chap 2 - organelles and their functions
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CHAPTER 2
PROKARYOTIC ANDEUKARYOTIC CELLS
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Cell Theory
1965 - Robert Hooke, an English scientist, observed a thin slice
of cork under a compound microscope which consists of
small boxes and named it as cells.
1838 - Matthias Schleiden, German botanist, suggested that all
plants consists of cells.
1839 - Theodore Schwann, a German zoologist, suggested thatanimals also consists of cells. He came up with two
theories:
a. All organisms consists of one or more cells.
b. A cell is the basic unit of structure and
function for all living organisms
1849 - Rudolf Virchow, a German scientist, came up with
another theory : all cells originate from pre-existing cells.
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Robert Hookes
compound microscope
a) The small units of a thin slice of cork
observed by Hooke. b) The plant cell
a. b.
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Cellular Structure and Function
Cytology - the study of cells and their submicroscopic structure
By using electron microscope, the microscopic structure of cells canbe observed.
Two types of cell:
1. Prokaryotic cell
pro before ; karyon nucleus
Prokaryotic cell, the DNA is concentrated in a region called the
nucleoid with no membrane enclosed it.
ex. Bacterial cell and Cyanobacteria
2. Eukaryotic cell
eu true
It has true nucleus bounded by a membranous nuclear envelope.
ex. Fungal cells, animal cells and plant cells
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A comparison between Prokaryotic Cell and Eukaryotic Cell
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All cells have the following structures:
i. Plasma membrane which functions as a barrier between
external and internal parts of a cell.
ii. Nucleus which contains genetic information and controls cell
activities.
iii. Cytoplasma which is a liquid medium where chemical
reactions and metabolism occurs, the site for synthesis of
enzyme, proteins and other materials needed by the cell.
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A view of the Eukaryotic CellsA
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Nucleus
Contains most of the genes
~ 5 m
Nuclear envelope enclosesthe nucleus
Chromosomes, a structure
that carries genetic
information
Chromatin, a complex of
proteins and DNA that builds
up chromosome
Nucleolus a mass of densely
stained granules and fibersadjoining part of the chromatin
Nuclear matrix a framework
of fibers extending throughout
the nuclear interior
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Nuclear envelope
Double membrane, each a lipid
bilayer with associated proteins,
separated by a space of 20-40 nm
Perforated by micropores ~ 100nm
that regulates the entry and exit of
certain large macromolecules and
particles
Chromosomes
An organized unit of DNA, carries the genetic information
Each chromosome is made up of a material called chromatin a
complex of proteins and DNA
A typical human cell has 46 chromosomes
a combination of 23 chromosomes of egg and sperm cells
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Nucleolus
a mass of densely stained
granules and fibers adjoining
part of the chromatin
rRNA is synthesized from
instructions in the DNA with the
protein from cytoplasm, into itssmall and large ribosomal
subunit in nucleolus
It will exit the nucleus to the
cytoplasm and assemble to
become the ribosome
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Ribosomes: Protein factories in the cell
Made of ribosomal RNA and protein that carry out protein synthesis
Cells that have a high protein synthesis have a large number of this cell
Not enclosed in membrane
2 types of ribosome based on its location:
1. Free ribosomes : suspended in the cytosol and build protein that
function in the cytosol. Ex: enzyme for sugar breakdown
2. Bounded ribosomes : attached to the outside of the endoplasmicreticulum or nuclear envelope; make proteins for insertion into membranes,
for packaging within certain organelles such as lysosomes
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The Golgi Apparatus (GA) : Shipping and receiving center
Functions: Center for manufacturing, warehousing, sorting and shipping
Consists of flattened membranous sacs cisternae that stack together
Vesicles concentrated in the vicinity of the GA are engaged in the
transfer of material between GA and other structures.
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Lysosomes : Digestive Compartments
A membranous sac of hydrolytic
enzymes that is used to digest
macromolecules
Lysosomal enzymes works in acidic
environment and perform
autodigestion which destroy the cell
itself
Hydrolytic enzymes and lysosomal
membrane are made by RER andthen transferred to the GA for
processing
Functions:
1. Intracellular digestion
2. Involved in phagocytosis.
Ex. InAmoeba
3. Autophagy recycle of cells
own organic materials
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Vacuoles : Diverse Maintenance Compartments
Found in plant or fungal cell
In mature plant cells, vacuoles enclosedby a membrane called tonoplast which
is selective in transporting solutes
Functions:
1. Hydrolysis (=lysosomes)
2. As food vacuoles
3. Contractile vacuoles
regulates water in the cell
4. As a storage cells in seed
5. As disposal sites for metabolic by-products
6. Protect the plant by containing compounds that are poisonous
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Mitochondria and chloroplasts:
Change energy from one form to another
Semiautonomous organelles that grow and reproduce within
the cell
Contains small amount of DNA that programs the synthesis of
proteins
Mitochondria
Chloroplast
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Mitochondria : Chemical energy Conversion
Functions : Sites of cellular
respiration, the metabolic process
that generates ATP from ADP by extracting
energy from sugars, fats and other
fuels with the help of oxygen.
Enclosed by two membranes, a
phospholipid bilayer withembedded protein
The outer membrane is smooth,
inner membrane is convoluted
forming cristae that increase the surface area for cellular respiration
Consists of two compartments : intermembrane space and
mitochondrial matrix
Mitochondrial matrix contains many enzymes, mitochondrial DNA and
ribosomes
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Chloroplasts : Capture of light energy
A type ofplastids
3 types of plastids:
1. Amyloplasts colourless plastids that store starch, particularly
in root and tuber
2. Chromoplasts contain pigments that give fruits and flowers
their orange and yellow hues
3. Chloroplasts contain the green pigment chlorophyll, along
with enzymes and other molecules that function in
photosynthetic production of sugars
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Lens-shaped, ~ 2 m by 5 m, enclosed by two membranes
separated by intermembrane space
Within the cell, there are thylakoids a flattened interconnectedsacs; a stack of thylakoids is called granum
The fluid outside the thylakoids is called stroma which contains the
chloroplasts DNA, ribosomes, starch and lipid granules and some
enzymes
Three compartments : the intermembrane space, the stroma and
the thylakoid space
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Differences Between Animal and Plant cells
Animal Cells Plant Cells
Only have cell membrane. Have cell membrane and therigid cell wall.
Do not chloroplasts. Have chloroplasts.
Have small or no vacuoles atall.
Have large vacuoles.
Have centrioles. Do not have centrioles.
Food storage : glycogen Food storage : starch
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Unicellular and Multicellular
Organisms
Two categories of cell
1. Unicellular organism
Single-celled organisms which function
as one unit to carry out activities like
growth, reproduction. Motility,excretion, transportation, respiration
and digestion.
Ex. Paramesium2. Multicellular organism
Consists of multiple cells. They depend
on coordination and cooperation
between different types of cells for
proper function.
Ex. Human, Fish, Elephant.