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Cells
The cell is the fundamental structural and functional unit of life
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This contains of chromosomes
which contain genetic material
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Studying cell biology is studying life
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Life is continuous
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The plasma membrane is semi-permeable, it controls what materials enter and
leave the cell
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The cytoplasm consists mostly of water and dissolved ions, small molecules and
soluble macromolecules (protein)
The genetic material is a single chromosome made up of circular DNA
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The ribosomes are made up of two subunits, 50s and 20s, they are the site of
protein synthesis
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It also helps in respiration, secretion (increases SA)
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Slime layer/glycocalyx can be found loose or think, it is tough to protects it from
WBC, it prevents the cell from drying out and helps the bacterium attach to other
cells
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Pili are elongated tubular structures made of protein
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It helps to attach it to rocks in streams or host
tissues
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Ribosomes: granular structures, composed of RNA and proteins (not surrounded by
membrane)
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They are found in cytoplasm or
attached to the RER and the site of protein synthesis
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Nucleus: has chromatin, nuclear matrix, nucleolus
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It separates the material inside
the nucleus from the cytoplasm
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It has nuclear pores; RNA + protein molecules move through them
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The
nucleus is the site of DNA replication, of genetic control of the cells activities, and
the nucleolus begins the assembly of ribsomes from specific proteins and RNA
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Tiny,

membrane-

surrounded droplets (vesicles) appear to move between the various components of
the endomembrane system
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•

Endoplasmic Reticulum: network of tiny tubular structure scattered in the
cytoplasm
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Hence ER divides the intracellular space into luminal (inside)
and extra luminal (cytoplasm)
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The RER segregates newly synthesised proteins away from the cytoplasm,
inside the RER the proteins can be chemically modified to alter their
function and destination
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Proteins become glycoproteins
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Golgi apparatus: many flat sacs (cisternae) parallel to each other
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Proteins enter
from the cis, are modified and leave through the trans and are sent to their
destination
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Lysosomes are the sites of breakdown of food and foreign objects
(phagocytosis)
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Autophagy: cell digests its own material
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Plant cells do not have lysosomes, they have a vacuole
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It is bound by tonoplast
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This may contribute to
plant survival

§

Structure; provide the turgor, support to nonwoody plants
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Cell walls resists the swelling
and provides strength
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They
attract animals for pollination and seed dispersal
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Contactile vacuole get rid of excess water
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Produce cellular energy (ATD) called
power houses
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Inner membrane has infoldings (cristae) which increase SA and large proteins that
participates

in

cellular

respiration
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Matrix poseess DNA, RNA, ribosimes
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Chloroplasts: site of photosynthesis, contain chlorophyll and carotenoid pigments
which trap light energy
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In the stroma there are membranals sacs
(thylakoids) -> chlorophyll pigments
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Connecting the thylakoids are stroma lamellae (membrane-lumen)
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Peroxisomes: collect toxic by-product peroxides
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Single
membrane and granular crystalline core interior containing enzymes (catalase)
Cytoskeleton: long, thin fibres
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It is
made up of microfilaments, intermediate filaments and microtubules
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)
ü Intermediate filaments; fibrous proteins in a ropelike tough structure
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ü Microbtubules; long, hollow cylinders made up of protein tubulin (α and β)
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Cilia and Flagella: hair-like outgrowths of the cell membrane
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Flagella cause cell movement
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The axoneme contains of 9 pairs of
doublets radially arranged and 1 pair at the centre (9+2 structure)
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Centriole is made up of mictrotubules as 9 sets of 3 fused microtubule each
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Tissues
A tissue is a group of similar cells performing a specific function
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Cell -> Tissue -> Organ -> Organ System
Epithelial tissue:
Simple Epithelium:

Stratified Epithelium

Simple layer of cells and functions as a

Two or more cell layers and protective

lining

function (e
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mouth, cervix, vagina)

ü Squamous: thin layer of flattened
cells with irregular boundaries
(e
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blood vessels, alveoli) –
diffusion boundaries
ü Cuboidal: cube-like cells
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g
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It repairs itself
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g
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Nuclei at the base (e
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lining of
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stomach, intestine) – secretion of
digestive juices, mucus by goblet
cells, and absorption (microvilli)
If they contain cilia they are called
ciliated epithelium (e
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bronchioles,
fallopian tubes)

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