INTRODUCTION TO CELLS

1. INTRODUCTION TO CELLS plant stem bacterium nerve cell Paramecium • Cells vary in size and shape and functions! • Despite these differences, eukaryotic cells • share similar chemistry!

2. THE DISCOVERY OF CELLS Robert Hooke, England, 1665 uses a light microscope to examine cork, and names these small chambers “CELLS” Anton van Leeuwenhoek describes various forms of bacteria based on his microscopic observations CELL THEORY (begin notes) • Matthias Schleiden (1838) and Theodor Schwann (1839) • recognized that: • all living organisms are made of cells; • cells form from divisions of existing cells; • cell is the smallest unit of life!

3. CELLS • Prokaryotic • Eukaryotic • Prokaryotic cells: bacteria, blue-green algae • Lack a membrane-bound nucleus • DNA is usually one circular chromosome located in an area of the bacterium • Lack membrane-bound organelles • Eukaryotic cells • Single or multicelled • DNA encased in a membrane • Possess membrane-bound organelles

4. THE PROKARYOTIC CELL E.coli • Two domains of prokaryotes – • Dramatically different from each other: • The simplest, most basic type of cell • Enormously diverse and occupy most every niche • Can be autotrophic or heterotrophic PROKARYOTES are cells lacking membrane- bound organelles and the internal compartmentalization characteristic of eukaryotes EUBACTERIA ARCHAEBACTERIA

5. THE PROKARYOTIC CELL E.coli • Two domains of prokaryotes – • Dramatically different from each other: • EUBACTERIA • more complex • true bacteria • ARCHAE • live in hostile environments • Methanogens • Halophiles • Thermoacidophiles • Phile = love

6. THEORY OF ENDOSYMBIOSIS internal membranes aerobic eubacteria engulfed mitochondrion ancestral eukaryotic cell eukaryotic cell with mitochondrion chloroplast photosynthetic bacterium eukaryotic cell with chloroplast

7. EVIDENCE SUPPORTING ENDOSYMBIOSIS If mitochondria and chloroplasts arose from prokaryotes, then we can predict that: • THESE ORGANELLES CONTAIN DNA, RNA, AND RIBOSOMES - Each genome consists of a single, circular molecule of DNA - 70S ribosomes and 23S and 16S rRNA, like prokaryotes • THE INNER MEMBRANE OF EACH ORGANELLE CONTAINS • ENZYMES AND PROTEINS SIMILAR TO THOSE OF • PROKARYOTES • Antibiotics inhibiting transcription or blocking translation (processes used to synthesize proteins) in bacteria similarly affect these processes in chloroplasts and mitochondria. • These antibiotics do NOT affect transcription of nuclear genes or protein synthesis within the cytoplasm of eukaryotes.

8. The Ribosome is the site of protein synthesis. Ribosomes are usually associated with the endoplasmic reticulum, but some are suspended freely in the cytoplasm. As you will see in this image, ribosomes are structurally different in bacteria and eukaryotes.

9. THE EUKARYOTIC CELL yeast • Eukaryotic cells are larger and more complex than those of the eubacteria and archae • Eukaryotes can be single-celled or multicellularorganisms • Importantly, eukaryotes contain membrane-bound organelles

10. ORGANELLES THE NUCLEUS • Surrounded by a • double-membrane • known as the • nuclear envelope • Nuclear envelope • Contains pores • to facilitate exchange of substances across the nuclear envelope Chromatin: the entire genetic material and associated proteins. Chromosomes: one long molecule of condensed chromatin (humans have 23 pairs = 46) • The nucleus contains DNA, usually as chromatin, • but this condenses to form chromosomes during cell division.

11. Chromatin and Chromosomes

12. ORGANELLES THE NUCLEOLUS • Area in nucleus not bound by a membrane • Not truly considered an organelle • Manufacture ribosomal subunits – the cell's protein-producing factories!

13. MITOCHONDRIA • Contain an outer • membrane and an • inner membrane • folded into cristae • in the interior • of the organelle • Contain DNA, RNA, and ribosomes, • all of which • are similar to those • of prokaryotic cells

14. MITOCHONDRIA • Are THE cellular powerhouses, achieved by producing ATP from the oxidation of food molecules in a process known as cellular respiration • Oxidation:process of a compound combining with oxygen and in the process, gives up electrons.

15. MITOCHONDRIA • Cellular Respiration Chemical Equation C6H12O6 + 6O2 CO2 + H2O + 36-38 ATP molecules

16. CHLOROPLASTS • Double membrane-bound organelle, with flattened sacs of membranes, called thylakoids, arranged in stacks,orgrana (one stack is a granum) • Use radiant energy to produce chemical bond energy • Contain DNA, RNA, and ribosomes, sharing features characteristic of prokaryotes

17. RIBOSOMES • Provides structural site of protein synthesis • Composed of two units: large and small subunits • Ribosomal subunits (large and small) are manufactured in the nucleolus

18. RIBOSOMES

19. ROUGH ENDOPLASMIC RETICULUM (ER) • Consists of • flattened sheets • of membranes • contiguous with • the outer • membrane of the • nuclear envelope • Possesses ribosomes • Functions in the • synthesis and • transport of proteins

20. SMOOTH ENDOPLASMIC RETICULUM (ER) • Consists of • flattened sheets • of membranes • contiguous with • the outer • membrane of the • nuclear envelope • Does not contain ribosomes • Functions in the • synthesis of: • cholesterol metabolism, • membrane synthesis, • detoxification, • Ca2+ storage along with other cellular processes.

21. SMOOTH ENDOPLASMIC RETICULUM (ER)

22. GOLGI APPARATUS • Comprised of • flattened • membrane- • enclosed sacs • Golgi receives • and modifies • molecules • synthesized in • the ER and • directs them for • export or to • other cellular • locations

23. LYSOSOMES • Small, membrane-enclosed organelles containing • enzymes for intracellular digestion PEROXISOMES • Small, membrane-enclosed organelles containing • oxidative enzymes that generate and destroy • hydrogen peroxide VACUOLES • Membrane-enclosed organelle can be used for • intracellular digestion and for structural support VESICLES • Small, membrane-enclosed spheres mediate the • exchange and transport of materials among • membrane-enclosed organelles and the exterior of the cell

24. CYTOSKELETON ACTIN FILAMENTS MICROTUBULES INTERMEDIATE FILAMENTS • Intermediate filaments: • constructed of proteins found in hair and nails • strengthen long axons of neurons • provide mechanical strength to cells • Actin filaments: • provide strength to cell • generate locomotion for cells to move • generates cytoplasmic streaming in cells • Microtubules: • provide rapid transport of organellessuch as vesicles and mitochondria in neurons • Migrate chromosomes during mitosis and meiosis • Present in all eukaryotic cells! CYTOSOL • The solution filled environment containing the molecules • necessary for essential cellular reactions!

26. Cell membranes function : • Barrier to prevent loss of intracellular contents to the surrounding medium • senses changes in environment and allows the cell to respond Cell Membranes

27. Cell membranes function : • enlarges to enable cell growth and reseals to prevent damage to the cell • regulates exchange of nutrients and waste Cell Membranes

29. ANIMAL CELL PLANT CELL YEAST CELL

30. Saccharomyces cerevisae Drosophila melanogaster C. elegans human mouse Arabidopsis thaliana MODEL ORGANISMS