1.1 introduction to cells: the evolution of multicellular organisms allowed cell specialization and...

1.1 Introduction to cells: The evolution of multicellular organisms allowed cell specialization and cell replacement.

Nature of science: Looking for trends and discrepancies—although most organisms conform to cell theory, there are exceptions. Ethical implications of research—research involving stem cells is growing in importance and raises ethical issues.

Understandings:•According to the cell theory, living organisms are composed of cells.•Organisms consisting of only one cell carry out all functions of life in that cell: nutrition, metabolism, growth, response, excretion, homeostasis and reproduction.•Viruses are not classified as living organisms.•Surface area to volume ratio is important in the limitation of cell size.•Multicellular organisms have properties that emerge from the interaction of their cellular components.•Specialized tissues can develop by cell differentiation in multicellular organisms.•Differentiation involves the expression of some genes and not others in a cell’s genome.•The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic development and also makes stem cells suitable for therapeutic uses.

Applications and skills:•Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate fungal hyphae.•Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism (Chlorella or Scenedesmus).•Use of stem cells to treat Stargardt’s disease and one other named condition.•Ethics of the therapeutic use of stem cells from specially created embryos, from the umbilical cord blood of a new-born baby and from an adult’s own tissues. Use of embryonic stem cells involves the death of early-stage embryos, but if therapeutic cloning is successfully developed the suffering of patients with a wide variety of conditions could be reduced.

PRACTICALUse of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. Scale bars are useful as a way of indicating actual sizes in drawings and micrographs.

International-mindedness: Stem cell research has depended on the work of teams of scientists in many countries who share results thereby speeding up the rate of progress. However, national governments are influenced by local, cultural and religious traditions that impact on the work of scientists and the use of stem cells in therapy. Theory of knowledge: There is a difference between the living and the non-living environment. How are we able to know the difference? Utilization: The use of stem cells in the treatment of disease is mostly at the experimental stage, with the exception of bone marrow stem cells. Scientists, however, anticipate the use of stem cell therapies as a standard method of treating a whole range of diseases in the near future, including heart disease and diabetes.

Topic 1: Cell Biology (15 hours)

To the right is a picture of the influenza virus. The bar is 100 nm. Calculate the magnification of this image.

Actual size =Measured length

Magnification

100 nm =34 mm

x X= 340,000

Solve for x

Convert to the same units before you divide!

34 mm 1000000 nm

1 mmx = 34000000 nm

100 nm =34000000 nm

x

34 mm34 mm

Biology Journal 8/20/2015

340,000“times magnified”

or, just no units


Write down the 3 properties of life that your group came up with yesterday. Then, talk to nearby students and add 3 more properties that you didn’t think of.

Science FictionZombies, Vampires, Aliens

Alive or not?

ScienceNanobacteria, HIV virus

Alive or not?


What have you heard about stem cells? What could these cells do?


What is the endosymbiotic theory? Why is it called that?What are some pieces of evidence that support the theory?


What is a stem cell?

Describe how stem cells can be used to treat a disease such as diabetes.

Stem cells can be removed from a patient, grown, and re-introduced into the patient, to have healthy, functioning cells, and correcting a disease.

A stem cell is a cell with the ability to differentiate into any kind of cell. As an adult, your stem cells can differentiate into some cells. Only embryonic stem cells can differentiate into any cell.


When would it be a good idea to adjust the diaphragm on your microscope?

Why would we use a chemical stain when making a microscope slide?


How do nanobacteria fit into IB’s functions of living things? Complete the below table.

Function How does/doesn’t nanobacteria do this?

Reproduction

Nutrition

Metabolism

Excretion

Growth

Response to stimulus

Homeostasis


How do nanobacteria fit into IB’s fuctions of living things? Complete the below table.


Reproduction Nanobacteria seem to make more of themselves. They have “transferability.”

Nutrition

Metabolism

Excretion

Growth


Homeostasis





Nutrition Nanobacteria make biofilm, however it seems possible to make similar particles without the nanobacteria.

Metabolism

Excretion

Growth


Homeostasis






Metabolism Nanobacteria don’t seem to die when exposed to sodium azide (a poison that inhibits cellular respiration)

Excretion

Growth


Homeostasis







Excretion Nanobacteria make biofilm, which could be a waste.

Growth


Homeostasis








Growth Nanobacteria make biofilm, which could be growth. Nanobacteria don’t seem to have detectable DNA.


Homeostasis









Response to stimulus Nanobacteria grow under some circumstances, but not others, such as dilution.

Homeostasis









Response to stimulus Nanobacteria grow under some circumstances, but not others, such as dilution.

Homeostasis Nanobacteria seem to stop or die from gamma radiation, and dilution.


You have probably used microscopes before. Suppose that you are given a microscope and a slide. Briefly summarize the steps you take to attempt to get a slide into focus on your microscope.

Turn on light, adjust diaphragm

Go to low power, use coarse focus first

Put slide under stage clips or in clamps (don’t snap the stage clips on the slide!)

Once you’ve got it in focus, you can move to higher power, and use fine focus

1.1 Introduction to Cells

Functions of Life

Function Brief DefinitionAll living things…

Nutrition … take in nutrients and break them down for energy

Reproduction … Make more of themselves and pass on DNA

Metabolism… … regulate chemical reactions which synthesize (make) and decompose (break down) molecules

Excretion … give off wastes

Growth … increase in size and develop over time

Response to stimulus … take actions in response to stimuli in the environment

Homeostasis … maintain a relatively constant internal environment

Stem cells and DifferentiationMulticellular organisms have specialized cells (these cells have properties that emerge from interacting with other cells).

Differentiation is the process where cells become different, or specialized.

In differentiation, some genes are expressed, and not others (every cell has the entire genome, and thus proteome).

Stem cells divide and differentiate during embryonic development, and to some extent, as an adult (so, stem cells can be used therapeutically to make replacement cells).

Above: stem cells in a developing embryo differentiate into every kind of tissue that a multicellular organism has. It does this through complex interactions that express some genes, and not others.

Youtube videosWhat are stem cells? – Craig A. Kohn A TED-Ed video, with great animations and narration explaining how stem cells work.https://www.youtube.com/watch?v=evH0I7Coc54

Making a trachea out of stem cells, shorter (1.5 min)News clip of how stem cells were grown to make a trachea and then implanted into the patient.http://www.youtube.com/watch?v=XL72Dn3rJ_E

Making a trachea out of stem cells, longer (4 min)http://www.youtube.com/watch?v=R-qRRZfz4cM

The IslandThe surgery scene from the movie The Island, featuring Michael Clarke DuncanThe Island (2/9) Movie CLIP - I Wanna Live (2005) HD https://www.youtube.com/watch?v=Ihd-NwI030c&ytsession=SAKqLz0LDfd2vY_y0UU_w6yX_WlwnhAwjuNm5qlz3YqyzMyTtpvpqCj8ig6hALdqnhh5t-6sMtCbkFE3TrUP7nYSKSnV-0UZtJXTPrLZFStEIvsEwPSGgLbTjhs4KsV8jWhIOrDX8fIpudeLDX6Olv5LsjX2sKrSBIVl5Xu_MFDh2VvTRDanqAvPcTeo6hjhEb3xu1tVYNtGMj9fRIQzwePT6kp6R3GTs0FTENQRW6iq8j8s3QliJuUXWKLk4kUxgr5GaZP19D0Dmd6R9iSd9RiNdRuYDeHg-2bopCBwZhqVYJ6xKk3Na-PfmbLZsk6REyYOEe5hTdQ

Example of stem cell therapy:

• Stargardt’s Disease is a mutation where the retina cells (the ones that detect light at the back of the eye) gradually degenerate, happening at 6 - 12 years old, leading to blindness.

• Stem cells are differentiated into retina cells, and injected into the eyes. These cells attach to the retina and function normally, improving vision!

Another Example of stem cell therapy:To treat lymphoma (a blood cell cancer)…1. Healthy blood stem cells are removed form the bone marrow and stored2. The bone marrow containing cancer is destroyed3. The healthy bone marrow cells are replaced, and production of blood cells resumes like normal.

The stem cell “debate” is around the source of stem cells. They can come from embryos or fetuses, which some object to. There are other sources, including adults, whose use is continually getting better.

The “younger” the stem cells are in this process the greater their ability to differentiate into any kind of tissue. However, science is getting better all the time using adult stem cells.

Where does Where does the term the term

“cells” come “cells” come from?from?

In 1665, Robert Hooke coined the term “cells” when he looked at cork under a microscope.

Robert Hooke and his epic weave

Robert Hooke’s drawing of the cells that he found in cork.

The Cell Theory

An early microscope

1.Cells are the smallest units of life.• Multicellular organisms

have specialized cells to carry out specific functions.

The plant cells that make up wood.

2. All living things are made out of cells• Organelles carry out various metabolic

functions of cells.• Cell components alone cannot survive.

The Cell Theory

3. Cells come only from other cells.• Cells multiply by division.

Binary fission in prokaryotes.

Mitosis and meiosis in eukaryotes.

• All cells descended from simpler, common ancestors.

The Cell Theory

Nature of science: Looking for trends and discrepancies—although most organisms conform to cell theory, there are exceptions.

Our striated muscle cells have an average length of 30 mm and can have as many as several hundred nuclei…in a single cell! (most human cells are 0.03 mm in length)

Fungi consist of narrow thread-like structures called hyphae. In some types of fungi, these hyphae are a long, uninterrupted tube with many nuclei.

Most algae are single-celled and microscopic. Not this one! Some species grow up to 100 mm and is a single cell with one nucleus!

The functions that define life are nutrition, metabolism, growth, response, excretion, homeostasis and reproduction.

Nucleus can divide to produce two when the cell is ready to divide.

Food vacuoles contain food that has been absorbed and will be digested

Cell membrane controls what substances enter and leave, such as O2 in and waste out.

Contractile vacuole that fills up with water and expels it to keep the amount of water balanced.

Metabolic reactions take place in the cytoplasm, including respiration. Enzymes are the catalysts behind these reactions.

Beating of the cilia moves Paramecium through the water so it can choose what direction to move in.

A paramecium is an example of a single-celled organism that can carry out all of these.

Viruses are not classified as living organisms (by most biologists)

Why do you think so?

Magnification


Magnification

Above: SEM (scanning electron micrograph) of skeet, skeet, skeet

You might need to convert units, so remember…

1 m = 1000 mm (1 meter = 1000 millimeters)1 mm = 1000 μm (1 millimeter = 1000 micrometers)1 μm = 1000 nm (1 micrometer = 1000 nanometers)

What is the actual length of this bacteria cell? Convert to appropriate units.

Measure it.


Magnification

It’s 80mm.Plug it in to the formula.

X =80 mm

90 000X= 0.00089 mm

Convert to appropriate units

0.00089 mm 1000 µm

1 mmx = 0.89 µm

Solve for x

Notice how magnification

has no units!

In 2015, a physicist and artist named Jonty Hurwitz blurred the line between art and science by creating the smallest sculptures ever made, and then photographing them.

Above: Thrust

Left: Cupid and Psyche

If the bar is 10 microns (µm), then what is the magnification of this image?


Magnification

10 µm =61 mm

x X= 610

Solve for x


6100“times magnified”

or, just no units

61 mm1000 µm

1 mmx = 61000 µm

10 µm =61000 µm

x

61 m

m

61 m

m

An HIV virus has a diameter of 120 nm. If a student wants to draw it as magnified by a million times, how many mm wide should the student draw it?


Magnification

120 nm =x

1 000 000 X = 120 000 000 nm

Convert to appropriate units

120 000 000 nm 1 mm

1 000 000 nmx = 120 mm

Solve for x

Magnification:No units, no problems…

A sperm cell has a tail that is 50µm long. A student draws it as 75mm. What is the magnification?

You don’t have to draw it, but you can if that helps!


Magnification

50 µm =75 mm

x X= 1500

Solve for x


1500 x magnified

75 mm1000 µm

1 mmx = 75000 µm

50 µm =75000 µm

x

A cell is 32 µm across. A student draws it as 250mm wide. What is the magnification?

You don’t have to draw it, but you can if that helps!


Magnification

32 µm =250 mm

x X= 7800

Solve for x


7800 times magnified

250 mm1000 µm

1 mmx = 250000 µm

32 µm =250000 µm

x

Surface area to volume ratio is important in the limitation of cell size.

Volume = l × w × hSurface area = l × w × 6Surface area to volume ratio = surface area ÷ volume

Formulas for a Cube

YouTube Videos

2.1.6 Explain the importance of surface area to volume ratio as a factor limiting cell size. This terrific video shows the agar/indicator/diffusion of HCl lab and narrates it well. 3 minutes.

https://www.youtube.com/watch?v=xuG4ZZ1GbzI#t=13

In one experiment, agar cubes of different sizes are put into a solution of dye for the same amount of time.•If the cubes were cells, which of the cubes “live” and “die”? Why?

1.1 introduction to cells: the evolution of multicellular organisms allowed cell specialization and...

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