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Microscopes provide
windows to the world of
the cell
The light microscope enables us to
see the overall shape and structure
of a cell
Electron microscopes~ can view
ultrastructures of cells


They use a beam of
electrons instead of
light
The greater resolving
power of electron
microscopes
The Cell Theory
• Robert Hooke (1600’s/ English)) used a
compound light microscope to study
cork, the dead cells of oak bark.
• Cells are the basic building blocks of
all living things.
• Schleiden & Schwann (1830;s,
German) their observations &
conclusions are summarized as the cell
theory
The cell theory is made up of
three main ideas:
1.All organisms are composed of
one or more cells.
2. The cell is the basic unit of
organization of organisms.
3. All cells come from preexisting
cells.
Why study cells?

Cells  Tissues  Organs  Bodies
bodies are made up of cells
 cells do all the work of life!

The Jobs of Cells

Cells have 3 main jobs

make energy
• need energy for all activities
• need to clean up waste produced
while making energy

make proteins
• proteins do all the work in a cell,
so we need lots of them

make more cells
• for growth
• to replace damaged or diseased cells
Our organelles
do all these
jobs!
2 Types of cells
bacteria
cells
Prokaryote
- no organelles
Eukaryotes
- organelles
animal cells
plant cells
Prokaryotic cells-Bacteria

small, relatively
simple cells
oThey do not have a nucleus
o enclosed by a plasma membrane and is
usually encased in a rigid cell wall
o Inside the cell are its DNA and other parts
Eukaryotic cells are partitioned into
functional compartments





All other life forms are made up of one or
more eukaryotic cells
These are larger and more complex than
prokaryotic cells
Eukaryotes are distinguished by the presence
of a true nucleus
The cytoplasm contains organelles
Many organelles have membranes as
boundaries
 These compartmentalize the interior of the
cell
 This allows the cell to carry out a variety of
activities simultaneously
Animal Cell
Plant Cell
Cell sizes vary with their
function

Cell size and shape
relate to function
Cell size comparison
most bacteria
Animal cell
Bacterial cell
 1-10 microns
eukaryotic cells
 10-100 microns
 micron = micrometer = 1/1,000,000 meter
 diameter of human hair = ~20 microns
Natural laws limit cell size
a cell must be large enough to house
the parts it needs to survive and
reproduce
 The maximum size of a cell is limited
by the amount of surface needed to
obtain nutrients from the environment
and dispose of wastes

A small cell has a greater ratio of
surface area to volume than a large cell
of the same shape
30 µm
Surface area
of one large cube
= 5,400 µm2
10 µm
Organelles

Organelles do the work of cells

each structure has a job to do
• keeps the cell alive; keeps you alive
They’re like
mini-organs!
Model Animal Cell
1. Cells need power!

Making energy

to fuel daily life & growth, the cell must…
•
•
•
•
ATP

take in food & digest it
take in oxygen (O2)
make ATP
remove waste
organelles that do this work…
•
•
•
•
cell membrane
lysosomes
vacuoles & vesicles
mitochondria
Cell membrane

phosphate
“head”
Function
separates cell from outside
 controls what enters or leaves cell

• O2, CO2, food, H2O, nutrients, waste

recognizes signals from other cells
• allows communication between cells

Structure

double layer of fat
• phospholipid bilayer

receptor molecules
• proteins
lipid “tail”
cytoplasm
jelly-like material holding
organelles in place
cell membrane
cell boundary
controls movement
of materials in & out
recognizes signals
Vacuoles & vesicles

Function


small food
particle

moving material
around cell
storage
Structure

membrane sac
vacuole filled w/
digestive enzymes
vesicle
vesicle filled w/
digested nutrients
Vacuoles have diverse
functions in cell maintenance

membrane-bound sacs
with varied functions.



Food vacuoles, from
phagocytosis, fuse
with lysosomes.
Contractile
vacuoles, found in
freshwater protists,
pump excess water
out of the cell.
Central vacuoles are
found in many mature
plant cells.
Food & water storage
food vacuole
plant cells
central vacuole
animal cells
contractile
vacuole
cytoplasm
jelly-like material holding
organelles in place
vacuole & vesicles
transport inside cells
storage
cell membrane
cell boundary
controls movement
of materials in & out
recognizes signals

Lysosomes
Function
 digest food
• used to make energy

clean up & recycle
• digest broken
organelles

lysosomes
Structure
 membrane sac of
digestive enzymes
digesting broken
organelles
small food
particle
vacuole
digesting food
A Job for Lysosomes
6 weeks
15 weeks
Connection: Abnormal
lysosomes can cause fatal
diseases

Lysosomal storage diseases are
hereditary
They interfere with other cellular
functions
 Examples: Pompe’s disease, TaySachs disease

ENERGY-CONVERTING
ORGANELLES
Mitochondria

Function

make ATP energy from cellular respiration
• sugar + O2  ATP
• fuels the work of life

Structure

double membrane
in both animal &
plant cells
ATP
cytoplasm
jelly-like material holding
organelles in place
vacuole & vesicles
transport inside cells
storage
mitochondria
make ATP energy
from sugar + O2
cell membrane
cell boundary
controls movement
of materials in & out
recognizes signals
lysosome
food digestion
garbage disposal &
recycling
Plants make energy two
ways!
 Mitochondria


make energy from sugar + O2
• cellular respiration
• sugar + O2  ATP
ATP
Chloroplasts

make energy + sugar from sunlight
• photosynthesis
• sunlight + CO2  ATP & sugar
• ATP = active energy
• sugar = stored energy
• build leaves & roots & fruit
out of the sugars
sugar
ATP
Chloroplasts


found in plants and some protists
convert solar energy to chemical energy in
sugars
Mitochondria are in both cells!!
animal cells
plant cells
mitochondria
chloroplast
cytoplasm
jelly-like material
around organelles
central vacuole
storage: food,
water or waste
cell wall
support
mitochondria
make ATP in
cellular respiration
cell membrane
cell boundary
controls movement
of materials in & out
recognizes signals
chloroplast
make ATP & sugars in
photosynthesis
lysosome
digestion & clean up
2. Cells need workers = proteins!

Making proteins

to run daily life & growth, the cell must…
• read genes (DNA)
• build proteins
• structural proteins (muscle fibers, hair, skin, claws)
• enzymes (speed up chemical reactions)
• signals (hormones) & receptors

organelles that do this work…
•
•
•
•
nucleus
ribosomes
endoplasmic reticulum (ER)
Golgi apparatus
Proteins do all the work!
one of the major job of cells is to make proteins,
because…
proteins do all the work!
structural
enzymes
signals
receptors
DNA
proteins
cells
Nucleus

Function
control center of cell
 protects DNA

• instructions for building proteins

Structure
nuclear membrane
 nucleolus

• ribosome factory

chromosomes
• DNA
cytoplasm
jelly-like material holding
organelles in place
vacuole & vesicles
transport inside cells
storage
lysosome
food digestion
garbage disposal &
recycling
nucleolus
produces
ribosomes
nucleus
protects DNA
controls cell
chromosomes
DNA
mitochondria
make ATP energy
from sugar + O2
cell membrane
cell boundary
controls movement
of materials in & out
recognizes signals
Ribosomes

Function



protein factories
read instructions to build proteins from DNA
Structure


some free in cytoplasm
some attached to ER
Ribosomes on ER
cytoplasm
jelly-like material holding
organelles in place
vacuole & vesicles
transport inside cells
storage
mitochondria
make ATP energy
from sugar + O2
cell membrane
cell boundary
controls movement
of materials in & out
recognizes signals
lysosome
food digestion
garbage disposal &
recycling
nucleolus
produces
ribosomes
nucleus
protects DNA
controls cell
ribosomes
build proteins
Endoplasmic Reticulum

Function

works on proteins
• helps complete the
proteins after ribosome
builds them


makes membranes
Structure

rough ER
• ribosomes attached
• Make membranes

smooth ER
• Synthesizes lipids
cytoplasm
jelly-like material holding
organelles in place
vacuole & vesicles
transport inside cells
storage
lysosome
food digestion
garbage disposal &
recycling
ribosomes
builds proteins
mitochondria
make ATP energy
from sugar + O2
cell membrane
cell boundary
controls movement
of materials in & out
recognizes signals
nucleus
protects DNA
controls cell
ER
works on proteins
makes membranes
Golgi Apparatus

Function

finishes, sorts, labels & ships proteins
• like UPS headquarters
• shipping & receiving department

ships proteins in vesicles
• “UPS trucks”

vesicles
carrying proteins
Structure

membrane sacs
transport vesicles
cytoplasm
jelly-like material holding
organelles in place
vacuole & vesicles
transport inside cells
storage
lysosome
food digestion
garbage disposal &
recycling
ribosomes
builds proteins
mitochondria
make ATP energy
from sugar + O2
cell membrane
cell boundary
controls movement
of materials in & out
recognizes signals
nucleus
protects DNA
controls cell
ER
helps finish proteins
makes membranes
Golgi apparatus
finishes, packages
& ships proteins
nucleus
control cell
protects DNA
nucleolus
make ribosomes
endoplasmic reticulum
processes proteins
makes membranes
ribosomes
make proteins
cytoplasm
jelly-like material
around organelles
central vacuole
storage: food,
water or waste
Golgi apparatus
finish & ship
proteins
cell wall
support
mitochondria
make ATP in
cellular respiration
cell membrane
cell boundary
controls movement
of materials in & out
recognizes signals
chloroplast
make ATP & sugars in
photosynthesis
lysosome
digestion & clean up
3. Cells need to make more cells!

Making more cells

to replace, repair & grow,
the cell must…
• copy their DNA
• make extra organelles
• divide the new DNA & new
organelles between 2 new
“daughter” cells

organelles that do this work…
• nucleus
• centrioles
Centrioles

Function

help coordinate cell division
• only in animal cells

Structure

one pair in each cell
cytoplasm
jelly-like material holding
organelles in place
vacuole & vesicles
transport inside cells
storage
lysosome
food digestion
garbage disposal &
recycling
nucleus
protects DNA
controls cell
centrioles
cell division
ribosomes
builds proteins
mitochondria
make ATP energy
from sugar + O2
cell membrane
cell boundary
controls movement
of materials in & out
recognizes signals
ER
helps finish proteins
makes membranes
Golgi apparatus
finishes, packages
& ships proteins
THE CYTOSKELETON


The cell’s internal skeleton that functions in
cell structural support and motility
A network of protein fibers makes up the
cytoskeleton
three main types of fibers in the cytoskeleton:
microtubules, microfilaments, and
intermediate filaments.



Microfilaments enable cells to change shape and move
Intermediate filaments reinforce the cell and anchor certain
organelles
Microtubules



give the cell rigidity
provide anchors for organelles
act as tracks for organelle movement
MICROFILAMENT
INTERMEDIATE
FILAMENT
MICROTUBULE
Cilia and flagella


locomotor
appendages that
protrude from
certain cells
Clusters of
microtubules drive
the whipping action
of these organelles
Cell Summary

Cells have 3 main jobs

make energy
• need food + O2
• cellular respiration & photosynthesis
• need to remove wastes

make proteins
Our organelles
do all those
jobs!
• need instructions from DNA
• need to chain together amino acids & “finish”
& “ship” the protein

make more cells
• need to copy DNA & divide it up to daughter cells