Cells

1. Cells Cell Theory, Prokaryotes, and Eukaryotes

2. Cell Theory • Living organisms are composed of cells. • Cells are the smallest unit of life. • Cells come from pre-existing cells.

3. Cell Theory • Discuss the evidence for the cell theory • Simple, get some broth, pour it in two flasks, boil both, leave one uncovered, and seal the other • What do you think will happen?

4. Cell Theory

5. Cell Theory Unicellular organisms carry out all the functions of life. • Metabolism • Response • Homeostasis • Growth • Reproduction

6. Characteristics of Cells Metabolism: the complete set of chemical reactions in a living organism Response: a change of internal or external behavior based upon environmental stimulus Homeostasis: the ability to regulate the internal environment of an organism

7. Characteristics of Cells Growth: an organism captures and stores energy from the environment (food), at a faster rate than it uses the captured energy (released as heat) Reproduction: new individual organisms are produced, can be sexual or asexual

8. Give an example... The human body is in homeostasis, name three aspects of the body that must be regulated and maintained at a constant level. • Blood sugar levels • Temperature • Oxygen • Blood and extracellular fluid pH

9. Cell Theory Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using the appropriate SI unit. • What does SI stand for? • What types of units are considered SI? • Put the above structures in order from smallest to largest, guess what size they might be, using SI units.

11. Levels of Complexity Appreciation of relative size is required, such as… • molecules (1 nm) • thickness of membranes (10 nm) • viruses (100 nm), • bacteria (1 μm) • organelles (up to 10 μm) • most cells (up to 100 μm) MTVBOC

12. Cell Theory • Calculate the linear magnification of drawings and the actual size of specimens in images of known magnification. • Magnification could be stated (for example, ×250) or indicated by means of a scale bar.

13. What is the Magnification of This Picture? 1 μm 10 cm

14. How Long are These Bacteria? 50 mm 50k X

15. Determination of Actual Size Actual Size = Measured Size Magnification Actual Size = 50mm (50x10-3m or 5x10-2mor 0.05m) 50,000 (5x10-4) Actual Size = 1μm(1x10-6m)

16. Cell Theory Explain the importance of the surface area to volume ratio as a factor limiting cell size. • The rate of heat production/waste production/resource consumption of a cell is a function of its volume, whereas the rate of exchange of materials and energy (heat) is a function of its surface area.

17. Surface Area Limits Cell Size The boundary of every cell acts as a barrier that allows sufficient passage of oxygen, nutrients, and waste to service the entire volume of the cell. Volume increase more rapidly than surface area as cells grow The rate of exchange with the environment is inadequate in a cell with a very large cytoplasm

18. Surface Area vs. Volume radius of a cell is 1mm surface area is about 13mm2 volume will be about 4mm3 radius is increased to 10mm 10x increase surface area is about 1300mm2 100x increase volume will be about 4000mm3 1000x increase

19. Cell Surface Area to Volume Ratio

20. Cell Theory Multicellular organisms show emergent properties. • Emergent properties arise from the interaction of component parts: the whole is greater than the sum of its parts. • Can you think of something else with emergent properties? • Did you think of computers? Some other technology?

21. Cell Theory Cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others. Even though every cell has the same DNA code, not every gene is being used at the same time Different cells use different genes

22. Cell Differentiation

24. Stem cells retain the capacity to divide and have the ability to differentiate along different pathways. Stem cells have not yet decided what type of specialized cells they will be. Kind of like students before the find careers. So how do cells decide? Cell Theory

25. How Stem Cells Decide • All participants will begin seated at a table or lab bench • If you are within arms reach of a member of the opposite sex, then stand up and put your stool under the table. • If you are standing and wearing pants, then take five steps in any direction. • If you took a shower this morning, then switch places with the nearest person to you. • If you are full IB, then put your right hand on top of your head. • If the person nearest you has their hand on their head, then put your left hand on your stomach. • If you have a hand on your head on your stomach, then pat your head and rub your stomach in a circular motion. Do not stop. • If you are still sitting, spin in a circle, click your heals together three times, and say, ‘there’s no place like home’.

28. Cell Theory • Outline one therapeutic use of stem cells. • This is an area of rapid development. In 2005, stem cells were used to restore the insulation tissue of neurons in laboratory rats, resulting in subsequent improvements in their mobility. • Stem Cell Video

29. Prokaryotes Simple, single celled organisms

31. Prokaryotic Structure • Cell wall: rigid structure surrounding cell, made of proteins • Plasma membrane: lipid bi-layer enclosing the cytoplasm • Ribosomes: site of protein synthesis, type 70s • Pilli: used for attachment • Flagella: used for locomotion in some bacteria • Nucleoid: region containing DNA • Cytoplasm: interior of cell

32. Prokaryote Genome • Prokaryotes do not have a nucleus • The DNA exists as a single circular chromosome • It does not have histone proteins, and is known as naked DNA • The region where the circular DNA strand is found is called the nucleoid

34. Prokaryotes • Draw and label a diagram of the ultrastructure of Escherichia coli (E. coli) as an example of a prokaryote. • The diagram should show the cell wall, plasma membrane, cytoplasm, pili, flagella, ribosomes and nucleoid (region containing naked DNA). • See page 98 of your textbook.

35. Prokaryotes

36. Prokaryotes You should be a able to identify structures in electron micrographs of E. coli.

37. Review • What a factor limits cell size? • Why?

38. Prokaryotes Binary fission is used by most prokaryotes for asexual reproduction. This process replicates the original, or mother, cell, to produce two identical daughter cells.

39. Binary Fission • The fission process begins when the DNA of the mother cell is replicated and joins into a circular structure, pair by pair. • Each circular DNA strand then attaches to the plasma membrane. • Near the site of attachment, the cell elongates and causes the two duplicated chromosomes to separate. • At this point, the plasma membrane invaginates, or pinches inward toward the middle of the cell. • When it reaches the middle, the cell splits into two daughter cells.

40. Binary Fission

41. Binary Fission

42. Eukaryotes Complex Cells with Organelles

43. Eukaryotes • Draw and label a diagram of the ultrastructure of a liver cell as an example of an animal cell. • The diagram should show free ribosomes, rough endoplasmic reticulum (rER), lysosome, Golgi apparatus, mitochondrion and nucleus. • See page 100 of your textbook

45. Plasma membrane Nucleus Nuclear envelope Nucleolus Ribosomes Endoplasmic Reticulum Golgi Apparatus Vesicles Lysosomes Mitochondria Centrioles Eukaryotes – Cell Parts

46. Plasma Membrane • Phospholipid bi-layer that surrounds cell • Functions to separate internal cell environment (cytoplasm) from exterior environment • Selectively Permeable: allows specific substances to cross membranes but not others • Contains various types of membrane proteins

47. Plasma Membrane

48. Nucleus • Location of genetic material (DNA chromosomes) • Consists of nuclear envelope, chromatin (DNA), nucleolus, and nuclear pores • Functions to separate DNA from the rest of the cell

50. Nuclear Envelope • Double membrane surrounding nucleus • Nuclear pores allow entry and exit of molecules between nucleus and cytoplasm • Continuous with rough endoplasmic reticulum