Download IB BIO I Cells – Cell Theory Van Roekel Cell Theory Outline the Cell

IB BIO I
Cells – Cell Theory
Van Roekel
Cell Theory
Outline the Cell Theory
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The cell Theory consists of three components.
All living things are made of one of more cells.
o To date, no living entity has been found that has not been made of
o Two Types of organisms
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Organisms – made up of
cells and have
cells to carry out specific functions of life
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Organisms – single-celled organisms and can carry out all functions of
life independently
o Evidence/Scientists:
 Robert Hooke- first observed
using homemade microscope.
Coined the term “cells”
 Antonie van Leeuwenhoek- first to observe
described
them as ‘animalcules’
Cells are the smallest unit of life
o All cells carry out/perform the
using different organelles.
o Organelles parts of the cell that cannot survive on their own and perform
specific functions of the cell(i.e. mitochondria)
o Functions of life:
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– all organisms grow/mature in one way or another
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– passing genetic material to offspring
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– based on internal or external stimulation and is essential to
survival
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– maintaining a constant internal environment
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– providing a source energy to organisms
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– all chemical reactions in an organism
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– all organisms get rid of waste
All cells come from pre-existing cells
o All cells descend from
o Cells multiply by
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performed by multicellular organisms to produce daughter cells
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performed by bacteria cells (unicellular organisms) to produce
daughter cells
o Evidence
 Louis Pasteur- Disproved theory of
.
 Robert Remak- discovered/observed
while studying chick
Exceptions to Cell Theory
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Fungal Hyphae- extremely large and
cytoplasm (not divided into individual cells)
Muscle Cells – very long and multinucleated (many nuclei in one cell)
(many nuclei in one cell). Have a
IB BIO I


Cells – Cell Theory
Van Roekel
Unicellular Organisms (Amoeba) cells (not normal cells) – larger than most single celled
organisms but still carries out functions of life
Viruses - Can only
using a host cell, do not perform all
Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles, and cells, using the
appropriate SI unit.
Plant cell
Animal cell
nucleus
Mitochondria
bacteria
virus
ribosome
Membrane
thickness
molecules
Units of microscopic organisms usually in micrometers or nanometers. Be able to convert from different measurements.
Unit
abbr.
Metric equivalent
Kilometer
km
1,000m
1 x 103m
meter
m
1m
1m
centimeter
cm
0.01m
1 x 10-2m
millimeter
mm
0.001m
1 x 10-3m
micrometer
μm
0.000 001m
1 x 10-6m
nanometer
nm
0.000 000 001m
1 x 10-9m
Calculate the linear magnification of drawings and the actual size of specimens in images of known magnifications.
Magnification=
Actual Size=
Sample Problems
A sperm cell has a tail 50 micrometers long (scale bar label). A student draws it as 75mm long (measured length). What
is the magnification of his drawing?
A student views an image of a cell magnified 350 times (magnification). The image is 250 mm long (measured length).
What is the actual length of the cell?
IB BIO I
Cells – Cell Theory
Van Roekel
Cell Size
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Cell size is a critical component of how cells function.
Key Points about cell size:
o Most chemical reactions occur
and its size affects the
of these
reactions.
o The membrane controls what goes
of the cell.
o THEREFORE, there has to be a correlation between cell size (surface area of plasma membrane) and
volume.
o Surface area to volume ratio is a factor that limits the size of cells
 Larger cells have
surface area to volume ratio and are
efficient
exchange processes
 Smaller cells have
surface area to volume ratio and
efficient exchange processes
 When cells become too large, they will
into two smaller cells with
surface area to volume ratios
o Benefits of having a large Surface Area : Volume Ratio
 A
SA:Vol ratio means the cell can act more
.
 Diffusion Pathways are
(and more efficient) in smaller cells.
 More efficient removal of
and
 More surfaces for
, which typically occur on cell
membranes and organelle membranes
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are easier to generate
o Maximizing Surface Area : Volume Ratio
 Cells
to make more, smaller cells, that are more efficient
 Cells
– have organelles w/ specific functions
 Larger cells typically have
or
of cell
membrane to increase surface area relative to their volume.
Cell Differentiation
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Cells have the ability to
by themselves to allow for
, or to replace
or
cells
All multicellular organisms start out as a
(embryo) that reproduces at a
rapid rate during development
During this time, cells will differentiate, or become
that carry out
(nerve cell, muscle fibers, liver, heart, skin, etc…)
Process of Differentiation
o All cells contain the same genetic material (
)
o Type of cell results from the
of certain
, and not others in DNA
o Genes are expressed/not expressed based on the
of cell,
or
present, or cell-to-cell
(other cells present)
IB BIO I
Cells – Cell Theory
Van Roekel
Stem Cells
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Stems cells – cells that retain the ability to
and
into various
cells (liver, heart, skin, etc.)
Types of Stem Cells
o Embryonic Stem Cells – found in the inner cell mass of the blastocyst (formed soon after fertilization)
with the ability to form
of
in an organism
o Adult Stem Cells – can be found in babies, children, and adults, and are undifferentiated cells found in
various tissues throughout the body (umbilical cord, bone marrow, mammary cells, intestinal cells)
o Meristematic cells – plant cells that are found at the roots and stem tips that are capable of becoming
various types of tissue within the roots and stems
Categories of Stem Cells
o Totipotent - Can differentiate into
type of cell. (Embryonic)
o Pluripotent - Can differentiate into
types of cell. (Embryonic)
o Multipotent (tissue-specific) - Can differentiate into a
types of cell. (adult)
o Unipotent - Can regenerate but can only differentiate into
cell type (e.g. liver stem cells
can only make liver cells).
Therapeutic Uses of Stem Cells
o Stargardt’s Disease
 Inherited disease that causes a defect in the processing of vitamin A, which is necessary for
light-sensitive cells in retina (back of eye) to function
 Cells (photoreceptors) in the retina will deteriorate
 Results in vision loss within first 20 years
 Treatment for Stargardt’s disease - March 2010, stem cells were designed to protect and
regenerate parts of the eye (photoreceptors) that are damaged by the disease.
o Leukemia
 Cancer of the blood or bone marrow, resulting in abnormally high levels of poorly-functioning
white blood cells.
 Chemotherapy and radiotherapy can be used to destroy the white blood cells, but these need to
be replaced with healthy cells. Bone marrow transplants are often used for this.
 Hematopoetic Stem Cells (HSCs) can be harvested from bone marrow, peripheral blood or
umbilical cord blood. As these can differentiate to form any type of white blood cell, they can be
used to repopulate the bone marrow and produce new, healthy blood cells. The use of a
patient’s own HSCs means there is far less risk of immune rejection than with a traditional bone
marrow transplant.
Therapeutic Cloning of Embryonic Stem Cells
o Therapeutic use of embryonic stem cells (ESCs) requires therapeutic cloning
o ESCs cells are obtained from embryos formed through in-vitro fertilization (IVF), which is the fertilization
of an egg outside the body
o The genetic material of these IVF embryos are then copied and replicated to create a large culture of
stem cells
IB BIO I

Cells – Cell Theory
Van Roekel
Issues with embryonic stem cell research
o Harvesting these cells results in the death of the embryo that some would argue is the same as taking a
life
o Opposite side says that embryos being cultured are clones and were never determined to become a
living thing
o ESCs ideally could be used to treat Alzheimer’s or Parkinson’s disease by replacing damaged brain cells.
Emergent Properties
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A result of cell reproduction and differentiation is that multicellular organisms have
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Simply put, the
is more than the sum of its parts
Properties of organism depend on the interactions between all
biological unit
Examples: (Pick two)
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of the