Cells

1. Cells Structures and Functions of Prokaryotic and Eukaryotic cells

2. All cells have: • Plasma membrane • Cytosol (semifluid substance in which the organelles are suspended) / Cytoplasm • Chromosomes (DNA) • Ribosomes

3. 2.2 Prokaryotic Cells

4. 2.2.1 2.2.2 Prokaryotic Cell

5. Prokaryotic cells • Prokaryotic = “before nucleus” • No nucleus or membrane-bound organelles • DNA floats freely in cytoplasm (in nucleoid region) • DNA is in the form of a loop • Very small (in general, 10x smaller than eukaryotes) • Bacteria • Thought to have appeared on Earth first

6. Prokaryotic Cell

7. Prokaryotic cell structures and functions Cell wall – forms a protective outer layer that prevents damage from outside (made of peptidoglycan) Plasma membrane – controls entry and exit of substances, pumping some of them out in by active transport. Cytoplasm – contains enzymes that catalyze chemical reactions and contains DNA in a region called nucleoid. Pili – hair-like structures projecting from cell wall; when connected to another bacterial cell, they can be used to pull cells together Flagella – used for locomotion in some prokaryotes Ribosomes – small granular structures which synthesize proteins Nucleoid – region of cytoplasm that contains “naked loop of DNA” (single, long, continuous circle of DNA)

9. Reproduction in bacteria:most bacteria can reproduce asexually or sexually Asexual = Binary Fission (1 bacterium splits into 2) Sexual = Conjugation bacteria exchange genetic material with other bacteria thru cell-to-cell contact. - Increases genetic diversity of bacteria

10. 2.2.4 Binary fission See Binary fission (p. 227)

11. 2.3 Eukaryotic Cells

13. Diagram of an animal cell

14. Liver Cell 2.3.3

15. Ultrastructure of a liver cell. 1:Nucleolus; 2:Chromatin; 3:Dense Chromatin; 4:Nuclear Pores; 5:Mitochondria;6:Rough Endoplasmic Reticulum; 7:Ribosomes; 8:Golgi Apparatus; 9:Smooth Endoplasmic Reticulum;10:Peroxisomes; 11:Lysosomes; 12:Bile Capillary; 13:Desmosomes; 14:Microvilli.

16. Diagram ofa plant cell

17. Plant cell

18. The cell nucleus

19. Nucleus • Large spherical structure surrounded by a double membrane with pores (called the nuclear envelope) • Contains nucleolus and chromosomes (DNA) • Control center of the cell. Controls the cell’s functions through the expression of genes.

20. Nucleolus • Ball-like mass of fibers inside nucleus • makes ribosomes

21. Plasma membrane Selectively-permeable: controls which substances can enter and exit a cell. It is a fluid structure that can radically change shape • The membrane is a double layer ofphospholipids (phospholipid bilayer) • Receptors in the outer surface detect signals to the cell and relay these to the interior • The membrane has pores that run from the cytoplasm to the surrounding fluid

22. Cell (Plasma) Membrane

23. Cytoplasm • Entire region of cell between membrane and nucleus (semi-fluid substance) • contains salts, minerals and organic molecules • Holds organelles which have membranes around them • Actual fluid portion of cytoplasm is referred to as cytosol)

24. Endoplasmic Reticulum (ER) An extensive network of membrane tubules or channels that extends thru the cell, outwards from the nucleus Two types: Smooth Endoplasmic Reticulum Rough Endoplasmic Reticulum

25. Smooth Endoplasmic Reticulum Lacks ribosomes Functions • Synthesizes phospholipids (and other lipids) • Storage of calcium ions (needed for contraction in muscle cells) • Detoxification of drugs in liver cells • Transportation of lipid-based compounds • Synthesizes sex hormones: testosterone and estrogen

26. Rough Endoplasmic Reticulum • Covered with ribosomes Functions • protein synthesis • Proteins made here are generally inserted into membranes or secreted out of the cell • Also a “membrane factory” for the cell: adds membrane proteins and phospholipids to its own membrane

27. Ribosomes • Found attached to Rough ER and also floating free in the cytoplasm • Composed of rRNA (ribosomal RNA) and protein • Made of 2 subunits • Function: Protein synthesis!

28. cis Golgi Apparatus trans • Flattened sacs called cisternae which are stacked on top of each other • Function: receives proteins from the rER and distributes them to other organelles or out of the cell • Collects, modifies, packages, and ships • Side closest to rough ER is cis side (it receives products from the ER). • Movement then continues through to the trans side. Small sacs called vesicles can be seen coming off the trans side carrying materials.

29. Secretory Pathway

30. Secretory Pathway

31. Lysosomes

32. Lysosomes • Membrane-bound sacs that contain hydrolytic (digestive) enzymes • Function: digestion of old or non-working organelles, food particles, bacteria and virus invaders

33. Mitochondria (singular: Mitochondrion)

34. Mitochondria • Structure: folded membrane within an outer membrane • The folds of the inner membrane are called cristae • Converts energy stored in food into usable energy for work (ATP) • Process is called cellular respiration Amount of mitochondria in cells is correlated with amount of energy the cell needs (ex. muscle cells- Lots of mitochondria)

35. Peroxisomes spherical organelles that contain enzymes Function: Breaks down hydrogen peroxide (a toxic compound that can be produced during metabolism)into water, rendering the potentially toxic substance safe for release back into the cell

36. the Cytoskeleton

37. Cytoskeleton • Structure: a network of thin, fibrous elements made up of microtubules (hollow tubes), intermediate filaments, and microfilaments (threads made out of actin) • Function: -acts as a support system for organelles-reinforces cell shape -functions in cell movement, Components are made of protein

38. Centrioles • Structure: composed of nine sets of triplet microtubules arranged in a ring • Exist in pairs • Function: centrioles play a major role in cell division (mitosis)

39. Cilia and Flagella Hair-like organelles that extend from the surface of cells Both are composed of nine pairs of microtubules arranged around a central pair. Function: cell motility Cilia: numerous, short, move together like oars in water Flagella: usually only one, propels cells through water (ex. Sperm tail)

40. Cilia

41. Flagella http://programs.northlandcollege.edu/biology/Biology1111/animations/flagellum.html

42. Vacuoles • Structure: a sac of fluid surrounded by a membrane • Very large in plants (Large Central Vacuole) • Function: used for temporary storage of wastes, nutrients, water, pigments, etc. • In some freshwater protists, there is a contractile vacuole which pumps out excess water out of the cell

43. Chloroplasts Only in plant and algae cells Site of photosynthesis: (conversion of light energy to chemical energy) Double membrane around stacks of flattened sacs (thylakoids)

44. Chloroplast Pigment Chlorophyll makes them green

45. Cell Wall • In plant cells only: rigid wall made up of cellulose, proteins, and carbohydrates • Function: boundary around the plant cell outside of the cell membrane that provides structure and support

46. Plant cells Cell wall outside plasma membrane makes cells rigid Chloroplasts Large central vacuole No cilia or flagella Store carbohydrates as starch Animal cells No cell walls, only plasma membrane, which makes cells more flexible No chloroplasts Vacuoles are much smaller Some have cilia or flagella Store carbohydrates as glycogen Comparison of plant and animal cells

47. Extracellular Matrix Animal cells lack a rigid cell wall, but most are embedded in a sticky layer of glycoproteins called the "Extracellular Matrix“ (ECM). It is an elaborate matrix of glycoproteins and collagen which forms strong fibers outside the cell. The ECM functions to hold cells together and can also have a protective and supportive function.

48. Extracellular Matrix