Cells

1. Cells

2. Do a camel & a virus have anything in common?

4. Are Viruses Alive? • Remember CHARGER! • They are not made up of cells • Cannot live independently outside of a host • They don’t perform cellular respiration, grow or develop Only once inside a host cell they can: • Reproduce/replicate • Regulate gene expression • Evolve/mutate

5. What is a virus? • A virus is a non-living particle made up of nucleic acid, protein, and in some cases lipids. • They can replicate only by infecting living cells • 100% of viruses are pathogenic

6. Structure of a Virus • All viruses are composed of nucleic acids surrounded by a protein coating (capsid). • The nucleic acid can be either DNA or RNA

7. - Capsid • A capsid is a virus’sproteincoat/shell • Function: • Contains projections that allow the virus to attach to a host cell Projections

8. Viruses are Specific • The structure and shape (morphology) of viruses play an important role in how they work • Each virus can only infect certain host cells because of their specific attachment proteins • A virus identifies its host by fitting its surface proteins to receptor molecules on the host cell • It works like a lock & key! • Anti-viral drugs bind to the surface protein projections on viruses to prevent them from attaching to the host cell.

9. Two Types of Infections • Once inside the host cell, phages follow one of two general paths in causing disease & destroying cells • Path 1: Lytic Cycle- Hostile Takeover • Viral DNA hijacks the cell, tricks it into making clones of its viral DNA & lyses (destroys) the cell when it releases it’s virus clones. • Path 2: Lysogenic Cycle- Biological Pirates • Viral DNA is integrated (embedded) into a host cell’s DNA. The host cell is not lysed (killed) until the lytic cycle is activated.

10. Lytic vs. Lysogenic Cycles

11. - Bacteriophages • The tail and its spikes help attach the virus to the host cell • Once attached, the tail releases an enzyme that breaks down part of the bacterial cell wall • The tail core then punches through the cell wall, injecting the phage’s DNA. • It works like a syringe!

12. Retroviruses • HIV (human immunodeficiency virus), some cancers, hepatitis, Ebola are caused by retroviruses • HIV infects & destroys helper T cells in the immune system. • HIV can incubate (lysogenic) for years before it becomes activated (lytic). • AIDS – acquired immunodeficiency syndrome – infected people cannot fight off other diseases because the helper T cell count is SO low!

13. Treating Viruses • Antibiotics are ineffective against viral infections because, antibiotics interfere with metabolic processes that viruses do not perform. • -Remember, a virus is NON-LIVING!! • Anti-virals are used to treat viruses • Unlike most antibiotics, antiviral drugs do not destroy their target pathogen; instead they inhibit their development. • Work by targeting proteins not found in host cells, but found in the viral particles

14. What are cells? • Cells are the basic units of life. • They can only be seen under the microscope. • Basic types of cells:

15. History of Cells • No one knows precisely when the first cells lived on Earth. • 1st cells lived when Earth’s atmosphere lacked oxygen. • Photosynthetic bacteria were the first organisms to perform photosynthesis (they released oxygen into the atmosphere). • Photosynthesis may have increased oxygen levels so much that oxygen became more prominent in Earth’s atmosphere, making it possible for organisms who rely on oxygen for cellular respiration to exist on land (eukaryotes came after). • The first cells were photosynthetic and did not require oxygen (anaerobic). • Aerobic= with oxygen Anaerobic= without oxygen

16. The Endosymbiotic Theory • Mitochondria and chloroplasts were once primitive bacterial cells that lived alongside some of the oldest cells on Earth that were single-celled prokaryotes in Domain Archaea. • The organelles were engulfed through endocytosis by bacterial cells and both the bacteria and organelles developed a mutualistic symbiotic relationship. • The bacteria benefited from the chloroplasts as they provided crucial nutrients such as carbohydrates (through photosynthesis), the mitochondria was able to extract energy from these carbohydrates (through cellular respiration), and the organelles benefited from the bacteria as they received protection and a steady environment in which to live.

17. Endosymbiotic Theory

18. The Endosymbiotic Theory • Evidence to support it: • Mitochondria and chloroplasts have many similarities with bacterial cells, such as their own DNA (which is separate from the DNA found in the nucleus of the cell) • Both organelles use their DNA to produce many proteins • Both organelles have a double membrane which suggests they were ingested by a primitive host • The organelles reproduce similar to bacteria by replicating their own DNA and directing their own division

19. History of Cells • Before microscopes, people couldn’t see cells and therefore, didn’t know they existed. • Diseases, human reproduction, and many other biological concepts were blamed on “magic” before the discovery of cells…

20. Robert Hooke (1635-1703) • Hooke invented the first microscope and observed a piece of cork in 1665. • The hollow spaces he observed reminded him of the chambers monks slept in, so he called them cells. • They weren’t living cells, but they were the first “cells” to be seen under the microscope.

21. Anton van Leeuwenhoek (1632-1723) • In 1675, the Dutch microscope maker, van Leeuwenhoek , was the first person to observe living cells. • van Leeuwenhoek used a microscope to view pond water. • He discovered many living creatures that he called animalcules (tiny animals). • Many of them were not animals, but single celled organisms (protists, bacteria). Rotifers Ciliates Dental plaque

22. The Cell Theory • A Theory is a well-tested explanation that unifies a broad range of observations and hypotheses, and enables scientists to make accurate predictions about new situations. • The cell theory states: • 1. All living things are composed of cells • There are 2 types of cells (prokaryotic & eukaryotic) • 2. Cells are the basic units of structure and function in living things • 3. New cells are produced from existing cells

23. Cell Size • There are about 100 trillion cells in the human body, most ranging in size from 5 m to 20 m in diameter. • Small cells function more efficiently than large cells. • Why? Surface Area-to-volume ratio. • Smaller cells move materials in and out of the cell faster than a large cell can

24. Animal cell Bacterial cell Cell size comparison most bacteria • 1-10 microns eukaryotic cells • 10-100 microns • micron = micrometer = 1/1,000,000 meter • diameter of human hair = ~20 microns

25. Two Basic Cell Types Prokaryote Pro=before • Hint: “Pro-No” (No Nucleus!) • Lacks internal compartments • Limited organelles • No true nucleus • Organelles: Have DNA, ribosomes & a cell membrane • Most are single-celled (unicellular) organisms • Examples: bacteria

26. Prokaryotic Cell Free-floating DNA Plasma or cell membrane

27. Two Basic Cell Types Eukaryote • Has several internal structures (organelles). • True nucleus. • Either unicellular or multicellular. unicellular example: yeast multicellular examples: plants, animals, fungi & protists

28. Eukaryotic Cell Note these key features NUCLEUS Multiple membranous organelles

30. Basic materials that make up cell parts Carbohydrate The 4 Major Organic Molecules 1) Carbohydrates 2) Lipids 3) Proteins 4) Nucleic Acids Phospholipid Protein

31. Organelles • Organelles (little organs) are the structures that carry out specific functions (jobs) within a cell. • Some organelles are found in all cells, while others are only found in eukaryotes…or even specific eukaryotes.

32. 4 common organelles in ALL cells… DNA • 1. Cell membrane-encloses the cell • 2. Cytoplasm-”gooey-stuff” in the interior of the cell • 3. Ribosomes-structures within cells where proteins are made • 4. DNA (even if the cell does not have a nucleus, it still contains DNA) Cytoplasm Cell Membrane Ribosomes

33. Cell Boundaries: Cell/Plasma Membrane • Cell Membrane / Plasma Membrane / Phospholipid bi-layer • Is selectively or semi-permeable • Controls materials entering & leaving cell- acts like a “bouncer” • Supports cell • Made of phospholipids

34. a.k.a. Phospholipid bi-layer

35. Cytoplasm • A jellylike fluid within the cell that helps to cushion the cell and other organelles. • Part between cell membrane and nucleus • Contains the other organelles

36. Ribosomes • These are the most numerous of the cell’s organelles Protein Factory • Proteins are assembled (synthesized) here • Located in the cytoplasm and on the Rough ER

37. Nucleic Acids (DNA and RNA) • In prokaryotes, the nucleic acid (DNA or RNA) is found in the cytoplasm • Bacterial DNA is called a plasmid and is circular • Remember, prokaryotes DO NOT HAVE A NUCLEUS • In eukaryotes, the DNA is wound into chromosomes in the nucleus • RNA is found both in the nucleus and in the cytoplasm in eukaryotes DNA in cytoplasm Prokaryote DNA in nucleus Eukaryote

38. Organelles found in Eukaryotes only • Eukaryotes have several organelles that prokaryotes do not. • Some, like chloroplasts, are only found in certain eukaryotes… • Others, like mitochondria, are found in all eukaryotes.

39. Nucleus-Control Center of Cell • Storehouse for most genetic information (DNA) in your cells. • DNA contains genes that are instructions for making proteins. • Chromatin: DNA wrapped around proteins • Chromatin condenses into chromosomes during cell division Nucleus

40. Nucleolus &Nuclear Envelope The Nucleolus: Dense region in the nucleus where ribosomes are assembled in order to make proteins. The Nuclear Envelope: Double membrane surrounding the nucleus. It is pierced with holes called pores that allow large molecules like RNA to pass between the nucleus & cytoplasm.

41. Endoplasmic Reticulum (ER) • The ER directs the traffic of the many molecules by creating a series of channels that act as a “highway system” through the cytoplasm. 1. Rough ER -contains ribosomes on its surface & it makes proteins 2. Smooth ER- location of lipid synthesis (making lipids) & ships out parts of cell membrane (phospholipids)

42. Golgi apparatusaka Golgi bodies or Golgi complex • Proteins generally move here from the ER. • “Warehouse of the Cell” • Processes, sorts & packages proteins to be either stored, shipped to other organelles in the cell or secreted out of the cell by vesicles.

43. TO: TO: TO: EndoplasmicReticulum Nucleus proteinon its way! DNA RNA vesicle vesicle ribosomes TO: protein finishedprotein Golgi Apparatus Making Proteins

44. Lysosomes • “Clean up crew/janitor” • Special vacuoles that contain enzymes that: • Digest food-used to make energy • Defend a cell from invading bacteria & viruses • Break down damaged or worn-out cell parts • The recycling centers of the cell • Only found in ANIMAL cells! small foodparticle lysosomes digesting brokenorganelles vacuole digesting food

45. Vacuoles • Fluid filled sac used for storage of materials needed by the cell • Material may include: water, food molecules, enzymes and waste products • Most animal cells have small vacuoles. • An exception is adipose (fat) cells in animals, which have a large vacuole to hold a droplet of oil (fat) • The central vacuole is unique to plant & takes up most of the space inside a plant cell. • The central vacuole strengthens the cells and help support the entire plant

46. Cilia Cilia & Flagella • Used for movement in unicellular organisms. • Used for movement of materials or absorption in multicellular organisms. • Cilia: hair-like structures that help organisms swim & capture food • Flagella: tail-like structure that help unicellular organisms swim

47. Cytoskeleton • Flexible network of proteins that provide structural support for the cell • Three main types of fibers make up the cytoskeleton • Microtubules: long, hollow tubes-give cell its shape • Intermediate filaments: smaller than microtubules- give cell its strength • Microfilaments: tiny threads that enable cells to move and divide-helps muscles contract & relax

48. Mitochondriafound in ALL eukaryotes • Mitochondria free up stored energy in the cell by breaking down sugar (glucose) molecules. • This freed up energy is then usable to the cell! • A.K.A. “powerhouse of the cell” • Mitochondria have 2 membranes: • Inner membrane-increases its surface area and is where food molecules are converted to usable energy • Mitochondria have their own ribosomes & DNA!

49. Special Eukaryotic Organelles • Some eukaryotic organelles are only found in certain groups of eukaryotes, such as: • Centrioles-Animals • Chloroplasts- Plants & some Protists • Cell walls- Plants, Fungi & some Protists • Central (LARGE) vacuole- Plants

50. Chloroplasts • Organelle that carries out photosynthesis • Found in plants and some protists • Converts solar energy into chemical energy • Sunlight -> energy-rich molecules (sugars) • Contains chlorophyll (green pigment) • Energy is stored here until freed up by the mitochondria! • Chloroplasts have their own ribosomes & DNA