Download Cytology

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)
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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
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
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 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.
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
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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 by 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
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
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