Cells: Prokaryotes and Eukaryotes in Three Domains of Life

1. Cells Prokaryotes and Eukaryotes

2. Three Domains of Life

3. Three Domains of Life

4. Three Domains of LIfe • Eukaryota- Eukaryotes (this domain includes organisms you are familiar with such as protists, plants, animals, fungi, and you!) • Bacteria & Archaea- Prokaryotes

5. Similarities Among the Domains • have cell membranes • cytoplasm & cytosol (materials inside the cell) • ribosomes (RNA+protein complex involved in protein synthesis) • have a common set of metabolic pathways (including glycolysis) • replicate DNA semiconservatively • use DNA as genetic material and a similar genetic code to make proteins This serves as evidence that all living things are related

6. Differences Among the Domains

7. Differences Prokaryotes Eukaryotes some eukaryotes are multicellular • all organisms are unicellular

8. Eukaryotes share a more recent common ancestor with Archaea then they do with Bacteria. • Genetic Evidence: Sequencing of ribosomal RNA (rRNA) genes has been useful in studying these relationships because • rRNA was present in the common ancestor of all life. • All free-living organisms have rRNA. • Lateral transfer of rRNA genes among distantly related species is unlikely. • rRNA has evolved slowly.

9. Prokaryote Structure • Cell membrane- encloses the cell, separates internal environment from external environment, regulates traffic of materials into and out of the cell • Nucleoid- region where DNA is located • Cytoplasm- inside the cell, constantly in motion • cytosol- water containing ions, small molecules and soluble macromolecules • Variety of filaments and particles, including ribosomes • Ribosomes- tiny complex of RNA and proteins, sites of protein synthesis • Found floating freely in the cytoplasm

10. Specialized Structures of (Some) Prokaryotes • Cell walls (most prokaryotes have)- supports cell and determines shape • Some bacterial cell walls made of peptidoglycan • Some bacterial cells have capsules than protect from white blood cells and help keep cells from drying out

11. Specialized Structures of (some) Prokaryotes • Flagella- for motion! little appendage anchored in the cell membrane made of motor proteins

12. Specialized Structures of Prokaryotes (In some prokaryotes) • Cytoskeleton- filaments that play a role in cell division • What kind of experiment could we design to know that flagella are for movement? • Why would this be an evolutionary advantage?

13. Prokaryotes are very diverse. super awesome examples: • Hypertehrmophiles-could have lived in ancestral Earth

14. Prokaryotes are very diverse. super awesome examples: • Hadobacteria- live in extreme environments • Thermusaquaticus- lives in hot springs • HUGE for PCR (and science in general) • Deinococcus- resistant to radiation and can consume nuclear waste and other toxic materials.

15. Prokaryotes are very diverse. super awesome examples: • Cyanobacteria (aka. blue-green bacteria)- photosynthetic bacteria, have chlorophyll and release for photosynthesis and release O2 • some can also fix nitrogen • responsible for transforming the earth's atmosphere

16. Prokaryotes are very diverse. super awesome examples: • Proteobacteria: largest group of bacteria • Mitochondria of eukaryotes were derived from a proteobacterium by endosymbiosis. • Examples: • Some are photoautotrophs that use light energy to metabolize sulfur • Rhizobium- nitrogen fixers • Escherichia coli- one of the most studied organisms on Earth. • Salmonella typhimurium- causes GI disease

17. Don’t get mixed up… Common Misconceptions • Not all bacteria are harmful. Most bacteria are harmless. Some are really important! Many play critical roles in decay, matter cycling and organismal health.

18. Before we move on to eukaryotes, let’s backtrack a second The Cell Theory • Cells are the fundamental units of life • All living things are composed of cells • All cells come from preexisting cells • Conceptual implications: • Studying cell biology is in some sense the same  as studying life • Life is continuous

19. Eukaryotes • Monophyletic (one common ancestor) • More closely related to Archaea than to Bacteria • Includes plants, animals, fungi, and protists • Protist- all the eukaryotes that are not plants, animals or fungi (non-monophyletic, many groups)

20. Eukaryotic cells have a cell membrane, cytoplasm, and ribosomes (sound familiar?) • Cytoplasm • Ribosomes- free in cytoplasm (just like prokaryotes), attached to endoplasmic reticulum, inside mitochondria and chloroplasts

21. Eukaryotic cells have a cell membrane, cytoplasm, and ribosomes • Cell membrane- selectively permeable barrier that allows cells to maintain homeostasis (stable internal environment) • phospholipid bilayer • decorated in proteins • vital for cell communication

22. The key is compartmentalization.   • Eukaryotes have organelles. • Each organelle plays a specific role in the cell.

23. MaD Skills: Surface Area-to-Volume Ratio

24. the volume of a cell determines the amount of metabolic activity • The surface area of a cell determines how much material can pass through Surface area-To-Volume Ratio as an object increases in volume, its surface area also increases, but not as quickly It limits cell size.

25. the volume of a cell determines the amount of metabolic activity • The surface area of a cell determines how much material can pass through Surface area-To-Volume Ratio as an object increases in volume, its surface area also increases, but not as quickly It limits cell size.

26. Important because as cells grow larger, metabolic activity increases and the cell needs more resources and to get rid of more waste Surface area-To-Volume Ratio as an object increases in volume, its surface area also increases, but not as quickly It limits cell size.

27. Surface Area Adaptations • Cells have adapted to maximize surface area when material exchange needs to be maximized. • Ex. Lung alveoli, and plant root hairs Surface area-To-Volume Ratio as an object increases in volume, its surface area also increases, but not as quickly It limits cell size.

28. What you need to be able to do: • Be able to calculate the surface area and volume of a 3D cell and determine the relative efficiency of material exchange. The formula sheet has formulas for surface area and volume for a variety of 3D shapes. Ex. Determine the relative efficiency of material exchange for a spherical cell with a radius of 10 μm, and a cubic cell with a side length of 10 μm. Surface area-To-Volume Ratio as an object increases in volume, its surface area also increases, but not as quickly It limits cell size.

29. Meet the Organelles- Nucleus • Nucleus • Usually the largest organelle • Where DNA is located • Where DNA is transcribed to RNA • Has nucleolus were ribosomes are made

30. Meet the Organelles- Endomembrane system • Endoplasmic Reticulum (ER) • Network of interconnected membranes • Extensive folding awesome surface area-to-volume ratio • Inside called lumen • Rough Endoplasmic Reticulum (RER) • Ribosomes attached (not permanently, just when they are synthesizing proteins to be modified by the RER) • Protein enters RER (if it has the right AA sequence) • Proteins are folded into their tertiary strucure • Proteins are chemically “tagged” (often with CHO groups) for delivery • Proteins are pinched off from ER and transported in vesicles • All secreted proteins and most membrane-bound proteins are made in RER

31. Bell Ringer • Which of these statements accurately reflects the relationship between cell size and surface area?   • Larger cells are most efficient at transporting materials across the membrane since their surface area is increased. • Smaller cells must have more phospholipids per area in order to adequately transport materials into the cell. • Cells must maximize their surface area to volume ratio in order to maintain homeostasis. • Cells must minimize their surface area exposure to the extracellular matrix in order to retain cytosol. • Calculatethe surface area and volume of a cubic epithelial cell with sides of 8 micrometers.  Then, illustrate the relationship between cell size (x axis) and surface area/volume ratio (y axis) on a graph.

32. Membranes and Transport • Membranes- separate the inside of the cell from the surrounding environment • structure and function determined by its composition    • it controls transport

33. Membrane- Fluid Mosaic Model

34. Membrane- Fluid Mosaic Model • Phospholipid bilayer • amphipathic- Hydrophilic outside, hydrophobic inside • Spontaneously form a bi-layer • Fluidity- molecules can move around within the membrane • dependent on lipid composition and temperature • cholesterol (steroid lipid) helps to maintain membrane fluidity

35. Plasma Membrane Selective Permeability • only small, non-polar molecules can move through the bilayer • Other materials must move through pores (made of proteins)

36. Plasma Membrane- Proteins Structure • Integral- penetrate one or both layers of bi-layer • Peripheral- don’t penetrate the bilayer

37. Plasma Membrane- Proteins Structure • Integral- penetrate one or both layers of bi-layer • Peripheral- don’t penetrate the bilayer Function include: • move materials through the membrane- pores • cell-cell recognition • receive chemical signals from environment

38. Plasma Membrane- Proteins