Cell Structure
& Function
Cell Theory
1. All living things are made of cells
2. Cells are the basic unit of life
3. All cells come from pre-existing
cells
What do all cells have in
common?
1.Genetic information
(DNA)
2.Cytoplasm – fluid-filled
region between center
and cell membrane
What do all cells have in
common?
3. Cell membrane (plasma
membrane) – surrounds cell
◦ Function: regulates what enters
and leaves cell
4. Ribosomes – make proteins
using instructions from DNA
How big is a cell?
Animation – Cell Size
Surface Area to Volume Ratio
•Why are cells so small?
•Ratio of surface area to volume
• Much greater for small cells
•Space is important for cells to receive nutrients,
oxygen, and to remove waste
•Volume increases faster than surface area as cells
grow
•Greater volume= more metabolic reactions BUT more
difficult to transport wastes and nutrients
•The smaller the cell, the more efficient it is to
transport materials across it
Organisms can be:
o Unicellular
o Consist of only 1 cell
o Multicellular
o Consist of multiple cells
2 Basic Cell Types
PROKARYOTIC
EUKARYOTIC
Prokaryotic
•Smaller/unicellular
•Simple
•No organelles
•No nucleus
•Ex: Bacteria
Eukaryotic
•Larger-multi or unicellular
•More complex
•Many organelles
• Structures that have a
specific function; “miniorgans”
•Nucleus – encloses DNA
• Control center of the cell
Eukaryotic
oEx: Plants,
animals, fungi,
protists
oUnicellular
eukaryotes =
Protists
Unicellular Eukaryote
Protists
Why are protists eukaryotes if they
are only made up of ONE cell?
Amoeba
Paramecium
Dinoflagellates
Prokaryote vs. Eukaryote
-What is different between the two types of cells?
Prokaryotes
•Simple internal
structure
•Nucleoid Region
(no nucleus)
•Flagellum → whiplike tail used for
movement
Prokaryotes
oPili – short
projects that
help bacteria
attach to
surfaces
oMost primitive
organisms
Bacteria
E. Coli
Strepococcus mutans
Bacteria
Staphylococcus aureus
Mycobacterium tuberculosis
Cell Organelles
and Functions
EUKARYOTIC CELLS INTERNAL
STRUCTURE
Eukaryotes
CAN BE SPLIT INTO
PLANT AND ANIMAL
CELLS
Animal
Cell
Animal Cell
Plant
cell
Nucleus
oFunction:
Control center of
the cell
oEukaryotic cells
ONLY!!!
Nucleus
3 parts:
◦1.Contains DNA
◦A. Chromosome – DNA coiled around
proteins called histones
◦Humans contain 46 chromosomes in
nucleus of all cells
◦ Exceptions: Red blood cells (no nucleus),
sex cells
◦B. Chromatin – uncoiled DNA; DNA usually
found in this form
Nucleus
2. Nuclear envelope
(nuclear membrane)
– membrane w/
pores to allow
materials in and out
of the nucleus
3. Nucleolus – inside
the nucleus; makes
ribosomes
Cytoplasm
oOrganelles can be
found in the
cytoplasm
oCytoplasm- portion
of the cell outside of
the nucleus
Endoplasmic Reticulum(ER)
Folded membranes
attached to nucleus
Smooth ER →
◦Not lined with
ribosomes
◦Synthesizes lipids
◦Detoxifies chemicals
(i.e. liver)
Rough ER
◦Lined with ribosomes
◦Function: Modifies
proteins that are being
transported
Ribosomes- made of RNA & protein
- Function: Assemble proteins
based on instructions from DNA
C4U
Difference between Rough and smooth ER
What are ribosomes? Where can they be found?
Golgi apparatus (golgi body)
Looks like a flattened stack
of pancakes
Functions:
◦Receives vesicles (sacs) from
the ER and finishes, sorts,
and ships protein
◦“Packages protein”
One side = receiving; other
side = shipping
Lysosomes
•Lysosome –
Function: Contains
powerful digestive
enzymes
•Digests food
particles to release
nutrients to cell
Fun Fact  enzyme in
lysosome destroys skin
between fingers/toes during
embryo development
Lysosomes
◦“Demolition/cleanup
crew”
◦Destroys damaged
organelles
◦Ex: neutrophils
(WBC) engulf
bacteria
◦Produced by the
Golgi
Peroxisomes
• Functions:
• Breakdown fatty acids, H2O2
(catalase), synthesis of myelin (for
nerve cells)
• Produced by the ER
• Disease: ALD – caused by
peroxisome not functioning
properly
Inside the
cell
WORKING AS A TEAM
Vacuoles
Function: Storage “containers”
◦ store various substances
Animals = small and numerous
Plants = one large central
vacuole
◦ Stores mostly water
◦ Helps with the structure of a
plant cell
Central Vacuole
•Also functions as a
large lysosomecontains enzymes which
break down materials
•Increases turgor
pressure (internal cell
pressure)
Turgor Pressure
Cell swells due to
influx of water
Cell shrinks due
to water loss
Vacuoles
Contractile vacuole → gets
rid of excess water; found
in some protists
◦Prevents bursting of cell &
dilution
Energy Organelles
CHLOROPLAST
•Plants only
•Some protists and algae
•Function:
•Site of photosynthesis
•Use sun energy to make
food energy
Energy Organelles
MITOCHONDRIA
•All eukaryotes
•Function:
•Site of cellular
respiration
•Creates energy for
cell (ATP) from food
Mitochondria
•Contain 2
membranes
•Outer membrane
•Inner membranefolded up inside
the organelle
Plant cells ONLY!
oCell Wall
oFunction: Rigid layer to protect and support
cell
oKeeps cell from bursting
oMade of cellulose (carbohydrate)
oChloroplasts – used for photosynthesis
oLarge central vacuole
Plant Cell
Cytoskeleton
- network of protein
filaments (fibers) that
help the cell maintain
its shape
• Function: Helps with support/internal
structure and movement
• Like wood and nails of house
Cytoskeleton
Cytoskeleton
• Made up of
microfilaments and
microtubules
Microfilaments
◦Made of solid
globular protein
called actin
◦Used for movement
and supports shape
◦Ex: Muscle
contractions
Intermediate Filaments
◦Made of fibrous
proteins
◦They reinforce cell
shape and anchor
organelles
◦Ex: Holds
nucleus in place
Microtubules
◦Hollow tubes of protein
called tubulin
◦They often disassemble
and reassemble
◦Helps with movement)
◦Ex: lysosome may slide
along to reach food
◦Ex: movement of
chromosomes when cells
divide
Movement
Both made of
microtubules wrapped in
membrane
Cilia → short and
numerous; beat together
◦ Ex: Cells of human windpipe sweep
pollen & mucous containing debris
from lungs
Flagella → few; long and
whip-like
◦ Ex: sperm cells
Centrioles
•Type of microtubule
•Function: Organize
DNA during cell
division
•ONLY IN ANIMAL
CELLS
PLANT
BOTH
ANIMAL
Use these terms to fill in
your Venn Diagram
Cell membrane
Golgi body
Rough & smooth ER
Mitochondria
Nucleus
Cytoskeleton
Ribosomes
Central vacuole
Chloroplast
Lysosome
Centrioles
Cell Wall
Small vacuoles