Biology 102

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Biology 102

• Lecture 8 Cell structure and function (Parts 1
  and 2)

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Lecture outline

• History of cell study
• Basic attributes of cells
• Cell structures

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I. The history of cell study

• Robert Hooke1665coined 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 Brown1831discovered the "nucleus"

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I. The history of cell study

• D. Theodor Schwann1838viewed animal cells in
  cartilage
• 1. Cells are the elementary particles of plants
  and animals
• E. Mattias SchleidenCells are the fundamental
  basis of life
• F. Virchow1858All cells come from cells

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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

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II. Attributes of cells

• A. Cell size
• 1. 1100µm

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II. Attributes of cells

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

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II. Attributes of cells

• B. Cell types
• 1. Prokaryoticno nucleus (or other
  membrane-bound organelles) circular DNA,
  ribosomes

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II. Attributes of cells

• B. Cell types
• 2. Eukaryoticlarger, nucleus, linear
  chromosomes, membranous organelles

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(No Transcript)
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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

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III. Cell structure

• A. All cells possess a plasma membrane,
  cytoplasm, genetic material and ribosomes (cont.)
• Genetic materialDNA, found in the nucleus (of
  eukaryotes)
• Within cytoplasm of prokaryotes
• 3. Cytoplasmwater, salts, organic monomers and
  polymers
• a. Contains organelles

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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

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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

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Flow of membrane within the cell

• Follow pathway of membrane flow
• Nucleus
• ER
• Golgi apparatus
• Lysosomes (and other packets of materials)
• Plasma membrane

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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

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Structure of a mitochondrion

• Note Different reactions occur in different
  parts of the mitochondrion

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Plant cells Have all the organelles previously
mentioned, and also
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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

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Maintenance of turgor pressure
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III. Cell structure

• B. Organelles (cont.)
• 7. Chloroplasts
• Note double membrane
• Greencontain 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

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III. Cell structure

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

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III. Cell structure

• B. Organelles (cont.)
• 8. Nucleus is control center of the cell

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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

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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!

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III. Cell structure

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

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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

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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

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III. Cell structure

• 2. Flagella longer and fewer