Robert Hooke - 1665

• Cell is the smallest unit of life

Antony van Leewenhoek - 1674

• First to observe bacteria and protozol

Matthias schleiden - 1838

• German botanist

  • Looked at plant tissues and noticed nuclei in them. Talking with his friend, Theodore Schwann – hypothesized that all plants are made up of cells

Theodore Schwann - 1838

• “All living things are made of cells” - Schwann and Schleiden

  • Talked with Mattias Schleiden about nuclei of plant and animal cells

  • Conducted studies to reveal that animal tissues are composed of cells with nuclei

  • His Cell Theory:

    • Cells are the unit structure of living things

    • Cells retain a dual existence as a distinct entity and a building block in the construction of organisms

    • Living cells formed in similar ways to crystals

Cells

• Cells were discovered in 1665 by Robert Hooke

• Early studies of cells were conducted by:

  • Mattias Schleiden (1838)

  • Theodore Schwann (1839)

• Schleiden and Schwann proposed the Cell Theory

Cell Theory

• Unifying foundation of biology

  • All organisms are composed of cells

  • Cells are the smallest living things

  • Cells arise only from pre-existing cells

    • Rudolph virchow (1858) (rejection of theory of spontaneous generation)

• All cells today represent a continuous line of descent from the first living cells

Cell Size is Limited

• Most cells are relatively small due relailnce on diffusion of substances in and out of cells

  • Rate of diffusionaffected by

    • Surface area available

    • Temperature

    • Concentration gradient of diffusing substance

    • Distance over which diffusion must occur

• Diffusion

  • High concentration → even distribution ← Low concentration

• Rate of diffusion affected by:

  • Surface area available

  • Temperature

  • Concentration gradient

  • Distance

Surface Area-to-Volume ratio

• Organism made of many small cells has an advantage over an organism composed of fewer, larger cells

  • Membrane surrounding the cell plays key role, provides only opportunity for interaction with environment

• A cells size increases, its volume increases much more rapidly than its surface area

• Some cells overcome limitation by being long and skinny- like neurons

  • As a cell gets larger, its volume increases at a faster rate than its surface area

Microscopes

• Not many cells are visible to the naked eeye

  • Most are less that 50μm in diameter

• Resolution - minimum distance two points can be apart and still be distinguished as two separate points

  • Objects must be 100μm apart for the naked eye to resolve them as two objects rather than one

    • Prokaryotic cells are generally 1 to 10 μm across

      • Most cells are microscopic in size

      • Vertebrae eggs are visible to the naked eye

Two Types Of Microscopes

• Light microscopes

  • Uses magnifying lenses with visible light

  • Resolve structures that are 200nm apart

  • Limit to resolution using light

• Electron microscopes

  • Use beam of electrons

  • Resolve structures that are 0.2nm apart

  • Two types of electron microscopes

    • Transmission electron microscopes

      • Transmits electrons through the material

    • Scanning electron microscopes

      • beam electrons onto the specimen surface

Basic Structural Similarities

• All cells resemble one another in four fundamental ways

  • Centrally Located Genetic Material

    • DNA

  • Cytoplasm

    • Semifluid matrix of organells and cytosol

  • RIbosomes

    • Protein synthesis

  • Plasma Membrane

    • Phospholipid bilayer + proteins

Prokaryotic Cells

• Simplest organisms

  • Lack a membrane-bound nucleus

    • DNA is present in nucleoid

  • Cell wall outside of plasma membrane

    • Contain ribosomes

      • No membrane-bound organelles

  • Two domains of prokayotes

    • Archea

    • Bacteria

      • The nucleoid is visible as a dance central region segregated form the cytoplasm

Bacterial Cell Walls

• Most bacterial cells are encased by strong cell wall

  • Composed of peptidoglycan

  • Cell walls of plants, fungi, and most protists different

• Protecgt the cell, maintain its shape, and prevent excessive eptake or loss of water

• Susceptibility of bacteria to abtibiotice often depends on the structure of their cell walls

• Some secrete a jelly- like protective capsule

Archaea

• Do not have peptidoglycan cell walls

  • Composed of polysaccrides and proteins

• Membrane lipides are distinctly different from lipids in bacteria

• DNA replication and protein synthesis similar to eukaryotes

Flagella

• BActerial, archaeal, eukaryotic cells all have external structures for motility

  • Long filaments made of protein

  • Appaer similar

  • Evolutionary distinct

Bacterial Flagella

• Constist of protein rings embebeded in plasma membrane and cell wall

  • Long fibers extend from the structure

• Proton gradient used motive force

Archaellun

• Related to bacterial pilus

• Disk of membrane proteins

  • Protein filaments extend from the cell

• ATP hydrolysis used as motive force

  • Both use bacterial and archaeal structures rotate like a propeller

  • Eukaryotic flagella use whiplike motion

Eukaryotic Cell

• Possess membrane-bound riders more complex than prokaryotic cells

  • Hallmark is compartmentalization

    • Achieved through use at membrane-bound organelles and endomembrane system Possesses a Cytosvelelton for support and to maintain cellular structure

Eukaryotic Cell Features

• Plasma membrane

• Cytoplasm

• Organelles

• Nucleus

• Endomembrane

• Cytoskeleton

Nucleus

• Repository of genetic information

  • most eukaryotic cells possess a single nucleus

    • Nucleolus - a region where ribosomal RNA synthesis takes place

Nuclear envelope

• 72 phospholipid bilayers

  • Nuclear Pores-Control Passage in and out

    • In eukaryotes, the DNA is divided into multiple linear chromosomes OChromatin is chromosomes plus protein

Ribosomes

• Cells protein Synthesis machinery

  • found in all cell types in all 3 domains

    • Ribosomal RNA (rRNA) - Protein Cpplex

  • Protein Synthesis also requires messenger RNA (mRNA) and transfer RNA (ARNA)

  • Ribosomes may be free in the cytoplasm or associated with internal membranes through endoplasmic reticulum

Endomembrane System

• Serious of Separate compartments formed throughout the cytoplasm by membrane-bound organelles - endoplasmic reticulum, Golgi Apparatus, lysosomes, vesicles

  • Divides cells into comportments where different cellular functions occur

    • one of the fundamental distinctions between eukarymptes s. Prokaryotes

Endoplasmic Reticulum

• Rough Endoplasmic Reticulum (RER)

  • The attachment of ribosomes to the membrane gives a rough appearance

  • Synthesis of proteins to be secreted, sent to lysosomes or plasma membrane Smooth Endoplasmic Reticulum (SER)

  • Relativity few band ribosomes

  • variety of functions-Synthesis, Store Cat, detoxification

    • The ratio of RER to SER depends on the cell's function *RER is blue SER is green)

Golgi Apparatus

• flattened stacks at interconnected membranes (Golgi bodies)

• Functions in packaging and distribution of molecules synthesized at one location and used at another within the cell or even outside of it

  • Cells post office

    • Has Cis and trans faces

    • Secretory vesicles transport molecules to the destination

  • The Golgi apparatus receives material for processing in transport vesicles on the is face and Sends the material packages in transport or secretory vesicles If the trans face

Protein Transport Through the Endomembrane System

• Proteins are synthesized by ribosomes in RER and then translated into the ER

  • Transported by residencies in RER

  • resides travel to cis face, then modified and Packaged into trons free

  • Vesicles either more posterns to other parts of the Cell or fuse with plasma membrane

Lysosomes

• Membrane-bonded digestive vesicles

• Arise from Golgi Apparatus

• Enzymes Catalyze breakdown of macromolecules

• Destroy cells or foreign matter that the cell has engulfed by Phagocytosis

Microbodies

• variety at enzyme-Bering, membrane-embedded vesicles

• Peroxisomes

  • contain enzymes involved in the oxidation of fatty acids

  • Hydrogen peroxide produced as a by-product-rendered harmless by Catalase

Proteosomes

• Large Cylindrical complexes

• Proteolytic activity

• misfolded, damaged, or no longer needed proteins

Plant vacuoles

• membrane-bounded structures in Plants

• various functions

• most conspicuous

  • Central vacuole found in most plant cells

    • Tonoplast - membrone Surrounding central vacuole

  • Allows cell to expand or contract depending on conditions

Mitochondria

• Mitocondria & Chioroplasts are the ATP-generating organelles at the cell

  • Mitochondria- All types of eukaryotic cells

  • Chloroplasts - All plants (and other eukaryotes live protists) not in animal (or fungal) cells

    • Metabolize organic compounds to generate ATP

  • Bound by 2 membranes

    • smooth outer membrane

    • rough inner membrane

    • Cristae-folds inner membrane Matrix-inside inner membrane on the Surface of the inner membrane and also embedded within it, are proteins that carry out oxidative metabolism

      • Wave their own DNA

Chloroplasts

• organelles present in cells at plants and some other eukaryotes use light to generate ATP and Sugars

  • Contain Chlorophyll for Photosynthesis

    • Give most plants Green color

    • surrounded by 2 membranes

      • Thylakoids are membranous Sacs within the inner membrane

    • Grana are stacks of thylakoids

      • Have their own DNA

Endosymbiosis

• proposes that some at today's eukaryotic Organelles evolved by Symbiosis arising between 2 cells that ware each free-living

  • one Cell, Prokaryote, was engulfed by and became part of another cell, which was the precursor at modern eukaryotes

    • Mitochondria & Chloroplasts

Cytoskeleton

• network at protain fibers found in all euhyptic Cells

  • supports the Shape at the call

    • keeps organesies in fixed locations

      • Dynamic System-constantly forming and dissembling

  • types of fibers

    • Actin (Micro) filaments

      • Two protein Chains loosen, twine together

      • Movements live contraction, crawling, "Pinching"

    • Microtubules

      • largest of the Cytosvelety elements

      • Dimers at a s B-tubulin subunits

      • Facilitate movements of cell is Materials within a cell

    • Intermediate filaments

      • Between the Size of actin filaments microtubules • Very stable-usually not broken down

Cell Movement

• All eukaryotic cells to more material from one place to another

  • Four components necessary to move material along microtubules

    • Vessicle or Organelle to be transported

    • Motor Protein

    • Connector molecule

    • Microtubule

Molecular Motors

• vehicles can be transported along microtubules using motor proteins that use ATP to generate force

  • The vesicles are attached to motor proteins by connector molecules

    • The motor protein dynein moves the connected vesicle along microtubules

Centrosomes

• the region surrounding pair of centroles in almost all animal Cells

  • Pair usually at right angles to each other, near nuclear Membrore

    • Microtubule organizing center

  • can nucleate the assembly of micnstubles

    • Animal Cells 's most protists are centrioles

      • Plants s fungi usually lack centrioles

Flagella & Cilia

• Flagella and Cilia have 972 arrangement of Microtubules

  • not like prokaryotic flagella

  • Cillia are Shorter S more numerous

  • many protists use flegela and Cilla to swim

  • Pairs of microtubules more past telomere using arms composed at the motor pooters dynein

  • The motor postern dynein moves the connected vesicle along microtubules

Cell Walls in Plants

• Plants, fungi, and Many Protists

  • Different from Prokaryote

    • Plants & Protists -cellulose

    • Fungui-Chitin

      • Plants - Primary is Secondary cell walls

Extracellular Matrix (ECM)

• Animal cells lack cell walls

  • Secrete an elaborate mixture of glycoproteins into the space around them - ECM

    • Collagen may be abundant

  • I Form a protective layer over the can surface

  • Integrins lime ECM to cells Gtosueleton

    • Proteins in Plasma membrone

    • Influence cell behavior

Cell-to-Cell connections

• In multicenar organisms these functions Include

  • Organization of tissues using connections between cells

  • can communication

  • Marriers of cell identity

    • Are made possible by member protein's and Secreted proteins

Cell Identity

• Glycolipids

  • most tissue speeifie cell-structure marker

    • A,B, O blood type

    • ORBC

  • MHC Proteins

  • Immme System

  • Self us Nonself

Cell Connections

• 3 categories at cell connections

  • Adhesive junctions

    • mechanicalin, attaches cytoskeletons of neighboring cells

  • Adherens junctions

    • Desmosomes

    • Hemidesmosomes

  • Separate or tight Junctions

    • connect the plasma membrane of adjacent cells in a sheet - no leakages from sheets of cells

Communicating Junctions

• Chemical or Electrical Signal passes directly from one cell to an adjacent one

  • Gap Junction

  • Plasmodesmata

Plant Cells

• Plasmodes Mata

  • specialized opening in their cell walls

  • The cytoplasm of adjusting cells are connected

  • Function Similar to Gap junctions in animal cells