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Chapter 7

Chapter 7. Cell Structure and Function. Recognize anything?. Getting to know your cells…. = we will see in lab!. Plant and animal cells. *If your slides look nothing like these, you need to let me know!. Elodea cell slide. o nion cell slide. h uman cheek cell slide. 7-1 life is cellular.

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Chapter 7

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  1. Chapter 7 Cell Structure and Function

  2. Recognize anything?

  3. Getting to know your cells… = we will see in lab!

  4. Plant and animal cells *If your slides look nothing like these, you need to let me know! Elodea cell slide onion cell slide human cheek cell slide

  5. 7-1 life is cellular • What is a cell? • The smallest unit of living things • One of the 8 characteristics of living things • If they are so small, how did we ever find them? • The invention of the microscope!

  6. The discovery of the cell • “out of sight, out of mind” • 2 inventors of the microscope • Robert Hooke • Looked at cork (plant) cells • First to use the term “cell” • Anton van Leeuwenhoek • We know him! • Saw organisms in pond water

  7. Cell theory • What is a theory? • Schleiden- claimed all plants made of cells • Schwann- claimed all animals made of cells • Virchow- claimed new cells only come from existing cells • The Cell Theory states: • 1. all living things are composed of cells • 2. cells are the basic unit of structure and function in living things • 3. new cells are produced from existing cells

  8. Exploring the cell • The advancement of microscopes • New technologies: • Fluorescent labels- track certain parts • 3D- structural detail • HD videos- show movement • Light microscopes still a challenge- why? • Light rays can be diffracted • So, what else can we use?

  9. Electron microscopy • Beams of electrons- show more detail • What are the 2 types? • Transmission EM • Shows internal structures • Specimen must be very thin • Scanning EM • Shows 3D surface images • Must be in a vacuum- preserved and dehydrated

  10. Scanning probe microscopes • 1990s • View the surface with very fine probes • No need for a vacuum • Can view single atoms

  11. Wide variety of cells • Cells come in all sizes- from 0.2nm to amoeba • 2 characteristics of ALL cells: • 1. Surrounded by a barrier (membrane) • 2. Contain DNA (at some point) • So if all cells have these, then how do we classify them…? • By the presence/absence of a nucleus!

  12. Prokaryotes & eukaryotes

  13. 7-2 eukaryotic cell structure • Eukaryotic cells = very complex • Drive processes of all living things • Remember the 8 characteristics? • Contain many common organelles • “Little organs”

  14. The cell as a “factory” • Each organelle has a specific function/role • 2 main parts: • Cytoplasm- part of the cell outside the nucleus • Nucleus- control center • “the boss”

  15. The Nucleus • Job: control center of the cell • Contains all DNA • Instructions for proteins, etc. to be made by cell • Structure: • Double membrane • Nuclear pores- allows material in/out • Chromatin- DNA + protein • Condenses to form chromosomes • Nucleolus- where ribosome production begins

  16. ribosomes • Job: make proteins! • Gets all “orders” from the nucleus • Consists of RNA and protein • Free or bound

  17. Endoplasmic reticulum (ER) • Job: conveyor belt for protein synthesis • For proteins goingoutof the cells • Rough ER: ribosomes attached • Smooth ER: no ribosomes • Enzymes here • Produce membrane lipids • Detox drugs (liver)

  18. Golgi apparatus • Job: modify, sort and package proteins • Sent to be stored or secreted • Like a UPS store- final touches and ship!

  19. lysosomes • Job: digestion of carbs, proteins and lipids for cell use • Enzyme filled “clean-up crew” • Get rid of “junk” • Old organelles

  20. vacuoles • Job: storage • Water, salt, proteins, carbs, etc. • Plants- large vacuoles- pressure gives support • Animals- maintain water balance • Maintaining a balance? What’s that called? • Homeostasis! • Ex: paramecium- contractile vacuole

  21. Supplying the cell with energy! • metabolism at the cell level • Living things get their energy from… • Food (animals) • The sun (plants)

  22. Mitochondria • Job: powerhouse of the cell • Chemical energy from food -> compounds the cell can use • Double membrane (inner is folded up) • Inherited from mother

  23. chloroplasts • Job: “solar powered” plants (photosynthesis) • Energy from sun -> energy the cell can use • Double membrane (internal folds up- chlorophyll)

  24. Organelle DNA • Mitochondria and chloroplasts have their own DNA • Lynn Margulis- endosymbiotic theory • Mitochondria and chloroplasts are descendants of prokaryotes • Symbiotic relationship with eukaryotic cell

  25. cytoskeleton • Job: structure and transport • Protein filaments- maintain shape • Microfilaments • Threadlike actin- tough/flexible • Microtubules • Hollow tubulin- cell shape and division • Mitotic spindle • Centrioles • Cell projections (cilia and flagella)- movement

  26. 7-3 cell boundaries • 1 of the 2 characteristics all cells have • What is the other one? • Separates the cell from the rest of its environment • Cell membrane: regulates what goes in/out • Cell wall: strong supporting layer

  27. Cell membrane • Thin, strong • Job: regulates what goes in/out • Protection/support • Lipid bilayer • “fluid mosaic” • Proteins within • Carb chain for identification • Protein channels

  28. Cell wall • Found in plants, bacteria, prokaryotes, etc. • NOT in animals • Outermost layer- outside membrane • Job: support/protection • cellulose

  29. Movement across membranes • Membranes regulate movement of liquid + dissolved molecules from one side to another • Permeable= when a membrane allows a substance to cross it • Impermeable= when a membrane does not allow a substance • Cell membranes are selectively permeable • Let some things in and not others

  30. concentration • Particles in a solution are always moving • Concentration: how much solute there is in a solution

  31. diffusion • Movement of particles from high concentration to low concentration • When equal on both sides: equilibrium is reached • Based on random particle movement- no energy needed! • Even at equilibrium, particles still move • Going in = going out

  32. osmosis • Diffusion of water through a selectively permeable membrane • isotonic solution: at equilibrium • hypertonic: greater concentration of solute • hypotonic: less concentration of solute

  33. Osmotic pressure • Pressure on the hypertonic end of a selectively permeable membrane • hypertonic solution- water out (cell shrinks) • hypotonic solution- water in (cell expands) • isotonic solution- stays same • bodily fluids are isotonic! • Cell walls prevent shrink/expanding

  34. Facilitated diffusion • some molecules travel easily thru membrane • Use protein channels • Protein “facilitates” (helps) diffusion • Still moving from hi to lo concentration- no energy needed!

  35. Active transport • For SMALL molecules… • Movement against concentration gradient • Requires energy (lots)! • Use protein “pump” • Changes shape and pumps molecules across

  36. Active transport • For LARGE molecules… • Movements of the cell membrane • Folds/extensions of membrane • Break off to form vacuole around molecule • Endocytosis- bring molecules IN the cell • Exocytosis – get molecules OUT of the cell

  37. 2 types of endocytosis • 1. phagocytosis: “cell eating” • Membrane and cytoplasm extend and engulf particle • 2. pinocytosis: take up liquid in tiny pockets of membrane Both processes move things INTO the cell!

  38. exocytosis Movement of things OUT of the cell!

  39. 7-4 the diversity of cellular life • Cells have many similarities • What are some? • They can also be very different • Specialization!

  40. Unicellular organisms • Carry out all the processes of a living thing • Only one cell

  41. Multicellular organisms • Depend on communication and cooperation among cells

  42. Cell specialization • Cell specialization: cells develop in different ways to perform different tasks (structure ->function!) • Specialized animal cells • RBC- O2 binding proteins • Muscle cells- overdeveloped cytoskeleton • Specialized plant cells • Guard cells- open/close stomata

  43. Levels of organization • Cells • Tissues: group of similar cells with specific functions • Organs: different tissues working together • Organ systems: group of organs working towards a certain function

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