TOPIC 2.1

Cell Theory (2.1.2, 2.1.1)  Cell theory developed over time as scientists made discoveries, disproved old theories, and developed what we currently know as the cell theory.  1. ALL living organisms are composed of cells.  2. Cells are the smallest units of life.  3. Cells come from pre-existing cells.  4. Cells are the structural and functional units of life.

Evidence for the Cell Theory  Prezi timeline: theory/ theory/

Cell Theory  What people used to believe:  Cells form by free-cell formation, similar to the formation of crystals (spontaneous generation).

Cell Theory  Question: How do living things come into being?  Observations:  Living things just suddenly “appear” – Maggots show up on meat, Mice were found on grain, Beetles showed up in cow dung  Conclusion: Life could arise from nonliving matter – “Spontaneous Generation”

Cell Theory  1668 – Redi’s experiment:

Cell Theory  This idea flew in the face of current doctrine. It implied that there was no spontaneous creation of cells from non-living matter.  Louis Pasteur in 1862 provided evidence of this idea with the following classic experiment.

Pasteur's experiment Nutrient broths were heated and sterilized in a flask with a straight neck and a curved neck. As his control, Pasteur used flasks with straight necks that permitted bacteria to settle into the broth. In these flasks, the broth was soon teaming with bacteria. The curved neck prevented bacteria from entering the flasks.

Unicellular organisms (2.1.3)  Unicellular organisms carry out all the functions of life:  Metabolism – all the chemical reactions in a living being  Response to stimuli  Homeostasis – a steady state of body functioning  Growth  Reproduction  Nutrition

Relative Sizes (2.1.4) molecules1 nm (nanometer = m) cell membrane thickness10 nm viruses100 nm bacteria 1 μ m (micrometer = m) organelles 10 μ m cells 100 μ m 1 milimeter (1 mm) = 1000 micrometers (1000 μ m) 1 micrometer (1 μ m) = 1000 nanometers (1000 nm) Check it out:

Calculating Magnification  Size in the picture = Actual size (real life) X magnification  300 cm = 3cm x 100x  This equation can be re-arranged to solve for any of the components. X =

Calculating Magnification Practice  Practice worksheets

Surface Area to Volume Ratio (2.1.6)  Surface Area = the cell membrane  Volume = everything inside the cell

Surface Area to Volume Ratio  Related to the VOLUME of a cell:  Heat production  Waste production  Resource consumption  Related to the SURFACE AREA of a cell:  Rate of exchange of materials  Rate of exchange of energy (heat)

Surface Area to Volume Ratio

Diffusion through a Cookie  The rate of milk diffusing through chocolate chip cookies is 1mm per 5 seconds.  Using math, determine how long it would take for milk to diffuse to the center of each of your cookies.

Multicellular Organisms (2.1.8)  Differentiation occurs when cells in multicellular organisms differentiate to do specialized functions.  This happens when cells express (turn on) some of their genes but not other genes.  ALL cells in an organism have the EXACT SAME genes, but they actually only use on a small portion of the genes to do their specific job.

Differentiation

Multicellular Organisms (2.1.7)  “The whole is greater than the sum of its parts.”  “Emergent properties” are those that come from the interaction of component parts.  This can happen because cells differentiate.

 Tissue: a group of similar cells that perform a particular function

Specialized Cells  Different types of cells perform different functions.  The structure of the cell is related to its function!

Stem Cells (2.1.9, )  Stem cells retain the ability to divide and can still differentiate along different pathways.  Essentially – they can become any type of cell.  The use of some types of Stem Cells are a source of huge moral and ethical debate.

Stem Cell Video  Watch these video and take notes so that you can answer the following question – it will be an open- note quiz after the video is finished:  Thoroughly discuss the pros and cons of stem cell research.  breakthrough.html (13 minutes) breakthrough.html  story/English (15 minutes) story/English