Which makes green tea faster: tea leaves or powder?

What will go cold faster: French fries or a baked potato? Why?

IN: Oxygen Nutrients Water The plasma membrane of a cell is the surface of exchange for materials between the inside and the outside of the cell. OUT: Carbon dioxide Waste Products (e.g. proteins) http://commons.wikimedia.org/wiki/Sphere

Therefore, a larger volume requires more exchange across the membrane. As the cell gets larger, it requires more resources to be imported and produces more products (and waste) to be exported. Therefore, a larger volume requires more exchange across the membrane. http://commons.wikimedia.org/wiki/Sphere

As the cell gets larger… http://commons.wikimedia.org/wiki/Sphere

Diffusion Pathways are shorter (and more efficient) in smaller cells with a larger surface are to volume ratio. http://commons.wikimedia.org/wiki/Sphere

As the cell gets larger… …the surface area to volume ratio actually gets smaller… …so the exchange processes become less efficient with increasing size. http://commons.wikimedia.org/wiki/Sphere

As the cell gets larger… …the surface area to volume ratio actually gets smaller… http://commons.wikimedia.org/wiki/Sphere

Answer Elephants do many different things with their big ears. One thing is that they can cool themselves down when they are hot. The blood flowing through the ears is close to the outside of the elephant body, and heat can be released as they flap them about.

Two Minute Essay Explain the importance of surface area to volume ratio as a factor limiting cell size

Big Cell Exceptions Epulopiscium is a giant species of bacteria. Read more about it here . E. coli 100μm Epulpoiscium, by AJ Cann on Flickr (CC) http://flic.kr/p/4Nzq9t

Big Cell Exceptions Caulerpa species of algae are one giant cell with many nuclei distributed throughout. http://en.wikipedia.org/wiki/Caulerpa

Structure/Function Natural selection favours adaptations that give an advantage. Folded structures are everywhere in nature, maximising the surface area to volume ratio for exchange of materials. Mammalian liver mitochondria: http://commons.wikimedia.org/wiki/File:Mitochondria,_mammalian_lung_-_TEM_(2).jpg

C E L S Surface are to volume ratio is a factor that limits the size of cells. By dividing to make more, smaller cells, the efficiency of the exchange processes across the membranes (into and out of the cells) can be kept high. Shorter diffusion paths. More surfaces for reactions. Removal of heat and waste D I V E 4-cell stage of a sea biscuit by Bruno Vellutini on Flickr (CC) http://flic.kr/p/daWnnS

Magnification The image we see through the light microscope has been magnified. Objective lens x eyepiece lens Image from wikimedia commons: http://commons.wikimedia.org/wiki/File:Microscope-blank.svg

Modern Microscopy Image: d2540-6 by USDA on Flickr (CC): http://flic.kr/p/dPqvvY

Modern Microscopy As we develop more and more sophisticated and precise imaging tools, we can see more detail of the cells and molecules that make us. Scanning electron microscopes deliver high-resolution, 3D surface images of structures, whereas transmission electron microscopes give us a view inside cells and organelles. Image: d2540-6 by USDA on Flickr (CC): http://flic.kr/p/dPqvvY

Emiliana huxleyi photosynthetic plankton Image from: http://earthguide.ucsd.edu/earthguide/imagelibrary/emilianiahuxleyi.html

Transmission electron micrograph of HIV particles. HIV-1. Transmission electron micrograph, via wikimedia commons: http://commons.wikimedia.org/wiki/File%3AHIV-1_Transmission_electron_micrograph_AIDS02bbb_lores.jpg

Scanning electron micrograph of HIV particles budding on a human lymphocyte. False-coloured scanning electron micrograph of HIV (green) budding on a lymphicoyte (blue) http://en.wikipedia.org/wiki/File:HIV-budding-Color.jpg OR http://phil.cdc.gov/phil/details.asp?pid=10000

Light Microscope Elodea - Aquatic Plant 40X 400X

Transmission Electron Microscope (TEM) Herpes Virus Plant Root Cell

Scanning Electron Microscope (SEM) Mosquito Head 200X 2000X

Scanning Electron Microscope (SEM) Fly Eye

Scanning Electron Microscope (SEM) Inside of Stomach Surface of Tongue Neuron

Scanning Electron Microscope (SEM) Pollen Yeast Red Blood Cell, Platelet, and White Blood Cell

TEM vs. SEM Viruses leaving a cell

50μm Human egg cell, from Gray’s Anatomy (1858). http://commons.wikimedia.org/wiki/Gray%27s_Anatomy_plates

5μm Human sperm cell, from Gray’s Anatomy (1858). http://commons.wikimedia.org/wiki/Gray%27s_Anatomy_plates

Scanning electron micrograph of human sperm and egg cells. smallest human cell largest human cell 5μm Image from wikimedia commons http://en.wikipedia.org/wiki/Spermatozoon

Calculate the linear magnification of drawings and the actual size of specimens in images of known magnification. What is the actual size of this specimen in micrometers (um)? Actual size = measured length/magnification 60mm/5 = 12mm 12mm x 1000 um =12,000 um Magnification x 5 Measured Length = 60 mm

μm = micrometers Some units that I use & know X 1,000 ÷1,000 ÷1,000 abbr. Metric equivalent kilometer km 1,000m 1 x 103m meter m 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 X 1,000 ÷1,000 ÷1,000 ÷1,000 μm = micrometers We usually use this in discussion of cells. There are 1,000μm in one mm. write this correctly

Practice

Practice

Practice 254X 8500X 320X 320,000X .38x 380x 5.4x10-5

Practice 11μm 40 μm 175μm 200μm

LAB TIME Measuring microscopic objects

Review notes from previous lesson Questions???

Exam question #1... 1) A picture in your textbook indicates that it is magnified 5x, and when measured with a ruler is .25 cm in length. What is its actual length in micrometers (um)? a) 5 um b) 50 um c) 500 um d) 5000 um c

Exam question #2... A red blood cell is 8 μm in diameter. If drawn 100 times larger than its actual size, what diameter will the drawing be in mm? A. 0.08 mm B. 0.8 mm C. 8 mm D. 80 mm B

Two Minute Essay Explain the importance of surface area to volume ratio as a factor limiting cell size. Free images from: Presentations ETC, University of Florida. http://etc.usf.edu/presentations/

Markscheme small cells have larger ratio (than larger cells) / ratio decreases as size increases; surface area / membrane must be large enough to absorb nutrients / oxygen / substances needed; surface area / membrane must be large enough to excrete / pass out waste products; need for materials is determined by (cell) volume; cell size is limited (by SA / vol ratio) / cells divide when they reach a certain size; reference to diffusion across / through membrane / surface area;

Emergent Properties the whole is more than the sum of its parts