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Chapter 7 Chapter 7 Presentation Transcript

  • Chapter 7 – Cellular Structure & Function
  • Chapter 7.1 – Cell Discovery & Theory pp. 182 - 186
  • Anton van Leeuwenhoek
    • constructed the first microscope in the 1600’s (single magnifying lens)
    • used a microscope to view, describe, and draw cells in pond water
  • Leeuwenhoek’s Microscope
  • Robert Hooke (1665)
    • examined cork cells from the bark of an oak tree (dead plant cells)
    • observed that the cork was composed of tiny, hollow boxes similar to the cells of a monastery
    • called the structures cells
  • Hooke’s Microscope
  • Matthias Schleiden (1830’s)
    • Observed a variety of plants
    • Concluded that all plants are made of cells
  • Theodore Schwann (1830’s)
    • Concluded that all animals are composed of cells
  • Rudolf Virchow
    • stated that all cells arise from the division of preexisting cells
    • Claimed that all living things come from other living things.
  • Light Microscope (100X) Scanning Electron Microscope (1500X) Transmission Electron Microscope (62,000X)
  • Cellular Structure and Function
    • Utilizes a series of glass lenses and visible light to magnify an image
    • Magnifies images up to 1,000 times the actual size
    Light Microscopes
  • Cellular Structure and Function
    • Magnifies images up to 500,000 times the actual size
    9560x Electron Microscopes
    • Utilizes magnets to aim a beam of electrons at
    a cell to produce an image
  • Cell Theory
    • All organisms are made of one or more cells.
    • The amoeba is a unicellular (one-cell) organism.
  • Cell Theory (Continued)
    • The cell is the basic unit of organization of organisms.
    • All cells come from preexisting cells; a cell divides to form 2 identical (daughter) cells.
    • Most organisms are multicellular.
    Human skin cells  Blood cells traveling through the blood  vessel
  • Two Basic Cell Types
    • Prokaryotes (before nucleus)
    • Eukaryotes (true nucleus)
  • Prokaryotic Cells
    • do NOT have a true nucleus
    • do NOT have organelles surrounded by a membrane
    • DNA is in a region called a nucleoid
    • most metabolic functions take place in the cytoplasm
    • most prokaryotic organisms are single-celled (ex. Bacteria)
  • Eukaryotic Cells
    • have a true membrane-bound nucleus
    • have membrane-bound organelles
    • different parts of the cell specialize in different functions
    • majority of cells in the living world are eukaryotic
    • either unicellular or multicellular
  •  
  • Eukaryotic Cell Prokaryotic Cell Nucleus- a distinct central organelle that contains the cell's genetic material (DNA) Organelles-Specialized structures that carry out specific cell functions. Organisms that are made up of eukaryotic cells are called eukaryotes. Plasma Membrane- Special boundary that helps control what enters and leaves the cell. Has no nucleus or organelles. Organisms that are made up of prokaryotic cells are called prokaryotes. This includes most unicellular organisms like bacteria.
  • Organelles
    • membrane bound structures within the cell that carry out specialized functions
    • nucleus is the largest organelle
  • 7.2 The Plasma (Cell) Membrane pp. 187-190
  • Plasma (Cell) Membrane
    • Like your home – sheltered and comfortable
    • Plasma membrane- Barrier between the internal components of a cell and its environment
  • Homeostasis
    • the regulation of an internal environment to provide conditions suitable for life
    • living cells maintain homeostasis by controlling materials that enter and leave
    • Examples In: water, glucose, other nutrients
    • Examples Out: wastes
  • How does the cell membrane maintain homeostasis?
  • Selective Permeable Membrane
    • Selective - the property of a membrane that allows some materials to pass through while keeping others out (doorway)
    • Permeable – means easily pass through
  •  
  • Functions of the Plasma Membrane
    • barrier
    • selectivity
    • molecular recognition
    • export of wastes and cell products
    • import of nutrients
    • change in response to its environment
  • Structure of the Plasma Membrane Outside of cell Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains Inside of cell (cytoplasm)
    • composed of the phospholipid bilayer .
    Cellular Structure and Function
    • phospholipid molecule is made of a glycerol backbone, 2 fatty acid chains, and a phosphate group.
  • Structure of the Plasma Membrane
    • made of 2 layers of phospholipid molecules (bilayer)
    • protein molecules are embedded in the lipid bilayers
  • Phospholipids
    • have polar, water soluble heads
    • have long nonpolar, water insoluble tails
    • phospholipids are not chemically bonded to each other and are free to move about
  • Phospholipid Molecule
  • Fluid Mosaic Model
    • Fluid because the membrane is flexible (phospholipids & proteins move) free to move sideways within the membrane.
    • Proteins create a pattern (mosaic).
  • Polar/Non Polar Molecules
    • Most cells have a watery environment on the inside and outside.
    • Polar phosphate group allows the membrane to interact with its environment (water is polar).
    • Fatty acid tails (nonpolar) avoid water forming the interior of the membrane.
    • Phospholipid heads face the watery environment outside the cell.
  • Polar/Nonpolar Molecules
    • This means that water soluble molecules will not easily move through the membrane because they are stopped by this water-insoluble (phospholipid) layer.
  •  
  • Other Components of Plasma Membrane
    • Cholesterol
      • Rigid molecules
      • helps strengthen & stabilize the phospholipids
      • Prevents fatty acid chains from sticking together
  • Membrane Proteins
    • Most of the functions of the membrane are carried out by proteins.
  • Functions of the Membrane Proteins
    • Identify other molecules
    • determine which particles can pass across the membrane
    • move materials through the plasma membrane
    • Communicate between a cell and its environment
  • Functions of Membrane Proteins
    • Act as markers that are recognized by chemicals from both inside and outside the cell. These markers are involved in fighting diseases.
    • serve as enzymes
    • Aids in cell’s internal support structure
  • 7.3 Structures & Organelles (pp. 191-200)
  • 2 Types of Eukaryotic Cells Plant Cell Animal Cell
  • Cytoplasm
    • Jelly-like material that fills the space between the nucleus and cell membrane
    • More than half the volume of a cell
    • Important chemical reaction occur here
    • Suspends the organelles
  • Cytoskeleton
    • Network of thin, fibrous elements that act as a scaffold to provide support for organelles
    • Helps maintain cell shape (like tent poles)
    • Constantly changing structure
  • Cytoskeleton: composed of
      • Microtubules – thin, hollow cylinders made of protein
      • Microfilaments – thin, solid protein fibers
  • Centrioles
    • Occur in pairs
    • Formed by groups of microtubules
    • Important in cell division
  • Nucleus
    • manages all cell functions, all organelles
    • contains the cell’s DNA - master instructions for building proteins
  • Nucleus
    • master set of instructions for proteins contained in the chromatin
    • chromatin-strands of genetic material, DNA
    • when cell divides, chromatin condenses to form chromosomes
  • Nuclear Envelope
    • a double membrane that surrounds the nucleus
    • has large pores so materials can pass back and forth between the nucleus and the rest of the cell
  • Nucleolus
    • an organelle in the nucleus
    • a region that produces ribosomes which make proteins
  • Ribosomes
    • Although not bound by a membrane , they are considered organelles
    • only job is to make proteins
  • Endoplasmic Reticulum (ER)
    • Folded system of membranes that forms a network of interconnected compartments inside the cell
    • Provides a large surface area
  • Endoplasmic Reticulum (ER)
    • Contain enzymes for almost all lipid synthesis
    • Serve as the site of lipid synthesis in the cell
      • Rough ER – studded with ribosomes
      • Smooth ER – no attached ribosomes
  • Smooth & Rough Endoplasmic Reticulum Smooth ER lacks ribosomes & makes proteins USED In the cell Rough ER has ribosomes on its surface & makes proteins to EXPORT
  • Golgi apparatus
    • Closely stacked flattened
    • membrane sacs
    • Have a shipping side & a receiving side
    • Receives newly synthesized proteins and lipids from the ER in vesicles and redistributes them
    • Modifies proteins chemically, then repackages
    • Transport vesicles with modified proteins pinch off the ends
    • The ‘post office’ of the cell
    Transport vesicle
  • Vacuole
    • Membrane bound, temporary storage spaces
    • Store food, enzymes, wastes
    • Contractile vacuole – collects excess water and pumps it out of the cell
    • Central vacuole – single large vacuole that stores water in a plant cell
  • Lysosomes
    • Contain digestive enzymes
    • Digest excess or worn out cell parts, food particles, and invading viruses or bacteria
    • Can fuse with vacuole and dispense contents
    • Example:
      • digestion of a tadpole’s tail
      • the anterior end of a sperm cell
  • Mitochondria
    • “ Powerhouse” of the cell
    • Produces energy (ATP) from glucose
    • Consists of an outer membrane and a highly folded inner membrane
    • Numbers vary based on function of cell
  • In Animal Cells:
      • Active cells like muscles have more mitochondria
    Mitochondria
  • Chloroplasts
    • Found in green plants
    • & a few protists
    • Transforms light energy, carbon dioxide and water into carbohydrates - photosynthesis
    • Contain chlorophyll
    • Has a double membrane
    • Inner membranes arranged in stacks called grana, look like coins
  • Chlorophyll
    • Green pigment
    • Traps the energy from sunlight
    • Gives plants their green color
  • Plastids
    • group of organelles that includes chloroplast
    • Used for storage
    • Store starches, lipids or pigments
    • Named according to their color or pigment
    • Example: chlorophyll=chloroplasts
  • Cell Wall
    • surrounds the plasma membrane
    • much thicker than the plasma membrane
    • found in the cells of plants, fungi, most bacteria, and some protists (not in animal cells)
    • made of cellulose in plants- interwoven fiber network to protect and gives support
    • made of chitin in fungi
    • does not select which molecules can enter
  • Cilia
    • Short, numerous
    • Hair-like projections
    • Beating movement is coordinated much like the stadium “wave”
    • Used in locomotion in single-celled organisms
    • Made of a central pair of microtubules surrounded by nine additional pairs
  • Flagella
    • Longer projections
    • Whip-like motion
    • Not as numerous as
    • cilia
    • Used in locomotion in single-celled organisms
    • Made of central pair of microtubules and surrounded by nine additional pairs
    • Organelles video clip
  • Similarities between plant cells and animal cells
    • Both have a cell membrane surrounding the cytoplasm
    Both have a nucleus Both contain mitochondria
  • Differences between plant cells and animal cells Animal cells Plant cells Relatively smaller in size Irregular shape No cell wall Relatively larger in size Regular shape Cell wall present
  • Differences between Plant Cells and Animal Cells Animal cells Plant cells Vacuole small or absent Glycogen as food storage Nucleus at the center Large central vacuole Starch as food storage Nucleus near cell wall
  • Cellular Organization
    • Unicellular
    • Multicellular
      • Tissue
      • Organs
      • Organ system
      • Organism
  • 7.4 Cellular Transport pp. 201-207
  • Brownian Motion
    • 1827, Robert Brown observed pollen grains suspended in water
    • Grains moved constantly in little jerks as if being struck by invisible objects
    • He was observing evidence of the random motion of molecules colliding.
  • Passive Transport
    • Passive transport is the movement of particles across membranes by diffusion .
    • The cell uses no energy to move the particles.
    • Only a few substances are able to pass directly through the phospholipid bilayer in this manner.
    • examples; water, lipids, lipid-soluble substances
  •  
  • Diffusion
    • Movement of particles from a region of high concentration to an area of low concentration
    • The random collisions (Brownian motion) tend to scatter particles of solute and water until they are evenly mixed.
  • Factors That Affect the Rate of Diffusion
    • Concentration
    • Temperature
    • Pressure
  • Examples of Diffusion
  •  
  • Diffusion Across a Cell Membrane
    • Only molecules of water, oxygen, nitrogen, carbon dioxide, and a few other small nonpolar molecules can diffuse directly across the lipid bilayer.
  • Diffusion Across a Cell Membrane
    • The lipid bilayer makes it difficult for charged ions or polar molecules to pass through by diffusion because they are not attracted to the nonpolar structures of the fatty acid tails.
  • Dynamic Equilibrium
    • The condition, in which there is continuous movement of particles but no overall change in concentration.
    • Particles evenly distributed
  • Water is equal inside the cell and outside the cell.
  • Facilitated Diffusion
    • The passive transport of materials across the plasma membrane by transport proteins
    • Channel (transport) proteins provide openings for particles to pass through.
    • examples: sugars, amino acids
    • Carrier proteins change shape helping move the particle(s) through the membrane.
  • Osmosis
    • The diffusion of water molecules through a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration.
    • Important in maintaining homeostasis
  • Osmosis Examples
    • Strong sugar solution - lower concentration of water
    • Weak sugar solution - higher concentration of water
    • Organisms are subject to osmosis because they are surrounded by water solutions.
  • Concentration Gradient
    • The difference in concentration of a substance across a space
  • Osmosis Animation
    • Link to animation
  •  
  • Osmosis (out of the cell)
    • A cell will lose water by osmosis if it is placed in an environment in which the water concentration is lower than that of the cell contents
    • More water is inside the cell
    • Therefore, water will move out of the cell.
  • Osmosis (into the cell)
    • A cell will gain water if the water concentration is greater than that of the cell contents.
    • More water is outside the cell
    • Therefore, water moves in the cell
  • Isotonic Solution
    • A solution in which the concentration of dissolved substances is the same as the concentration inside the cell
    • Although water molecules move into and out of the cell, there is no net movement.
    • No osmosis occurs.
  • Isotonic Environment
  • Hypotonic Solution
    • A solution in which the concentration of dissolved substances is lower than the concentration inside the cell.
    • Osmosis will cause water to move into the cell.
    • The cell swells and its internal pressure increases.
    • Pressure that exists in a cell is called turgor pressure.
  • Hypotonic Environment
  • Hypertonic Solution
    • A solution in which the concentration of dissolved substances is higher than the concentration inside the cell.
    • Osmosis will cause water to leave the cell.
  •  
  •  
  • Hypertonic Environment
  •  
  • Osmosis Simulation View Internet Site
  • Key to Osmosis
    • The key to remember about osmosis is that water flows from the solution with the lower solute concentration into the solution with higher solute concentration.
  • Animal Cells in a Hypertonic Solution
    • Animal cells placed in a hypertonic solution will shrivel because of decreased pressure in the cells.
  • Effects of a Hypertonic Solution
    • You do not salt meat before cooking because the salt forms a hypertonic solution on the meat’s surface and the water inside the meat’s cells diffuses out. The result is cooked meat that is dry and tough.
  • Plant Cells in a Hypertonic Solution
    • If a plant cell is placed in a hypertonic environment, it will lose water and shrink away from the cell wall.
    • The resulting loss of turgor pressure is called plasmolysis.
    • This process will cause the plant to wilt.
  •  
  • Active Transport
    • Movement of molecules from an area of lesser concentration to an area of higher concentration
    • The cell must use energy .
    • Requires moving materials against a concentration gradient
    • examples: nutrients such as minerals that are scarce in the environment
  • How Active Transport Occurs
    • A transport protein binds with a particle of the substances to be transported.
    • Chemical energy is used to change the shape of the protein so that the particle to be moved is released on the other side of the membrane.
    • Once the particle is released, the protein’s original shape is restored.
    • Particles can be moved in or out of the cell.
  •  
  • Na + /K + ATPase Pump
    • Found in plasma membrane in animals
    • Maintains level of Na + /K + inside & outside the cell
    • 3 Na + out and 2 K + in
  •  
  • Transport of Large Particles
    • Endocytosis - the cell surrounds and takes in material from its environment
    • does not pass directly through the membrane
    • It is engulfed and enclosed by a portion of the cell’s membrane and creates a vacuole.
  • Transport of Large Particles
    • Exocytosis - the expulsion or secretion of materials from a cell
      • Expel wastes such as indigestible particles
      • Secrete substances such as hormones produced by the cell
    • Both endocytosis and exocytosis require energy and are forms of active transport.
  •  
  • Types of Transport Proteins
    • Channel Proteins
      • Passive transport – requires NO energy
      • Provides openings through which small particles, especially ions diffuse
    • Carrier Proteins
      • Active transport – requires energy
      • Picks up ions or molecules and carries them across the membrane to the other side