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Life is Cellular
Cell Structures & Functions
Biology I
Introduction to Cells
• Before the 17th century, no one
knew cells existed
• Most cells are too small to be seen
with the unaided eye
• In the early 17th century
microscopes were invented & cells
were seen for the 1st time
• Anton Von Leeuwenhoek, a
Dutchman, made the first handheld microscope & viewed
microscopic organisms in water &
bacteria from his teeth
• In 1665, an English scientist named
Robert Hooke made an improved
microscope and viewed thin slices
of cork viewing plant cell walls
• Hooke named what he saw "cells“
•
The Cell Theory
The combined work of scientists Schleiden, Schwann, &
Virchow is known as the Cell Theory :
• Principles of the Cell Theory
• All living things are made of one or more cells
• Cells are the basic unit of structure & function in
organisms
• Cells come only from the reproduction of existing cells
Cell Diversity
• Not all cells are alike
• Cells differ in size, shape, and function
• The female egg cell is the largest cell in the body & can be
seen without a microscope
• Bacterial cells are some of the smallest cells & are only
visible with a microscope
Cells come in a variety of
shapes, & the shape helps
determine the function of the
cell
(e.g. Nerve cells are long to
transmit messages in the
body, while red blood cells
are disk shaped to move
through blood vessels)
Basic Structure of a Cell
Introduction to Cells
Cells are the basic units of organisms
All cells have a cell membrane and
cytoplasm
Basic types of cells:
Animal Cell
Plant Cell
Bacterial Cell
Number of Cells
Organisms may be:
• Unicellular –
composed of one cell
• Multicellularcomposed of many
cells
Cells Are Divided Into Two
Categories
Prokaryotes include bacteria &
have NO nucleus or membranebound organelles
 Eukaryotes include most other
cells & DO have a nucleus and
membrane-bound organelles
Prokaryotic Cells
• Kingdoms:
1. Monera (Eubacteria)
2. Archaea (Archaebacteria)
• Characteristics:
1. are usually simpler and smaller than
eukaryotes
2. have NO nucleus or membrane-bound
organelles
3. Contains a cell membrane and a cytoplasm
Prokaryotes
•Nucleoid region
contains the DNA
•DNA is circular
(plasmid)
•Have a cell
membrane & cell wall
•Contain ribosomes
to make proteins in
their cytoplasm
Prokaryotic Cell - Bacteria
Eukaryotic Cells
• Kingdoms:
1. Protista
2. Fungi
3. Plantae
4. Animalia
• Characteristics:
1. have a nuclear membrane
2. have membrane-bound organelles
Eukaryotic Cell
Contain 3 basic cell
structures:
• Nucleus
• Cell Membrane
• Cytoplasm with
organelles
Eukaryotic Animal Cell
Eukaryotic Plant Cell
Two Main Types of Eukaryotic
Cells
Plant Cell
Animal Cell
Cell Membrane
• The boundary of every cell
• Is said to be selectively permeable because it controls
what enters and leaves the cell.
• Made of protein and phospholipids
• Other Names:
– Phospholipid bilayer
– Plasma membrane
– Selectively permeable membrane
Hydrophobic region
Hydrophilic
region
Cell Wall
• main function=provide support, shape, &
protection for the cell
• located outside cell membrane
• found in plants and algae & nearly all eukaryotes
(not animal cells)
• In plants the cell wall is
composed of cellulose
• In fungi the cell wall contains
chitin
• In bacteria it contains peptidoglycan
Cytoplasm
• Jelly-like substance that holds organelles in
place.
• Entire region between the nuclear membrane and
the cell (plasma) membrane.
Cytoplasm
cytoplasm
Nucleus
• Only found in eukaryotes.
• Contains the genes (DNA
- chromosomes)
• Called the “brain” of the
cell because it controls
all cell activities.
nucleus
Vacuoles
•Large membrane-closed
sac
for cellular storage.
• Contains water,
sugars, proteins, and
nutrients.
• Called the “central
vacuole” in plant cells
because it is much
larger.
Vacuole
Organelles Found in Cells
 Nucleolus – makes ribosomes
 Golgi Apparatus– packages &
ships proteins (Modifies, stores
and transports products from the
ER to the plasma membrane)
 Lysosomes – digests & gets
rid of wastes; filled with
digestive enzymes
 Ribosomes- site of
protein synthesis
Smooth & Rough Endoplasmic
Reticulum
•Smooth ER lacks
ribosomes &
makes proteins
used in the cell
•Rough ER has
ribosomes on its
surface &
transports
ribosomes
Mitochondria
• Found in both plants and animal cells.
• It is the site of cellular respiration, a process that uses
energy extracted from organic macromolecules (like
glucose) to produce ATP (energy).
• Also known as the “powerhouse”
• Has a double membrane.
• Has its own DNA.
Outer
Inner
membrane
membrane
Chloroplast
• Found in photosynthetic plants cells.
• The site of photosynthesis, a process that uses light energy
(sun) and water to produce organic macromolecules (glucose).
Stroma
Outer Membrane
Inner Membrane
Thylakoid
Granum
Cytoskeleton
• network of protein filaments
that help the cell to maintain its
shape, also involved in cell
movement
• Aids in cellular support and movement
• Composed of two different components
– microtubules-hollow tubes of protein, can serve as “tracks”
along which organelles move
– microfilaments-long, thin fibers that function in the
movement & support of cells
Cilia, Flagella, and
Pseudopodia
•
•
•
•
Extensions of the cell (plasma) membrane.
Aids in movement….
Cilia = hair-like structures all around the cell
Flagella = long hair-like structure from the tail
region
• Pseudopodia = “splat” like structure
Different kinds of animal cells
white blood cell
Amoeba
red blood cell
muscle cell
cheek cells
sperm
nerve cell
Paramecium
Differences between plant
cells and animal cells
Animal cells
Plant cells
Relatively
smaller in size
Relatively
larger in size
Irregular shape
Regular shape
No cell wall
Cell wall present
Differences between Plant
Cells and Animal Cells
Animal cells
Plant cells
Vacuole small or
absent
Large central
vacuole
Glycogen as food
storage
Starch as food
storage
Nucleus at the
center
Nucleus near cell
wall
Levels of organization
• Cells are
grouped
together and
work as a
whole to
perform
special
functions
Levels of Organization
 CELLS
(muscle cells,nerve cells)
 TISSUES (muscle, epithelium)
 ORGANS (heart, lungs, stomach)
 SYSTEMS (circulatory system)
 ORGANISM (human)
It’s You!
• The cell membrane is a
structure that forms the
outer boundary of the cell
and allows only certain
materials to move into and
out of the cell.
• Food, oxygen and water
move into the cell through
the membrane. Waste
products also leave through
the membrane.
• The Endoplasmic
Reticulum (ER) is a folded
membrane that moves
materials around in the cell.
• The ER is like a system of
conveyor belts in a
business. They act as
tunnels in which materials
move from one place to
another within the cell.
• In a business, products are made, packaged, and moved
to loading docks to be carried away.
• In cells, structures called Golgi Bodies are stacks of
membrane-covered sacs that package and move
proteins to the outside of the cell. Golgi bodies are the
packaging and secreting organelles of the cell.
•
• Just like a taxi transports people, vesicles transport
protein packages created by the golgi bodies.
• An active cell constantly produces
waste products. In the cytoplasm,
organelles called lysosomes
contain chemicals (enzymes) that
digest wastes and worn-out cell
parts. These chemicals also break
down food.
A Lysosome acts as a wrecking ball that breaks apart wastes or worn out cell parts.
• The largest organelle in
the cytoplasm of a
eukaryotic cell is usually
the nucleus, a structure
that directs all the activities
of the cell.
• The nucleus is like a
manager who directs
everyday business for a
company and passes on
information to new cells.
The nucleus contains
genetic blueprints for the
operations of the cell.
• Cells require a continuous
supply of energy.
Mitochondria are
organelles where food
molecules are broken down
and energy is released. The
energy is then stored in
other molecules that can
power cell reactions easily.
• Just as a power plant
supplies energy to a
business, mitochondria
release energy for the cell.
• Cytoplasm is the gellike material inside the
cell membrane and
outside the nucleus.
• Cytoplasm contains a
large amount of water
and many chemicals
and structures that
carry out the life
processes in the cell.
These structures that
the cytoplasm contains
are called organelles
• One chemical that takes part in
nearly every cell activity is
protein. Proteins are needed for
chemical reactions that take
place in the cytoplasm.
• Cells make their own proteins on
small structures in the cytoplasm
called ribosomes.
• Ribosomes are either free
floating in the cytoplasm of a cell
or attached to Endoplasmic
Reticulum in a cell.
Popeye is active because he eats spinach.
However, for Popeye's cells to be active,
his ribosomes help create proteins
• Remember the last vacation you took? Your
suitcase temporarily stored your clothes. Within a
cell, a vacuole fills a similar role as a temporary
storage space for the cell.
• Vacuoles store water, food, pigments, waste or
other materials.
• Vacuoles are large in plant cells and small in
animal cells.
Bell Ringer…
Complete the following Venn Diagrams
Prokaryotes
Eukaryotes
Animal Cells
Plant Cells