Download Cell Structure

Basic Structure of a Cell
Prokaryotic
Cells
•No nucleus
•Archaea & Eubacteria
•One circular chromosome
•Extremely small
Eukaryotic
Cells
• Has a nucleus!!!
• Membrane-bound organelles
• Plants, Animals, Fungi, &
Protists
Prokaryotes – The first Cells
• Cells that lack a nucleus
or membrane-bound
organelles
• Includes bacteria
• Simplest type of cell
• Single, circular
chromosome
Prokaryotes
• Nucleoid region
(center) contains the
DNA
• Surrounded by cell
membrane & cell wall
(peptidoglycan)
• Contain ribosomes (no
membrane) in their
cytoplasm to make
proteins
Prokaryotes
• Bacterial cells may have
plasmids, small accessory
rings of DNA.
• Some bacteria have a
capsule or a slime layer.
• Most bacteria have
flagella.
• Some also have fimbriae
that help cells attach to
surfaces.
• Bacteria have a great
metabolic diversity.
Comparison of Eukaryotic and
Prokaryotic Cells
Eukaryotes
• Eu-, “true,” karyon,
“nucleus”
• Genetic material
contained in a
nucleus
• Membrane-bound
organelles
• Evolved from
prokaryotic cells
• Includes protists,
fungi, plants, and
animals
•Eukaryotic
•No cell wall
•Heterotrophic
•Often highly
specialized in
multi-cellular
organisms
•May be motile
DNA
Nucleolus
Nuclear
envelope
Centrosome
Rough ER
Cell wall
Smooth ER
Ribosomes
CENTRAL
VACUOLE
Golgi
complex
Microfilaments
Intermediate
filaments
Microtubules
Mitochondrion
Lysosome
Plasma
membrane
CHLOROPLAST
CELL
WALL
Wall of
adjacent cell
•Outer layer that
maintains cell’s
shape & rigidity and
protects cell from
mechanical damage
•Made primarily of
cellulose
Central vacuole
•Stores nutrients &
breaks down waste
products
•Contributes
significantly to plant
growth
Chloroplast
•Contains chlorophyll,
which is the primary
pigment responsible
for photosynthesis
Organelles
• Very small (Microscopic)
• Perform various functions for a cell
• Found in the cytoplasm
• May or may not be
membrane-bound
Cell Wall
• Nonliving layer that
supports and protects
the cell
• Found in plants, fungi,
& bacteria
• Made of cellulose in
plants
• Made of peptidoglycan
in bacteria
• Made of chitin in Fungi
Cell wall
Cell Membrane in Plants
Cell membrane
• Lies immediately
against the cell wall
in plant cells
• Pushes out against
the cell wall to
maintain cell shape
Cytoplasm of a Cell
cytoplasm
• Jelly-like substance
enclosed by cell
membrane
• Provides a medium
for chemical
reactions to take
place
More on Cytoplasm
cytoplasm
• Contains organelles
to carry out specific
jobs
• Found in ALL cells
The Control Organelle - Nucleus
• Controls the normal
activities of the cell
• Contains the DNA in
chromosomes
• Bounded by a
nuclear envelope
(membrane) with pores
• Usually the largest
organelle
More on the Nucleus
Nucleus
Chromosomes:
• Tightly coiled DNA & Protein
• Contain hereditary material (genes)
• Chromosomes not dividing called
chromatin
• Each type of organism has a certain
# of them
• Humans = 46 (23 pairs)
• Fruit fly = 8 (4 pairs)
Inside the Nucleus The genetic material (DNA) is found
DNA is spread out
And appears as
CHROMATIN
in non-dividing cells
DNA is condensed &
wrapped around proteins
forming
as CHROMOSOMES
in dividing cells
What Does DNA do?
DNA is the hereditary
material of the cell
Genes that make up the DNA
molecule code for different
proteins
Nuclear Envelope
• Double membrane surrounding
nucleus
• Also called nuclear membrane
• Contains nuclear pores for
materials to enter & leave nucleus
• Connected to the rough ER
Nuclear
pores
Nucleolus
• Inside nucleus
• Cell may have 1 to 3
nucleoli
• Disappears when
cell divides
• Makes ribosomes
that make proteins
Endomembrane System
• System of transport
throughout the cell
• Nuclear envelope
• Endoplasmic
reticulum
• Golgi apparatus
• Lysosomes
• Vacuoles
Endomembrane System
Includes nuclear membrane connected to ER
connected to cell membrane (transport)
Endoplasmic Reticulum - ER
• Network of hollow membrane tubules throughout the
cytoplasm
• Connects to nuclear envelope & cell membrane
• Functions:
– Transports materials
through the cell
– Contains enzymes that
allow chemical reactions
– Wastes & other toxic
chemicals are made
harmless
• Two types:
– Smooth ER
– Rough ER
The endoplasmic reticulum
Rough ER:
•Studded with ribosomes
•Makes membrane
proteins and proteins for
export out of the cell
Smooth ER:
•Lacks ribosomes on its surface
•Is attached to the ends of rough ER
•Makes cell products that are used
inside the cell
•Site of synthesis of lipids (including
phospholipids and steroids)
•Destroys toxic substances
Ribosomes
•
•
•
•
•
Made of PROTEINS and rRNA
Made in the nucleolus
Found mostly on ER but also floating in cytoplasm
Found in all types of cells
“Protein factories” for cell
• Join amino acids to
make proteins
(process called
protein synthesis)
Golgi Complex (or Apparatus)
• Flattened membrane
sacs
• Present in
almost all cells
• Receives protein and
lipid-filled vesicles
from ER
• Modifies, sorts, and
packages molecules
from ER for storage or
transport out of the cell
Vacuoles and Lysosomes
Vacuoles (large) and
vesicles (small) are
membranous sacs in the
cell that store
substances.
Lysosomes are vesicles
produced by the Golgi
apparatus.
Lysosomes contain
hydrolytic enzymes and
are involved in
intracellular digestion.
Vacuoles
• Fluid filled sacks for storage
• Small or absent in animal cells
• Plant cells have a large Central Vacuole
• In plants, they store Cell Sap
• Includes storage of
sugars, proteins,
minerals, lipids,
wastes, salts, water,
and enzymes
• No vacuoles in
bacterial cells
• Many protists have
contractile vacuoles
Contractile Vacuole
• Found in unicellular
protists like paramecia
• Regulate water intake by
pumping out excess
(homeostasis)
• Keeps the cell from lysing
(bursting)
Lysosomes
• Contain digestive
enzymes
• Break down food,
bacteria, and worn out
cell parts for cells
• Some cells (i.e. certain
types of protists) take
in food by phagocytosis
• Lysosomes digest the
food and get rid of
wastes
Energy-Related Organelles
The two energyrelated organelles of
eukaryotes are
mitochondria and
chloroplasts .
Both organelles house
energy in the form of
ATP.
Mitochondrion
(plural = mitochondria)
• Found in all eukaryotic
cells
• “Powerhouse” of the cell
• Site of Cellular
Respiration: generate
cellular energy (ATP) by
burning glucose
• More active cells like
muscle cells have MORE
mitochondria
Mitochondrion
(plural = mitochondria)
Structure:
• Surrounded by a DOUBLE
membrane
• Folded inner membrane
called cristae (increases
surface area for more
chemical reactions)
• Interior called matrix
• Has its own DNA
Interesting Fact --• Mitochondria Come
from cytoplasm in
the EGG cell during
fertilization
Therefore …
• You inherit your
mitochondria from
your mother!
Chloroplasts
• Organelle found only in
producers
• Never in animal, fungal, or
bacterial cells
• Contains enzymes &
pigments for Photosynthesis
• Photosynthesis: Use
energy from sunlight to
make food (glucose)
• Energy from sun stored in
the Chemical Bonds of
Sugars
• Contains its own DNA
Chloroplasts
Structure:
• Surrounded by DOUBLE membrane
• Outer membrane smooth
• Inner membrane modified into
sacs called Thylakoids
• Thylakoids contain Chlorophyll –
a green pigment which absorbs
energy from the sun
• Thylakoids are organized into
stacks called Grana and are
interconnected
• Stroma – gel like material
surrounding thylakoids
Process that uses solar
energy to convert carbon dioxide and water into glucose and oxygen
Structure of Chloroplast:
• Surrounded by double
membrane
• Outer membrane is smooth
• Inner membrane is
modified into sacs called
Thylakoid Discs
• Thylakoid membranes
contain Chlorophyll
• Thylakoids are organized
into stacks called Grana and
are interconnected
• Stroma – gel like material
surrounding thylakoids
Outer
membrane
Granum
Thylakoid
discs
Inner
membrane
Stroma
Cytoskeleton
• Network of filaments and tubules
that extends from the nucleus to
the plasma membrane
• Made of proteins
• Helps cell maintain cell shape
• Also help move organelles around
• Types:
– Microfilaments – threadlike
and made of Actin
MICROTUBULES
– Microtubules – tubelike
and made of Tubulin
MICROFILAMENTS
– Intermediate filaments
Centrioles
• Found only in animal cells
• Paired structures near
nucleus
• Made of bundle of
microtubules
• Appear during cell
division forming mitotic
spindle
• Help to pull chromosome
pairs apart to opposite
ends of the cell
Cilia & Flagella
• Made of protein tubes
called microtubules
• Microtubules arranged
(9 + 2 arrangement)
• Function in moving cells,
in moving fluids, or in
small particles across the
cell surface
Cilia & Flagella
• Cilia are shorter
and more
numerous on
cells
• Flagella are
longer and fewer
(usually 1-3) on
cells
Cell Movement with Cilia &
Flagella