Biology 110

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Chapter 3 Cells and Tissues

• Biology 110
• Tri-County Technical College
• Pendleton, SC

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Generalized Cell

• No one cell type exactly like all others
• Do have same basic parts and certain functions
  common to all cells
• GENERALIZED CELL constructed to demonstrate these
  typical features
• We will concern ourselves with generalized
  eukaryotic (eucaryotic) cell

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General Areas of Eukaryotic Cell

• In general, eukaryotic cells have 3 main regions
• NUCLEUS located near center of cell
• CYTOPLASM is semifluid material that surround
  nucleus and extends to the PLASMA MEMBRANE which
  forms the outer boundary of the cell

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Organelles

• little organs
• Specialized cellular COMPARTMENTS designed to
  perform SPECIFIC job
• Most bounded by membrane (some bilayer)
• Compartmentalization crucial to their ability to
  perform specialized functions
• ER, Golgi apparatus, lysosomes, mitochondria,
  peroxisomes, cytoskeleton

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Functions and Parts of Nucleus

• Control cell for cell containing its DNA
• Surrounded by bilayer nuclear membrane
• Has three distinct regions (structures)
• NUCLEAR MEMBRANE
• NUCLEOLUS (nucleoli)
• CHROMATIN

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The Nuclear Membrane

• Bilayer of phospholipids with nuclear pores
• Semipermeable
• Controls what enters and exits the nucleus
• Encloses the nucleoplasm
• Jellylike fluid in which the nucleoli and
  chromatin are suspended

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The Nucleolus

• May only be one, but some cells have several
• Stains darker than other regions of DNA
• Is site where ribosomal RNA is transcribed off
  info in DNA
• Combined with protein(s) to form functional
  ribosome
• Review ribosomes are actual site of protein
  synthesis

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DNA and its Forms

• CHROMATIN is loose network of threads of DNA
• Unwound, not supercondensed or supercoiled
• Easy for replication and transcription to occur
• Must be duplicated in S of interphase
• In dividing cells, chromatin condenses into
  CHROMOSOMES (Xwell, kind of)

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The PM and moremuch more

• Bilayer of phospholipids with proteins and other
  molecules floating in layer
• Review fluid mosaic model
• Pores, carriers, transporters, receptors,
  enzymes
• Cholesterol and glycoproteins in layers
• GPs determine blood type act as receptors for
  certain bacteria, viruses, or toxins play role
  in cell-to-cell interactions

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The PM, continued

• Specializations (epithelial cells lining hollow
  body cavities such as small intestine) occur as
  MICROVILLI and/or MEMBRANE JUNCTIONS
• MICROVILLI increase surface area of cell so
  absorption can occur more quickly
• Membrane junctions vary structurally depending on
  their role

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Types of Membrane Junctions

• Tight junctions are impermeable junctions that
  bind cells into leakproof sheets
• Stomach and small intestine best examples
• Desmosomes are anchoring junctions that prevent
  cells subjected to mechanical stress from being
  pulled apart
• Button-like thickenings of PM connected by fine
  protein filaments
• Gap junctions allow for communication
• Heart and between embryonic cells
• Neighboring cells connected by CONNEXONS
• Composed of protein that span entire width of
  abutting membranes

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Cytoplasm

• Cellular material outside nucleus and inside PM
• Site of most cellular activities
• Has 3 major components
• CYTOSOL is semitransparent fluid that suspends
  other elements
• ORGANELLES (already defined)
• INCLUSIONS are nonfunctioning units
• Most are stored nutrients or cell products
• Fat droplets, glycogen, pigments (melanin) mucus,
  secretory products, and various kinds of crystals

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The Mitochrondrion

• Powerhouse of the cell
• Important in aerobic respiration
• Krebs cycle and chemiosmosis
• Important parts outer membrane, inner membrane
  highly folded (CRISTAE)
• Gelatinous fluid inside the cristae called the
  MATRIX

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Ribosomes

• Composed of rRNA and proteins
• Actual site of translation (protein synthesis)
• Some float free in cytoplasm while others
  attached to endoplasmic reticulum (RER)
• Functional ribosome composed of two subunits
• 80S and 70S and never the twain will meet

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Endoplasmic Reticulum

• System of fluid-filled cisterns in cytoplasm
• Rough ER studded with ribosomes
• Very important in manufacturing proteins destined
  for export from the cell
• Enzymes that catalyze membrane lipid synthesis
  reside on outer surface of RER
• Smooth ER has no ribosomes
• Cholesterol synthesis and breakdown, fat
  metabolism, and is detox center for the cell
• Liver cells and cells that synthesize
  steroid-based hormones packed with SER

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Golgi Apparatus

• Stack of flattened membranous sacs associated
  with swarms of tiny vesicles
• Traffic director for cellular proteins
• UPS of the cell
• Receives, modifies, packages, and ships cellular
  products
• Transport vesicle?Golgi?secretory vesicles
• Most SVs exit cell by exocytosis (mucus and
  digestive enzymes)
• Also produces lysosomes

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Lysosomes

• Breakdown bodies filled with potent digestive
  enzymes
• Recycle old/worn-our cellular structures digest
  most foreign substances that enter cell
• Are cells demolition sites
• Especially abundant in WBCs that engulf bacteria
  other harmful substances
• Lysosomal enzymes made by ribosomes and packaged
  by Golgi apparatus

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Peroxisomes

• Membranous sacs containing oxidase enzymes to
  detoxify harmful/poisonous substances
• MOST important function is to neutralize free
  radicals (by product of respiration)
• Unpaired electrons electron stealing
• Superoxide radical hydrogen peroxide
• CATALASE converts hydrogen peroxide to water and
  oxygen
• Numerous in liver and kidney cells

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Cytoskeleton

• Elaborate network of protein structures extending
  throughout cytoplasm
• Bones and muscles which furnish internal
  framework that determine cell shape, supports
  other organelles, and provides machinery needed
  for intracellular transport and various types of
  cellular movements
• Can be assembled and disassembled as needed
• Some components fairly permanent

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Cytoskeleton Components

• Intermediate filaments help form desmosomes and
  important to internal stability
• Microfilaments (actin/myosin) involved in cell
  motility and cell shape changes
• Microtubules determine overall shape of cell and
  distribution of organelles
• very important in cell division

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Centrioles

• Paired centrioles lie close to nucleus in animal
  cells
• Rod-shaped and lie at right angles to each other
• Composed of microtubules
• Direct formation of mitotic spindle
• Responsible for cilia and flagella

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Organelles of Locomotion

• Cilia and Flagella
• Cilia responsible for moving substances across
  cells surface
• Flagella responsible for moving the cell itself
• Respiratory tract and oviduct have cells with
  cilia
• Only flagellated human cell is a sperm cell

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Major aspects of cell physiology

• Most cells have ability to metabolize
• Use nutrients to build new cell material, break
  down substances, and make ATP
• Also have ability to digest food, dispose of
  wastes, reproduce, grow, move, and respond to a
  stimulus (irritability)
• We like to think of the human entity as total or
  complete but all of items above OCCUR at the
  cellular level

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Bodys Fluid Compartments

• INTRACELLULAR fluid (nucleoplasm and cytosol) is
  solution containing small amts of gases,
  nutrients, and salts
• INTERSTITIAL FLUID is fluid that bathes the
  exterior of cells
• Rich, nutritious, and unusual soup
• Contains 1000s of ingredientsnutrients (amino
  acids, sugars, fatty acids, vitamins), regulatory
  substances (hormones/neurotransmitters), salts,
  and wastes products

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Selective Permeability

• Means barrier that allows some substances to pass
  through while excluding others
• PM of cell is selective permeable
• Allows nutrients to enter cell but keeps many
  undesirable products out
• Keeps valuable cell proteins and other substances
  within cell
• Allows wastes to pass out of cell

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Passive Processes

• Cell does NOT have to invest any energy for
  passive transport processes
• Simple diffusion and filtration
• Review on diffusion available space kinetic
  energy and down gradient
• Affected by size of molecule and temperature
• Review PM bilayer structure
• Unassisted diffusion of solutes through PM
  simple diffusion
• Lipid soluble, O2, CO2, some small ions

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Facilitated Diffusion

• Substances too large for pores require transport
  protein in PM
• still moving down their gradient
• Glucose (lipid insoluble and too large for pores)
• Binds to transport protein causing change in its
  shape?transported into cell?released
  inside?transport protein returns to its original
  shape
• REMEMBER simple diffusion and facilitated
  diffusion are PASSIVE processes

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Water, water, everywhere.

• Osmosis defined as movement of water through a
  selectively permeable membrane
• Not quite accurate, but close enough
• Remember water is POLAR
• Does pass through pores created by proteins
• Aquaporins
• Movement determined by gradient
• Greater of nonpermeable solutes in solution,
  the lower the water of that solution and the
  greater the osmotic pressure

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Osmosis, continued

• Water always tends to diffuse toward solutions of
  greater osmotic pressure
• Ability of solution to change size and shape of
  cells by altering amount of water they contain is
  called TONICITY
• HYPERTONIC, HYPOTONIC, ISOTONIC
• ISOTONIC Ringers lactate, 5 dextrose, 0.9
  saline solution
• KEY water will move (if it can) from hypotonic
  to hypertonic solution

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Filtration

• Process by which water and solutes are forced
  through membrane (or capillary wall) by fluid
  (hydrostatic) pressure
• Passive process and gradient is involved
• Gradient involved is PRESSURE GRADIENT
• From higher to lower pressure
• Filtration necessary for kidneys to do their job

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Active Transport Processes

• Active transport occurs when cell uses ATP to
  move substances across membrane
• Substances may be too large, nonlipid soluble,
  charged, or may have to move AGAINST their
  gradient
• Best two examples of active transport are SOLUTE
  PUMPING and BULK TRANSPORT

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Solute Pumping

• Requires transport proteins in membrane and
  expenditure of ATP
• Amino acids, some sugars, and most ions
  transported via SP
• Sodium-potassium pump necessary for normal
  transmission on nerve impulses
• SP provides way for cell to be very selective in
  cases where substances cannot pass by diffusion

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Bulk Transport

• Endocytosis-processes by which cell takes up, or
  engulfs, extracellular substances by enclosing
  them in small membranous vesicle
• If large particles engulfed, endocytosis process
  called PHAGOCYTOSIS (to eat)
• WBCs
• If cell takes in liquids that contain dissolved
  fats/proteins, or ions, endocytosis called
  PINOCYTOSIS (to drink)
• Pinocytosis regular activity for most cells
  (small intestine lining and kidney tubule cells

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Bulk Transport, continued

• EXOCYTOSIS moves things out of the cell
• Hormones, mucus, cellular products, or cellular
  wastes
• Product to be released packaged by Golgi
  apparatus into small vesicles which migrate to
  PM, fuses with PM, releases product to outside of
  cell

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Mitosis and Cytokinesis

• Mitosis is nuclear division process that KEEPS
  THE COUNT THE SAME
• Cytokinesis process that divides the cytoplasm
  and organelles
• Mitosis produces clones barring a mutation
• KEY Mitosis produces two daughter cells and
  keeps the chromosome count the same

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Cell Cycle

• Chalk-talk time on cell cycle
• G1, S, G2, mitosis/meiosis, cytokinesis
• G1, S, G2 collectively called Interphase
• Chromatin is replicated during S phase
• Mitosis/Meiosis consists of Prophase, Metaphase,
  Anaphase, and Telophase
• KEY EVENTS OF EACH

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Protein Synthesis

• Transcription and Translation
• DNA, mRNA, tRNA, and rRNA
• Initiation, elongation, and termination
• Codons and anticodons
• Genetic code
• Chalk talk time on protein synthesis
• GENES are sections of DNA that code for
  functional products (carries info for building
  one protein/one polypeptide

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