1. Cells: the basic unit of life

2. Cells  Living things are made up of tiny structures called cells.  Small in size (microscopic) – so weren’t discovered until invention of microscopes (mid-1600).  Constitute structures of organisms and perform various functions.

3. Cell discovery  In 1665, Robert Hooke built a microscope & looked at a thin slice of cork. Cork is found in the bark of cork trees. The cork looked like it was made of little boxes. Hooke named these boxes cells.  Hooke also looked at feathers, fish scales, and the eyes of houseflies. But he spent most of his time looking at plants and fungi.  The cells of plants and fungi have cell walls. This makes them easy to see.

5. Finding cells in other organisms  Anton van Leeuwenhoek 1673, saw small organisms in the water. He named these organisms animalcules, which means "little animals” – Protists.  Leeuwenhoek also looked at animal blood. He observed that blood cells in fish, birds, and frogs are oval. Blood cells in humans and dogs are round and flat.

6. Cell theory In1938, Matthias Schleiden studied cells in plants. In 1939, Theodor Schwann studied cells in animals. Schwann wrote the first two parts of the cell theory. 1.All organisms are made up of one or more cells 2.The cell is the basic unit of living things. Rudolf Virchow 1858 added third part of the cell theory. 3. All cells come from existing cells.

7. Cell size and shapes  Cells vary in shape and size – In general, prokaryotic are smaller in size & eukaryotic cells are larger in size.  The ratio of the cell's outer surface area to the cell's volume is called the surface area-to- volume ratio, which can be calculated by using the following equation:

8. Parts of the cell  All cells have the following parts in common. 1.The cell membrane & Cytoplasm 2.Organelles 3.Genetic material

10. 1. The cell membrane & Cytoplasm  cell membrane is a protective layer that covers the cell's surface and acts as a barrier (controls transport (nutrients, water, wastes, etc).  Two layers of phospholipids  Inside the cell is a fluid. This fluid is called the cytoplasm

11. 2. Organelles  Organelles are structures that perform specific functions within the cell & they carry out various life processes.  Most organelles are surrounded by membranes.  Some organelles float in the cytoplasm. Other organelles are attached to membranes or other organelles.

12. 3. Genetic Material  All cells contain DNA that carries information needed to make new cells and new organisms  In some cells, the DNA is enclosed inside an organelle called the nucleus

13. Cells  Unicellular(Eubacteria,Archaebacteri a) and multicellular (Most of plants & animals).  Two kinds of cells: Prokaryotic and Eukaryotic

15. Prokaryotes

16. Eubacteria/Bacteria  Don’t have a nucleus but do have DNA.  Don’t have membrane covered organelles.  Have ribosomes.  Have cell wall.  Cell membrane & cell wall allow material into & out of the cell.  They live in soil & water. They also live as parasite in other organisms.  Have flagellum  e.g. bacteria on your teeth, in digestive system.

18. Archaebacteria  Called as Archae.  Live in extreme environments.  Can be of three types: o Heat loving o Salt loving o Methane loving

19. Prokaryotic and eukaryotic cells

20. Eukaryotic cells  Protists– unicellular eukaryotes  (paramecium, amoeba)  Humans – multicellular eukaryotes  Plants - multicellular eukaryotes  Multicellular organisms are all eukaryotic.

22.  Cell wall - A rigid structure that gives support to a cell  Plant cell wall – cellulose  Fungi cell wall – chitin  Bacterial cell wall - peptidoglycan  Animal cells don’t have cell walls 1. Cell wall

23.  cell membrane - A protective barrier that encloses a cell.  It allows nutrients to enter and wastes to exit the cell.  The cell membrane contains proteins, lipids, and phospholipids.  The cell membrane has two layers of phospholipids. 2. Cell membrane

24. 3. Cytoskeleton  Network of proteins  Provide support, protect cell from collapsing  Contains three types of proteins  One protein is a hollow tube.  The other two are long, stringy fibers

25. 4. Nucleus  Membrane bound organelle contains DNA  DNA contains information about protein synthesis  Covered by two membranes (inner and outer)  Only in eukaryotes (plants and animals)  The nucleus has a dark area called the nucleolus - where a cell begins to make its ribosomes.

26. Nucleus

27. 5. Ribosome  Organelles involved in protein synthesis  Some ribosomes float freely in the cytoplasm. Others are attached to membrane or the cytoskeleton.  Proteins are made of amino acids - 20 different organic molecules that are used to make proteins.

28. 6. Endoplasmic reticulum  System of folded membranes  Transport and delivery of substances  Extended network throughout the cell  Endoplasmic reticulum is either rough ER or smooth ER.  If the ribosomes are attached on ER - rough ER – synthesize protein  Without ribosomes -smooth ER  The functions of smooth ER include making lipids & detoxification of the cell.

29. Endoplasmic reticulum

30. 7.Mitochondria  Power house of a cell.  Two membranes (inner and outer)  Sugars are broken down to produce energy  Energy generated is stored in form of ATP  Mitochondria have their own DNA and ribosomes  They can divide within a cell

31. Mitochondria

32. 8. Chloroplast  Found in plants & algae cells. Absent in animal cells.  Chloroplasts contain green colored pigment known as chlorophyll which absorbs light for photosynthesis  Chloroplasts also have two membranes  Chlorophyll is found inside the inner membrane of a chloroplast.  During photosynthesis, plants produce sugars and oxygen by using CO2, sunlight and water  The sugar produced is utilized by mitochondria to produce ATP

33. Chloroplast

34. 9. Golgi complex  Package and distribute proteins  Materials (lipids, proteins etc.) are delivered from ER to Golgi complex and are processed & modified there  The final material leaves Golgi complex enclosed in a piece of Golgi membrane. The membrane pinches off to form a small bubble.  The bubble transports its contents to other parts of the cell or out of the cell.

35. Golgi complex

36. 10. Vesicle  The bubble that forms from the Golgi complex's membrane is a vesicle.  A vesicle is a small sac that surrounds material to be moved into or out of a cell.  vesicles carry new protein from the ER to the Golgi complex.  Other vesicles distribute material from the Golgi complex to other parts of the cell.

37. 11. Lysosomes  Lysosomes are vesicles involved in cellular digestion  They contain digestive enzymes  Degrade foreign material or damaged cellular material, get rid of wastes

38. 12. Vacuoles  Vacuoles are vesicles meant for storage  They have variety of sizes and store different types of materials  e.g. some store digestive enzymes  Plant vacuoles are larger in size. They store water and salts. When there is enough water, plant vacuole swell and help in supporting plant cells. Vacuoles with less water result in wilting.

39. Lysosomes and vacuoles

43. Summary