Download Introduction to Cells 1p1 2014

Lesson 1:
What is life?
What is Biology?
 The study of life.
 What is life?
All living things are able to
carry out the Functions of Life:
Reproduction – creating
genetically related offspring
Metabolism – controls the
chemical reactions of life
Growth – increase in size and
mass through nutrition and
metabolism
Nutrition – acquires the
chemical building blocks
needed to sustain life
Homeostasis – maintaining a
balanced internal environment
Excretion – removal of waste
products created by living
Responsiveness – changing
actions or behavior due to
environmental signals
Lesson 2:
Introduction to Cells
What is a cell?
 The usually microscopic unit from which
living things are built
 A “bag” of gel-like cytoplasm inside a
plasma membrane
 The smallest unit capable of all the
functions of life
Egg and sperm cells
Cell Theory:
living things are composed of cells
Evidence:
All organisms ever investigates (millions), no matter
their size, are made of one or more cells.
Cholera bacteria
Elephant cells
These cells are of similar sizes and have similar
chemicals and structures (membrane, ribosomes, etc.)
Cell Theory:
living things are composed of cells
Challenges:
1.Aseptate fungal hyphae: the
fungal “threads” dissolve the
cell walls and combine the
cells into one.
2.Muscle cells (fibres): mitosis
produces many nuclei but all
the nuclei remain within a
single cell.
3.Acetabularia (a giant alga):
there is only a single “cell”,
so large that the word “cell”
seems inappropriate.
Unicellular v. Multicellular
 Unicellular organisms: cells are
generalists -- each cell capable of
performing every life function
 Multicellular organisms: cells are specialists
-- each cell is adapted to a specific function.
Often no single cell can do all life functions.
Light microscopes
 View natural color
 Can observe movement
 Can use live specimens
 Cheap and easy!
 Range includes larger objects than
electron microscopes
Electron Microscopes
 SEM: scanning electron
microscope, surface image
 TEM: transmission electron
microscope, view through a
thin slice of specimen
MAJOR advantage:
HIGHER resolution!
Electron microscopes can achieve better than 50 pm
(1000 pm = 1 nm) resolution and magnifications of up to
about 10,000,000x whereas ordinary light microscopes
are limited by diffraction to about 200 nm resolution and
useful magnifications below 2000x.
1 m = 1,000 mm
1 mm = 1,000 µm
1 µm = 1,000 nm
Relative sizes (lengths)
Organelle
Scale interactives here (microscope) and here (universe).
Determining sizes
 Magnification = image size  specimen size
Resizing changes magnification 
 Scale bar: a line added; the scale shows
the actual length the line represents.
Resizing image also resizes scale bar 
x4000
Example calculations
 A mitochondrion has a length of 12 um.
 It is drawn 8.4 cm long.
 What is the magnifcation?
Mag. = Image / Specimen
= 8.4 cm / 12 um
= 84,000 um / 12 um
= 7,000 x
8.4 cm
Example calculations
 An image of a nucleus is 122 mm wide
 The image has a magnification of 1500x
 How wide is the nucleus?
Mag = Image size / Specimen size
Specimen size = Image size / maginfication
Specimen size = 122 mm / 1500
Specimen size = .081 mm = 81 um
3.4 cm
9.8 cm
Example calculations:
Microscopes
Cow embryo
400x
 Given: the microscope has a field of
view (FOV) of 500. um at 400x
 What is the size of the cell?
 FOVimage/FOVactual=magnification
9.8 cm / 500 um = 196
3.4 cm / actual size of cell = 196
Actual size of cell = 170 um
Example calculations: scale bar
 Scale bar must represent a reasonable,
appropriate, round value (1, 5, 10, 20, etc.)
 An image is magnified 4000 x.
 How long would a scale bar of 10 um be?
Magnification = Image size / Specimen size
4000 x = image size / 10 um
Scale bar image = 40000 um = 40 mm
 Determine the magnification of the image
 Determine the size of the viral head.
16 cm
Mag = Image / Specimen
= 20 cm / 100 nm
= 200000000 nm / 100 nm
= 2,000,000 x
Specimen = Image / Mag
X = 16 cm / 2,000,000 x
X = .000008 cm = 80 nm
20 cm
Interested in Microscopy?
 Check out some great SEM images
here.
 Recent microscope image award
winners here and here.
Lesson 3:
Cell Origins and Differentiation
Where do cells come from?
 Cells come only from pre-existing cells.
Frogs do not form from mud; flies are not
made by a piece of meat, etc.
 Cells divide to create new cells.
Binary fission
Mitosis
Pasteur:
Cells from pre-existing cells
• When existing bacteria cannot reach the broth, no
bacteria will ever be found.
• Once existing bacteria reach the broth, a large
population of bacteria will soon develop.
Pasteur’s Variations
Connections:
What is pasteurization?
Interested in
pasteurization of milk?
Read more here and
here!
Alternative views here.
Then where did the first cells
come from?
ABIOGENESIS: The first cells came
from non-living material.
 Conditions were different on early Earth.
The building blocks of cells would have
formed spontaneously.
 Over time, the most stable forms, especially
forms that could divide and multiply with
time, became more common.
Interested in abiogenesis?
 Learn more:
Read chapter 2 from
the classic book The
Selfish Gene (Haiku)
Watch a video here.
 Many cultures and
Miller and Urey simulated the
conditions of early Earth and
found organic molecules
religions have other
stories about the start
of life.
Multicellular organisms:
why not one big cell?
 The answer has to to with surface area and volume.
 Surface area finds the area
 Volume finds the amount of
of each face of a solid (2D)
space taken by a solid (3D)
Ex. A cube has 6 faces, with all sides
the same length.
6(s x s) = SA (units2)
Ex. A height, length, and width of a
cube are equal.
s x s x s = volume (units3)
Surface area to volume ratio
 Surface area / Volume
2: SA
 Explore surface area and volume here.
V
SA:V
 Calculate the surface area to volume
ratio of cubes with sides of 2, 4, or 8 cm.
 Volume increases faster than surface
4: SA
area
V
SA:V
= 24 cm2
= 8 cm3
= 24:8
=3
= 96 cm2
= 64 cm3
= 96:64
= 1.5
8: SA = 384 cm2
V = 512 cm3
SA:V = 384:512
=0.75
Advantage of
increased surface area
 Surface area determines the rate of
exchange (how quickly nutrients are
absorbed and wastes removed.)
 Volume determines the rate of
resource use and waste production.
 DISCUSS which cube (right) would be
better for a living thing.
 These two cubes have equal volume but different
surface areas
 They need to use the same amount of resources
 Resources must cross the surface in order to enter
 The bottom cube: much easier to absorb enough
nutrients and get rid of wastes.
How does a multicellular organism
get different types of cells?
 Most multicellular
 Genes that are “turned
organisms start as one
on” make specific
cell that then divides
proteins
 Each cell has exactly the  Proteins influence what
same DNA (genome)
a cell can do and how it
develops
 BUT each cell uses only
SOME of its genome
 Known as differentiation
Stem cells are needed for
embryonic development
• It is not enough that the starting cell can divide; it
must be able to differentiate.
• Stem cells can differentiate along different chemical
pathways; activating some genes & turning others off.
• Adult humans do not have (totipotent) stem cells, but
early embryos do. Why?
Emergent properties
 When all cells in the multicellular organism work
together, new abilities appear
 The whole is greater than the sum of the parts
 These abilities are not found in any of the
individual cells or groups of cells
 Ex. Conscious thought
 Life itself can be considered an emergent property
Just for interest:
Origins of different cell types
Just for interest:
How is DNA turned off (or on)?
 Methylation of DNA (turns off)
 Transcription factor proteins
Zinc fingers, leucine zippers, etc.
Stem cell therapy
 Some human cells will
NOT heal if damaged or
destroyed
 Many severe or deadly
illnesses could be cured
if stem cells could be
controlled
 Embryos are a
controversial source of
stem cells
 Adult cells can be
chemically
reprogrammed as stem
cells (to some extent)
Stem Cell Controversy
 Possible sources of stem cells:
Embryonic tissue (specially created, left
over from IVF or aborted)
Fetal blood from the umbilical cord
“Reprogrammed” adult cells
 Conditions that might be treated:
Stargardt’s Disease
Leukemia and lymphoma
Type 1 Diabetes
Paralysis from spinal cord injury
Parkinson’s Disease
Links to help explore stem
cell therapies
 Stargardt’s
 Leukemia
 Wikipedia
 StemEx
 Personal blog
proliferation study
 A teen’s story
 Factsheet on stem
cells for blood
cancers (Haiku)
(woman w/
Stargardt’s and a
stem-cell recipient)
 Stem-cell company
ACT website
 ACT progress report
(Haiku)
For your interest:
Stem-Cell Burgers
 Cow and other
animal muscle can
be grown in the lab.
 Possible advantages
include:
 Less energy needed
 More sanitary
 Fewer carbon
emissions
 Less land needed
Lesson 4: Types of Cells
There are many types of cells
Eukaryotic
Plant
Animal
Fungus
Protist
Prokaryotic
Bacteria
Archaea
Two major divisions of cells
 Prokaryotic
 Bacteria
 Only one membrane (the
cell plasma membrane)
 One compartment (the
inside of the cell)
 Relatively simple internal
structure
 Eukaryotic
 Everything else
 Cell plasma membrane
AND lots of membranes
inside cell
 Multiple compartments
(closed off by internal
membranes)
 Relatively complex
internal structure
Further Differences between
Prokaryotic and Eukaryotic Cells
 Prokaryotes
 Smaller or about the
size of a mitochondrion
 Single, circular DNA
without histones
 DNA in cytoplasm (no
nucleus)
 Small ribosomes (70S)
 Eukaryotes
 Larger, containing
multiple mitochondria
 Multiple strings of DNA
organized by proteins
 DNA in nucleoplasm
(protected inside nucleus)
 Large ribosomes (80S)
Functions of Prokaryotic Cell Parts
 Cytoplasm – mostly water
and free floating molecules;
it provides the environment
for all cell reactions
 Nucleoid – area that
contains the DNA, which
controls cell functions
 Cell plasma membrane –
phospholipid bilayer that
controls what enters and
leaves the cell
 70s Ribosomes – made of
protein and rRNA, they build
proteins according to mRNA
messages
Function of Prokaryotic Cell Parts
 Cell wall – stiff layer of
carbohydrate and protein
that provides shape and
support and prevents the
cell from absorbing too
much water
 Flagella – protein
“propeller” used for motion
 Pili – proteins extending
from the cytoplasm to the
outside, used for exchange
of genetic info and adhesion
E. Coli electron micrographs
CELL MEMBRANE
FLAGELLA
PILI
CYTOPLASM
Identify Prokaryotic Structures
ribosome
nucleiod
Cell membrane
Cell wall
cytoplasm
Animal
cell
Cytoplasm
80s
Functions of Eukaryotic Cell Parts
 Plasma membrane,
cytoplasm, sometimes cell
wall – function same as in
bacteria
 80s Ribosomes – link
amino acids into proteins
 Free ribosomes make
proteins for use in cytoplasm
 Ribosomes bound to ER make
proteins for excretion or use in
lysosomes
 Mitochondria – double
membrane, for aerobic
respiration / energy
release
 Nucleus – double
membrane protects the
DNA, site of ribosome
manufacture (nucelolus)
Functions of Eukaryotic Cell Parts
Rough ER
Ribosomes
“Other” membrane bound
organelles
Golgi apparatus – folded
membrane for processing
and packaging lipids and
proteins
Rough ER – folded
membrane with attached
ribosomes, makes proteins
for outside the cell
Sometimes lysosomes –
enzymes for digestion and
protection
Sometimes chloroplasts for photosynthesis
Eukaryotic Cell Micrographs
Rough ER
Mitochondrion
Free ribosome /
cytoplasm
Eukaryotic Cell Micrographs
Mitochondrion
Rough ER
Cell membrane
Nucleus
Intracellular Transport animated
Membranes are flexible; they can pinch apart or
merge together.
Proteins for export:
1. Rough ER 
2. vesicle 
3. Golgi 
4. vesicle 
5. plasma membrane
Exocrine Gland Pancreas Cells
• A special example of transport
• Exocrine cells release lots of
protein
• Protein for export is made by
ribosomes on the rough ER
• Golgi apparatus processes the
proteins forming vesicles
(condensing vacuoles)
• The Golgi packages products,
converting condensing vacuoles
into secretory vesicles
(zymogen granules) .
• These vesicles (granules) fuse
with the plasma membrane to
release protein from the cell.
• Role of DNA? Mitochondria?
Palisade Mesophyll Leaf Cell
 Palisade mesophyll
is long for best light
absorption
 Chloroplasts for
photosynthesis are
many, mitochondria
are few
 The vacuole and cell
wall provide
structure and
support
 Why are
mitochondria few?
Origins of Eukaryotes
 The first cells on Earth would
have been prokaryotes
 How did eukaryotes evolve?
Endosymbiosis
Mitochondria
Chloroplasts
Cilia / Flagella?
Nucleus? (more evidence for
progressive infolding of plasma
membrane)
Endosymbiosis:
Let’s work together - FOREVER
Usually prokaryotes were engulfed to digest for food, but in this
case kept for useful genes, prokaryote protected, both benefit!
Endosymbiotic origin of
mitochondria and chloroplasts
 EVIDENCE – what would you imagine if they
were once free-living prokaryotes?
 Double membranes (one from prokaryote, one from the
vesicle in endocytosis)
 Grow and divide on their own schedule by binary fission
 Have their own circular DNA (naked, without histones)
containing vital genes
 Make some of their own proteins on (small, bacterial
sized) 70S ribosomes
 Interesting article here about possible 3-parent babies
when mother has a mitochondrial disorder
 Paramecia and Chlorella are known to show endosymbiosis!
Origin of Nucleus
Infolding of plasma
membrane leads to
ER and nuclear
envelope.
NOT endosymbiotic
- OR -
DNA from two species
(green and black)
combines. Endosymbiotic.