Cells 1.1-1.2

Objective 1.1 Introduction to cells Understanding (Statement objectives) 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. 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. It also makes stem cells suitable for therapeutic uses. Applications Question the cell theory using atypical examples, including striated muscle, giant algae, and aseptate fungal hyphae. Describe the functions of life in Paramecium and one named photosynthetic unicellular organism. Name and briefly explain these functions of life: nutrition, metabolism, growth, response, excretion, homeostasis and reproduction. Chlorella or Scenedesmus are suitable photosynthetic unicells, but Euglena should be avoided as it can feed heterotrophically. Explain the use of stem cells to treat Stargardt’s disease and one other named condition. Describe the 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. Nature of science Describe different trends and discrepancies: although most organisms conform to cell theory, there are exceptions. State ethical implications of research: research involving stem cells is growing in importance and raises ethical issues. Describe stem cells and outline therapeutic uses of stem cells. Skills Describe the use of a light microscope to investigate the structure of cells and tissues. Draw cell structures as seen with the light microscope. Calculate the magnification of drawings and the actual size of structures shown in drawings or micrographs. Calculate images using scale bars.

The Cell Theory States…

C E L S All living things are made of Longitudinal section of a root tip of Maize (Zea mays) by Science and Plants for Schools on Flickr (CC) http://flic.kr/p/bNNM6M

C E L S All living things are made of Unicellular organisms are single-celled and can carry out all of the functions of life independently. Multicellular organisms have specialized cells to carry out specific functions. Longitudinal section of a root tip of Maize (Zea mays) by Science and Plants for Schools on Flickr (CC) http://flic.kr/p/bNNM6M

C E L S are the smallest units of life. Paramecium multimicronucleatum by Proyecto Agua on Flickr (CC) http://flic.kr/p/7W7J3y

C E L S are the smallest units of life. Specialized structures within cells (organelles) carry out different functions. Organelles cannot survive alone. Paramecium multimicronucleatum by Proyecto Agua on Flickr (CC) http://flic.kr/p/7W7J3y

C E L S come only from existing cells. 4-cell stage of a sea biscuit by Bruno Vellutini on Flickr (CC) http://flic.kr/p/daWnnS

C E L S come only from existing cells. Cells multiply through division. All life evolved from simpler ancestors. Mitosis results in genetically identical diploid daughter cells. Meiosis generates haploid gametes (sex cells). Pasteur disproved the theory of spontaneous generation with his experiments. come only from existing cells. 4-cell stage of a sea biscuit by Bruno Vellutini on Flickr (CC) http://flic.kr/p/daWnnS

1665 All living things are made of cells. Hooke names “cells” in his book “Micrographia” after observing cork under a lense. All living things are made of cells. Hooke’s Micrographia in full! http://lhldigital.lindahall.org/cdm/ref/collection/nat_hist/id/0

All living things are made of cells. 1676 van Leeuwenhoek, a master microscope maker identifies “animalcules” and becomes the father of microbiology. All living things are made of cells. http://en.wikipedia.org/wiki/Antonie_van_Leeuwenhoek

1833 Robert Brown names the cell nucleus. Cells are the smallest units of life. He also discovered Brownian motion: Robert Brown: http://en.wikipedia.org/wiki/Robert_Brown_(botanist) http://en.wikipedia.org/wiki/Brownian_motion

1855 Robert Remak discovers cell division and confirms the existence of the plasma membrane. Cells come only from pre-existing cells. Robert Remak: http://en.wikipedia.org/wiki/Robert_Remak

1864 Pasteur disproves the prevailing theory of “spontaneous generation” with his swan-neck flask experiments. Populations need to be seeded by existing populations: cells come only from pre-existing cells. Image from Amoeba Mike’s Blog (go read the original post): http://amoebamike.wordpress.com/2009/10/06/spontaneous-generation-a-brief-history-of-disproving-it

Unicellular Organisms carry out all the functions of life Nutrition Growth Response Excretion Metabolism Homeostasis Reproduction Paramecium bursaria by Proyecto Agua on Flickr (CC) http://flic.kr/p/7WXdFz

Given the right conditions, cells can survive outside their normal habitat. Art from Petri dishes_1 by Image in Science and Art on Flickr (CC) http://flic.kr/p/838xjC

VIRUSES Are they living or non-living? Hmm….. Image: Swine Flu H1N1 virus influenza 9.0 by hitthatswitch on Flickr (CC) http://flic.kr/p/74e4SP

Which dissolves faster: sugar cubes or sugar crystals? Why? Sugar Cubes by Uwe Hermann on Flickr (CC) http://flic.kr/p/cFMMc