BIOLOGY
Biology
Theory of Spontaneous Generation
Aristotle (Greek Philosopher) 384-322 BC
One of the earliest recorded scholars to articulate the theory of spontaneous generation, the notion that life can arise from nonliving matter.
Francesco Redi (Italian Physician) 1626 - 1697
Experimented in 1668, which was one of the first to refute spontaneous generation.
Louis Pasteur
Swan-Neck flask experiment – 1861
Experimental disproof of spontaneous generation.
Pasteur’s set of experimental results irrefutably disproved the theory of spontaneous generation and earned him the prestigious Alhumbert Prize.
The Discovery of Cell
Robert Hooke (1665) – British
First scientist to use the word “cells” in 1665
introduced the term cell because of cellulose walls of dead cork cells reminded him of the blocks of cell occupied by monks called “cellulae”
Observed that the thin sections of honeycomb are similar to cells.
Antonie Van Leeuwenhuek (1673) – Dutch
Dutch microscopist
Significantly improved the quality of microscopist.
He improved the lenses to the point that he could see protozoa, a single-celled or unicellular organism.
He called these organisms “animalcules” which means “miniature animals” and now called “microorganisms”
“Father of microbiology”
Robert Brown (1831)
Scottish Botanist
Recognized the occurrence of nuclei in plant cells.
Made a series of discoveries about cell organelles, and ultimately discovered that the cell on orchids have a nucleus and this became a major breakthrough in the history of biology.
Theodor Schwann (1839)
Resulted in the conclusion that cell is the smallest unit of all living matter.
Cytology (study of cells) begun.
Animal tissue
Matthias Jakob Schleiden (1838)
Plant tissue
Proposed the first foundational belief about cells, that all plants are made up of cells.
Rudolph Virchow (1855)
“Father of Pathology”
- sickness
- illness
- diseases
“Cellular Pathology” popularized the concept of cell theory.
“Omnis cellula a cellula” - “all cells arise from cells”
The Cell Theory
All living organisms are made up of one or more cells.
Unicellular or single-celled organisms – one cell
Bacteria
Protozoa
Multicellular or multi-celled organisms – more than one cell
Animals
Plants
Fungi
The cell is the basic structural and functional unit of life
All biological or living processes that occur within the body for it to survive happen in the cell.
Cells arise from pre-existing cells.
Postulate of cell theory refers to the process of cell division.
Modern Cell Theory
Energy flow occurs within cells.
Heredity Information (DNA) is passed on from cell to cell.
All cells have the basic chemical composition.
- Lipis
- nucleic acid
- proteins
- carbohydrates
Plant cells and bacteria have cell wall
Plant cells and animal cells have vacuoles
Plant cells have bigger vacuoles
Vacuoles are for the storage of materials in the cell
Cell organelles
Cell structures that have a specific function and are surrounded by a membrane are found in eukaryotes only.
Covered with membrane compounds of a thin layer of lipids and carbohydrates.
Only plant cells have chloroplasts
Only animal cells have centrioles
Cell Structure and Functions
Cell Wall
Found outside the cell membrane in plant cells and bacteria only.
Contains cellulose that provides support (rigidity) and protection.
Cell/Plasma Membrane
semi permeable
Facilitate the movement of molecules inside and outside the cell.
Hydrophobic - anti-water
Hydrophilic - goes well with water
Cytoplasm
A viscous fluid or jelly-like material
Viscous: resistance to flow.
Jelly-like features secure the organelles in plants and animals so that they remain in place.
Part and processes where the cell can be found.
Ribosome
Each cell contains thousands of ribosomes.
Make proteins.
Found on the endoplasmic reticulum and floating throughout the cell cytoplasm.
Organelles
Enclosed in plasma and membrane
Nucleus
Covered with a membrane that allows materials to pass in and out of the cell.
Called the “control center”
Brain of a eukaryotic cell
Nucleolus
Makes ribosomes that make proteins.
Found both in plants and animals
Chromatin
In nucleus
Genetic material (DNA) of a cell in its non-dividing state.
Ie. Uncoiled chromosomes
Contains instructions for traits and characteristics.
Endoplasmic Reticulum
A series of tunnels throughout the cytoplasm.
Known as the transport center of the cell.
Smooth Endoplasmic Reticulum
Ribosome free
Produces lipids, is involved in carbohydrate metabolism, and detoxification of drugs and poison/s.
Rough Endoplasmic Reticulum
Network of continuous sacs, studded with ribosomes.
Helps in the synthesis of membrane-bound and secretory proteins.
Golgi apparatus/ Golgi bodies/ Golgi complex
Receive proteins and other compounds from the ER.
Package these materials and distribute them to the plant and animal cells.
Lysosomes
Contains hydrolytic enzymes – break down things that can be reused.
Mitochondria
Powerhouse of the cell
Produce energy
membrane-bound organelles that are the site of cellular respiration.
Vacuoles
Storage area of the cell.
Animal Vacuole
Membrane-bound sacs for storage, digestion, and waste removal.
Contain a water solution
Plant Vacuole
Have larger vacuoles that store water and nutrients needed by the cell.
Help support the shape of the cell
Cytoskeleton
The cell’s skeleton
Made of microtubules (cell division) and filaments (strength and stability)
Give the cell shape, strength, and ability to move.
Microfilament
cell shape
Muscle
Interfilament
Stability
Chloroplast
Found in plant cells
Contains green pigment – chlorophyll
Where photosynthesis takes place
Produces plant food (sugar) and oxygen gas
Centrioles
Found only in animal cells
Self replicating
Made with bundles of microtubules
Help in organizing cell division
Microvilli
Absorption
Hair-like
Parts of the Microscope
Microscope
A scientific instrument that magnifies objects, allowing us to see details that are not visible to the naked eye.
They are commonly used in biology to study cells, microorganisms, and other tiny structures.
Can come in various types (light, electron, and stereo)
Compound microscopes
Zacharias Janssen,1590
The simplest is a magnifying glass (10X magnification)
An optical or light microscope
2 types of lenses
Ocular or eye piece
Eyepiece that you look into
Objective lenses
The lens closest to the object.
Eyepiece lens
Usually 10X or 15X power.
Lens at the top that you look through.
Objective lens
Types:
Scanning (4X)
Low power (10X)
High power (40X)
Oil immersion (100X)
Tube
Connects the eyepiece to the objective lens
Arm
Supports the tube and connects it to the base.
Base
Bottom of the microscope
Used for support
Illuminator
A steady light source used in place of a mirror (110 volts)
Stage
Flat platform where you place your slides
Stage clips hold the slides in place.
Revolving nose piece/turret
Part that holds 2 or more objective lenses and can be rotated to easily change power.
Diaphragm or iris
Under the stage, upper the illuminator
Used to adjust the amount of light reaching the specimen, enhancing image, contrast, and clarity.
Coarse adjustment
Used to focus the microscope
Always used first, it is used only with low-power objective
Fine adjustment
Used with the high-power objective to bring the specimen to better focus
PROKARYOTIC CELLS VS EUKARYOTIC CELLS
Prokaryotes
Do not have a nucleus or organelles
Nucleoid - DNA
Unicellular
Smaller in size (1-10 μm)
The cell wall is made up of peptidoglycan
Eukaryotic cells
Have a nucleus and organelles (plants, fungi, animals, protists)
Larger in seize (10-100 um)
Cell wall is made up of cellulose or chitin (sugar and amino acids)
Widely known as the multicellular
Pilus (plural:pili)
Helps bacteria attach to the surface
Absorption
Involved in conjugation
Capsule
Protects the cell from desiccation and immune system attack; helps in adhesion to surfaces.
Cell Wall
Maintains shape
Protects against mechanical stress or osmotic pressure.
Plasma membrane
Regulated entry and exit of substances site of some metabolic processes.
Nucleoid
Region containing the cell’s single circular DNA
Controls cell activities
Flagellum
Movement
motility
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