The Cell

1. The Cell

2. Discovery of the Cell • Microscope invented in 1535 by Zacharias Jansenn. This first microscope magnified 20-30 times • Anton van Leeuwenhoek (1600’s) began to make microscopes as a hobby and invented one that magnified 200 times. First time could see water teeming with microbes. • Robert Hooke discovered that living things were composed of cells.

3. Cell Theory • All living things are made of cells. • Cells are the basic units of life. • Cells come only from other cells.

4. Prokaryotic Cells • Small, 3 basic shapes: • coccus, bacilli, spirochete • Lack membrane bound organelles • No nucleus • Capable of only simple activities • All unicellular NOVA | Killer Microbe

5. Capsule- covering that protects bacteria, helps it to adhere to other structures • Cell wall- outside of bacteria, keeps shape • Cell membrane- regulates what enters and leaves the cell

6. Pili (Fimbriae)- hair like structures that help a bacteria stick to surfaces • Flagellum- whip like structure that helps bacteria move • Ribosomes- protein synthesis • Plasmid- circular piece of DNA • Nucleoid region- contains bacterial DNA

7. Cell Size • Cells have to be in constant contact with their environment. • In order to exchange materials, they have to be small enough to allow diffusion into the center of the cell. • The surface area to volume ratio gets smaller as the cell gets larger. At some point, this becomes too small to sustain the cell.

8. Endosymbiotic Theory Originally aerobic prokaryotes and photosynthetic prokaryotes “joined” with a host to cell for protection and over time became 1 cell

9. Eukaryotes • Contain specialized organelles • Contains nucleus • Capable of greater activities • Can be unicellular or multicellular • All cells that are not bacteria

10. Nucleus- organelle that helps direct cell activities, contains DNA • Nuclear envelope surrounds nucleus • Nucleoplasm allows movement of materials within nucleus • Nuclear pores allows materials into and out of nucleus • Nucleolus produces • ribosomes • DNA contains genes- • these code for proteins

11. Ribosome- sites of protein synthesis

12. Endomembrane System • Vesicles- storage & transport materials, dispose of wastes, • ex. Lysosome (digestion and discharge of toxins contain lysozyme) Peroxisomes (specific enzymes) • Vacuoles-contractile (storage, regulation, excretion of water); • food (intake and storage)

13. Endoplasmic reticulum- transport of cellular materials rough (has ribosomes attached); smooth • Golgi bodies- sorting, packaging and distribution of materials from er

14. Energy Organelles • Mitochondria- breakdown glucose to produce chemical energy (ATP) by cellular respiration, special DNA and ribosomes, composed of inner and outer membranes-cristae and matrix

15. Chloroplasts- convert light energy into chemical energy (glucose) through photosynthesis, contain special DNA and ribosomes, contains a double membrane, stroma, thylakoids, and grana with chlorophyll and other pigments.

16. Cytoskeleton- shapes and supports the cell, composed of microtubules, microfilaments, intermediate filaments • Microtubules form other structures such as spindle fibers and centrioles (used during cell division)

17. Flagella and Cilia- used for locomotion and feeding, connected by basal bodies • Pseudopods- locomotion and feeding

18. Cell Walls • Plant cells have a primary cell wall composed of cellulose fibrils. Some plants have a secondary cell wall that adds strength. • Fungal cell walls are composed of chitin and they do not have secondary cell walls (less strength).

19. Plasma Membrane • Phospholipid bilayer with embedded proteins called the fluid-mosaic model. • The fluidity allows the cells to remain pliable. • The outside of animal cells have an extracellular matrix (EMC), which contains proteins and complex carbohydrate molecules.

20. Construction of the Cell Membrane

21. Carbohydrates on membrane • Glycolipids and glycoproteins give animal cells a “sugar coat” which offers proteins and can act as signaling molecules, cell to cell recognition and allow for adhesion between cells • The possible diversity of carbohydrate chains is enormous. This gives each cell its own “fingerprint”.

22. Protein functions • Channel-allows molecules in and out of cell • Carrier- combines with substance and helps it to move into or out of the cell • Cell recognition-glycoproteins that allow one cell to recognize another • Receptor- have a shape that allows specific molecules to bind to it • Enzymatic-biological catalyst that aid in reactions • Junction-join cells so that a tissue can fulfill its function

23. Permeability • Selectively permeable • Small non charged molecules can freely cross the membrane (ie CO2, O2, alcohol) • The molecules move in response to their concentration gradient • Water molecules pass through a channel protein called aquaporin

24. Diffusion • Movement of molecules from high concentration to lower- until equilibrium is reached • Effected by temperature, pressure, electrical currents, molecular size

25. Osmosis • Water movement across the membrane • Osmotic pressure- pressure that develops in a system due to osmosis • Isotonic- solute and water concentration same on inside and outside of cell • Hypotonic- concentration of water outside cell is larger than inside the cell • Hypertonic- concentration of water outside the cell is smaller than inside the cell Animation: How Osmosis Works

27. Facilitated transport • A molecule combines with carrier protein to be rapidly transported into the cell. • Occurs through ion channels in membrane

28. Active Transport • Requires ATP • Molecules move against their conc. Gradient • NaK pumps NaK pump cotransport

29. Endocytosis • Large molecules are taken into the cell • Requires Energy • 3 forms • Phagocytosis- ingestion of food particles, many cells cannot do, formation of food vacuoles • Pinocytosis- ingestion liquid or dissolved solute • Receptor-mediated- engulfed particles bind to receptors in membrane endocytosis

30. Exocytosis • Waste materials are released from cell • Vesicles bind to special sites on inside of plasma membrane and then discharge contents