1 Cells 8What is a cell? A cell is a membrane bound unit containing hereditary material and other compounds that make metabolism, growth and reproduction possible. Plasma membrane Hereditary material Cytoplasm

2 Cells 8Overview of cell structure 8Cells are surrounded by a plasma membrane. 8DNA the hereditary material is packaged in one or more chromosomes located in a nuclear region or nucleus. 8The cytoplasm contains molecules and organelles needed for cellular activities. 8Ribosomes are the factories in which proteins are manufactured.

3 Cells 8How were cells discovered? Robert Hooke Examined cork in simple microscope. Saw empty compartments and called them ‘cellulae’ (small rooms) Anton Van Leeuwenhoek Made his own microscope that could magnify 200 X. Observed living things. Called them ‘Animacules’ (little animals).

4 Cells 8Formation of the cell theory Matthias Schleiden Concludes that all plants are made of cells or their derivatives. He called this theory phytogenesis Theodore Schwann All animal tissue is made of cells and within an organism these cells are identical. 8The theory they presented from these observations is often called the Schleiden and Schwann Cell Theory

5 Cells Rudolph Virchow Studied pathenogens and concluded ‘omnis cellula e cellua’ which means that all cells arise from pre-existing cells. 8Principles of the Cell Theory 8All organisms are composed of one or more cells. 8Cells are the basic unit of life. 8Cells arise only by division of a previously existing cell.

6 Cells 8Cell size 8Does small cell sizes have advantages? 8The surface area increases as the square (10 )of the diameter of a sphere, but the volume increases as the cube (10 ). small cube - surface area small cube - volume  m 10  m) = 600  m6 x (10  m x 10  m x 10  m x 10  m = 1000  m 3 2

7 Cells 8big cell - surface area 8big cell - volume 30  m x 30  m x 30  m =  m 3 6 x (30  m x 30  m) = 5400  m 2

8 Cells 8Comparing different sizes 8Surface area 1 small = 600  m 27 small =  m 1 big = 5400  m 8Volume is the same for 1 big and 27 small 8The ratio of surface to volume 827 small 16200/27000 = 0,6 81 big 5400/27000 = 0,2 8surface area of small is 3X greater 2 2 2

9 Cell size 8Why aren´t cells larger? 8limitations of molecular diffusion 8faster passage through small cells 8more efficient communication 8limitations of surface/volume ratio 8with in size greater in volume 8interaction occurs only at surface 8insufficient exchange of materials at plasma membrane

10 Structure of prokaryotes 8Strong cell wall made of carbohydrate matrix and peptide units. 8Slime capsule (some times with pili), not always present.

11 Structure of prokaryotes 8Simple interior organization 8lack internal compartmentalization 8reactions not separated, one metabolic unit 8lack membrane-bound organelles 8infolding of plasma membrane 8Rotating flagella 8cell movement - screw like motion

12 Structure of prokaryotes 8Ribosomes in the cytoplasm 8protein synthesis 8Circular nuclear matter (DNA) 8located in the nucleoid region 8Plasmids 8small independent circular DNA 8Mesosome 8infolding of plasma membrane often associated with photosynthesis

13 Structure of eukaryotes 8More complex than prokaryotes 8They are compartmentalized 8possess internal membrane bound organelles 8ribosomes 8rough endoplasmic reticulum (rER) 8lysosomes 8Golgi apparatus (complex) 8mitochondria 8nucleus 8chloroplasts

14 Structure of eukaryotes 8Nucleus the largest organelle 8the nuclear envelope 8double layer of membranes, 8outer continuous with ER 8nuclear pores 8restrict passage of molecules to proteins and RNA 8chromosomes - chromatid 8contain hereditary material 8divided into linear chromosomes, associated with histone protein

15 Structure of eukaryotes 8the nucleolus 8an assembly plant for ribosomal subunits 8ribosomal proteins are made in the cytoplasm 8ribosomal RNA made in the nucleus

16 Organelles 8Endoplasmic reticulum 8Thin membrane not visible in the light microscope. 8Divides interior into compartments. 8Cytoskeleton, holds the cell shape. 8Rough ER 8covered with ribosomes 8manufactures proteins for export 8Smooth ER 8lacks ribosomes 8carbohydrate and lipid synthesis

17 Organelles 8Ribosomes 8Made of two parts. 8Made in the nucleus. 8Assist in the manufacture of proteins. 8Golgi apparatus

18 Organelles 8Mitochondrion 8Lysosome

19 Organelles 8Chloroplast

20 Cells 8State two similarities between prokaryotic and eukaryotic cells. 8State two differences between the eukaryotic nucleus and the prokaryotic nuclear material.

21 Endosymbiosis 8Symbiosis is two organisms living in close association. 8Mitochondria and chloroplasts are thought to be ancient bacteria that became incorporated into eukaryotic cells. 8Evidence supporting Theory: 8both are surrounded by double membranes 8mitochondria and bacteria hvae similar size 8mitochondrial ribosomes resemble bacterial ribosomes 8both have circular DNA like bacteria 8mitochondria divide by simple fission

22 The Plant Cell Wall