Chapter 6
A Tour of the Cell
Much of our knowledge of cells has come
about with the assistance of
microscopes. Many scientists studied
various aspects of living things. With this
knowledge, we have come to accept
three basic ideas regarding living
things…
These ideas are known as
The Cell Theory.
The Cell Theory is one of the
most important theories in
biology.
All living things are composed of cells
Cells are the smallest unit of structure and
function in living things.
Cells can only come from pre-existing cells
All cells are classified into one of the
following categories
Eukaryotic (complex)
Prokaryotic (simple)
Nucleus
No nucleus
Organelles (many)
No organelles
10-1000 micrometers in
size
1-10 micrometers in
size
Fossil evidence dates
back to 3.5 bya
Unicellular
Bacteria
Fossil evidence dates back
to 1.5 bya
Unicellular or multicellular
Plants, Animals, Protists,
and Fungi
Highly compartmentalizedcell is separated into
“rooms” by membranes
“walls”
Prokaryotic vs. Eukaryotic
Notice that the prokaryotic
cell has a “nucleoid region”
and a cell wall.
If you were looking at a
picture of a cell, what would
you look for to determine if
the cell is a prokaryote of a
eukaryote?
Nucleus?
Organelles?
Size?
All cells have a cell
membrane & ribosomes.
Basic Structures and
Organelles in Eukaryotic Cells
Why is each cell structure crucial to the function
of the cell and to the whole organism?
Cell (“Plasma”) Membrane
Structure:
Phospholipid Bilayer
studded with proteins
and other molecules
Function:
Gate Keeper – regulates
what enters and exits
the cell and maintains
homeostasis
Location:
Surrounds cell
Cell Wall
Structure:
Made of cellulose
chitin ( fungi)
or
Function:
Structure/Support/Protection
Location:
Outside of the cell membrane
(only in plants, algae, bacteria and
fungi)
Nucleus
Structure:
Large and membrane-bound
Function:
Contains DNA (chromatin)
Control center of cell- directs
the activity of the cell
Location:
Animal – center
Plant – near the cell membrane
Nuclear Membrane “Envelope”
Structure:
Double membrane with
many pores
Function:
Keeps DNA (chromatin)
contained and allows
substances to enter/exit
the nucleus
Location:
Surrounds nucleus
Nucleolus
Structure:
Dark structure in the
nucleus/made of RNA
and protein
Function:
Produces ribosomes
Location:
Inside the nucleus
Cytoplasm
Structure:
Cytosol (fluid) and
organelles
Function:
Allows movement of
substances throughout the
cell
Location:
The area outside nucleus
and inside cell membrane
Ribosomes
Structure:
Made of RNA, small, not
membrane bound
Functions:
Manufactures proteins
Location:
Free floating in
cytoplasm, or attached
to Endoplasmic
Reticulum
Found in both
Prokaryotic &
Eukaryotic cells
Chloroplast
Structure:
Double outer membrane with
inner membrane in the form of
disks and tubules
Contains chlorophyll
Function:
Converts solar energy
into chemical energy
(carbs) by photosynthesis.
Location:
In cytoplasm
(found in plants, + algae)
Structure:
Bean-shaped organelle Mitochondria
with a highly folded
inner membrane.
Function:
Cellular Respiration
Converts energy in
food (carbs) to a form
of energy the cell can
use (ATP)
“Powerhouse” of cell
Location:
Cytoplasm (all
Eukaryotic cells)
Endoplasmic
Reticulum (ER)
Structure:
System of membranes extending
throughout cytoplasm.
Passageways/tunnels through cell
Function:
Smooth ER – w/o ribosomes (builds
lipid molecules)
Rough ER – w/ribosomes attached
(proteins for export)
Location:
Cytoplasm - from nucleus to cell
membrane
Golgi Apparatus
Structure:
Membranes in
flattened sacs
Function:
Recieves proteins
from ER, modifies,
stores, or packages
(proteins) and other
substances for
export
Location:
Cytoplasm
Vacuoles
Structure:
Membrane-bound sacs
Plants – 1 large (water)
Animals – many small
Function:
Storage
Location:
Cytoplasm
Structure:
Small membrane bound sacs
filled with digestive enzymes
Mainly found in Animal
cells/very few plant cells have
them
Function:
Digests old/worn out
structures, organelles or
molecules or engulfed
organisms
Location:
Cytoplasm
Lysosome
Cytoskeleton
Microtubules
Structure-straight hollow
tubes of protein
Function–give rigidity and
shape to cell, tracks for
organelles to move along
Microfilaments
Structure-thin solid rods
of protein (internal
skeleton)
Function-allow cell to move
or change shape
Location:
Cytoplasm
Cell Analogy Activity
ANALOGY: similarity between like features
of two things, on which a comparison
may be based.
Example: the heart is similar to a
(water) pump
?
Flagella
StructureLong, thin, whip-like tail
(microtubules)
FunctionMovement
Cilia
Structureshort hair-like (many)
(microtubules)
Functionmove fluid over
surface or movement
Plastids
Double layered
membranous sacs (Plants
only)
Storage
Leukoplasts – starch,
lipids or proteins
Chromoplasts produce/store pigments
Chloroplasts –
chlorophyll/photosynthesis
Adensosine Triphosphate the most
important energy-storing molecule in living things!
ATP transports energy within cells.
Energy is stored in the bonds between the phosphate groups.
In order to release energy from ATP, the terminal (last)
phosphate group must be removed/ This can be accomplished
through hydrolysis.
Hydrolysis of ATP (energy is released
and made available for the cell.)
When cells need energy, a phosphate group is removed from ATP
and it is converted to ADP and energy is released.
RELEASE ENERGY
STORE ENERGY
If cells want to store energy, ADP can be converted
to ATP by adding a phosphate group back on.
Formation of ATP – cells use the ADP to store
energy.
They add the phosphate group back on to ADP
converting it to ATP.
phosphate removed
36 ATP – glucose
80 ATP – Triglyceride
Cells use 1 million ATP /sec
Plant Cells
•Cell Membrane
•Nucleus
•Cell Wall
•Nuclear Membrane
•Chloroplast
•Nucleolus
•1 Large Vacuole
•Cytoplasm
(water)
•Ribosomes
•Plastids
•Mitochondria
•Stores energy as •Endoplasmic Reticulum
starch
•Golgi Apparatus
•Cytoskeleton
Animal Cells
•Many Small
vacuoles
•Lysosomes
•Stores energy as
glycogen
Plant vs. Animal Cells (Eukaryotic cells)
Levels of organization in
multicellular organisms
Cells
Cells are the basic unit of structure and
function in living things.
The cells of multicellular organisms are
specialized and perform many
different functions.
Animal-neuron, muscle, RBC, epithelial, bone,
etc…
Plant-guard, epidermal, etc…
Different kinds of plant cells
Onion Epidermal Cells
root hair
Root Hair Cell
Guard Cells
Different kinds of animal cells
white blood cell
Amoeba
red blood cell
muscle cell
cheek cells
sperm
nerve cell
Paramecium
Unicellular Protists
Tissue
A group of similar cells that perform a particular function
Animals: epithelial,
muscular, connective,
nervous
Plants: epidermal, vascular,
mesophyll
Organ
Different tissues group
together to carry out
specialized functions
Heart: consists of
muscles, nervous tissue
and blood vessels
(kidney, liver, pancreas)
Leaf: consists of
epidermis, mesophyll and
vascular tissue
(roots, stems, flowers)
System
Several organs and
tissues work together to
carry out a particular set
of functions in a
coordinated way
Human: digestive,
respiratory,
excretory, circulatory
reproductive systems,
etc…
Plant: root and shoot
systems
The Respiratory System
Organism
The highest level
of organization in
any living thing!
Example: you
Levels of Organization

CELLS (muscle cells,nerve cells)

TISSUES (muscle, epithelium)

ORGANS (heart, lungs, stomach)

SYSTEMS (circulatory system)

ORGANISM (human)
Plant Cells vs. Animal Cells
Plant Cells
Animal Cells
Cell wall
No cell wall
Large central vacuole
Small vacuoles or none
Chloroplasts
(plastids)
No chloroplasts or
plastids
No lysosomes
Lysosomes
Store energy as
Store energy as
starch
glycogen
Both: Cell membrane, Nucleus, Nucleolus, Nuclear
membrane, Cytoplasm, Ribosomes, Mitochodria, Endoplasmic
Reticulum, Golgi Apparatus, Cytoskeleton