Fundamental Properties of Life

What Is Life?

• Life is a complex phenomenon that is challenging to define precisely.
• Movement alone is not a sufficient diagnostic of life, as many non-living objects move.
• Sensitivity, or the ability to respond to stimuli, is also inadequate to define life.
• Death, as a criterion, is a circular definition and inadequate for defining life.
• Complexity is a necessary but not sufficient criterion for identifying living things.

Fundamental Properties of Life

• Life encompasses various characteristics and processes and can be characterized by key features, including cellular organization.
• Living organisms exhibit a high level of structural organization, with cells as the basic unit of life.
• Sensitivity refers to how living organisms respond to external stimuli, demonstrated through mechanisms like movement, chemical reactions, and behavior.
• Growth involves metabolic processes, such as energy conversion and nutrient utilization, for maintenance and reproduction.
• Development is how living organisms grow and develop over time, increasing in size and complexity, demonstrated through cell division, differentiation, and tissue specialization.
• Reproduction allows living beings to produce offspring that are either sexually or asexually produced to continue their species
• Organisms pass on their DNA to the offspring which results in offspring with species consistent traits
• Regulation ensures tiny organisms have regulatory mechanisms to manage internal functions
• Organ systems assist in managing the body's performance of distributing oxygen, eliminating waste, delivering nutrients, and regulating body temperature.
• Homeostasis enables living organisms to maintain internal stability despite changes

Primordial Soup

• The primordial soup theory suggests that the early Earth's atmosphere, rich in methane, ammonia, hydrogen, and water vapor, combined with lightning and ultraviolet radiation, led to the synthesis of organic molecules.
• These organic molecules, including amino acids and nucleotides, accumulated in the oceans to form a "soup" from which life could have emerged.
• Over time, simple organic compounds underwent reactions, leading to complex molecules such as proteins, nucleic acids, & lipids
• The primordial soup provided the chemical environment for the origin of life on Earth billions of years ago.

Electric Spark and Bubble Hypothesis

• Volcanoes erupted under the sea, releasing gasses enclosed in bubbles, creating concentrated gasses inside of bubbles reacting and producing simple organic molecules
• Bubbles persisted long enough to rise, then they popped, releasing their contents to air
• Sun's UV radiation, lightning, and energy prompted simple organic molecules to react to form complex organic molecules.
• Complex organic molecules return to sea in raindrops, then enclosed by bubbles so the process can begin again.

Panspermia

• Panspermia is a hypothesis that suggests that life exists throughout the universe and can be spread from planets and moons by natural means.
• Microbial life or the building blocks of life, could travel through space to planets, moons, meteoroids, comets, debris, etc, seeding new environments upon impact.
• Lithopanspermia: life transferred rocks and meteoroids
• Directed panspermia: deliberate seeding of life via civilizations
• Astrobiology plus space exploration is involved in investigating panspermia

RNA World

• RNA played a role in early evolution, serving as genetic material and catalysts for biochemical reactions.
• Self-replicating RNA molecules may have arisen spontaneously on early Earth, facilitated by conditions like UV radiation, lightning, and volcanic activity.
• Early RNA molecules could have replicated and evolved, leading to more complex RNA-based systems.
• RNA molecules can both store information similarly to DNA and catalyze chemical reactions like proteins.
• RNA could have been a transitional stage between prebiotic chemistry and biochemistry.

Community Clay

• Clay mineral materials are suggested to have acted as templates and agents toward the assembly of organic molecules
• Clay minerals act as templates/catalysts in assembling amino acids and nucleotides
• Amino acids are building blocks of proteins and nucleotides
• Organic molecules may become concentrated and organize on surfaces of clay minerals
• Concentration and organization of minerals may lead to the formation of complex molecules and promote the emergence of early life forms

The Fundamental Unit of Life

• All organisms are made of cells
• Cells are a collection of matter that can be alive
• Humans are composed of around 100 Trillion individual cells
• 50 cells cover the area of a dot on the letter “i”

Robert Hooke

• Born on July 18, 1635
• Died on March 3, 1703
• Wrote and published “Micrographia”
• Known as the “English Father of Microscopy”

Discovery of Cells

• In 1665, Robert Hooke discovered cells looking at a thin slice of cork through a microscope.
• Hooke described the cells as tiny boxes or a honeycomb.
• Hooke believed cells only existed in plants and fungi.
• His observations lead to coining the word "Cell" translated from a latin word meaning "Little rooms"
• After discovering the cells, he compared with the space that monks lived in.

Anton Van Leeuwenhoek

• Leeuwenhoek used a handmade microscope to observe pond scum and discovered single-celled organisms in 1673.
• He called the organisms "Animalcules".
• Observed blood cells from fish, frogs, birds, dogs, & humans
• Cells are found in animals and plants

Development of Cell Theory

• Around 1838, Matthias Schleiden, a famed German botanist, concluded that every plant element is cellular.
• In 1839, German Physiologist, Theodor Schwann who was friends with Schleiden, came to the conclusion that every animal tissue is comprised of cells
• Circa 1858, Rudolf Virchow, German Physician, deduced that all cells are constructed from pre-existing cells after comprehensive cellular pathology learning.
• Remak & Virchow (1858) noted that "All cells come from pre-existing cells"

The Cell Theory

• Key contributors to the Cell Theory are Matthias Schleiden, Theodor Schwann, & Rudolph Virchow.
• Organisms are composed of 1+ cells. (Schleiden & Schwann)(1838-39)
• The cell is the basic unit of life in all living organisms (Schleiden & Schwann)(1838-39)
• Cells are produced through the division of preexisting cells. (Virchow)(1858)

Cell Diversity

• Cells have enormous diversity in Size, Shape and internal organization
• Female egg is the largest cell
• Cells are visible with Microscope

Cell Size

• A female egg is the largest cell in the human body and can be seen without a microscope
• Most cells are only visible with a microscope.
• Cells are small in size because they are limited in the Ratio between the outer surface area and their volume
• A small cell has more surface area than a large cell

Cells Are Small

• When the size of a cell doubles: surface area and volume increases, and the SA:V decreases by half.
• Cells rely on diffusion for getting substances in and out of their cells
• As a cell grows, it has less membrane.
• Diffusion is not highly rapid or efficient in distributing materials over long distances
• Cells overcome issues by dividing, growing taller or thinner and by folding cells in the membrane.

Cell Shape

• The diversity of form reflects a diversity of function.
• The shape of a cell depends on its function

Internal Organization

• Prokaryotic vs eukaryotic cells
• Eukaryotic cells have organelles, cytoplasm, nucleus
• Cells both have a cell membrane

Microscopy

• Microscopes are used because cells are very small
• Microscopes come in two types
• Simple: one lens "magnifier"
• Compound/light: two lenses used in series, magnifying together the image of the specimen.

Imaging Techniques

• Optical Microscopy

  • Image Formed By: Light Rays
  • Lowest Resolvable Unit: Microns (µm)
  • Approx Lower Limit: 1 μm (monochromatic light)

• Confocal Microscopy

  • Image Formed By: Coherent Light Source (Laser)
  • Lowest Resolvable Unit: Microns (µm)
  • Approx Lower Limit: .1 μm (X-Y Direction)

• Transmission Electron Microscopy (TEM)

  • Image Formed By: Electrons
  • Lowest Resolvable Unit: Angstroms (Å)
  • Approx Lower Limit: 2 Å (high resolution TEM)

• Scanning Electron Microscopy (SEM)

  • Image Formed By: Electrons
  • Lowest Resolvable Unit: Nanometers (nm) to Angstroms (Å)
  • Approx Lower Limit: 10 nm (100 Á)

• Atomic Force & Scanning Tunneling Microscopies (AFM/STM)

  • Image Formed By: Molecular Mechanical Probes
  • Lowest Resolvable Unit: Angstroms (Å)
  • Approx Lower Limit: 40 Á (theoretical)

The Light Microscop

• With a light microscope, only the nucleus and cytoplasm are visible
• Dyes and simple staining make internal and external structures more visible by increasing contrast with background
• The limit of resolution for a light microscope is 200 nm.
• Total magnification is the magnification of its ocular multiplied by its objective lenses.

Optical Microscope Parts:

• Ocular lens
• Objective turret
• Objective lens
• Coarse adjustment
• Fine adjustment
• Stage
• Light source
• Condenser
• X-Y Control

Types of Electron Microscopes

• Scanning Electron Microscopy (SEM)
• 3-D imaging and examining surfaces:
• Transmission Electron Microscopy (TEM)
• Observing internal cell structure down to the molecular level

Light Microscopy vs. Transmission Electron Microscopy (TEM)

• Light: Small vs TEM: very big, needs an operator and special rooms!
• Light can view living/dead vs TEM only dead
• Light: simple preparations vs TEM: lengthy and complex preparation
• Light: less expertise vs TEM: Expertise
• Light: Cheaper vs TEM: Expensive
• Light: magnifies up to 1500x, TEM: magnifies up to 500000x
• Light: Low resolution vs TEM: High Resolution

Light Microscope vs Electron Microscope (advantages and Disadvantages)

• Light Microscope Advantage:
  • Inexpensive to buy
  • Inexpensive to operate – uses a little electricity;
• Light Microscope Advantage:
  • small and portable, easily used anywhere
  • Unaffected by magnetic fields, Quick prep.
  • Does not distort.
  • View live/dead material, natural colors.
  • Disadvantage magnifies objects up to 1500x,
  • Resolve objects up to 200nm apart, restricted depth of field.
• Electron microscope Disadvantage:
  • Expensive to buy and Run (100,000 volts to make a electron beam.), Large,
  • needs special rooms, Affected by magnetic fields.
  • Requires complex equipment, May distort, High vacuum (kill live material, cannot be observed), B&W
• Electron microscope Advantage:
  • Magnifies objecs over 5000,000x,
  • Resolving power is a biological specimens of around 1nm.
  • Greater depth of field can be investigated