BIOL 202 - Lecture 1: Overview of Biology and Introduction to Chemistry
What is Life?
Biology is literally the study of life. But what is life? This task isn’t easy, but what can guide us are the shared characteristics of living organisms and living systems:
Cellular structure - a complex, ordered organization consisting of one or more cells that carry out the functions necessary for life.
Metabolism - a means of acquiring, using, and transforming energy to carry out tasks.
Sensitivity and responsiveness to the environment, including adaptation to changes in environment.
Homeostasis - an ability to maintain relatively constant internal conditions that may differ from the external environment.
Made from organic molecules - organic molecules contain carbon and make up all living organisms
Growth, development, and reproduction.
Evolutionary adaptation - the phenomenon within populations of changes in traits over time.
The Main Fields of Study in Biology
There are five main themes in the study of biology:
Evolution - populations have the capacity to change over time. As a consequence of the change in genetic characteristics of a population over time, populations may become better adapted to their environments. These changes may be manifest in the physical, physiological, biochemical, and behavioural features of the individuals within a population. On a larger scale, the tremendous variety of adaptations resulting from evolution accounts for the great diversity of organisms on earth.
Example: The lichen huntsman spider’s camouflage is the result of evolution. The spiders without camouflage would become prey to predators more easily, and those with more camouflage would survive and reproduce (natural selection).
Example: The finches Darwin studied illustrate the adaptations that occurred in response to varying environmental pressures, such as food availability and habitat, leading to the development of distinct beak shapes suited for different feeding strategies.
Example: Humans developed a complex social structure that enhances cooperation and communication, allowing for the sharing of resources and knowledge, which ultimately increases survival and reproductive success in diverse environments.
Example: The peppered moth is another classic example, where the coloration of the moths shifted from light to dark during the industrial revolution due to pollution, demonstrating how environmental changes can drive evolutionary adaptations.
Structure and function - across all levels of organization, the physical features of organisms are closely related to function.
Example: The spines on a wild carrot seed enhance dispersal by sticking to the fur of passing animals.
Example: The alveoli (small sac-like structures) in the lungs provide a way for gas exchange between the lungs and blood.
Information flow, exchange, and storage - genetic information (instructions for biochemical, physical, and behavioural traits) is carried in all organisms and passed to their offspring. Its expression influences the organisms’ growth and functioning.
Example: Before cell division, DNA is precisely replicated to ensure each daughter cell inherits an identical copy of genetic information.
Pathways and transformations of energy and matter - within organisms, pathways of chemical reactions use energy to transform matter and enable growth, movement, reproduction, and other processes. Systems. Life is organized on many interconnected levels within individual organisms, including molecules, cells, tissues, and organs. And in the larger world, organisms themselves are organized into many levels: populations, communities, and ecosystems within the biosphere.
Example: The sun provides virtually all the energy used by living organisms on Earth. This energy is captured through photosynthesis in plants, which serves as the foundation for food chains and energy flow in ecosystems.
Systems - life is organized on many interconnected levels within individual organisms, including molecules, cells, tissues, and organs. And in the larger world, organisms themselves are organized into many levels: populations, communities, and ecosystems within the biosphere.
Elements and Atoms
Elements are the basic building blocks of matter. These are substances that cannot be further broken down into other substances. Some elements include, gold, iron, sodium, copper, and so on (see the periodic table). If you cut down an element into smaller pieces, each piece will behave exactly the same.
For instance, the smallest piece of pure gold will still have the softness, reflectivity, and malleability characteristic of that element.
Elements are made up of atoms; these are the smallest unit of an element that retains the properties of that element. In fact, the word “atom” comes from a Greek word meaning “indivisible”. Atoms have four essential components:
Nucleus - the central and most massive part of an atom, usually made up of up to two types of particles, protons and neutrons, which move about the nucleus.
Protons - a positively charged particle in the atomic nucleus; it is identical to the nucleus of the hydrogen atom, which lacks a neutron and has atomic number 1.
The number of protons in an atom’s nucleus is its deciding factor; that is what determines its atomic number. When the number of neutrons and protons in a nucleus is the same, the mass of an atom is about twice its atomic number.
Neutrons - a particle in the atomic nucleus with no electrical charge. Neutrons have approximately the same mass compared to protons.
Electrons - A negatively charged particle that orbits the atomic nucleus. An electron’s weight is infinitesimally small.
Note that an atom is made up of the combined mass of its protons and neutrons (electrons’ mass is negligible).
The most essential components for life consist of 4 types of atoms (or elements on the periodic table):
H (hydrogen), atomic number 1
C (carbon), atomic number 6
N (nitrogen), atomic number 7
O (oxygen), atomic number 8
Here are some extra elements useful for the sake of this class:
Na (sodium)
P (phosphorus)
Cl (chloride)
K (potassium)
Different chemical elements have different chemical properties because they have a different subatomic structure:
Different number of protons and neutrons in the nucleus
Different number of electrons orbiting the nucleus
Here is some key information you should keep in mind:
An element’s atomic number is equal to the number of protons it contains
The number of protons in an element is equal to its number of electrons
An element’s atomic mass is equal to the number of protons and neutrons it has
An atom has electron shells, which can accomodate 2, 8, and 8 electrons from the innermost to outermost (valence) shell.
Isotopes
Atoms can have different number of neutrons, and these atoms have a different atomic mass but share the same chemical properties.
Carbon-12 has 6 protons, 6 neutrons, and 6 electrons, with an atomic mass of 12. It consists of 99% of the oxygen found in nature.
Carbon-13 has 6 protons, 7 neutrons, and 6 electrons, with an atomic mass of 13. It consists of 1% of the oxygen found in nature.
Carbon-14 has 6 protons, 8 neutrons, and 6 electrons, with an atomic mass of 14. It consists of 0.00000000001% of the oxygen found in nature.
Carbon-14 is unstable, which is why it is referred to as a radio isotope.
Molecules
Molecules are formed by combinations of atoms. For instance, water consists of two hydrogen atom and one oxygen atom.
Atoms are joined together my chemical bonds
The Electron Shell
The outermost electron shell determines if chemical bonds are formed
If it is full, then there cannot be any chemical bonds
If it is not full, there is room for chemical bond formation
Inert Gasses
Inert gasses are a category of elements on the periodic table which are unable to form chemical bonds because their outermost (valence) shell is full
Helium (its first and only electron shell is full, with 2 electrons)
Neon (its second and last electron shell is full, with 8 electrons)
Argon (its third and last electron shell is full, with 8 electrons)
Different Chemical Bonds
There are three types of chemical bonds you must memorize:
Covalent (strongest)
Two hydrogen atoms, with one electron each, are flying around. They each have a need to fill their electron shell. So they will share their electrons.
Strongest chemical bonds because atoms are sharing electrons
A good example is H2 (hydrogen gas)
Covalent bond is indicated by a line: H - H
These electrons span an equal amount of time across each atom, therefore these two atoms are joined together with an equal force
This is a non-polar covalent bond (e.g., atoms are attracted by equal forces)
Another example of a non-polar covalent is O2 (oxygen gas)
2 atoms are joined together by covalent bonds
2 vacancies in outermost shells, must share 2 electrons
This creates a double bond (denoted by two lines: O = O)
Double bonds are stronger than single bonds because they’re sharing two electrons rather than only one
Another example of a non-polar covalent bond is methane gas (CH4)
1 carbon atom in the centre, with 4 vacancies in the outermost shell (meaning it can form up to 4 chemical bonds)
Carbon shares 4 electrons with 4 hydrogen atoms, with an equal force
When covalent bonds are formed, sometimes electrons spend more time surrounding one atom over the other, creating a small charge in the molecule in which one atom has a positive charge and the other a negative charge. These are known as polar covalent bonds.
Unequal pull of electrons between atoms creates small charges
The more protons an atom has, the more strongly it will pull electrons into its orbit
Water molecule (H20) is made with polar covalent bonds
The oxygen atom in water has a stronger electron pull compared to the hydrogen atoms, creating a negative charge for the oxygen atom and a positive charge for the hydrogen atoms
Non-polar vs. Polar:
Two of the same atoms have equal pull, therefore are non-polar covalent bonds
Carbon and Hydrogen have equal pull, therefore are non-polar covalent bonds
Oxygen attracts electrons more strongly than Hydrogen, so are polar covalent bonds
Fluorine attracts electrons more strongly than Hydrogen, so are polar covalent bonds
Nitrogen attracts electrons more stongly than Hydrogen, so are polar covalent bonds
Ionic (weaker)
Ionic bonds are chemical bonds formed by ions. Ions are atoms with an electrical charge. Let’s talk sodium chloride (NaCl) as an aexample:
Sodium has 1 atom in its outermost shell, meaning it has 7 vacancies.
Chloride has 7 atoms in its outermost shell, meaning it has 1 vacancy.
Sodium donates its atom to the chloride atom, creating two atoms with negative (Cl) and positive charges (Na), e.g., ions
Positive and negative ions are attracted to each other; this is what forms an ionic bond (electrical charges - negative and positive are attracted)
Because covalent bonds involve the sharing of electrons, they are stronger than ionic bonds, which simply function through the attraction of ions
Hydrogen (weakest)
If molecules are created by polar covalent bonds, they are known as polar molecules. They have slight charges, so different polar molecules will be attracted to each other (e.g., the negative side of polar molecule 1 will be attracted the the positive side of polar molecule 2).
This is what hydrogen bonds are; one slightly polar hydrogen atom being pulled towards another polar molecule.
Hydrogen bonds are similar to ionic bonds in that they consist of negative and positive charges being pulled towards one another. However, the charges between polar molecules is not very strong compared to ionic bonds.
Water (H2O) and Hydrogen Fluoride (FH) , or Ethanol (CH4) are examples of hydrogen bonds, where the positive hydrogen atoms will be attracted to a negative charge of another polar molecule.
Summary:
Two hydrogen atoms and one oxygen atom are joined by a polar covalent bond
Each water molecule is joined by hydrogen bonds
Polar covalent bonds are found within a water molecule
Hydrogen bonds are found between water molecules
Properties of Water
Properties of Water That are Important to Life
Cohesion/Surface Tension:
Hydrogen bonds make water molecules “stick together”, water droplets are round and spherical because of this cohesion
Tall trees rely on the cohesive nature of water to deliver it from the ground into each of its branches
Water molecules are strongly connected with a hydrogen bond, so it is difficult to break water’s surface (e.g., their strong connection creates surface tension)
Adhesion:
Allows for water to stick to other substances (like plant cell walls or glass)
Large Heat Capacity:
Water temperatures don’t change rapidly
Heat from the sun is used for rearranging hydrogen bonds rather than increasing the water temperature
Living organisms in water live in a relatively constant environment
Low Density as a Solid:
Solid water (ice) is less dense than liquid water
Ice remains on the surface of liquid water
Creates a surface for living organisms
Insulation for water below (temperature remains relatively constant, which is why a diversity of wildlife can flourish during the winter)
Good Solvent:
Water can dissolve substances really well (such as glucose, a solute)
Water can also dissolve ions (such as NaCl, or table salt)
Allows different chemical reactions to occur in living organisms
Hydrophilic molecules easily dissolve in water
Ions (such as salt)
Polar molecules (such as sugar)
Hydrophobic molecules don’t dissolve in water
Oil
Non-polar molecules
PH Scales: Acids and Bases
Ionization of Water
Even water can be ionized!
Small proportion of wate rmolecules dissociate into two ions;
Hydrogen ions (positive charge, donate an electron)
Hydroxide ions (negative charge, gain an electron)
Pure water contains an equal amount of OH- and H+ ions
The amount of H+ ions changes depending on the materials dissolved in the water
Different Forms of Hydrogen
Hydrogen atoms are always found together, because we have to fill in the first electron shell (covalent bonds - hydrogen gas; H2).
Or you lose the electron, the Hydrogen atom becomes positively charged (ion) and becomes a proton (no electron orbiting)
pH Levels
pH is an indicator of H+ ions in a solution.
More H+ means a low pH, indicating an acidic solution
Coffee, tea, soda
Sour in taste
H+ ions are very reactive
pH 7 is neutral
Water
Less H+ means a high pH, indicating a basic solution
Mr. Clean, soap, baking soda
Strong bases are caustic to your skin
Slippery and bitter in taste
Note that aquatic life is sensitive to pH change (can kill pet fish in a aquarium)