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Chapter 6: A Tour of the Cell. Essential Knowledge. 2.a.2 – Organisms capture and store free energy for use in biological processes (6.2). 2.b.3 – Eukaryotic cells maintain internal membranes that partition the cell into specialized regions (6.2-6.5).

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essential knowledge
Essential Knowledge
  • 2.a.2 – Organisms capture and store free energy for use in biological processes (6.2).
  • 2.b.3 – Eukaryotic cells maintain internal membranes that partition the cell into specialized regions (6.2-6.5).
  • 4.a.2 – The structure and function of subcellular components, and their interactions, provide essential cellular processes (6.2-6.5).
  • 4.b.2 – Cooperative interactions within organisms promote efficiency in the use of energy and matter (6.4).
light microscope lm
Light Microscope - LM
  • Uses visible light to illuminate the object
  • Relatively inexpensive type of microscope
  • Can examine live or dead objects
  • Light passes through specimen and then through various lenses
  • Lenses refract/bend light to magnify
light microscope
Light Microscope

Occular Lens

Objective Lens

Stage with specimen

Light Source

limitations lm
Limitations - LM
  • Miss many cell structures that are beyond the magnification of the light microscope
    • Ex: lysosomes, centrioles
  • Need other ways to make the observations
electron microscopes
Electron Microscopes
  • Use beams of electrons instead of light
  • Invented in 1939, but not used much until after WWII
  • Advantages:
    • Much higher magnifications
    • Magnifications of 50,000X or higher are possible.
    • Can get down to atomic level in some cases
disadvantages of em
Disadvantages of EM
  • Need a vacuum
  • Specimen must stop the electrons
  • High cost of equipment
  • Specimen preparation
other types of microscopes
Other Types of Microscopes
  • Transmission Electron Microscope - TEM
    • Sends electrons through thinly sliced and stained specimens
    • Gives high magnification of interior views. Many cells structures are now visible
  • Scanning Electron Microscopes – SEM
    • Excellent views of surfaces
    • Produces 3-D views
    • Live specimens possible
limitations to em
Limitations to EM
  • TEM:
    • Specimen dead; specimen prep is difficult
  • SEM:
    • Lower magnifications than the TEM; only see surface of specimen

TEM - interior

SEM - surface

cell biology or cytology
Cell Biology or Cytology
  • Cyto = cell - ology = study of
  • Should use observations from several types of microscopes to make a total picture of how a cell is put together
  • Directly related to biochemistry
tools for cytology
Tools for Cytology
  • Cell Fractionation
  • Chromatography
  • Electrophoresis
cell fractionation
Cell Fractionation
  • Disrupt cells
  • Separate parts (organelles and membrane) by centrifugation at different speeds
    • Separates by size and density of the various structures
  • Result - pure samples of cell structures for study
  • Technique for separating mixtures of chemicals
  • Separates chemicals by size or degree of attraction to the materials in the medium
  • Ex - paper, gas, column, thin-layer
  • Separates mixtures of chemicals by their movement in an electrical field
  • Used for proteins and DNA
cell history
Cell History
  • See alternate Ppt
history of cells
History of Cells
  • Robert Hooke - Observed cells in cork
  • Coined the term "cells” in 1665
    • Came from “jail cells” and/or monastery cells
  • Cells:
    • Al life is made of cells!!!
    • Cells are the simplest form of life
history of cells1
History of Cells
  • 1833 - Robert Brown, discovered the nucleus
  • 1838 - M.J. Schleiden, all plants are made of cells
  • 1839 - T. Schwann, all animals are made of cells.
  • 1840 - J.E. Purkinje, coined the term “protoplasm”
  • Late 1800s – Rudolf Virchow (“Omnis cellula e cellula” - All cells are from other cells)
cell theory 3 parts
Cell Theory: 3 Parts
  • All living matter is composed of one or more cells.
  • The cell is the structural and functional unit of life.
  • Cells come only from existing cells.
two types of cells
Two Types of Cells
  • 1) Prokaryotic- lack a nucleus and other membrane-bound structures.
  • 2) Eukaryotic- have a nucleus and other membrane-bound structures.



cell diversity
Cell diversity
  • Most cells are between 5-50 micrometers
  • Mycoplasmas - bacteria that are .1 to 1.0 mm. (1/10 the size of regular bacteria)
  • # of cells: uni- and multicellular
why are cells so small
Why Are Cells So Small?
  • Cell volume to surface area ratios favor small size
  • Nucleus to cytoplasm consideration (control)
  • Metabolic requirements
surface area v volume
Surface area v. Volume
  • Vol and SA are proportionate (if one increases, the other increases)
  • Vol increases more than surface area (as cell grows)
    • Smaller objects have a greater ratio of sa to vol
  • Structure/Function:
    • Villi in intestinal cells – inc sa so cells can absorb more materials from food
basic cell organization
Basic Cell Organization
  • Membrane*
  • Nucleus
  • Cytoplasm*
  • Organelles
  • DNA/RNA*

*EVERY cell has these 3 parts

cell membrane
Cell Membrane
  • Separates the cell from the environment
  • Boundary layer for regulating the movement of materials in/out of a cell
  • Often called plasma membrane
  • Bilayer of phospholipids
  • Allows oxygen, nutrients, wastes to pass through a series of processes:
      • Diffusion
      • Osmosis
      • Active transport
  • Cell substance between the cell membrane and the nucleus
  • The “fluid” part of a cell.
  • Neutral pH (serves as a natural buffer)
  • Exists in two forms:
    • gel - thick
    • sol - fluid
  • Term means "small organ”
  • Formed body in a cell with a specialized function
  • Important in organizational structure of cells
  • More prominent/numerous in eukaryotic cells
  • Ex: Mitochondria, Endoplasmic reticulum, lysosomes
  • Most obvious organelle
  • Usually spherical, but can be lobed or irregular in shape
  • Contains genetic info
  • Found ONLY in euk cells
  • Function/s:
    • Control center for the cell
    • Contains the genetic instructions
    • Controls protein synthesis by making mRNA and rRNA (from DNA)
structure of nucleus
Structure of Nucleus
  • Nuclear membrane
  • Nuclear pores
  • Nucleolus
  • Chromatin
nuclear membrane
Nuclear Membrane
  • Otherwise known as Nuclear Envelope
  • Double membrane (lipid bilayer) separated by a 20-40 nm space
  • Inner membrane supported by a protein matrix (nuclear lamina) which gives the shape to the nucleus
  • Separates nuclear contents from cytoplasm
  • Dissolves during cell division
nuclear pores
Nuclear Pores
  • Regular “holes” through both membranes
  • 100 nm in diameter
  • Protein complex gives shape
    • Lines every nuclear pore
  • Allows materials, such as macromolecules, in/out of nucleus
  • Dark staining area in the nucleus
  • 0 - 4 per nucleus
  • Storage area for ribosomes
  • rRNA made here (from DNA)
  • No membrane encloses it??? (Research about nucleolus continues!!!)
  • Chrom: colored - tin: threads
  • DNA and protein in a “loose” format
  • Will form the chromosomes during Interphase of cell division (Chromosomes more condensed)
  • Each eukary cell has specific #
  • Structure: 2 subunits made of protein and rRNA
  • No membrane
  • Function: protein synthesis
    • The more occurrences of protein synthesis, the more ribosomes
    • Ex: Pancreatic cells have over 1.2 million ribosomes
ribosome structure
Ribosome structure
  • 2 Subunits:
    • 1) Large
      • 45 proteins, 3 rRNA molecules
    • 2) Small
      • 23 proteins, 1 rRNAmolecule
  • 2 Locations:
    • 1) Free in the cytoplasm- make proteins for use in cytosol
    • 2) Membrane bound- make proteins that are exported from the cell (Attached to rough ER)
endomembrane system
Endomembrane System
  • Series of membranes connected by direct physical continuity or by transfer of membrane segments called vesicles
  • Includes: ER, Golgi, vesicles
  • Function: protein synthesis, transport of proteins, move lipids, detoxify proteins
  • Works closely with: nucleus, lysosomes, ribosomes, plasma membrane
endoplasmic reticulum
Endoplasmic Reticulum
  • Often referred to as ER
  • Makes up to 1/2 of the total membrane in cells
  • Often continuous with the nuclear membrane/pores
    • All cisternae (inner portion) are connected
  • Structure:
    • Folded sheets or tubes of membranes
    • Very “fluid” in structure with the membranes constantly changing size and shape.
2 types of er
2 Types of ER
  • 1) Smooth ER: no ribosomes
    • Used for lipid synthesis, carbohydrate storage, detoxification of poisons
    • Ex: store calcium ions, sex hormones contain LOADS of these (lipid synthesis)
  • 2) Rough ER: with ribosomes
    • Makes secretory protein and lipid parts of cell membrane
    • Ex: liver cells (add water to detoxify proteins to secrete), insulin (secretory protein)
    • Most proteins are called glycoproteins (contain protein and carb parts)
golgi apparatus or dictyosomes
Golgi Apparatus or Dictyosomes
  • Structure: parallel array of flattened cisternae (looks like a stack of Pita bread)
  • 3 to 20 per cell
  • Likely an outgrowth of the ER system
  • Think of the UPS man
2 faces of golgi
2 Faces of Golgi
  • 1) Cisface- side toward the nucleus Receiving side
    • Located near ER
  • 2) Trans face- side away from the nucleus. Shipping side
    • Gives rise to vesicles
  • Both contain varying polarity
function of golgi
Function of Golgi
  • Processing - modification of ER products
  • Distribution - packaging of ER products for transport
  • Sorting and Shipping
  • UPS man/organelle!!!
  • Found in large #s in secretory cells
  • Ever-changing organelle
transport vesicles
Transport Vesicles
  • Secretory proteins in transit from one organelle to another
  • Two kinds:
    • 1) From ER to Golgi
    • 2) From Golgi to ?
      • Otherwise known as Golgi vesicles
golgi vesicles
Golgi Vesicles
  • Small sacs of membranes that bud off the Golgi Body
  • Transportation vehicle for the modified ER products
    • May become polypeptide chains or amino acids
  • Contain identifiers to help determine where destination is
  • Single membrane – made by rough ER
  • Made from the Trans face of the Golgi apparatus
  • Functions:
    • Breakdown and degradation of cellular materials
      • Carry out intracellular digestion
    • Digest cell’s own materials
      • Called autophagy
      • Digest old, non-repairable items
    • Contains hydrolytic enzymes to breakdown fats, proteins, polysaccs, and nucleic acids
lysosome function cont
Lysosome Function, cont.
  • Important in cell death (apoptosis)
  • Missing enzymes may cause various genetic enzyme diseases
    • Examples:
      • Tay-Sachs, Pompe’sDisease
      • Tay-Sachs: Can’t break down lipid in brain (accumulates and causes nervous system disorders)
  • Structure - single membrane, usually larger than the Golgi vesicles
  • Function - depends on the organism (most control hydrolysis and store materials)
  • Types - Food, contractile, central
  • Function:
    • Water regulation - hydrolysis
    • Storage of ions
    • Storage of hydrophilic pigments (e.g. red and blues in flower petals)
      • Helps attract pollinators
protist vacuoles
Protist vacuoles
  • Contractile vacuoles - pump out excess water.
  • Food vacuoles - store newly ingested food until the lysosomes can digest it
plant vacuoles
Plant vacuoles
  • Large single vacuole in mature (making up to 90% of the cell's volume)
  • Tonoplast - vacuole membrane
    • Regulatory (Semi-permeable)
  • Function:
    • Used to enlarge cells and create turgor pressure
      • Absorb water
    • Store enzymes (various types)
    • Store toxins
    • Coloration (may contain pigment)
  • Contain specialized enzymes for specific reactions
  • Peroxisomes: use up H peroxide
    • Some break down fatty acids, detoxify poisons
  • Glyoxysomes: lipid digestion
    • Found in plant seeds (used for energy storage)
energy transforming organelles
Energy Transforming Organelles
  • 1) Mitochondria
    • Found in ALL cells (plant, animal, etc)
  • 2) Chloroplasts
    • Found only in plant, plant-like cells
  • Considered to be energy transforming organelles
    • Mitochondria – food  ATP
    • Chloroplast – sun/water/CO2  food
  • 2 membranes:
    • Inner and outer (each is phospholipid bilayer)
    • The inner membrane has more surface area than the outer membrane.
  • Matrix: inner space
  • Intermembrane space: area between the membranes
  • Have ribosomes
  • Have their own DNA
  • Can reproduce themselves
  • May have been independent cells
  • Found in nearly ALL eukaryotic cells
  • Function:
    • Site for cell respiration - the release of energy from food.
    • Major location of ATP generation
    • “Powerhouse” of the cell
inner membrane of mito
Inner Membrane of Mito
  • Folded into cristae
  • Amount of folding depends on the level of cell activity
  • Contains many enzymes
    • Serve as catalysts for cellular respiration
  • ATP generated here
  • Function: performs photosynthesis
  • Structure
    • Two outer membranes
    • Complex internal membrane
    • Fluid-like stroma is around the internal membranes
  • 3 components/parts:
    • 1) Stroma
    • 2) Thylakoid OR Grana
    • 3) Intermembrane space
  • Contain ribosomes
  • Contain DNA
  • Can reproduce themselves
  • Often contain starch
  • May have been independent cells at one time
inner thylakoid membranes of chloroplast
Inner/Thylakoid Membranes of Chloroplast
  • Arranged into flattened sacs called thylakoids
  • Some regions stacked into layers called grana
  • Contain the green pigment chlorophyll
  • Network of rods and filaments in the cytoplasm
  • Components:
    • 1) Microtubules
    • 2) Microfilaments
    • 3) Intermediate Filaments
cytoskeleton functions
Cytoskeleton Functions
  • Cell structure and shape
  • Cell movement
  • Movement of organelles
  • Cell division - helps build cell walls and move the chromosomes apart
  • VERY important to animal cells
    • Why? Because animal cells lack the extra support of cell wall
  • Structure - small hollow tubes made of repeating units of a protein dimer
  • Size - 25 nm diameter with a 15 nm lumen; can be 200 nm to 25 mm in length
  • Thickest of three components
  • Contains protein called tubulin
  • Regulate cell shape
  • Coordinate direction of cellulose fibers in cell wall formation
  • Tracks for motor molecules
    • Ex: Guide vesicles from Golgi
  • Form cilia and flagella
  • Internal cellular movement
  • Make up centrioles, basal bodies and spindle fibers
cilia and flagella
Cilia and Flagella
  • Cilia - short, but numerous
    • Hair-like
  • Flagella - long, but few
    • Tail-like
  • Functions –
    • Flight/Movement/Locomotion, reproductive processes, filter water
  • Structure - arrangement of microtubules, covered by the cell membrane
  • Dynein- motor protein that connects the tubules
dynein protein
Dynein Protein
  • A contractile/motor protein
  • Uses ATP
  • Creates a twisting motion between the microtubules causing the structure to bend or move
  • Made of several polypeptide chains
    • Quaternary structured protein
  • Usually one pair per cell, located close to the nucleus
  • Found in animal cells
  • 9 sets of triplet microtubules
  • Help in cell division
  • 5 to 7 nm in diameter
  • Structure - two intertwined strands of actinprotein
  • Solid rods of linear filaments
functions of microfilaments
Functions of Microfilaments
  • Muscle contraction
  • Cytoplasmicstreaming
  • Pseudopodia (ex: amoeba)
  • Cleavage furrow formation (ex: cell division)
  • Maintenance and changes in cell shape
intermediate filaments
Intermediate Filaments
  • Fibrous proteins that are super coiled into thicker cables and filaments 8 - 12 nm in diameter
  • Made from several different types of protein
  • Functions:
    • Maintenance of cell shape
    • Hold organelles in place
cell wall
Cell Wall
  • Nonliving jacket that surrounds some cells
  • Function as the cell's exoskeleton for support and protection
  • Found in:
    • Plants
    • Prokaryotes
    • Fungi
    • Some Protists
plant primary cell wall
Plant: Primary Cell Wall
  • Thin and flexible
  • Cellulose fibers placed at right angles to expansion
  • Placement of fibers guided by microtubules
plant secondary cell wall
Plant: Secondary Cell Wall
  • Thick and rigid
  • Added between the cell membrane and the primary cell wall in laminated layers
  • May cover only part of the cell; giving spirals
  • Makes up "wood”
cell wall middle lamella
Cell wall: Middle Lamella
  • Thin layer rich in pectin found between adjacent plant cells
  • Glues cells together
  • The Inner Life of the Cell - Harvard University
intercellular junctions
Intercellular Junctions
  • Plants - Plasmodesmata
    • Channels between cells through adjacent cell walls
    • Allows communication between cells
    • Also allows viruses to travel rapidly between cells
intercellular junctions1
Intercellular Junctions
  • Animals:
    • Tight junctions
    • Desmosomes
    • Gap junctions
tight junctions
Tight Junctions
  • Very tight fusion of the membranes of adjacent cells
  • Seals off areas between the cells
  • Prevents movement of materials around cells
  • Bundles of filaments which anchor junctions between cells
  • Does not close off the area between adjacent cells
  • Coordination of movement between groups of cells
gap junctions
Gap Junctions
  • Open channels between cells, similar to plasmodesmata
  • Allows “communication” between cells
  • Recognize the types and uses of microscopes in the study of cells.
  • Recognize the limitations on cell size.
  • Recognize why cells must have internal compartmentalization.
  • Identify the structures and functions of cell organelles.
  • Identify the structures and functions of the cytoskeleton.
  • Recognize the surface features and inter-cellular connections of plant and animal cells.