Topic 1 - Cells Cell Theory Functions necessary for life Microscopy Surface area to volume Multicellular vs Unicellular

The Cell Theory 1. All living things are made of cells ….or at least one cell. Cells carry out the functions of life, and have certain common features: Surrounded by a membrane Contain genetic material, which gives instructions to perform actions Most actions are reactions – enzymes Cells have their own energy system Look at these handsome gentlemen.

2. The smallest living thing is a cell! Unicellular organisms are made up of a single cell, and they carry out all of the functions of life by themselves. These functions are: Nutrition Growth Metabolism Reproduction Response Excretion Homeostasis Multicellular organisms have properties that emerge by the interaction of their different cellular components. These are called emergent properties. Ex. A bunch of Liver Cells together make a Liver. Individually, they could not perform all of the functions that they can together 3. All Cells must come from other living cells This is done through mitosis in eukaryotes and binary Fission in prokaryotes…..more on that later

And yet….it is all relative. Check out this awesome image from Learn.genetics.edu.

Some units that I use & know Unitabbr.Metric equivalent kilometerkm1,000m1 x 10 3 m meterm1m centimetercm0.01m1 x m millimetermm0.001m1 x m micrometerμm m1 x m nanometernm m1 x m ÷1,000 X 1,000 μm = micrometers We usually use this in discussion of cells. There are 1,000μm in one mm. write this correctly

Focusing a microscope Put the slide on the stage ALWAYS focus at low power first At low power, use the COARSE adjustment knob, then once you have found the image use the fine adjustment knob Increasing Magnification Align the image in the middle of the Field of View Switch to the next highest magnification Use the FINE adjustment knob to bring the image in to focus

Eyepiece – Always 10x for us Objective – 4x, 10x, 40x, 100x Total Magnification for a Microscope is: Eyepiece x Objective Lens

Eyepiece – Always 10x for us Objective – 4x, 10x, 40x, 100x Total Magnification for a Microscope is: Eyepiece x Objective Lens Our mikes have these objectives Low Medium High Highest

What you will see when looking through a microscope If the magnification for each of these images is the total magnification, can you identify what objective lens you are looking through for each? What would the field of view (FOV) be for each?

Stem Cells retain the capacity to divide and can differentiate along divergent pathways. Totipotent Can differentiate into any type of cell. Pluripotent Can differentiate into many types of cell. Multipotent Can differentiate into a few closely-related types of cell. Unipotent Can regenerate but can only differentiate into their associated cell type (e.g. liver stem cells can only make liver cells). Image from:

By Fwfu at en.wikibooks [Public domain], from Wikimedia Commons Stem Cells retain the capacity to divide and can differentiate along divergent pathways.

Screenshot from this excellent tutorial:

Screenshot from this excellent tutorial: Differentiation (specialization) of cells: All diploid (body) cells have the same chromosomes. So they carry all the same genes and alleles. BUT Not all genes are expressed (activated) in all cells. The cell receives a signal. This signal activates or deactivates genes. Genes are expressed accordingly and the cell is committed. Eventually the cell has become specialized to a function. Key Concept: Structure vs Function How do the structures of specialized cells reflect their functions? How does differentiation lead to this?

Stargardt’s Macular Dystrophy Causes total vision loss as a result of a mutation of a gene in retinal cells Develops in children between 6-12 Started with mice -> progressed to human trials Embryonic Stem Cells lead to the recovery of a woman’s sight at the age of 50. Step 1 – Harvest ESC Step 2 – Induce ESC to diff. in to retinal cells Step 3 – Introduce in to patient, allow to grow to full maturity

Therapeutic Uses of Stem Cells Animated tutorials from: Treatment for Leukemia Problem Cancer of the blood or bone marrow, resulting in abnormally high levels of poorly- functioning white blood cells. Treatment 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. Role of Stem Cells 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. From : Animation of this process:

30 Minute Inquiry - Stem Cell Ethics Your group must research one of the types of stem cells in hopes of understanding the following aspects of it: Ethics/ Morals, Economics, Social, Environmental. You should divide into groups of 3-4, and construct a whiteboard to deal with each of the four facets. It should follow the example below: EthicsEconomics SocialEnvironmental

Limitations on Cell Size In the cytoplasm of the cell, many chemical reactions take place: METABOLISM The rate of these reactions is proportional to the volume of the cell The cell acquires materials for these reactions through the cell membrane. (and excretes as well) Notice the relationship between SA and Volume. How does this change as the cell gets larger?

Which of these two sizes of cells would be more efficient?