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Biology 102

Biology 102. Lecture 8: Cell structure and function (Parts 1 and 2). Lecture outline. History of cell study Basic attributes of cells Cell structures. I. The history of cell study. Robert Hooke—1665—coined the word cell, looked at cork cells Antonie van Leeuwenhoek

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Biology 102

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  1. Biology 102 Lecture 8: Cell structure and function (Parts 1 and 2)

  2. Lecture outline • History of cell study • Basic attributes of cells • Cell structures

  3. I. The history of cell study • Robert Hooke—1665—coined the word cell, looked at cork cells • Antonie van Leeuwenhoek • Created optics that could visualize single cells • His technology “lost” for nearly 200 years • C. Robert Brown—1831—discovered the "nucleus"

  4. I. The history of cell study • D. Theodor Schwann—1838—viewed animal cells in cartilage • 1. Cells are the elementary particles of plants and animals • E. Mattias Schleiden—Cells are the fundamental basis of life • F. Virchow—1858—All cells come from cells

  5. I. The history of cell study • F. Cell theory • All living things are composed of one or more cells • What about viruses? • 2. Cells are the basic unit of structure and function • 3. All cells come from preexisting cells

  6. II. Attributes of cells • A. Cell size • 1. 1–100µm

  7. II. Attributes of cells • 2. Why is there a limit to cell size? • a. Surface-to-volume ratio • b. Distance from surface to center

  8. II. Attributes of cells • B. Cell types • 1. Prokaryotic—no nucleus (or other membrane-bound organelles) circular DNA, ribosomes

  9. II. Attributes of cells • B. Cell types • 2. Eukaryotic—larger, nucleus, linear chromosomes, membranous organelles

  10. III. Cell structure • A. All cells (prokaryotes and eukaryotes) possess a plasma membrane, cytoplasm, genetic material and ribosomes • 1. Plasma membrane has phospholipid bilayer, embedded glycoproteins • a. Isolates cytoplasm from environment • b. Regulates molecular movement into and out of cell • c. Interacts with other cells/environment

  11. III. Cell structure • A. All cells possess a plasma membrane, cytoplasm, genetic material and ribosomes (cont.) • Genetic material—DNA, found in the nucleus (of eukaryotes) • Within cytoplasm of prokaryotes • 3. Cytoplasm—water, salts, organic monomers and polymers • a. Contains organelles

  12. III. Cell structure • B. Organelles • 1. Ribosomes assemble amino acid monomers into polypeptide chains • a. Associated with the ER in eukaryotes • Composed of RNA and proteins • Both prokaryotes and eukaryotes have ribosomes • NOTE: Other organelles are present only in eukaryotes

  13. III. Cell structure • Organelles (cont.) • 2. Endoplasmic reticulum consists of folded membranes contiguous with outer nuclear membrane • Rough ER: protein synthesis and secretion • Smooth ER: lipid synthesis and secretion • Golgi apparatus: membranous sacs associated with the ER • Sorts proteins and lipids by destination • Modifies some molecules • Packages these materials, then transports them to appropriate location • 4. Lysosomes are Golgi-derived vesicles containing digestive enzymes

  14. Flow of membrane within the cell • Follow pathway of membrane flow • Nucleus • ER • Golgi apparatus • Lysosomes (and other packets of materials) • Plasma membrane

  15. III. Cell structure • B. Organelles (cont.) • 5. Mitochondria provide energy for cellular functions • Membrane-bound (two membranes) • Most concentrated in metabolically active cells (i.e. muscles) • Break down molecules to obtain their energy • Energy stored “short-term” as ATP • c. Have their own DNA and ribosomes; self-replicate

  16. Structure of a mitochondrion • Note: Different reactions occur in different parts of the mitochondrion

  17. Plant cells: Have all the organelles previously mentioned, and also…

  18. III. Cell structure • B. Organelles (cont.) • 6. Vacuoles • a. Large, water-filled spaces (cell sap) • b. Can take up over 90% of cell volume • Surrounded by tonoplast (a single membrane) • d. Functions: • 1) Storage of red/blue anthocyanins, acids, salts, wastes • 2) Maintain cell pressure (turgor pressure)—wilting

  19. Maintenance of turgor pressure

  20. III. Cell structure • B. Organelles (cont.) • 7. Chloroplasts • Note double membrane • Green—contain chlorophyll pigment • Stacks of thylakoids (grana) within stroma (fluid) • As for mitochondria, diff. parts have diff. functions • Have their own DNA and ribosomes; self-replicate

  21. III. Cell structure • B. Organelles (cont.) • 8. Other plastids • Storage of materials such as pigments and starch (as in potatos)

  22. III. Cell structure • B. Organelles (cont.) • 8. Nucleus is control center of the cell

  23. III. Cell structure • B. Organelles (cont.) • Functions of the parts of the nucleus • Nuclear envelope (membrane) with pores • Water, ions and ATP can pass through pores • Other materials are regulated by “gatekeeper” proteins in the pores • Nucleolus • Site of ribosome assembly • Chromatin • Between nucleolus and envelope • DNA and protein (not in nucleolus!) • Replication and transcription

  24. III. Cell structure • C. Cell walls in plant cells, prokaryotic cells, fungi • Plants • Cell walls of cellulose (Ch. 3) • Fungi • Cell walls of chitin (Ch. 3) • Function: support, protection • NOTE: Animal cells do not have cell walls!

  25. III. Cell structure • Cytoskeleton • Network of protein fibers to which organelles and even enzymes are attached • Microfilaments Intermed. Fil. Microtubules

  26. III. Cell structure • Cytoskeleton functions • Cell shape • Organization of cellular structures • Cell movement • Caused by assembly, disassembly and sliding of the filaments • Organelle movement • Ex: Endocytosis • Movement of membrane from ER to Golgi apparatus, etc… • Cell division

  27. III. Cell structure • E. Cilia and flagella are protein microtubule extensions of the plasma membrane • Cilia: short and numerous • Examples: within oviducts to move eggs, filter-feeding in invertebrates, movement of particles out of respiratory system

  28. III. Cell structure • 2. Flagella: longer and fewer

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