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Cytology
By:Dr.ISAM AL-MUSAWY
 Objectives:
– Compare prokaryotic and eukaryotic cells
– Investigate the anatomy (structure) and physiology (function) of a
typical cell
– Compare animal and plant cells
 Cytology : is the study of the structure and function of cells.
 Cytoplasm : is the area of space outside the nucleus but which is
contained within the cell membrane. It contains the organelles and fluid.
 The organelles are tiny structures in the cytoplasm which perform various
jobs for the cell.
 The fluid part of the cytoplasm is called the cytosol.
 Cell : the basic unit of structure and function in living organisms
 Nucleoplasm : is the area of space found inside the nucleus.
Prokaryotic Cells
 They lack a nuclear membrane as well any other membrane covered
organelles in their cytoplasm.
 Considered to be “Primitive Cells”
 Example : Bacteria & Blue-Green Algae
Eukaryotic Cell
The Nucleus
 is the computer or control center of the cell.
 contains the genetic material of life DNA (Deoxyribonucleic acid).
 Long chains of DNA form Chromatin.
 Short sections of DNA along a piece of chromatin form Genes.
 The Human Genome consists of about 30,000 Genes.
1. Nucleolus / Nucleoli (plural) : is a dark spherical structure that is
the site of ribosome formation.
2. Nuclear Membrane or Envelope surrounds the nucleus
3. Nuclear pores control what moves in and out of the nucleus
DNA Structure
The building blocks of DNA are called Nucleotides
A nucleotide consists of a :
1. phosphate group
2. sugar
3. nitrogen base : 4 types
adenine (A)
thymine (T)
cytosine (C)
guanine (G)
DNA consists of two nucleotide chains connected together to form a twisted
ladder called a Double Helix
Chromatin
 Consists of DNA and protein ( histone,)
 Condense to rod-shape chromosome just prior to nuclear division Carry
genetic materials which determine organisms’ characteristics and transmit
these characteristics to next generations
DNA Replication
Figure 33-21
Mitosis
 Divides duplicated DNA into two sets of chromosomes
– DNA coils tightly into chromatids
– Chromatids connect at a centromere
1. Prophase
– Centriole pairs move to cell poles
– Microtubules (spindle fibers) extend between centriole pairs
– Nuclear envelope disappears
2. Metaphase
– Chromosomes align in a central plane (metaphase plate)
3. Anaphase
 Microtubules pull chromosomes apart
 Daughter chromosomes group near centrioles
4. Telophase
i.
ii.
iii.
iv.
Nuclear membranes reform
Chromosomes uncoil
Nucleoli reappear
Cell has two complete nuclei
Cytokinesis
– Division of the cytoplasm:
 Cleavage furrow around metaphase plate
 Membrane closes, producing daughter cells
Organelles
 Ribosomes
 Endoplasmic Reticulum (Rough and Smooth)
 Golgi Apparatus
 Lysosomes
 Ribosomes : tiny non-membrane bound structures that synthesize
proteins.
 Proteins : composed of long chains of amino acids , makes up 75% of
a cell’s dry weight.
 Proteins are important because they :
(1) provide the main structural component of you
(2) act as Hormones, which are chemical messangers
(3) act as Enzymes, which control all chemical reactions in your cells
Rough Endoplasmic Reticulum (RER):
membrane bound canals with a rough appearance due
to ribosomes
Smooth Endoplasmic Reticulum (SER):
membrane bound canals that lack ribosomes , hence
the smooth appearance. Lipids (fats) are transported
through the SER
Golgi Apparatus / Golgi Bodies / Golgi Complex:
Is often referred to as the “cell’s post office”.
Proteins from the RER travel to Golgi, where they are : (1) sorted,
(2)addressed, & (3) packaged into membrane bound vesicles called
Lysosomes
 Lysosomes
Vacuole –
special vesicle that store water (water vacuole) or stores food particles (food
vacuole)
Water vacuoles are small in animal cells.
Mitochondria (plural) :
is a membrane bound oval shaped organelle that function as the cell’s
“power plant”.
This is where glucose is broken down to release energy during a chemical
reaction called “Cellular Respiration”
This energy released is stored in energy carrying molecules called ATP.
It takes 36 ATP molecules to store the energy released from the break down
of one glucose molecule.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Endoplasmic
reticulum
Cytoplasm
Phagocytosis
Golgi
apparatus
Food
vesicle
Lysosomes
Plasma
membrane
Digestion of
phagocytized
food particles
or cells
Transport
vesicle
Old or damaged
organelle
Extracellular
fluid
Breakdown
of old
organelle
Cellular Respiration
C6H12O6 + 6O2 + enzyme
6CO2 + 6H2O + Energy
This energy will be stored in 36 ATP molecules.
Only eukaryotic cells have mitochondria.
Mitochondria have their own DNA! ??
(Scientists think that the mitochondria was once a cell that was engulfed by
another cell producing the first Eukaryotic cell)
Anaerobic Respiration
Breaking down glucose without the use of O2
(+) quick supply of energy
(-) small amount of energy/build up of Lactic Acid
C6H12O6
2 C3H6O3 + E
Only 2 ATP molecules are needed to store this energy
Cytoskeleton
Composed of protein found in the cytoplasm and provides a support system
for the cell
Microfilaments
Composed of actin and makes up most of the cytoskeleton.
Microtubules
Composed of small hollow protein tubes called tubulins
Make up cilia and flagellum which are used for cellular locomotion
Cell membrane
Chemical components :consists of 60% protein, 35% phospholipid and 5%
polysaccharides Two models:
Unit membrane model
Fluid mosaic model
Fluid mosaic model a three-layered ( trilaminar) structure
Hydrophobic tails of two layers of phospholipid molecules point inward to
form a phospholipid bilayer, while the protein molecules is embedded in the
phospholipid bilayer or transmembrane .
Fluidity : due to the lateral movement of phospholipid molecules.
 Mosaic: protein molecules are interspersed among phospholipid
molecules.
Function of cell membrane
(i) Compartmentalization
(ii) Control exchange of substances between two sides of membrane
selective / differentiate permeability
(iii)Site of membrane-bound enzyme reaction
(iv) For recognition of stimuli , e.g insulin
(v)For cell identity e.g. antigen
(vi) For endocytosis and exocytosis
 Provides electrical insulation
by
Centrioles –
2 bundles of rod-shaped fibres that function in cell division
Only found in Animal cells
CILIA & FLAGELLA (Non-membranous)
 Cilia – short, numerous, move substances over free surfaces
 Flagella – long, singular, move cell
 Microvilli – thin folds of cell membrane, increase surface area to
maximize absorption