The Chemistry of Life Topic 2 SL and Topic 6

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The Chemistry of Life(Topic 2 SL and Topic 6 7
HL)

• Major Sub-Topics
• 1. Chemical elements and water
• 2. Carbohydrates, Lipids, and Proteins
• 3. Enzymes
• 4. DNA structure and replication
• 5. Protein synthesis
• 6. Cellular respiration
• 7. Photosynthesis
• (SL and HL level topics)

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Subtopic OneChemical Elements and Water
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Objectives

• Define matter
• Define element
• Define atom and describe its general structure
• List and describe the role of the 4 major
  elements and some other types of elements found
  in living organisms
• Define and describe ionic bonding
• Define and describe covalent bonding
• Describe the structure of a water molecule and
  its polar nature
• Describe the unique properties of water and how
  they make it essential to living organisms

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Matter and Atoms

• Matter is any material that has mass and occupies
  space.
• All materials nonliving and living in the
  universe is composed of matter.
• All matter is composed of small units called
  atoms. The types of atom, their arrangement, and
  how they interact with one another gives the type
  of matter its specific chemical and physical
  properties.

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Atomic Structure (Review)

• Atoms are composed of subatomic particles each
  with their own unique properties. They are
• a. Protons - Positive charge, atomic mass unit
  of one. Gives the atom its identity (Atomic
  Number). Located in the nucleus or center of the
  atom.
• b. Neutrons No charge (neutral), atomic mass
  unit
• of one. Their numbers can vary from atom to
  atom
• of the same element. Responsible for forming
  isotopes. Located in the nucleus.
• c. Electrons - Negative charge, no atomic mass
  unit. Located
• outside of nucleus in regions called orbitals.
  They are involved
• with the process of chemical
  bonding between atoms. They
• can be shared or transferred
  between atoms in the bonding
• process therefore, their numbers can
  vary between atoms of the same
• element. If atoms gain or lose electrons
  they become electrically charged and are called
  ions. They are responsible for the reactive
  chemical properties of atoms.

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Basic Atom Structure
Neutron No charge Amu 1
Proton charge Amu 1
electron orbital

• Electron
• Charge
• Amu 0

Nucleus composed of protons and neutrons. Gives
the atom its atomic mass, determined by adding
the number of protons and neutrons together.
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Periodic Table of Elements
An element is a pure substance made up of one
type of atom. The elements which are most common
in all living things are Hydrogen (H, atomic
number 1), Carbon (C, atomic number 6), Nitrogen
(N, atomic number 7), and Oxygen (O, atomic
number 8). These atoms compose the backbone or
framework of the molecules such as proteins,
lipids, nucleic acids, and carbohydrates found in
living things.
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Hydrogen, Carbon, Nitrogen, and Oxygen
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Other Biologically Important Elements

• Calcium (Ca) Formation of bones and shells in
  animals, involved with muscle contraction and
  neuron activity in animals.
• Phosphorous (P) Forms energy storing compounds
  ATP, Nucleotides (A,T, G, C, U), and membrane
  building molecules (phospholipids).
• Sulfur (S) amino acids and protein structure
• Sodium (Na) Neuron activity, water balance, and
  membrane transport
• Potassium (K) membrane transport and muscle
  activity
• Iron (Fe) oxygen transport of red blood cells as
  a component of hemoglobin.
• Magnesium (Mg) light activated atom component of
  chlorophyll molecules.

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Chemical Bonding Review

• Chemical bonds form to increase the stability of
  atoms by filling their outer most electron energy
  level. In order to do this atoms will transfer
  electrons ( one atom will lose electrons and the
  other atom will gain electrons) to form ionic
  bonds or atoms will share a pair of electrons
  (each atom will share one electron for each bond
  that is created between them) to form covalent
  bonds.

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Ionic Bonding
In order to increase stability, the Na atom will
transfer its outermost electron to the Cl atom.
Outermost Energy Levels
Na
Cl
Cl
Chlorine (Cl) 17
Sodium (Na) 11
Protons 11 17
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17 Neutrons 12 18
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18 Electrons 11
17
10 18 Charge
Neutral Neutral
positive
negative Ion Neutral
Neutral cation
anion
Stability is achieved because the outer energy
levels of both atoms, now ions are filled by
electrons.
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Covalent Bonding
Each pair of electrons represents the
formation of a covalent bond.

Hydrogen (H) 1
Carbon (C) 4
Methane CH4
Stability is again achieved because the outer
energy levels of both atoms, now the outer
energy levels are filled by electrons due to
sharing of electron pairs between the atoms!
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Water

• Water is a molecule that is essential to life as
  we know it here on Earth. It is a component of
  all living things and serves many functions.
  Water has many unique properties due to the
  nature of its molecular composition.
• Water is a polar covalent substance. Although it
  is formed by covalent bonds between two atoms of
  hydrogen and one oxygen atom, there is an unequal
  sharing of electrons between the two types of
  atoms. Oxygen is a larger molecule and has a
  higher affinity (attraction) for the electrons
  than the hydrogen atoms. Therefore, the
  electrons tend to be around the oxygen atom than
  the hydrogen atoms. This results in a slightly
  negatively charged region of the molecule where
  the oxygen atom is located and a slightly
  positively charged region of the molecule where
  the hydrogen atoms are located. This produces
  polarity in the molecule and leads to some unique
  properties of water.

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Water Molecule Structureand Hydrogen Bonding
Covalent bonds between hydrogen and oxygen
Positively charged hydrogen end
Due to the positively charged and negatively
charged regions on each molecule, the positive
region of one molecule becomes attracted to the
negatively charged region of another molecule
forming Hydrogen Bonds. The molecules stick
together.
Negatively charged oxygen end
Hydrogen Bonds
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Important Properties of Water

• High specific heat It requires much heat energy
  to raise the temperature of water one degree
  Celsius. Important in regulating the temperature
  of living things. This results in a high heat of
  vaporization.
• High heat capacity It requires a long period of
  time for water to gain or lose heat energy.
  Important in regulating temperature, important to
  aquatic organisms.
• Universal Solvent Many materials organic and
  inorganic will dissolve in water. Important in
  the role as a transport medium for living things.
  Animal blood and the sap of plants are primarily
  composed of water with other materials dissolved
  in it.
• Cohesive properties Water molecules hydrogen
  bond together to form a film layer on the
  surface of water called surface tension, capable
  of supporting certain plants and animals. This
  property also plays a role in capillary action
  (the movement of water up and through small
  diameter tubes).
• Adhesive properties Water molecules due to their
  polar nature tend to stick to other substances.
  This property along with cohesion is responsible
  for capillary action and the formation of a
  meniscus in a glass tube.
• Water Expands as It Freezes The solid form of
  water is less dense than the liquid, therefore
  ice floats! This is important in aquatic
  environments because they will always freeze from
  the top surface down. The ice usually creates an
  insulating layer from the colder air temperature,
  allowing the organisms below the surface of the
  ice to survive. However, this property is also
  dangerous to organism with soft tissues. When
  the water inside their cells freeze, it expands
  and destroys the cells. Frost bite in humans is
  a result of this property.