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1. Introduction
To Cells Biology

2. Cell biology (formerly cytology,
from the Greek kytos, "container") is
an academic discipline that studies
cells • their physiological properties
• their structure,
• the organelles they contain
•interactions with their
environment,
•their life cycle, division and
death.

3. Cell – basic unit of life structurally
and functionally.
History:
a. Robert Hooke (1665)using his microscope
discovers cells in cork
b. Schleiden ; Schwann and Virchow
Cell theory:
1. All organisms are composed of
one or more cells
2. The cell is the structural unit of life
3. Cells can arise only by division
from preexisting cells

4. Dynamic Nature of Cell
-it has the capacity
 to grow
 to reproduce
 become specialized
 ability to respond to stimuli
 adapt to changes in its environment

6. Two Main Classes of Cells:
a. Prokaryotic cells – nonucleus
- simpler structure (bacteria)
b. Eukaryoticcells - contain nucleus
- more complex structure(protists,
fungi, plants & animals)

8. The animal cell

10. A plant cell

12. The Main Functions of the Membrane-bounded
Compartments of a Eukaryotic Cell
Compartment Main Function
Cytosol contains many metabolic pathways
protein synthesis
contains main genome
DNA and RNAsynthesis
synthesis of most lipids
synthesis of proteins for distribution to many organelles and
plasma membrane
modification, sorting, and packaging of proteins and lipids
for either secretion or delivery to another organelle
intracellular degradation
sorting of endocytosed material
ATP synthesis by oxidative phosphorylation
ATP synthesis and carbon fixation by photosynthesis
Nucleus
Endoplasmic
reticulum (ER)
Golgi apparatus
Lysosomes
Endosomes
Mitochondria
Chloroplasts (in
plant cells)
Peroxisomes oxidation of toxic molecules

13. Organisms:
1. Unicellular (eg. bacteria, amoebas &
yeasts) – capable of independent self-
replication
2. Multicellular(eg. Humans)- composed
of collection of cells w/c fxns in a
coordinated manner w/ diff cells
specialized to perform particular tasks.

14. All organisms: 1 or more cells
PROKARYOTES
EUKARYOTE
S

15. Prokaryotes
bacteria, archaea
~ 1-10 µm
Eukaryotes
protists, fungi, plants, animals
~ 10-100 µm (sperm cells,apart
from the tail, are smaller)
real nucleus withdouble
membrane
linear molecules (chromosomes)
with histone proteins
RNA-synthesis inside the nucleus
protein synthesis in cytoplasm
60S+40S
highly structured by
endomembranes and a
cytoskeleton
flagella and cilia containing
microtubules; lamellipodia and
filopodia containing actin
one to several thousand (though
some lack mitochondria)
in algae and plants
single cells, colonies, higher
multicellular organisms with
specialized cells
Mitosis (fission or budding)
Meiosis
1.5 × 107 to 5 × 109
Typical organisms
Typical size
Type of nucleus nucleoid region; no real nucleus
DNA circular (usually)
RNA-/protein-synthesis coupled in cytoplasm
Ribosomes 50S+30S
Cytoplasmic structure very few structures
Cell movement flagella made of flagellin
Mitochondria none
Chloroplasts none
Organization usually single cells
Cell division Binary fission (simple division)
DNA content (basepairs) 1 × 106 to 5 ×106
Table 1: Comparison of features of prokaryotic and eukaryotic cells