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Introductory Questions #1. 1)What is the basic unit of measurement used by biologists to measure cells? What about internal organelles? 2) What are the approximate sizes for: -human egg cell-mitochondria -virus-protein

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Introductory Questions #1

1)What is the basic unit of measurement used by biologists to measure cells? What about internal organelles?

2) What are the approximate sizes for:

-human egg cell-mitochondria


3) What are the magnification limits of the human eye, a light microscope, and an electron microscope

4) How does a TEM differ from an SEM? What is the main limitation with using electron microscopes?

5) Briefly explain what the cell fractionation process does and how differential centrifugation can be helpful in the study of Cytology.

6) How do cells keep their internal contents separate from the outside environment?

7) Why is the surface to volume ratio an important factor with regard to cell size limits?

Introductory Question #2

1) Name three structures found in prokaryotic cells, eukaryotic plant cells, and eukaryotic animal cells.

2) Name the three layers that surround and protect a prokaryotic cell. Why are prokaryotes considered to be “simple” cells and eukaryotic are called “complex” cells?

Matching Ex.

Cellular respiration A. Nucleolus

Digests waste, worn out organellesB. Endoplasmic Ret.

Produces rRNA and ribosomes C. Ribosomes

Produces H2O2 D. Golgi Complex

Forms Mitotic spindle in Mitosis E. Lysosmes

Site for protein synthesis F. Peroxisomes

Site for the synthesis of lipidsG. Mitochondria

Modifies, packages and ships protein H. Centrioles

IQ #3

What purpose do vesicles serve in the cell?

  • Name all of the organelles that are a part of the endomembrane system.

    4) Explain how the rough ER is different from the smooth ER,

    5) How is a lysosome different from a peroxisome?

    6) What do the chaperone proteins in the ER do?

Introductory Questions # 4

  • Name the people that helped to develop the cell theory. What contribution did each person make (what did they discover)?

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A Tour of the Cell

Chapter 6

(Pgs 94-123)

  • History & discoveries

  • Microscopy

  • Limits to Cell Size

    (Surface area to volume ratio)

  • Cell Fractionation

    (Structure & Function of Organelles)

  • Prokaryotic vs.Eukaryotic

  • Plant cells vs. Animal

  • Endomembrane System

  • Cytoskeleton

  • Intercellular junctions

History & Discovery of Cells

  • Anton Van Leeuwenhoek (pond water 1600’s)

  • Robert Hooke (Cork Cells, 1665)

  • Robert Brown (Nucleus, 1833)

  • Matthias Schleiden (Plant Cells, 1838)

  • Theodor Schwann (Animal Cells, 1839)

  • Rudolf Virchow(All Cells arise from other cells)

  • Cell Theory: 3 aspects

  • Below is a list of the most common units of length biologists use (metric)

Table 4.2

Biological Size and Cell Diversity (Pg. 95)

Human Eye: 1mm - meter+

LM: 1m – 1mm

EM: 1nm – 1mm

Chicken Egg (largest cell)

Mitochondria (1m)

Ribosomes (20-30 nm)

Viruses (80-100 nm)

Microscopes provide windows to the world of the cell

  • The light microscope enables us to see the overall shape and structure of a cell

Image seen by viewer



Objective lens


Condenser lens

Light source

Figure 4.1A

  • Scanning electron microscope (SEM)

  • Scanning electron micrograph of cilia

Figure 4.1B

  • Transmission electron microscope (TEM)

  • Transmission electron micrograph of cilia

Figure 4.1C

Cytology: science/study of cells

  • Light microscopy

  • resolving power~ measure of clarity

  • Electron microscopy (2 types)

    •TEM~ electron beam to study cell ultrastructure

    •SEM~ electron beam to study cell surfaces

  • Cell fractionation~ cell separation; organelle study

  • Ultracentrifuges~ cell fractionation; 130,000 rpm

Cell Fractionation-Pg 97

Cell Fractionation

  • Physically separates and purifies cell parts

  • Spun in a centrifuge (up to 500,000 rpm)

  • Two fractions: supernatant & pellet

  • Differential: successively at higher speeds

  • Density gradient: forms bands in tube according to density differences of organelles

Cell Size

  • Is it more advantageous to be a single cell that is large or to be broken down into several small cells ?

    (Explain your answer)

  • A small cell has a greater ratio of surface area to volume than a large cell of the same shape

30 µm

10 µm

Surface areaof one large cube= 5,400 µm2

Total surface areaof 27 small cubes= 16,200 µm2

Figure 4.3

Cell size - (surface area:volume)

  • As cell size increases, the surface area to volume ratio decreases (sa/vol)

  • Rates of chemical exchange may then be inadequate for cell size

  • Cell size, therefore, remains small

Natural laws limit cell size

  • At minimum, a cell must be large enough to house the parts it needs to survive and reproduce

  • The maximum size of a cell is limited by the amount of surface needed to obtain nutrients from the environment and dispose of wastes

The Prokaryotic Cell-(See Fig. pg 98)(Also See Pages 534-547 in Ch. 27)

  • Characteristics include:

    • No true distinct nucleus

    • Have a “Nucleoid” region = DNA & Plasmids

    • No complex, membranous organelles (Ribosomes only)

    • Most have rigid cell walls

    • Flagella (rotary type structure & not composed w/microtubules)

    • Some have pigments (autotrophic)

    • Classified according to their metabolic needs

    • Eubacteria & Archeabacteria

    • Some have sticky capsules, pili, peptidoglycan, Endospores

    • Asexually Reproduce: Binary Fission, Budding, Fragmentation

    • Genetic Material Can be exchanged by 3 mechanisms:

      • Transformation, Transduction, and Conjugation

A Prokaryotic Cell

The Eukaryotic Cell

  • “Eu” = true“Karyo” = kernal (nucleus)

  • Protists, Plants, Fungi, and Animals

  • Internal Membrane System

  • Has many membranous organelles (Table 4.1) that include:


    -Golgi complex-Endoplasmic reticulum (R & S)

    -Mitochondria-Chloroplast (plastids)

    -Peroxisomes (glyoxysomes)-Vesicles

    -Vacuole (food, contractile)-Ribosomes

  • Cytoskeleton: microtubules, microfilaments, and int. filaments

  • Centrioles (nine triplets of microtubules)

  • Cilia & Flagella (9+2 microtubule arrangement)

  • Extracellular matrix (ECM)-proteins & carbodydrate










Not inanimalcells





Cell wall



Plasma membrane

Figure 4.5B

Smooth endoplasmicreticulum



  • An animal cell


(exception is some plants)

Not in most plant cells







Plasma membrane





Figure 4.5A

Endomembrane Function

Nucleus, Ribosomes, Rough & Smooth ER,

Flow of Genetic information and protein Synthesis

Nucleus (Pg. 103)

Control Center of the Cell

Genetic material:



Nucleolus: ribosome synthesis

Double membrane envelope with pores

1st part of Protein synthesis:

Transcription (DNAmRNA)

Nuclear pores



Two membranesof nuclearenvelope





Figure 4.6


  • Manufactures Protein

  • Free •cytosol; •protein function in cell

  • Bound •endoplasmic reticulum; •membranes, organelles, and export

Endoplasmic Reticulum (pg. 105)

Endoplasmic reticulum (ER)

  • Continuous with nuclear envelope

    Smooth ER

    •no ribosomes;

    •synthesis of lipids

    •metabolism of carbohydrates

    • detoxification of drugs and poisons

    Rough ER

    •with ribosomes

    •synthesis of secretory proteins (glycoproteins), membrane production

    **Found extensively in Pancreas

Transport vesiclebuds off



Secretory(glyco-) proteininside transportvesicle








Rough Endoplasmic Reticulum makes membrane and proteins

  • The rough ER manufactures membranes

  • Ribosomes on its surface produce proteins

Figure 4.8







Figure 4.9

Golgi Complex (pg. 106)

  • Golgi apparatus

  • •ER products are modified, stored, and then shipped

  • Cisternae: flattened membranous sacs

  • trans face (shipping) & cis face (receiving)

  • Transport vesicles

The Golgi apparatus finishes, sorts, and ships cell products

  • The Golgi apparatus consists of stacks of membranous sacs

    • These receive and modify ER products, then send them on to other organelles or to the cell membrane

  • The Golgi apparatus

Golgi apparatus


“Receiving” side ofGolgi apparatus

Transportvesiclefrom ER


“Shipping”side of Golgiapparatus

Transport vesiclefrom the Golgi

Figure 4.10

Lysosomes digest the cell’s food and wastes (Pg.107)

  • Lysosomes are sacs of digestive enzymes budded off the Golgi



Figure 4.11A


  • Contain lysosomal enzymes (hydrolytic enzymes)

  • digests food molecules (macromolecules)

  • destroys bacteria

  • recycles damaged organelles

  • function in embryonic development in animals

  • undergoes phagocytosis & engulfs material

  • Recycle cell’s own organic material

  • **Found extensively in Macrophages (WBC’s)


Rough ER

Transport vesicle(containing inactivehydrolytic enzymes)



Engulfmentof particle






Figure 4.11B

Lysosomes can cause Fatal Diseases

  • Lysosomal Storage Diseases are hereditary that interfere with other cellular functions


    Pompe’s disease (build up of glycogen)

    Tay-Sachs disease (lipid build up)

    (Pgs. 93, 331)


-Membrane-bound sacs (larger than vesicles)

-Food (phagocytosis)


(pump excess water)


(storage in plants)

-Tonoplast membrane

Vacuoles function in the general maintenance of the cell

  • Plant cells contain a large central vacuole

    • The vacuole has lysosomal and storage functions



Figure 4.13A

Peroxisomes (Pg. 111)

  • Single membrane

  • Oxidative organelle

    ***strips e-’s (H’s) from substances

  • Produce hydrogen peroxide (H2O2) in cells

  • Metabolism of fatty acids; detoxification of alcohol (liver)

  • Hydrogen peroxide then converted to water

Mitochondria & Chloroplasts

-Energy Harvesting Organelles

Mitochondria -Site of Cellular Respiration(Pg. 110)

Mitochondria harvest chemical Energy from food

  • Site for Cellular Respiration---Prod. of ATP

  • Uses O2 to extract energy from sugar, fats, and other molecules

  • Found in cells that are motile and contractible

  • Has a double membrane

  • Has Convoluted inner membranes: Cristae

  • Two spaces: Matrix & intermembrane space

  • Not part of the endomembrane system

  • Has its own DNA and rbosomes (able to regenerate & divide)---Semiautonomous







Figure 4.16

Chloroplasts convert solar energy to chemical energy

  • Chloroplasts are found in plants and some protists

  • Chloroplasts convert solar energy to chemical energy in sugars



Inner and outer membranes



Figure 4.15

The Chloroplast(pg. 111)

  • Site for Photosysnthesis: combines CO2 & H2O

  • Converts solar energy into chemical energy (sugar molecules)

  • A Type of Plastid

    • Three types: (Amyloplastid, chromoplast, and chloroplast)

  • Double membrane w/ thylakoids (flattened disks)

  • Grana (stacked thylakoids)

  • Three compartments


    -Intermembrane space

    -Within the thylakoid membranes

  • Has its own DNA

The Cytoskeleton (pg. 112-113)

-Fibrous proteins (actin & tubulin)

-Support, cell motility, biochemical regulation, organelle movement

-Microtubules: •thickest (nm) •tubulin protein; •shape, support, transport,

chromosome separation


•thinnest ( nm)

•actin protein filaments;

•motility, cell division, shape

-Intermediate filaments:

• middle diameter; •keratin; •shape, nucleus anchorage

The cell’s internal skeleton helps organize its structure and activities

  • A network of protein fibers makes up the cytoskeleton

Figure 4.17A

Comparing Cytoskeletal Filaments

  • Scan image

The Cytoskeleton


Actin subunit

Fibrous subunits

25 nm

7 nm

10 nm




Figure 4.17B

  • Intermediate filaments reinforce the cell and anchor certain organelles

  • Microtubules

    • give the cell rigidity

    • provide anchors for organelles

    • act as tracks for organelle movement

  • Microfilaments of actin enable cells to change shape and move

Cytoskeletal Movement(Polymerization & De-polymerization)

Centrosomes/Centrioles(pg. 114)

  • Centrosome: region near nucleus

  • Centrioles: 9 sets of triplet microtubules in a ring;

    (used in cell replication; only in animal cells)

Cilia/Flagella (pg. 115-116)

-Locomotive appendages

-Ultrastructure: “9+2”

(9 doublets of microtubules in a ring)

(2 single microtubules in center)

-Connected by radial spoke

-Anchored by basal body

(nine triplets of microtubules)

-Dynein arm proteins (red)

Cilia and flagella move when microtubules bend

  • Eukaryotic cilia and flagella are locomotor appendages that protrude from certain cells

  • A cilia or flagellum is composed of a core of microtubules wrapped in an extension of the plasma membrane


Electron micrograph of sections:

Outer microtubule doublet




Outer microtubule doublet


Basal body

Basal body(structurally identical to centriole)

Figure 4.18A

Dynein Arm Function(pg. 116)

  • Clusters of microtubules drive the whipping action of these organelles

Microtubule doublet


Dynein arm

Figure 4.18B

ECM Composition

  • Extracellular matrix (ECM) composed of:

    -Proteins & Carbodydrate






    -collagen (50% of all protein in the body)

Extracellular Matrix (ECM) - Pg. 118-120

Glycoproteins: •proteins covalently bonded to carbohydrate


(50% of protein in human body

•embedded in proteoglycan

(another glycoprotein-95% carbohydrate)


bind to receptor proteins in plasma

membrane called integrins

(cell communication?)

  • Animal cells are embedded in an extracellular matrix

  • It is a sticky layer of glycoproteins

  • It binds cells together in tissues

  • It can also have protective and supportive functions

Intracellular Junctions(pg. 121)


  • Plasmodesmata:

    cell wall perforations; water and solute passage in plants


  • Tight junctions~ fusion of neighboring cells; prevents leakage between cells

  • Desmosomes~ riveted, anchoring junction; strong sheets of cells

  • Gap junctions~ cytoplasmic channels; allows passage of materials or current between cells

Cell surfaces & Junctions

-Cell wall: •not in animal cells

•protection, shape, regulation

-Plant cell: •primary cell wall produced first

•middle lamella of pectin (polysaccharide)

-Holds cells together

•some plants have a secondary cell wall; strong durable matrix; wood

(between plasma membrane and primary wall)

Walls of two adjacent plant cells



Layers of one plant cell wall


Plasma membrane

Figure 4.19A

  • Tight junctions can bind cells together into leakproof sheets

  • Anchoring junctions link animal cells

  • Communicating junctions allow substances to flow from cell to cell





Plasma membranes ofadjacent cells


Figure 4.19B

Movin’ on to Chapter 7

Science and Art

The Art of Looking at Cells

  • Artists are often inspired by biology and biology depends on art

  • The paintings of Wassily Kandinsky (1866-1944) show the influence of cellular forms

  • Illustration is an important way to represent what scientists see through microscopes

  • The anatomist Santiago Ramón y Cajal (1852-1934) was trained as an artist

    • He drew these retina nerve cells

Eukaryotic organelles comprise FOUR functional categories

Table 4.20

Summary of Organelles & their Function

Table 4.20 (continued)

A review of the endomembrane system

  • The various organelles of the endomembrane system are interconnected structurally and functionally

Transport vesiclefrom Golgi

Transport vesiclefrom ER

Rough ER






Smooth ER


Figure 4.14

Extraterrestrial life-forms may share features with life on Earth

  • It is almost certain that Earth is the only life-bearing planet in our solar system

  • But it is conceivable that conditions on some of the moons of the outer planets or on planets in other solar systems have allowed the evolution of life

Figure 4.21

Samples of Various Types of Cells



  • These pump out excess water

  • Protists may have contractile vacuoles

Figure 4.13B

  • Cell, stained for mitochondria, actin, and nucleus

Figure 4.1x

  • Prokaryotic cells, Bacillus polymyxa

Figure 4.4x1

  • Prokaryotic cell, E. coli

Figure 4.4x2

  • Pili on a prokaryotic cell

Figure 4.4x3

  • Prokaryotic flagella

Figure 4.4x4

  • Prokaryotic and eukaryotic cells compared

Figure 4.4x5

  • Paramecium, an animal cell

Figure 4.5Ax

  • Plant cells

Figure 4.5Bx1

  • Chloroplasts in plant cells

Figure 4.5Bx2

  • Nuclei (yellow) and actin (red)

Figure 4.6x

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