preferable for first year students

1. CELL AND CELL
ORGANELLES
Alfna Rahman
Assistant lecturer
Biochemistry

2. What is a Cell???
All organisms are built from cells.
Cell is the functional unit of life.
Cells make up all living matter.
All cells arise from other cells.
Genetic information required during the
maintenance of existing cells and the
production of new cells passes from one
generation to the next.
Anabolism and catabolism takes place in
the cell.

4. Types of Cells
1. The prokaryotic cells,
2. The eukaryotic cells.
1) Prokaryotic cells:
• Includes bacteria and cyanobacteria.
• CHARACTERISTICS:
• Has minimum of internal organization
and smaller in size.
• No membrane bound organnelles
present

5. •Genetic material not enclosed by a
nuclear membrane.
•Histones are not present in
prokaryotes.
•Respiratory system closely associated
with its plasma membrane.
•Sexual reproduction does not involve
mitosis or meiosis.

6. 2)Eukaryotic cells:
• Includes protists,fungi,plants and animals
including humans.
• Cells are larger in size.
• CHARACTERISTICS:
• Many internal distinctive membrane bound
structures having specific functions.
• Nucleus is the site for informational
components collectively called chromatin.

7. •Sexual reproduction involves both
mitosis and meiosis.
•Respiratory site is the mitochondria.
•In plant cells,chloroplast converts the
radiant energy into chemical energy.

8. Cell Organelles
1. NUCLEUS
2. MITOCHONDRIA
3. ENDOPLASMIC RETICULUM
4. GOLGI COMPLEXES
5. LYSOSOMES
6. PEROXISOMES
7. CYTOSKELETON
8. CYTOPLASM

10. NUCLEUS
• Contains more than 95% of cells DNA and
is the control centre of the eukaryotic cell.
i. Nuclear envelope:double membrane
envelope separates nucleus from
cytosol.
ii. Nuclear pore complexes:embedded in
the nuclear envelope.these control the
movement of proteins and the RNAs
across the nuclear envelope.

12. i. Chromatin:DNA in the nucleus is coiled
into a dense mass called chromatin,so
named because it is darkly stained with
certain dyes.
ii. Nucleolus:a second dense mass closely
associated with the inner nuclear
envelope.
iii. Nucleoplasm:contains various enzymes
such as DNA polymerase,RNA
polymerase.

14. Functions of nucleus
• DNA replication and RNA transcription takes
place in nucleus
• Transcription is the first step in the
expression of genetic information and is the
major metabolic activity.
• Nucleolus is non membrane bound and
contains RNA
polymerase,RNAase,ATPase,and other
enzymes,but no DNA polymerase.
• Ribosome subunits assemble in nucleolus.

16. Mitochondrion
• Power house of cell.
• Number:it varies.some algae contain only
one,whereas protozoan chaos contain half
a million.
• Size: Vary greatly in size. Diameter of 0.2-
0.8 and a length of 0.5-1.0 seen in a typical
mammalian liver cell.
• Shape:sausage shaped.

17. Structure and functions
• Bounded by two concentric membranes
which have markedly different properties
and biological functions.
• Outer mitochondrial membrane:
• Consists mainly of phospholipids and
contains little amount of cholesterol.
• Also contain many copies of protein called
“PORIN”.

19. Functions of porins and other
proteins
a) These proteins form channels that permit
substances with mw less than 10,000 to
diffuse freely across the outer
mitochondrial membrane.
b) Other proteins carry out various
reactions in fatty acid and phospholipid
biosynthesis and responsible for some
oxidation reactions.

20. •Inner mitochondrial membrane:
•Rich in proteins and the ratio of lipid
to protein is only 0.27:1 by weight.
•Contains high proportion of
cardiolipin.
•It is impermeable to polar and ionic
substances.

21. Cristae:
• Inner mitochondrial membrane that is highly
folded.
• Tightly packed inward folds are called cristae.
INNER MEMBRANE SPACE:
• Space between outer and inner membrane.
MITOCHONDRIAL MATRIX:
• Region enclosed by inner membrane.
• Contain enzymes needed for citric acid cycle
and fatty acid oxidation,ribosomes,DNA
strands.

23. Functions:
• Many enzymes are located here.
• Metabolism of
carbohydrate,fattyacid,nitrogen.
• ETC and oxidative phosphorylation
enzymes.
• It is specialized for the rapid oxidation of
NADH and FAD.
• Energy produced is stored as ATP for
further use of energy in the body.

24. Endoplasmic reticulum
• Eukaryotic cells are characterized by several
membrane complexes that are interconnected by
separate organelles.
• These organelles are involved in protein
synthesis,transport ,modification,storage and
secretion.
• Varying in size,shape,and amount the ER extends
from cell membrane,coats the nucleus,surrounds
the mitochondria and appears to connect directly
to golgi apparataus.
• These membranes and the aqueous channels they
enclose are called”CISTERNAE”.

26. TYPES:2
• ROUGH surfaced ER:also known as
“ergastoplasm”.they are coated with
ribosomes.near the nucleus,this type of ER
merges with the outer membrane of the
nuclear envelope.
• SMOOTH surfaced ER:They donot have
attatched ribosomes.

27. Functions
a) Functions of Rough ER:
• Synthesize membrane lipids and secretory
proteins.
• These proteins are inserted through the ER
membrane into the lumen of cisternae
where they are modified and transported
through the cell.

28. b) Functions of smooth :
• Involved in lipid synthesis.
• Modification and transport of proteins
synthesized in the rough ER.

30. GOLGI APPARATUS
• Also called dictyosomes.
• Unique stack of smooth surfaced
compartments or cisternae that make up
the golgi complex.
• ER is usually closely associated with the
golgi complexes,which contain flattened
fluid filled golgi sacs.
• It has a “proximal” or “cis”
compartment,a “medial” and a “distal” or
“trans” compartment.

31. Funtions
• On the proximal or cis side:golgi complex receive
newly synthesized proteins by ER via tranfer
vesicles.
• The post translational modifications takes place in
golgi lumen,where the carbohydrates and lipid
precursors are added to proteins to form
glycoproteins and lipoproteins respectively.
• On the distal or trans side they release proteins via
modified membranes called secretory vesicles.
• These secretory vescicles move to and fuse with
the plasma membrane where the contents may be
expelled by a process called “exocytosis”.

33. LYSOSOMES
• Contains packet of enzymes.
• Discovered by belgian biochemist de Duve in 1955.
• SIZE:Mean diameter is approximately 0.4
micrometer.surrounded by lipoprotein membrane.
• Found in all animal cells,except erythrocytes in
varying numbers and types.
• pH: Inside lysosome is less than that of
cytosol.optimum is around 5.Acid phosphatase is a
marker enzyme of this organelle.

35. Lysosomal enzymes
1. Proteolytic
enzymes
2. Nucleic acid
hydrolysing
enzymes
3. Lipid hydrolyzing
enzymes
4. Carbohydrate
splitting enzymes
• Cathepsins,elastase,
Collagenase.
• Ribonuclease,DNA
ase
• Lipase,fattyacyl
esterases.
• Alpha-
glucosidase,hyaluroni
dase.

36. PEROXISOMES
•Also called microbodies.
•Approx:0.5 micron in diameter.
•Probably formed by budding from
smooth ER.

38. Functions:
i. They carryout oxidation reactions in which
toxic hydrogen peroxide is produced,which
is destroyed by the enzyme catalase.
ii. Liver peroxisomes have an unusually active
beta oxidation system capable of oxidising
long chain fattyacids.
iii. In plants,peroxisomes present in seeds rich
in lipids are called”glyoxysomes”,where
fattyacids are degraded to succinate by
glyoxylate pathway.

39. CYTOSKELETON
• Comprises of a complex network of fine
structures
called:microtubules,microfilaments,microtrab
eculae.
• Microtubules:long unbranched slender
cylindrical structures made by self-assembly
of the heterodimer”tubulin”having mw
50,000.
• Assembly and diassembly of the spindle
structures during mitosis,helps in maintaining
shape of the cell.
• May be involved in transmembrane signals.

41. • Micro filaments:more slender cylinder like
structure made up of contractile
protein”actin”.they are linked to inner face
of plasma membrane.
• Involved in the generation of forces for
internal cell motion.
• Microtrabeculae:very fragile tubes that
form a transient network in the cytosol.

43. CYTOPLASM
• Simplest structure of cell.
• Organelles freesap is called as cytosol.
• No specific structure for cytosol.
• High protein content.
• Support synthesis of proteins on the RER by
supplying co factors and energy.
• Contain free ribosomes in the polysome form.
• Contain different types of proteins and ribosomal
RNA or r-RNA.
• Exists as 2 subunits and act as the site of protein
synthesis.