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BTY100-Lec#3.2
Cell Organelles
Outline
Introduction to Cell Organelles
Cell structure
Cell Functions
Why do I need to study cell parts
• Suppose you want to
drive a car.
• To drive a car you first
need to know its parts
and functions.
Similarly we will be studying
about cells is this course and
therefore you need to know
about its parts and their
functions.
Cell Organelles
Building blocks of Cell
Provide Compartmentalization
Cell Wall
• Tough, rigid layer that surrounds some types
of cells.
• Located outside the cell membrane.
• Different composition in different cells
Bacteria: Peptidoglycan
Fungi: Chitin.
Plants: Cellulose
Animals: Missing
Functions
• Provides structural support and protection.
• Acts as a pressure vessel, preventing overexpansion when water enters the cell.
Plasma membrane
• Every cell is surrounded by
a plasma membrane, a
continuous
membrane
composed of a lipid bilayer
with proteins floating
within it and protruding
from it.
• Fluid-Mosaic Model:
Fluid: Lipids
Mosaic: Proteins
Introduce the term
Biomolecules for
lipids and proteins
• Roles of the plasma membrane:
Acts as a selectively permeable barrier.
Is an interface for cells where information is
received from adjacent cells and extracellular
signals.
Allows cells to maintain a constant internal
environment.
Has molecules that are responsible for binding
and adhering to adjacent cells.
Cytoplasm
Consists of primarily of water, salts
(ions), organic monomers and
polymers, the building blocks of large
macromolecules.
It also contains various organelles as
well as dissolved gasses and nutrients.
Membrane Bound Organelles
• Double Membrane
– Nucleus
– Mitochondria
– Chloroplast
• Single Membrane
– Endoplasmic Reticulum
– Golgi Apparatus
– Lysosomes
• Non Membranous
–
–
–
–
Ribosomes
Cytoskeleton
Centrioles
Cillia and Flagella
Double Membrane Bound Organelles
Nucleus
Introduce the terms
• Known as the “ control centre of the Cell”
– a membrane-bound sac evolved to store the cell’s
chromosomes(DNA)
– stores the genetic material of the cell in the form of
multiple, linear chromosomes
– To control the activity of cell by regulating gene
expression
– surrounded by a nuclear envelope composed of 2
phospholipid bilayers
– in chromosomes – DNA is organized with proteins to
form chromatin
Mitochondria and Chloroplast
Organelles With DNA
Mitochondria :
Known as power house of the cell.
Chloroplasts:
Known as kitchen of the cell
found in photosynthetic organisms
Mitochondria
• Break down fuel molecules and
convert the energy in the bonds of
glucose and oxygen to readily
available energy in the form of
ATP. (cellular respiration)
– Glucose
– Fatty acids
• exterior and interior membranes
• Fluid is called matrix
• interior partitioned by cristae
Chloroplasts
Contain chlorophyll
for photosynthesis
Parts: Thylakoids are
membranous sacs
within the inner
membrane
and
Grana are stacks of
thylakoids.
Fluid inside is called
stroma
17
Single Membrane Organelles
Endoplasmic Reticulum
Is a set of folded membranes and tubes throughout the system.
The general structure: Membranous network of cisternae.
Two types:
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
Introduce basic
difference: Ribosomes
Functions
• Provides a large surface area on which chemical
reactions can take place.
• It synthesizes lipids, phospholipids and steroid.
• It also carries out the metabolism of carbohydrates, drug
detoxification.
• Attachment of receptors on cell membrane proteins.
• RER involved in protein synthesis
Golgi Apparatus
• Collection of Golgi bodies
• Cisternae – stacked membrane folds
• Front - Cis , Back – Trans
• Collect, package, and distribute molecules synthesized
at one location in the cell and utilized at another
location
• Vesicles from the endoplasmic reticulum fuse with the
network and subsequently progress through the stack
to the trans Golgi network, where they are packaged
and sent to their destination
Lysosomes
• Organelles that contain hydrolase enzymes that
break down waste materials and cellular debris.
Disposal Bags/ Suicidal Bags of Cell
• Cell damaged- membranes of Lysosomes breakenzymes release- components of cells brokenavailable for surrounding cells.
• Also play part in normal development of an
organism.
• Lysosomes combine with food vacuoles. Eg:
Paramecium
• Used in destruction of engulfed harmful
microbes
Vacuoles and Vesicles
Vacuoles and vesicles are storage organelles in cells. Vacuoles are larger
than vesicles. Either structure may store water, waste products, food, and
other cellular materials.
In plant cells, the vacuole may take up most of the cell's volume. The
membrane surrounding the plant cell vacuole is called the tonoplast.
Non-Membranous
Organelles
Ribosomes
• Ribosomes are RNA-protein complexes
composed of two subunits that join and attach
to messenger RNA.
• Site of protein synthesis
• Each ribosome is divided into two subunits:
the smaller subunit and the larger subunit
Cytoskeleton
Network of protein fibers supporting cell shape and anchoring
organelles
Actin filaments: Cell movement
Intermediate filaments: Stable- don’t break down
Microtubules: Hollow tubes, Facilitate cell movement
Functions:
Supports the shape of the cell
keeps organelles in fixed locations
helps move materials within the cell
Cytoskeleton
Cilia and flagella

Both cilia and flagella are constructed from microtubules

Both provide locomotion for the cell
Plant or animal cell?
Next Class: Biobricks