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Chapter 3 –
Cell Structure
Cells: Microscopic, Characteristics and Size
Cell Membrane
Consistency of a bubble not a hard shell
 Protection is like a gated community – only
certain objects can pass through
 Phospholipid – a phosphate group and
two fatty acids
 Lipid Bilayer – nonpolar tails make up the
interior and polar heads appear on interior
and exterior

Nucleus
The “brain” of the cell – controlling all the
activities
 Surrounded by a double layer – the nuclear
envelope to separate it from cytoplasm
 Stores DNA (genetic information)
 Nucleolus – partially assembly of
ribosomes location
 Nuclear Pores – locations where
ribosomes are transferred to the nucleolus

DNA & Cell Specialization
DNA hold instructions for every
expression a cell gives off
 Each cell has specialized instruction for
their “duty”
 Instructions can code for a specific cell
 Example

◦ A cell can be a skin or muscle cell just by
reading the information coded in the DNA
◦ A skin cell cannot just become a muscle cell
and then a skin cell again
Production of Proteins
Endoplasmic Reticulum – a system of
internal membranes that move proteins and
other substances through the cell
 Rough ER – location where ribosomes are
attached and transports the proteins made
 Vesicle – a small sac that pinches of the ER
to transport substances like proteins
 Smooth ER – no ribosomes – creates lipids
and breaks down toxic substances

Section 1 - Looking at Cells
Cells Under the Microscope
 Human body cells smaller than a grain of
sand
 Hooke & Cork Cells
◦ Thin slice of cork has tiny boxes that were
named cells

Anton van Leeuwenhoek
◦ Discovered single-celled organisms based
off Hooke's observations
Measuring Cell Structures
 Metric or International Systems (SI)
 Based on powers of 10
  = micro (1/millionth of a meter)

Table 1
Characteristics of Microscopes

Light Microscopes
◦ light passes through one or more lenses to
enlarge an image

Electron Microscope
◦ beam of electrons forms an image

Magnification
◦ quality of enlarging an image
◦ example: 200x = 200 times larger
Characteristics Continued.

Resolution
◦ measure of clarity of the image

Electron microscope has better
magnification and resolution
Section 2 - Cell Features
The Cell Theory - Observed by Schleiden,
Schwann & Virchow
 All living things are made of one or
more cells
 Cells are the basic unit of structure
and function in organisms
 All cells arise from existing cells
Cell Size
 Small
cells:
◦ more efficient than large cells
◦ able to diffuse through membranes
◦ have higher surface area to volume
ratio
Table 2
Common Features of Cells
Cell Membrane: controls which
particles enter and leave the cell
 Cytoplasm: jelly-like substance that
holds all the internal materials in
place
 Ribosome: a cellular structure that
produces proteins
 DNA: genetic code that provides
instructions for all cellular processes

Prokaryotes
 smallest
and simplest cells
 lacks a nucleus and other structures
 example: bacteria
Characteristics of Prokaryotes

Exist within a large range of environments
◦ some need oxygen and other don’t, some
make their own food
Cytoplasm split into compartments since
there are no internal structures
 DNA is circular and located near the
center of the cell (where the nucleus
would be)

Characteristics continued
Cell wall: gives structure and support
outside of the cell membrane
◦ only in plants and fungi
◦ made of polysaccharide strands
connected by amino acids (building
blocks of proteins)
 Flagella: long, thread-like structure used for
movement

Eukaryotes
Eukaryote:
◦ an organism whose cells have a
nucleus
 Nucleus:
◦ internal compartment containing
DNA
 Cilia:
◦ small hair-like structures used for
movement

Cytoskeleton
Interior framework of an animal cell
that contains protein fibers
 Supports the shape of the cell
 Three types of fibers

◦ Actin fibers
◦ Microtubules
◦ Intermediate fibers
Types of Fibers
Actin fibers
 Microtubules
 Intermediate fibers

Actin Fibers
Just beneath the cell surface
 Contraction and expansion plays a major
role in providing the cell’s shape

Microtubules
Acts as a “highway” system
 Transports information from the nucleus to
different parts of the cell
 Motor proteins move RNA proteins along
these microtubules to transport
information required for cell activities

Intermediate Fibers
Frame of the cytoskeleton
 Ribosomes and enzymes reside on these
fibers in certain location around the cell to
provide efficient metabolic activities

Packing of Proteins

Golgi apparatus – flattened, membrane
sacs that packaging and distributing center
◦ Modifies and adjusts proteins from the ER

Lysosomes – spherical organelles that
contain digestive enzymes
Processing of Proteins
Rough ER ribosomes produce proteins
 Vesicles transport proteins from rough ER
to Golgi
 Golgi processes proteins and packages
them into new vesicles

Vesicles leave to
move outside of
the cell membrane
Vesicles can also remain
within the cytoplasm like
lysosomes that break
down proteins, nucleic
acids, lipids & carbs
Mitochondria
An organelle that obtains energy from
organic compounds to produce ATP
 The amount of mitochondrion that reside
in the cell depends on requirement amount
of energy that cell has

◦ ex. muscle cell – high or low?

Have their own DNA and ribosomes
◦ Most of their protein is made by free
ribosomes
Unique Structures of Plant Cells
Cell Wall – a wall that is made up of
proteins, carbohydrates and polysaccharide
cellulose that protects the cell from
damage
 Chloroplasts – uses light energy to
produce carbohydrates from water and
carbon dioxide
 Central Vacuole – large membranebound sac that stores water, ions, nutrients
and wastes
