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Eukaryotic Cells. Animals & Plants. The Cell. Building block of the all organisms, from single-celled to human. 200 Types of cells in the human body, categorized by cell shape. Cell size limited by the volume and surface area ratio.

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eukaryotic cells

Eukaryotic Cells

Animals & Plants

the cell
The Cell
  • Building block of the all organisms, from single-celled to human.
  • 200 Types of cells in the human body, categorized by cell shape.
  • Cell size limited by the volume and surface area ratio.
    • If the cell is too big, it cannot support itself or absorb nutrients/excrete wastes effeciently.
classes of cell shapes
Classes of Cell Shapes
  • Squamous: Thin & flat cells covering surfaces or lining “tubes”
    • Example: Skin, lining of the esophagus
  • Cuboidal: Square or cube shaped; approximately as wide as they are tall.
    • Example: Liver cells
  • Columnar: Much taller than they are wide.
    • Example: Lining of the intestines
  • Spheroid: Egg cells and fat cells; round or oval.
  • Fusiform: Thick in the middle and tapered towards the ends.
    • Example: Smooth muscle cells
  • Stellate: Star-shaped cells.
    • Example: Some nerve cells
cell theory
Cell Theory
  • Based on Robert Hook, Theordore Schwann, & Louis Pasteur
  • Modern Cell Theories’ Generalizations:
    • All organisms are composed of cells and cell products.
    • The cell is the simplest structural and functional unit of life.
    • All functions and structures are ultimately due to the activities of cells.
    • Cells come only from pre-existing cells.
    • The cells of all species have many fundamental similarities.
general cell structure
General Cell Structure
  • Eukaryotic cells all have the following general structures:
    • Cell Membrane
    • Cytoplasm
    • Nucleus
    • Intracellular Organelles
cell membrane
Cell Membrane
  • All cells are surrounded by a plasma membrane made up of proteins and lipids
  • Bilayer of lipids with diverse proteins embedded in it
  • 98% of membrane molecules are lipids
    • 75% of these are phospholipids
cell membrane1
Cell Membrane
  • Phospholipid Bilayer:
    • Two phospholipid layers thick
    • Hydrophilic heads facing the water on each side of the cell membrane.
    • Hydrophobic tails directed toward the center of the membrane (avoiding the water)
    • Membrane is dynamic and “fluid”
cell membrane2
Cell Membrane
  • Cell Membrane is the target site of many pharmaceutical agents
  • Proteins only make up 2% of the molecules in a plasma membrane, but are larger then lipids and make up around 50% of the membrane weight.
cell membranes
Cell Membranes
  • Integral or Transmembrane Proteins: Pass across the plasma membrane and are responsible for many functions. Integral proteins function as…
    • Receptors: Specific for one messenger
    • Second-messenger Systems: Triggered by messengers that bind with surface receptors
    • Enzymes: Produce second messengers and help with digestion in the small intestine
    • Channel Proteins: These molecules have “pores” & allow passage of water & other solutes through the membrane
    • Carriers: Also called “PUMPS” they actively transport molecules into the cell utilizing ATP in the process
  • The “fuzzy” coat external to the plasma membrane on all animal cells, including humans
  • Acts as an “identification” tag that enables the body to distinguish its own healthy cells from transplanted tissue, invading organism, and diseased cells.
surface extensions
Surface Extensions
  • Surface extensions aid in absorption, movement, and sensory processes.
  • Microvilli: Extensions of the plasma membrane; serve primarily to increase a cell’s surface area; best developed in cells that specialized in absorption (e.g. the cells lining the small intestine)
surface extensions1
Surface Extensions
  • Cilia: Multiple hair-like processes that project from the surface of the cell
    • Nonmotile Primary Cilium: Nearly every human cell has a single nonmotile primary cilium.
    • Motile Cilia: Less widespread but occur widely in respiratory tract and fallopian tubes; “wave” to help move materials through internal tubes
surface extensions2
Surface Extensions
  • Flagella: A single whip-like structure much longer than cilia.
    • The only functional flagellum in humans is the tail of the sperm cell.
  • Cytoplasm: The fluid that is contained inside the plasma membrane.
    • Crowded with fibers, tubules, passageways, and compartments.
    • Contains cytoskeleton (supportive framework) and intracellular organelles embedded in the cytosol or Intracellular fluid (ICF).
extracellular fluid
Extracellular Fluid
  • Extracellular fluid (ECF) is the fluid outside the cell.
  • Nucleus: The structure at the center of the cell containing the genetic information for the organism.
  • Nucleic Acid: DNA or RNA.
    • DNA is the principle type of nucleic acid contained in the cell nucleus.
      • DNA contains the genetic code for organisms and is involved in protein synthesis, cell division (mitosis), and reproduction of the organism.
plasma membrane
Plasma Membrane
  • Plasma Membrane: Acts as a barrier and gateway between the cytoplasm and the extracellular fluid.
  • Selectively Semi-Permeable: The plasma membrane lets some things through and blocks other things; this is tremendously important in clinical practice!
plasma membrane1
Plasma Membrane
  • Methods of Transporting Substances: Passive and Active transport.
  • Passive Transport includes…
    • Filtration
    • Diffusion
    • Osmosis
  • Active Transport requires ATP and includes…
    • Active transport
    • Vesicular transport
  • Filtration: The process by which particles are driven through a filter, or selectively permeable membrane, via hydrostatic pressure exerted on a membrane by water.
    • Example: Coffee Filter
      • Weight of water forces water through the grounds and coffee filter.
      • Filter holds back the larger particles (coffee grounds)
    • Most important filtration in the human body occurs in the capillary wall – transfer of water, salts, nutrients, etc. from blood stream to tissue and extracellular fluid & wastes to kidneys
simple diffusion
Simple Diffusion
  • Simple Diffusion: The net movement of particles from an area of higher concentration to an area of lower concentration.
    • The result of constant, spontaneous movement of molecules known as Brownian Movement.
  • Concentration Gradient: When the concentration of a substance differs from one point to another.
  • Movement occurring down or with the concentration gradient is movement from the higher concentration area to the lower.
simple diffusion1
Simple Diffusion
  • IF the membrane is semi-permeable and permeable to that substance, than diffusion will occur.
  • IF the membrane is not permeable to the substance, it will not diffuse across the membrane.
diffusion rates
Diffusion Rates
  • Diffusion Rates: Important to cell survival because they determine how quickly a cell can acquire nutrients or rid itself of wastes.
  • Factors affecting diffusion rate:
    • Temperature: The higher the temp, the faster the diffusion rate.
    • Molecular Weight: Heavy molecules diffuse more slowly.
    • Membrane Surface Area: The more surface area the faster the diffusion rate.
    • “Steepness” Of Concentration Gradient: The greater the concentration difference, the faster the diffusion.
    • Membrane Permeability: The permeability of the membrane.
    • Diffusion Distance: Distance diffusion occurs across.
    • Facilitated Diffusion: Whether a solute binds to a specific transporter (changes the shape and releases the solute on the other side of the membrane).
  • Osmosis: The diffusion of water through a selectively permeable membrane from the area of higher concentration to the area of lower concentration.
    • The higher solvent (water) concentration area has a low solute concentration.
    • The higher solute concentration has a low solvent concentration.
  • Tonicity: The ability of a solution to affect the fluid volume and the pressure in a cell.
    • If a solute cannot pass through a plasma membrane, but remains more concentrated on one side of the membrane than on the other, it triggers osmosis.
  • Hypotonic Solution: Area surrounding a cell has a lower concentration of nonpermeating solutes than the intracellular fluid.
    • Cells absorb water, swell, and lyse (burst).
  • Hypertonic Solution: Area surrounding cell has a higher concentration of nonpermeating solutes than the intracellular fluid.
    • Cells will lose water and crenate (shrivel).
  • Isotonic Solution: The area surrounding the cell has the same total concentration of nonpermeating solutes as the intracellular fluid.
    • Cells will neither loose nor gain water molecules & do not change size or shape.
active transport
Active Transport
  • Active Transport: The carrier-mediated transport of a solute through a plasma membrane but against a concentration gradient.
    • Utilizes ATP and energy to move against the normal concentration gradient from an area of low concentration to high concentration.
  • Example: The sodium-potassium pump.
sodium potassium pump
Sodium-Potassium Pump
  • Used to regulate the balance of sodium and potassium within the cell.
  • 1 ATP molecule exchanges 3 sodium atoms (Na+) for 2 potassium (K+) atoms.
    • Keeps the potassium higher and sodium lower within the cell.
    • Plasma membrane continuously leaks Na+ and K+, so the pump keeps the balance corrected.
    • Na+ and K+ play a critical part in nerve impulses and cardiac function.
vesicular transport
Vesicular Transport
  • Vesicular transport moves large particles and droplets of fluid or numerous molecules through the plasma membrane all at once.
  • Endocytosis: Vesicular processes that bring matter into the cell. Two types:
    • Phagocytosis: “Cell eating” where foreign particles are engulfed (e.g. monocytes)
    • Pinocytosis: “Cell drinking” where droplets of extracellular fluid containing molecules used by cells are taken in.
  • Exocytosis: Vesicular processes that release matter from the cell.
  • Organelles: The internal structures within a cell that carry out specific functions.
    • Some are surrounded by one or two layers of a unit membrane and are therefore referred to as “membranous organelles.”
  • Membranous Organelles: Nucleus, mitochondria, lysosomes, endoplasmic reticulum, golgi complex.
  • Non-Membranous Organelles: Ribosomes, centrosome, centrioles, basal bodies.
membranous organelles nucleus
Membranous Organelles: Nucleus
  • Nucleus: The largest organelle, spheroid in shape.
    • Most cells have a single nucleus
    • Nucleus surrounded by nuclear envelope or membrane
  • Nucleoplasm: The material contained within the nucleus.
    • Includes…
      • Chromatin (DNA and protein)
      • Nucleoli (produces ribosomes)
membranous organelles endoplasmic reticulum er
Membranous Organelles: Endoplasmic Reticulum (ER)
  • Endoplasmic Reticulum: “Little network within the cytoplasm”
  • A system of interconnected channels that extend through the cytoplasm and reach the nuclear membrane.
    • Channels called Cisternae
membranous organelles endoplasmic reticulum er1
Membranous Organelles: Endoplasmic Reticulum (ER)
  • Two Types:
    • Rough Endoplasmic Reticulum: Channels are covered with ribosomes (synthesize proteins).
    • Smooth Endoplasmic Reticulum: Extends from the Rough ER to form membranous tubules network.
  • Smooth ER synthesizes steroids & lipids
  • Rough ER is responsible for detoxifying alcohol and other drugs
  • Rough ER most abundant in cells that produce large amounts of proteins – such as those in the digestive glands
membranous organelles golgi complex
Membranous Organelles: Golgi Complex
  • Golgi Complex: The small system of cisternae which synthesize carbohydrates and put the finishing touches on protein and glycoprotein synthesis.
membranous organelles golgi complex1
Membranous Organelles: Golgi Complex
  • Primary function is to package protein into membrane-bound golgi vesicles
  • Some become secretory vesicles and store cell products such as breast milk & digestive enzymes
    • Some of these can become lysosomes
membranous organelles lysosomes
Membranous Organelles: Lysosomes
  • Lysosomes: A package of enzymes which are bounded by a single unit membrane – usually produced by the Golgi complex
    • Primary function is to hydrolyze or digest proteins, nucleic acids, complex carbohydrates, and phospholipids
    • Autophagy: The digestion of surplus cells by their own lysosomal enzymes (as in the liver).
membranous organelles peroxisomes
Membranous Organelles: Peroxisomes
  • Peroxisomes: Resemble lysosomes but are smaller and contain different enzymes (oxidase) and are not produced by the Golgi Complex\
membranous organelles mitochondria
Membranous Organelles: Mitochondria
  • Mitochondria: Organelles specialized for synthesizing ATP
    • Power-house of cells
    • Bean shaped
    • Outer and inner membranes
    • Generate most of the cell’s ATP
    • Cristae contain enzymes for aerobic respiration
    • Matrix enclosed in the inner membrane; site of oxidation of organic molecules; contains DNA and ribosomes.
non membranous organelles ribosomes
Non-Membranous Organelles: Ribosomes
  • Ribosomes: Small granules of protein and ribosomal RNA found in several places in the cytoplasm:
    • On Rough ER
    • In the Nuclear Envelope
    • Floating freely in cytoplasm
  • Primary function is protein synthesis.
non membranous organelles ribosomes1
Non-Membranous Organelles: Ribosomes
  • Responsible for assembling amino acids based on messenger RNA codes.
non membranous organelles centrioles
Non-Membranous Organelles: Centrioles
  • Centrioles: A short cylindrical assembly of microtubules.
    • 2 centrioles lie at right angles to each other within a small clear area of cytoplasm called the centrosome
      • Play a role in cell division – Mitosis
  • Cytoskeleton: A collection of protein filaments and cylinders that determine the shape of a cell.
    • Lend structural support
    • Organize cellular contents
    • Help move stuff through the cell
    • Contribute to movements of the cell
    • Connected to integral proteins of the plasma membrane
    • Made up of microfilaments and microtubules
  • Inclusions: 2 Kinds
    • Stored cellular products such as glycogen granules or fat droplets OR foreign bodies such as dust particles
    • NO unit membrane
    • Not essential to cell survival
    • Not organelles
    • Temporary structures; not permanent
  • Mitosis: The process by which cells divide to grow or to repair damage. 4 Stages:
    • Prophase
    • Metaphase
    • Anaphase
    • Telophase
  • Prophase: Condensing of chromatin fibers into chromatid pairs
  • Metaphase: The chromatid pairs line up along the metaphase plate
  • Anaphase: The centromeres joining the chromatids split, identical sets move to opposite sides of the cell
  • Telophase: Nucleoli reappear around two new sets of chromosomes and cell begins to split for cytokinesis – the division of the cell material.