organelles are suspended and held
together by a fatty membrane.

22.  It contains many different organelles which are
considered the insoluble constituents of the
cytoplasm, such as:
 The mitochondria,
 Lysosomes,
 Microbodies (Peroxysomes and Glyoxysome),
 Ribosomes,
 Vacuoles and
 Cytoskeletons,
 as well as complex cell membrane structures such as:
 the endoplasmic reticulum and the
 Golgi apparatus that each have specific functions
within the cell.

23.  Known as cellular
powerhouse of cell.
 The site of much of the
energy harvest by cells have
double membrane structure.
 Inner membrane folded into
inward projections called
cristae.
 two spaces within the
mitochondrion - the matrix
and the intermembrane
space.

24.  The site of oxygen consumption within cells.
 Have their own DNA that is similar to prokaryotic
DNA.
 Have their own ribosomes that are similar in
construction to prokaryotic ribosomes.
 Synthesize many, but not all, of their own proteins
 Mitochondria replicate by binary fission - similar to
prokaryotic cell division

25.  Particles consisted of proteins and ribosomal RNA (rRNA)
 Function = protein synthesis that’s why it’s called protein
factory.
 Prokaryotes = 70S, eukaryotes = 80S

26.  Free ribosomes in cytosol synthesize proteins
that function within cytosol.
 Bound ribosomes are attached to the outside of
the endoplasmic reticulum or nuclear envelope:
membrane protein, organelle proteins or
secretory protein.
 Bound and free ribosomes are structurally
identical and can alternate between the two
roles.

27.  ER consists of a network of
membranous tubules and sacs
called cisternae (cisterna = a
reservoir for a liquid).
 The network are interconnected.
 The ER membrane is continuous
with the nuclear envelope and
the cisternal space of the ER is
continuous with the space
between the two membranes of
the nuclear envelope.

28. Smooth ER:
 Synthesis of lipid (oils, phospholipids, and
steroids)
 Glycogen metabolism in the liver cells
 Detoxification of drugs and poisons
 Store calcium for muscle contraction

29.  Ribosomes are attached to the outside.
 Is abundant in cells that secrete protein.
 Synthesis secretary proteins, cell membrane protein
and organelle protein (proteins are targeted to
determined location according to the sorting signals.
Sorting signals are encoded in a.a sequences or in the
attached oligosaccharides).
 Synthesis of phospholipids and ER associated protein.

30.  Major sites for carbohydrate symthesis
 Sorting and dispatching station for the products of the ER
 Consists of flatten membranous sacs, cisternae
 Unlike ER cisternae, the Golgi cisternae are not physically
connected.

31.  Transport vesicle from ER fuses to the cis face to transfer the
material to the Golgi.
 Proteins and lipids are altered; glycosylation and
phosphorylation (tagging the sorting signal).
 Oligosaccharides portion of the glycoproteins are modified:
Golgi removes some sugar monomers and substitutes others.
 Some polysaccharides are synthesized in the Golgi e.g pectin
and cellulose of the plant cell wall and most of the
glycosaminoglycans of animal extracellular matrix.
 Golgi products (that will be secreted) depart from the trans
face of the Golgi by transport vesicle for the correct docking.

32.  Principal sites of intracellular digestion.
 Contain hydrolytic enzymes (required acidic pH) to digest
proteins, polysaccharides, fats and nucleic acids (if those
hydrolases leak out of the lysosmes, they are not likely to do
damage unless the cells become acidic).

33.  Lysosomal enzymes and membranes are made by rough ER and
transferred to the Golgi for processing.
 Lysosomal membranes are highly glycosylated to protect them
from lysosomal proteases.
 Food particles engulfed as a food vacuole (phagocytosis) or an
endosome (product of receptor-mediated endocytosis) is fused
with the lysosome.
 The digestion products are passed to cytosol and become
nutrient for the cell.
 Autophagy = process which cells recycle its own organic material.

35.  Membrane-bound sacs.
 Diverse functions in cell maintenance.
 Food vacuoles: formed by phagocytosis and digested by
lysosomes.
 Contractile vacuoles: (in protists) pump excess water out of
the cells.
 Central vacuole: (a versatile compartment in plants) stores
protein and metabolic by-products, reservoir of inorganic
ions, pigments.

37.  Is one of the generalized plant structure called plastids. Found in
mesophyll cells of the leaves and in algae.
 2-4 μm wide and 5-10 μm long.
 Membranes: inner and outer membrane
 Stroma ~ matrix of mitochondria
*ds circular DNA
*70S ribosomes
*enzyme for carbohydrate biosynthesis

39.  Electron-dense cytoplasmic particles bound by a single
membrane. Contain oxidative enzymes: D-amino acid
oxidase, ureate oxidase and catalase.
 They are not formed in the Golgi complex.
 They are self replicating, like the mitochondria. e.g.
peroxisomes, glyoxisomes

40. Peroxisome:
 Single membrane, contain enzymes that transfer
hydrogen from various substrate to oxygen and produce
H2O2 as intermediate product but peroxisomes contain
another enzyme that convert H2O2 to H2O.
 Some peroxisomes break down fatty acids to smaller
molecules that are transported to mitochondria for fuel
Glyoxysomes:
specialized peroxisomes (found in fat storing tissues of
plant seeds) convert fatty acid to sugar which can be used
as energy for seedling.

41. A network of fibers extending throughout the cytoplasm
 Function:
 provide mechanical strength to the cell
 establish cell shape
 locomotion (several types of cell motility)
 intracellular transport of organelles
3 main types of fiber:
1.microtubules: determine the positions of membraneenclosed
organelles and intracellular transport.
2.microfilament: determine the shape of the cell and necessary for
the whole cell locomotion.
3.intermediate filament: provide mechanical strength and resistance
to shear stress.

43.  Cytosol functions (many in conjunction with
other processes).
 Cell signaling
 Cytokinesis
 Protein synthesis
 Glycolysis
 gluconeogenesis

44.  Cell physiology (including cellular electrophysiology) is the
biological study of the activities which take place in acell to keep it
alive. The term "physiology“ refers to all the normal functions that
take place in a living organism.