Cell Structure
Chapter 3
Looking at Cells
1st microscope invented in the 1600s
 Robert Hooke (Cork Cells)
 Scientists use the Metric System or
International Systems of Measurements
 SI units are based on powers of 10
– μ = micro
μm = micrometer

Characteristics of Microscopes

Light Microscope
– Light passes
through one or
more lenses to
produce an
enlarged image

Electron Microscope
– Forms an image
of a specimens
using a beam of
electrons rather
than light
Characteristics of Microscopes
MAGNIFICATION – is the quality of
making an image appear larger than its
actual size
 RESOLUTION – is the measure of the
clarity of an image

Types of Microscopes

Compound Light Microscopes
– 2 lenses
– Objective Lens (40 X)
– Ocular Lens (10 x)
Magnification up to 2000 X
 View images from 0.5 μm to 0.5 cm
 Used to view images such as living cells
 Lower magnification than electron
microscopes

Types of Microscopes

Electron Microscope
– Magnification up to 200,000 X
– Object & electron beam are placed in a
vacuum chamber
– Object is stained with metal ions
– Electron beam is absorbed by the ions
– Electrons produce a fluorescent image
called the TEM
Types of Microscopes

Scanning Electron Microscope
– Electrons bounce off the specimen
– Creating a 3-D image

Scanning Tunneling Microscope
– Uses needle-like probe to measure
differences in voltage caused by electrons
that leak from the surface
– 3-D images
– Living organisms can be viewed with this
scope
Section 1 Review
1. How many cm are in a m?
 2. What is the difference between
resolution and magnification?
 3. What measurement system do
scientists use?
 4. Why can living cells not be viewed
under an electron microscope?
 5. The English scientist Robert Hooke
used a crude microscope to examine
these….

Section 2: Cell Features
Schleiden, Schwann, Virchow
 CELL THEORY
– 1) All living things are made of one or
more cells
– 2) Cells are the basic units of
structure and function in organisms
– 3) All cells arise from existing cells

Cell Size
Small cells are more efficient than large
cells
 All substances that enter or leave a
cells have to cross the cell’s surface
 Surface area- to- Volume

– LOW – substances can not enter or leave

Small cells have a higher surface areato – volume ratio
– Shorter distance to travel
Common Features of Cells

CELL MEMBRANE – encloses the cell
– Regulates what enters & leaves the cell
CYTOPLASM – cell’s interior
 CYTOSKELETON – fibers suspended
in the cytoplasm
 RIBOSOMES – cellular structures on
which proteins are made
 DNA – instructions for the cell

Prokaryotes
The smallest and simplest cells
 Are single-celled organisms
 Lack a NUCLEUS
 Examples: Bacteria
 Reproduce Rapidly
 Do not need oxygen to survive
 Some can make their own food

Characteristics of Prokaryotes
CYTOPLASM – semi-solid material that
surrounds everything inside the cell
– DNA, Ribosomes & enzymes
 CELL WALL – surrounds the cell
membrane
– Function: Provides support &
structure
– Found in plants, fungi & some
bacteria
– Made of polysaccharides

Characteristics of Prokaryotes

Capsule – surrounds the cell
– Cling to lots of things

Flagella – long, threadlike structures
that extend from the cell surface
– Function: helps the cell move
Eukaryotic Cells
Have a Nucleus
 NUCLEUS – houses the DNA
 Organelles - internal compartments

– Carry out specific activities in the cell
Vesicles – move proteins & other
molecules from cell to cell
 CILLIA – short hair-like projections

– Functions: Movement & transport of
materials across the cell membrane
Eukaryotic Cells
CYTOSOL – fluid material that makes
up the cytoplasm
 CYTOSKELETON

– Made of protein fibers
– Function: Holds the cell together
– All connected to one another
– 3 kinds of fibers – Actin Fibers,
Microtubules & Intermediate Fibers
Cytoskeleton
Actin Fibers – determine the shape
 Microtubules – act as a highway
system
– Transport info from the nucleus to the
rest of the cell
 Intermediate Fibers – are an anchor
for ribosomes & enzymes

The Cell Membrane

Selective Permeability
– Only let certain things enter or exit

Phospholipid = 1 lipid + 2 fatty acids
– Head  Polar
• Phosphate Group
• Attracted to water
– 2 Tails  NonPolar
• Repel water
The Cell Membrane





LIPID BILAYER – double layer of
phospholipids
Marker Proteins -- “Name Tags”
– Direct cells to the proper location
Receptor Proteins -- “Antenna”
– Receive and transmit info
Transport Proteins -- “Locked Door”
– Allow only certain ions and molecules to
cross the cell membrane
Enzymes – assist in biochemical reactions
Section 2 Review
1. Describe the importance of surfacearea-to volume ratio of a cell.
 2. How are Prokaryotic & Eukaryotic
Cells similar? Different?
 3. Describe the function of 2 cell
membrane proteins.
 4. What does the cell theory state?
 5. What does the term “selectively
permeable” mean in regards to a cell
membrane?

Section 3: Cell Organelles

Cell functions are controlled by the
NUCLEUS
– Surrounded by the NUCLEAR
ENVELOPE
• Made up of 2 lipid bilayers
• NUCLEAR PORES
–Ribosomal RNA pass through the pores
into the cytoplasm
• Ribosomes are partially assembled in the
NUCLEOLUS
The Nucleus
DNA stored inside the nucleus
 Eukaryotic DNA is wound around
proteins
 CHORMOSOMES – DNA strands

– Humans = 46
– Garden Peas = 14
Ribosomes & the ER

RIBOSOMES make protein & RNA
– Mobile in the cytoplasm
– Stationary on the Rough ER

ENDOPLASMIC RETICULUM
– Move proteins & other substances
throughout the cell
– Has a membrane that is made up of a lipid
bilayer
Ribosomes & the ER

VESICLE – is a small membrane bound
sac that transports substances inside the
cell
– Separates proteins made on the Rough ER
from proteins made in the cytoplasm

SMOOTH ENDOPLASMIC RETICULUM
– Lacks ribosomes
– Function: Makes lipids & breaks down toxic
substances
Packaging & Distribution of
Proteins

GOLGI APPARATUS
– Is a set of flattened, membrane-bound sacs
that package & distribute
– Proteins are modified in the GA & enter new
vesicles
– Vesicles take the proteins outside the cell
OR
– Vesicles remain in the cell & become
LYSOMES
• Contain digestive enzymes
Mitochondria
Function: Harvest energy to make ATP
 Muscle cells can have 100s – 1000s
 2 Membranes (Inner & Outer)

– Here chemical reactions produce ATP

Also has DNA
– Circular – similar to prokaryotic DNA
Structures of Plant Cells
3 Organelles NOT found in Animal Cells
 1) CELL WALL

– Adds additional support, give shape,
protects from damage & connects with
adjacent cells

2) Chloroplasts
– Use light to make carbohydrates from
carbon dioxide and water
– Surrounded by 2 layered membrane &
contains DNA
Structures of Plant Cells

3) Central Vacuole
– Takes up most of volume
– Contains
•
•
•
•
Water
Ions
Nutrients
Waste
– When full it makes the cell rigid
– Allows the plant to stand upright
Section 3: Review
1. Describe the role of the nucleus in
cell activities.
 2. Sequence the course of newly made
proteins from the rough ER to the
outside of the cell.
 3. Name 2 organelles a plant has that
an animal cells does not.
 4. The mitochondria has the nickname
“The Powerhouse”. Why is this a good
nickname?
