Cell Theory and Discovery

Spontaneous Generation Theory

• States that living organisms originate from inanimate objects.

Key Cell Researchers

• Robert Hooke (1665) observed cells in cork and coined the term "cells".
• Antonie Van Leeuwenhoek (1673) observed living cells and is known as the Father of Microscopy.
• Robert Brown (1827-1833) coined the term "nucleus" and discovered Brownian motion.
• Matthias Schleiden (1838) was a botanist who concluded that all plants are made of cells.
• Theodor Schwann (1839) was a zoologist who concluded that all animals are made of cells.
• Rudolph Virchow (1855) stated that all cells come from pre-existing cells.

Cell Size and Exchange

• Small cell size facilitates efficient material exchange with the environment.
• As cell size increases, surface area decreases, which limits cell size.

The Cell Theory

• All living things are composed of one or more cells.
• Cells are the basic units of structure and function in an organism.
• Cells come only from pre-existing cells.

Modern Cell Biology

• Energy flows within cells.
• Hereditary information is passed from cell to cell.
• All cells have the same basic chemical composition in organisms of the same species.

Cell Types: Prokaryotes

• Simple cells lack internal membranes.
• The name comes from the Greek words "pro" (before) and "karyon" (nut or kernel).

Cell Types: Eukaryotes

• More complex cells contain internal, membrane-bound structures.

Common Features of Prokaryotic and Eukaryotic Cells

• Both contain DNA, the genetic material located in a non-membrane bound nucleoid region in prokaryotes and a membrane-bound nucleus in eukaryotes.
• Both have a plasma membrane, a phospholipid bilayer with proteins that separates the cell from the surrounding environment and acts as a barrier for the import and export of materials.
• Cytoplasm is the material within the plasma membrane, excluding the nucleoid region or nucleus, consisting of a fluid portion called the cytosol and the organelles and other particles suspended within.
• Ribosomes are the organelles in which protein synthesis takes place.

Organelles

• These are the cellular machinery within a cell.
• There are two general kinds of Organelles: those derived from membranes and those that are bacteria-like.

Symbiogenesis/Endosymbiotic Theory

• Cells grow in size and develop infoldings.
• Infoldings pinch off, forming an endomembrane system and enclosing the nucleoid, which forms a eukaryote.
• Aerobic proteobacteria becomes an endosymbiont or a cell living inside another cell.
• A proteobacterium becomes mitochondria, leading to cellular respiration.
• Another endosymbiont, like cyanobacteria, becomes chloroplasts, leading to photosynthesis.

Evidences for the Endosymbiotic Hypothesis: Mitochondria and Chloroplasts

• Similar to bacteria in both size and structure
• Bounded by a double membrane where the outer membrane may represent the engulfing vesicle, and the inner membrane from the prokaryote.
• Each contains circular DNA and divides by splitting.
• Have their own ribosomes and produce some proteins like prokaryotes.
• Have RNA base sequences suggesting a prokaryotic origin.

Function Categories of Cell Structures

• Manufacturing
• Breakdown
• Energy Processing
• Support, movement, and communication between cells

Parts of the Plant Cell: Nucleus

• A cellular organelle that contains the DNA.
• It is the control center of the cell.
• Contains the nucleolus.
• Separated from the cytoplasm by a nuclear membrane.

Parts of the Plant Cell: Plastid

• A group of membrane-bound organelles occurring in photosynthetic eukaryotic cells.
  • Chloroplasts are green and the site of photosynthesis.
  • Leucoplasts are colorless and store starch or oil.
  • Chromoplasts are colored or pigmented and produce pigments that contribute to the color of fruits.

Parts of the Plant Cell: Mitochondrion

• An intracellular organelle associated with cellular respiration.

Parts of the Plant Cell: Ribosome

• Is a cellular organelle for protein synthesis.

Parts of the Plant Cell: Endoplasmic Reticulum (ER)

• Smooth type lacks ribosomes.
• Rough type has ribosomes embedded in the surface.

Parts of the Plant Cell: Golgi Body

• Modifies, packages, and sorts proteins that will be secreted or sent to the plasma membrane or other organelles.

Parts of the Plant Cell: Vacuole

• Is a large fluid-filled, membrane-bound sac within the cytoplasm that contains a solution of salts, ions, pigments, and waste materials.

Parts of the Plant Cell: Cytoskeleton

• Maintains the cell's shape.
• Involved in cellular movement.
• Composed of microtubules and microfilaments.

Parts of the Plant Cell: Cell Wall

• A comparatively rigid supporting wall exterior to the plasma membrane in plants, fungi, prokaryotes, and certain protists.

Parts of the Plant Cell: Cellulose

• The most abundant organic polymer on Earth.

Parts of the Plant Cell: Plasmodesmata

• A narrow thread of cytoplasm that passes through the cell walls of adjacent plant cells and allows communication through them.

Parts of the Plant Cell: Plasma Membrane

• The surface membrane of a cell
• Acts as a selective barrier to the passage of materials in and out of the cell.

Parts of the Plant Cell: Phospholipids

• Have two fatty acids attached to glycerol and a phosphate group at the third position.

Parts of the Plant Cell: Cytoplasm

• A gel-like mixture
• Surrounded by the cell membrane.

Visible Light Microscopy: Bright Field Microscopy

• Visible light is transmitted through the specimen.
• Uses a compound light microscope.
• It has multipurpose use.

Visible Light Microscopy: Dark Field Microscopy

• Visible light is reflected through the sides of the specimen.
• Uses a compound light microscope with a "stop" on the condenser.
• Used to view the shape and movement of cells.

Visible Light Microscopy: Phase-contrast Microscopy

• Light patterns move through denser regions of the cell.
• Regions of the cell are transformed into a density map.

Ultraviolet Microscopy: Differential Interference Contrast Microscopy

• Utilizes two beams of light and two prisms.
• Colored, resulting in a 3D image.

Ultraviolet Microscopy: Fluorescence Microscopy

• Fluorescent dyes attach to specific cell structures.
  • Examples include DAPI, Fluorescein, and Texas-red
• Used to view internal/external structures of cells and viruses.
• Used to view interactions of cell biomolecules in 2D.

Ultraviolet Microscopy: Confocal Microscopy

• Fluorescent dyes attach to specific cell structures.
• It is used to view internal/external structures of cells and viruses.
• It is used to view interactions of cell biomolecules in 2D or 3D.

Explore the history and principles of cell theory, including contributions from Hooke, Leeuwenhoek, Schleiden, Schwann, and Virchow. Understand the importance of cell size for efficient material exchange and the fundamental tenets of cell theory.