1.1 Introduction to CellsDP Biology

R. Price

v. 1 2015

#1: According to cell theory, living organisms are composed of cells.

Essential Cell Theory

1. Cell membrane separates cell from everything else outside.

2. Genetic material as information for cell’s activities.

3. Many activities are chemical reactions, catalyzed by enzymes

4. Own energy release system

5. Smallest living structures

Light microscopes

Skill: Calculation of magnification & actual size

Application: Questioning the cell theory using atypical examples, including striated muscle, giant algae, and aseptate fungal hyphae

Striated muscle: muscle fibers are large (30 mm and can have hundreds of nuclei)

Fungi hyphae may have long structures with many nuclei

Giant algae (Acetabularia) can be 100 mm across with only 1 nucleus

#2: Organisms consisting of only one cell carry out all functions of life in that cell

Functions of life

• Nutrition

• Metabolism

• Growth

• Response

• Excretion

• Homeostasis

• ReproductionParamecium

Chlamydomonas

#3: Surface area to volume ratio is important in the limitation of cell size

Surface Area to Volume Ratio

Metabolism

• Substances needed by the cell must cross the cell membrane

• Waste products must cross the cell membrane (accumulate issue)

Heat

• Heat produced lost over cell surface (overheating issue)

#4: Multicellular organisms have properties that emerge from the interaction on their cellular components

Whole is greater than its parts

Caenorhabditis elegans

• 1 mm long & 959 cells

• Cooperative groups of cells

• Mouth, pharynx, intestine, anus

• Hermaphrodite

• Third of cells are neurons

• Cells organize themselves

interactBy Bob Goldstein http://labs.bio.unc.edu/Goldstein/movies.html (Own work) [GFDLhttp://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via

Wikimedia Commons

What looks like a large inflatable tube is actually

a pyrosome. And while it appears to be one behemoth

creature, it is actually many hundreds or thousands of

animals called zooids embedded in a gelatinous tube.

“One long pyrosome is actually a collection of thousands

of clones, with each individual capable of copying itself

and adding to the colony,” writes marine biologist Rebecca

Helm inDeep Sea News.

The creature's name means “fiery body” due to its

bioluminescence, a bright green-blue glow that can light

up the colony when disturbed….

These “cylinders in the water” can grow to formidable

sizes, sometimes exceeding 12 meters (40 ft) in length.

Each zooid feeds by sucking in water, filtering small

particles and blowing the waste back out. This is also the

method that propels the colony into motion, albeit at a

very slow pace. When the zooids pause this process, the

colony can sink 500-700 (1,640-2,295 ft) meters below the

surface of the sea, according to New Scientist.

#5:Specialized tissues can develop by cell differentiation in multicellular organisms

Cell division of labor

• Ideal structure

• Necessary enzymes

• Cell development to carry out specific function is called differentiation.

Muscle cells

NeuronRed blood cells

#6: Differentiation involves the expression of some genes and not others in a cell’s genome

Same Genetics

• Each cell in a multicellular organism have the same set of genes

Gene Expression

• Gene is turned on, and information used.

• Protein or other product made

Cell differentiation happens because a different sequence of genes is expressed in different types of cells

The control of gene expression is the key to development.

#7: The capacity of stem cells to divide and differentiate is necessary in embryonic development.

Animal life Reproduction

1. Sperm fertilizes egg -> zygote

2. Zygote divides -> embryo

3. Embryo cells divide many times

4. “Stem cell” = name for zygote & early embryo cells

Stem cells can divide many times to make large amounts of tissue. Stem cells will differentiate into any cell type.

By Mike Jones [CC BY-SA 2.5 (http://creativecommons.org/licenses/by-sa/2.5)], via Wikimedia Commons

Properties of stem cells suitable for therapeutic uses

Stem cell properties

• Can divide many times to make copious amounts of tissue.

• Useful to grow tissues or replace lost, damaged, or malfunctioning cells.

• Not fully differentiated. Can differentiate in many ways to make different cell types.

By OpenStax College [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

By Mikael Häggström (All used images are in public domain.) [Public domain], via Wikimedia Commons

Stem cells and Stargardt’s disease

Stargardt’s Disease

• Stargardt’s macular dystrophy

• Develops in children between 6 & 12 years

• Recessive mutation of gene ABCA4

• Membrane protein in retina cells to malfunction

• Photoreceptive cells fail

• Can cause blindnessBy Mchollrigl (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

Stem cells and Stargardt’s disease

Stargardt’s Disease Treatment• November 2010, United

States• Adult woman, age 50,

Stargardt’s• 50,000 retina cells from

embryonic stems cells injected into her eyes

• Cells attached to the retina• Cells stay attached for 4

month trial• Improvement in vision, no

side effects

Source: Irina Klimanskaya / Advanced Cell Technology

Credit: Nelson Hsu, Melanie Taube, Julia Ro / NPR

Stem cells and Leukemia

Leukemia

• Type of cancer (non tumor)

• Mutation in genes for cell division

• Leukemia -> production of abnormally high numbers of white blood cells

• To cure leukemia, must destroy the bone marrow cells over producing white blood cells (chemotherapy)

By Mikael Häggström (All used images are in public domain.) [Public domain], via Wikimedia Commons

Stem cells and Leukemia treatment

1. Fluid is removed from patient’s bone marrow.

2. Adult stem cells are extracted from fluid and frozen.

3. Patient is treated with chemotherapy. Cancer cells in the bone marrow is destroyed.

4. Adult stem cells returned to patient. Stem cells multiply and produce red & white blood cells.

This may cure leukemia completely

Stem cell transplant. (Step 1): blood from a

vein in one arm of the donor, who could be the

patient or other person is removed. The blood

passes through a machine that separates the

stem cells. The blood then returns to the donor

through a vein in the other arm. (Step 2): the

patient receives chemotherapy to kill cells that

form the blood and can also receive

radiotherapy (not shown). (Step 3): the patient

receives stem cells through a catheter placed

in a blood vessel in the chest.

http://www.cancer.gov/espanol/pdq/tratamiento/leucemia-mieloide-adultos/Patient/page3

Sources of stem cells and the ethics of using them

Sources

ContentAllott, Andrew, and David Mindorff. Biology: Course Companion. 2014

ed. Oxford: Oxford UP, 2014. Print. Oxford IB Diploma Programme.

Walpole, Brenda. Biology for the IB Diploma. 2nd ed. Cambridge: Cambridge UP, 2014. Print.

Images

Unless otherwise noted, images are obtained from Pixabay(www.pixabay.com) and used under the CC0 Public Domain license.