Chapter 1: Introduction to Environmental Sciences (Part 1)

The Chemical and Biological Foundations of Life 

• Some of the most abundant elements in living organisms

  • Carbon

  • Hydrogen

  • Nitrogen 

  • Oxygen

  • Sulfur

  • Phosphorus 

• These elements above create fundamental components of living matter;

  • Nucleic acid

  • Proteins

  • Carbohydrates

  • Lipids

• The building blocks which are very important for unique structures of atoms that make up molecules 

• These allow the formation of cells, tissues, organ systems, and entire organisms

• Life is made up of matter

  • The matter is any sort of substance that uses up space and has mass

  • Elements are unique forms of matter with very specific properties (chemical and physical)

    • These can not be broken down into any smaller substances

    • There are 118 chemical elements 92 occur naturally

    • The remaining 26 elements are synthesized in laboratories and are unstable 

• The 5 elements common to living organisms are

  • Oxygen (O)

  • Carbon (C)

  • Hydrogen (H)

  • Nitrogen (N)

  • Phosphorus (P)

• In a world where non-living organisms reside elements are found in different proportions 

• Some elements are common to living organisms and are rare on the earth as a whole 

Ex. 

• The atmosphere is rich in nitrogen and oxygen but contains little carbon and hydrogen whilst the earth’s crust does contain oxygen and small amounts of hydrogen it has little nitrogen and carbon 

• Despite all the differences, all elements and chemical reactions between them obey the same chemical and physical laws where they are a part of the living or non-living world 

Chart of the approximate percentage of elements in living organisms (bacteria, humans) compared to no living wold 

(trace = less than 1%)

The Structure of an Atom 

• Atoms are the smallest unit of matter that retains all the chemical properties found of an element 

Ex. 

• One gold atom has all of the properties of gold in that it is a sold metal at room temperature. One gold coin is simply a very large number of golf atoms molded into the shape of a coin and containing small amounts of other elements known as impurities. 

• Gold atoms can’t be broken down into anything smaller whilst retaining the properties (of gold)

• Atoms are composed of 2 regions

  • Nucleus - the center of the atom and which contains the protons and neutrons

  • Outermost - holds its elections in orbit around the nucleus 

• Atoms contain protons, neutrons and electrons among other subatomic particles 

• The only exception is hydrogen which is only made up of one proton and one electron with no neutrons

• Here is a simple diagram of an atom

  • They have protons and neutrons in the nucleus and electrons surrounding the nucleus 

  • Protons and neutrons have approx. the same mass about 1.67(10-24) 

  • Scientists define this about of mass as one atomic mass unit (AMU)

  • Although they do have different electric charges

    • Protons are positively charged 

    • Neutrons are negatively 

  • Therefore the number of neutrons in an atom does contribute to its mass but not its charge 

• Electrons are much smaller in mass than protons

  • Weighing online 9.11(10-28) grams (or 1/1800)AMU

  • They don’t really contribute to the elements overall mass 

  • Electrons contribute a lot towards the charge of the atom 

  • Each electron has a negative charge which is equal to the positive charge of a proton

  • In neutral atoms (uncharged) the number of electrons orbiting the nucleus equal to the number of protons in the nucleus

  • In such atoms, positive and negative charged cancel each other out which can lead to an atom with no net charge 

  • Protons neutrons and electrons are mostly empty space which is 99%

  • Electrons that surround all atoms are negatively charged and negative charges repel each other 

  • When atoms gain or lose electrons, ions are formed 

    • These are charged forms of atoms 

  • Positive ions (sodium Na+) lose one or more electrons 

  • Negatively charged ions (chloride (C1-), gain one or more electrons 

Molecules 

• These are formed when two or more atoms join together through chemical bonds to form a unit of matter 

• Ex. 

  • CO2 is a molecule because it is made up of one carbon atoms and 2 oxygen atoms 

• Some ions molecules are charged due to the ions they contain 

• Ex. 

  • Nitrate (NO3-) - common source for plants

  • It contains one nitrogen atom and three oxygen atoms and has an overall 

    •  charge of negative one 
      Isotopes 

    • These are different forms of an element that have the same number of protons but different  number of neutrons

    • Elements such as carbon, potassium and uranium have naturally occurring isotopes 

    • Carbon-12 contains six protons, six neutrons and six electrons, therefore its mass number is 12 (six protons + six neutrons) 

      • These are alternate forms of carbon are isotopes 

  • Radioisotopes/ radioactive isotopes 

    • emit neutrons, protons, and electrons and attain more stable atomic configurations (lower level of potential energy)

    • Radioactive decay describe the energy loss that occurs when an unstable atom’s nucleus release radiation 

    • Ex.Carbon-14 losing neutrons to become carbon-12
      
      

    • Carbon 
      

      • The basic functional unit of life is a cell 

        • All organisms are made up of one or more cells

      • Macromolecules 

        • Cells are made of many complex molecules 

          • Proteins

          • Nucleic acids (RNA and DNA)

          • Carbohydrates 

          • Lipids 

        • These are a subset of organic molecules that are very important for life 

      • A fundamental component of all macromolecules is carbon 

      • Carbon has unique properties that allow it to form covalent bonds with as many as four different atoms 

      • Carbon is also a versatile element for basic structural components of macromolecules 

      • Hydrocarbons 
        
        

        • These are organic molecules that consist entirely of carbon and hydrogen 

        • Ex. 

          • Methane (CH4) - these covalent bonds between atoms in hydrocarbons store great amounts of energy and is released when molecules are oxidized (burned) methane is an excellent fuel and is also the simplest hydrocarbon molecule 

      • 
        

        • 
          

          This is a carbon molecule that shows a carbon atom in the middle and four hydrogen atoms (different) surrounding it. 

          
          

          Methane has a tetrahedral geometry with four hydrogen atoms spaced 109.5° apart. 

          
          

          This three-dimensional shape of macromolecules is critical to how they function.

          
          
          

          • Hydrocarbons may exist as linear carbon chains, carbon rings and combinations of both

        • Biological molecules

          • Life on earth is made of four primary major classes of biological molecules (biomolecules) 

            • Carbohydrates

            • Lipids

            • Proteins

            • Nucleic acids 

        • 
          

          Carbohydrates 

          • One type of macromolecule (especially when it comes to what we eat)

          • Essential to our diet (grains, fruits and vegetables are all natural sources of carbohydrates) 

          • They provide energy to our bodies (mainly through glucose) 

            • Glucose is a simple sugar that is a component of starch and an ingredient that is common in many foods

          • Carbohydrates have important functions in humans, animals and plants

          • Its formula - (CH2O)n - n is the number of carbons in the molecule 

            • Ratio form - 1:2:1 (carbon to hydrogen to oxygen)

          • This formula explains the origin of the term “carbohydrates”

            • “Carbo” the components of carbon

            • “Hydrate” the components of water 

        • 
          

          Glucose 

          • The chemical formula for glucose is C6H12O6

          • During cellular respiration, energy is released from glucose 

            • Help make adenosine triphosphate (ATP)

          • Plants synthesize glucose using carbon dioxide and water 

            • In turn, glucose is required for energy for the plant 

          • The excess is stored as starch that is a breakdown of larger molecules by cells (catabolized) 

            • By humans and other animals that feed on plants 

            • The starch is stored in different parts of the plant including roots and seeds

            • The starch in the seeds provides food for the embryo as it germinates and can provide food for animals and humans

        • 
          

          Lipids 

          • Include a diverse group of compounds such as fats, oil, waxes, phospholipids and steroids (nonpolar in nature)

            • Nonpolar molecules are “water-fearing” (hydrophobic) or insoluble in water

          • Lipids have important roles in storing energy and building cell membranes throughout the body

        •     Proteins 

          • One of the most abundant organic molecules in living systems and have a diverse range of functions of all macromolecules 

          • They can be structural, regulatory, contractile or protective

          • They may serve in transport, storage or membranes or they may be toxins or enzymes

          • Each cell in a living system may contain thousands of proteins with unique functions

            • Their structures and functions vary greatly 

        • 
          

              Enzymes 

          • Produced by living cells, speed up biochemical reactions (ex. digestion) and are usually complex proteins 

          • Each one has specific shapes or formations based on how it’s used 

          • They may breakdown, rearrange or synthesize reactions 

        • 
          

              Proteins 

          • Have different shapes and molecular weights 

          • Proteins shapes are critical to its functions and many different types of chemical bonds maintain this shape 

          • Protein can denature when the temperature is changed, pH or exposure to chemicals (permanent and can cause it to lose function)

          • All proteins are made of different arrangements of the same 20 types of amino acids (amino acids are units that make up proteins)

          • Ten of these are considered essential to humans because the human body can’t produce them and are gained from their diet

          • The sequence and number of amino acids determines the protein’s shape, size, and function 

        • 
          

          Nucleic acids 

          • Are the most important macromolecules for continuing life 

          • They carry the genetic blueprint of a cell and carry instructions for functioning cells 

          • 2 main types of nucleic acids

            • Deoxyribonucleic acid (DNA)

              • Genetic material found in all living organisms 

              • Controls all cellular activities by turning “on” or “off”

              • Has a double helix structure

        • 
          
          

          Native DNA is an antiparallel double helix. The phosphate backbone (indicated by the curvy lines) is on the outside and the base is on the inside. Each base from one strand interacts via hydrogen bonding with a base from the opposing strand. 

          
          
          
          
          
          
          

          • Ribonucleic acid (RNA)

            • Mostly involved in protein synthesis 

        • 
          
          

          Biological organization 

          • All living things are made of cells 

            • The cell itself is the smallest basic unit of structure and function in living organisms 

          • In most organisms, cells have organelles that give specific functions for the cell

          • Properties of living organisms 

            • All are highly organized

            • All require energy for maintenance and growth

            • All grow over time and respond to their environment

          • All organisms adapt to the environment and all reproduce contributing genes to the next generation

          • Some organisms consist of a single cell and others are multicellular

          • Organisms are individual living entities 

            • Ex. each tree in a forest is an organism 

        • 
          

              Population

          • All individuals of a species living within one specific area 

          • These vary based on a number of factors 

            • Seasonal and yearly changes in the environment 

            • Natural disasters (forest fires, volcanic eruptions)

            • Competition for resources (between species)

        •     Community 

          • The sum of populations inhabiting the same area 

          • Ex. 

            • All trees, insects, and other populations in a forest form the forest’s community (the forest is an ecosystem) 

        •     Ecosystem 

          • Consists of all living things in a particular area together with abiotic, non-living parts of that environment (nitrogen in the soil or rainwater)

        •     Biosphere 

          • Collection of all ecosystems and represents the zones of life on earth

            • Land

            • Water

            • Atmosphere (to a certain extent)