Chapter 3
BASIC UNIT OF LIFE:
THE CELL
All Organisms are made up of cells
EukaryotesMoth
Juniper
Protozoans
Ciliates in water on
plant
Prokaryotes
Bacteria in insect gut
and on surface of
insect and tree
Cell theory
 All living organisms are
made up of cells
 All cells come from
other cells
Theory refers to the body
of knowledge that has
been developed
through scientific
inquiry
Two Cell Categories
Prokaryote
Eukaryote
 Cell membrane
 Cell membrane
 Cytoplasm
 Cytoplasm
 DNA (in a loop)
 DNA (in strands)
 Ribosomes (for creating
 Ribosomes
proteins)
 Cell wall
 Very small
 DNA is loose in cytoplasm
 Many other organelles
 Cell wall in plants
 Variable size – larger than
prokaryotes
 Nucleus holds DNA
The organisms that cause colors in the hot springs of
Yellowstone are single celled and have been around
since the beginning of life on this planet. Would
these organisms be prokaryotes or eukaryotes? Would
their cells have a nucleus?
A. Prokaryotes, yes
B. Prokaryotes, no
C. Eukaryotes, yes
D. Eukaryotes, no
http://serc.carleton.edu/microbelife/extreme/extre
meheat/yellowstone.html
Basic Cell Structures
 Cell Membrane
 Nuclear double
membrane around
nucleus
 Mitochondria for
energy
 Processing and
packaging organelles
 Lysosomes – digestion
 Cytoskeleton - support
Plasma Membranes
Bilayer Structure
Molecules Found in the cell
Membrane
Cholesterol increases
membrane flexibility
Types of Membrane Proteins
1. Receptor proteins –
 Bind to external molecules which cause reactions in cell
 Ex. Target cells can detect hormones in blood – regulate
development of secondary sexual characteristics
2. Recognition proteins
 Typically have attached carbohydrate chains
 Give the cell identity – other cells can recognize them
 Ex. During development cells interact & work together to
develop structures. Recognition is essential.
 Ex. Autoimmune disease = faulty self-recognition
Visual examples
Receptor proteins
Recognition proteins
Types of Membrane Proteins
3. Transport proteins
 Move other molecules across the cell membrane
 Transmembrane proteins only
 Ex. Nerve cell fire – Na ions moved across
4. Enzymatic proteins
 Increase rate of chemical reactions associated
with the cell membrane
 Ex. cAMP formation regulated – internal
messenger created
Visual Examples
Transport proteins
Enzymatic proteins
Why is the cell membrane
considered a fluid mosaic?
A. It’s primarily made up of water with dispersed
fats and proteins in a mosaic pattern
B. Proteins move back and forth through the
membrane from inside to outside of the cell
and back in a fluid mosaic pattern.
C. It’s made up of several different types of
molecules, like a mosaic, and many of those
molecules float around in the lipid bilayer.
Cell Structure and Function
 Cells are factories
 Need raw materials to enter the cell
 Need to eliminate wastes
 Need to export products produced in the cell
 Need to keep up-to-date on needs of surrounding
cells and tissues
Endocytosis
Exocytosis
Animation of endocytosis and
exocytosis
 http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::535
::535::/sites/dl/free/0072437316/120068/bio02.
swf::Endocytosis%20and%20Exocytosis
Other means of movement
Passive Transport
Active Transport
 Requires no input of
 Requires energy input to
energy
 Diffusion
 Osmosis (diffusion of
water across a
membrane)
move molecules across
the cell membrane or
around in the cell
 Primary – uses ATP
 Secondary
Diffusion
Key:
Molecules tend to
move from an area of
high concentration to
an area of
low concentration
When moving
across a
membrane –
diffusion may be
facilitated by a
transport protein
Osmosis
Irrigation problems
 Irrigation can lead to a build up of soil salinity
 If soil develops a similar (or higher) salt
content than the plant cells, water doesn’t
flow as easily into plant roots.
 Soil salt concentrations make plants and soil more
alike in fluid concentration (isotonic) - so water
doesn’t flow across the cell membranes into the
plant roots.
 Soil salinity creates drought like conditions in
which plants can’t get water
Passive
Transport
Active Transport
The object depicted in
the figure:
A) is a bacterial cell.
B) could be either a plant or an animal cell.
C) is a ribosome.
D) is an animal cell.
E) is a plant cell.
Cell Wall
Not found in animals
A major component of
the cell wall is the
complex carbohydrate,
Cellulose
If the concentrations of a particular
molecule are equal on both sides of the
membrane, facilitated diffusion will:
A) insure that the molecule becomes
concentrated outside the cell.
B) insure that the molecule stays impermeable to
the membrane.
C) insure that the molecule becomes
concentrated inside the cell.
D) insure that the concentrations inside and
outside the cell are both increased.
E) be ineffective.
Connections
Between Cells:
1. Tight Junctions
> hold cells in place
> keep fluids from passing
around edges of cells
blood brain barrier
lining of gut
Connections
Between Cells:
2. Desmosomes
> throughout body
Connections
Between Cells:
3. Gap Junctions
>Allows small molecules,
but not large proteins
and organelles to move
between cells.
Cell Size
 Chicken egg = 40-60 mm
 (1mm = 1/1000 m)
 Paramecium caudatum = 60X 230 um
 (1 um = 1/1000 mm)
 Red blood cell = 1.9-7.5 um
 Bacteria 0.5-2 um
Why not bigger?
What limits the size of cells?
 Much of what occurs in a cell depends on the
movement of materials in and out of the cell
through the plasma membrane
 Rate of production and waste removal is
dependent on cell volume
 Rate of movement across the membrane
depends on surface area of cell
 As cell size increases, volume increases as a
cubed unit while surface area as a square unit.
Surface to volume ratio
Radius
1 cm
2 cm
3 cm
Surface
area
(cm2)
12.57
50.26
201.06
Volume
(cm 3)
4.19
33.51
268.08
3
1.5
0.75
SA/V
Nucleus and chromosomes
Cytoskeleton
Made up of protein fibers that can expand, contract,
move past one another.
Microfilaments
underlie the cell
membrane and
cytoskeletal
elements can
break down and
reform to allow
changing shape
in Amoeba.
Cell locomotion:
Mitochondria – have own DNA!
Mitochondria con’t
 Number in a cell may vary
 Cells with high energy demands like
muscles have more than other cells
 Process known as aerobic respiration (Kreb cycle
& electron transport phosphorylation) takes place
here.
 Sugar (C6H12O6) + 6H2O + 6O2 => 6 CO2 + 12 water (H2O) + Energy
 Breaks down sugar to release the energy in the chemical bonds
 Oxygen is used and Carbon dioxide is a waste biproduct.
Chloroplasts
Only in Plant Cells
and Single-celled
Algae
Have own DNA!
Similar in some
ways to bacteria
that do
photosynthesis –
especially DNA
Evolution of
Eukaryote Cells
Lysosomes – Waste removal
Up to 50 different types of enzymes!
Endoplasmic Reticulum
Rough Endoplasmic Reticulum
Smooth Endoplasmic Reticulum
Golgi Apparatus
Vacuoles
Cells can be Single-celled
Organisms
 Euglena can engulf
other organisms or do
photosynthesis to get
food for building blocks
and energy.
 Eyespot
 Flagellum
 Contractile Vacuole
Cells Specializations Within a
Multicellular Organism
 All cells have the same
genetic material.
 Cells specialize because
some genes are turned
off and others are
turned on.
 Ex. Lining of small
intestine
 Ex. Nerve cell
Design Organelle Analogies
 Analogy
 Includes similes and metaphores
 Similes compare things using words “as” or “like”
 Ex. You are as stubborn as a mule.
 Ex. Life is like a box of chocolates.
 Metaphores compare 2 unlike things for
secondary meaning
 Ex. The gum was bursting with flavor.
 Ex. The relationship between them began to thaw.
The organelle in the figure
is found in:
A) animals only.
B) plants only.
C) plants, animals, and bacteria.
D) plants and animals.
E) bacteria only.
What is it?
The lysosomes in a human cell contain
approximately ________ different
type(s) of digestive enzymes.
A) 1
B) 500
C) 10
D) 4
E) 50
According to the theory of
endosymbiosis, the origin of
chloroplasts probably involved:
A) the formation of cell walls around the
photosynthetic pigments.
B) the formation of colonies of cyanobacteria.
C) the engulfing of small photosynthetic
prokaryotes by larger cells.
D) the accumulation of free oxygen in ocean
waters.
E) All of the above are correct.
Read chapter 4 on Energy