Download Ch 6 Chemistry of Life Lecture

Biology
Chapter 6: The Chemistry of Life
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Name_____________________________________
Per_______________
Learning Goals
o You will be able to describe the parts of an atom and how atoms interact with each other
o You will be able to describe the different methods of how elements are able to bond
together to form molecules and compounds
o You will be able to explain the importance of hydrogen bonds and water to organisms
o You will be able to explain the process and importance of diffusion
o You will be able to identify and describe the base structures and functions of the four types
of biomolecules
Atoms
o When constructing a picture of how our world is built, scientists begin with the atom.
o Atoms are the basic building blocks of all matter
o Essentially, every living and non-living thing in our universe is a series of atoms held
together by electrical charges
o Though they come in different sizes, atoms all have the same basic shape
o The center of the atom is the nucleus.
o Inside of the nucleus are two types of particles, protons and neutrons
 Protons are positively charged, like the positive end of a battery
 Neutrons are the same size and shape as a proton, but with no charge (they are
neutral)
o Surrounding the nucleus in specific “shells” are electrons.
o Electrons are negatively charged particles, and are much smaller than protons.
o If the atom is stable, then the number of electrons will equal the number of protons in an
atom.
o The overall charge of the atom is zero, but the nucleus is positively charged and the outside
shells are negatively charged.
Electrons
o Electrons are peculiar. They tend to hang out in specific shells surrounding the nucleus
o The first shell has only two electrons. Almost every shell after that has 8 (not really, but this
is simplified)
o If an atom’s outer shell does not have the right amount of electrons, it will be unstable.
o Each atom can donate or accept other electrons to become more stable
Protons
o “Elements” and “atoms” are the same thing
o Each element is a different type of atom.
o The number of protons in an atom’s nucleus determines the element
 Oxygen has 8 protons, therefore any atom with 8 protons must be an oxygen.
 The number of neutrons and electrons doesn’t matter
Sketch Area
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Isotopes of Elements
o An isotope is an element with the same number of protons but different numbers of
neutrons
o Sometimes the extra neutrons cause the atom to be unstable and the neutrons break off of
the nucleus
o When they break off, the energy that held them in the nucleus is released
o This energy is called radiation
 Compounds and Bonds
o Compounds are combinations of elements that make a new substance
 H2O is…?
 Water
 NaCl is…?
 Table Salt
 NH3 is…?
 Ammonia
o Atoms combine with other atoms to form a compound more stable than the atom by itself
o The key to stability is getting the outer shell to 8 electrons
 The one exception is Hydrogen, which only needs two
o Covalent bonds share the outermost electrons to make a completed outer shell
o Since all atoms are stable, the bond is also stable
o The second type of bond is an Ionic bond
o Ionic bonds form when one atom uses another atom to fill it’s shell
o The second atom’s shell isn’t completely filled, so it’s still unstable and highly reactive.
 Reactions occur when two atoms FORM a bond or BREAK a bond
 Covalent bonds: atoms share electrons; not reactive
 Ionic bonds: one atom borrows electrons from another atom; highly reactive
o Why do we care in biology?
o Compounds held together by covalent bonds are stable and are typically used by organisms
as a form of storage or structure
 Food and Energy; Bones; Tissues
o Compounds held together by ionic bonds are unstable. Organisms use them for any type of
reaction
 Nerve conduction; Muscle contraction
Sketch Area
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Acids and Bases
o Acids and Bases are compounds that undergo reactions when in contact with water.
 Since most organisms contain or react with water, acids and bases react with water
as well
o The type of reaction determines whether or not the compound is an acid or a base
o Acidity or Basicity is determined by the pH scale.
 If a substance has a pH under 7, it’s an acid
 If a substance has a pH over 7, it’s a base
o An acid is any substance that forms Hydrogen (H+) ions in water
o A base is any substance that forms Hydroxide (OH-) ions in water
 Water
o It’s the most important molecule on the planet by far.
o Water makes up important molecules
 Blood, tears, sap,
o Water transports materials
 Oxygen to lungs, nutrients through roots
o Water insulates and protects
 Sweating, Atmosphere
o Water is a polar covalent molecule
 Hydrogen and Oxygen share electrons, but not equally
 The result is that each molecule has a slightly positive end and a slightly negative
end.
 Hydrogen Bonds
o Hydrogen bonds form between two polar molecules (molecules with charges)
o Hydrogen bonds are easy to break and easy to form
o Hydrogen bonds allow water molecules to cling to each other
o Hydrogen bonds also allow water to cling to other molecules like salt and sugar (dissolving)
 Properties of Water
o Each oxygen in water (the negative charge of the molecule) forms a hydrogen bond with the
hydrogen’s (positive charge) of a different water molecule
o This allows for several important properties of water
 Specific Heat: water can absorb and hold lots of heat energy without changing
temperature
 This makes it difficult for water to gain heat or lose heat.
 Solvent: water breaks apart molecules by using it’s charge to bond with parts of
other molecules
 NaCl—Sodium (Na) is positively charged. Chlorine (Cl) is negatively charged.
 In the presence of water, Na+ will attract to oxygen and the Cl- will attract
to the hydrogens
 Cohesion. Water molecules can bond to each other
 Water flows freely without breaking up
 This makes water excellent for transport
 Water can move up plant roots or plumbing (capillary action)
Sketch Area
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Surface Tension
 Hydrogen bonds cover the surface of water
 Organisms can float on the surface if they do not break the bonds
Density
 Water is unique because it is less dense as a solid than a liquid, so ice will
float on water
 Life exists below frozen lakes because of this
Diffusion
o When you pour food coloring into water, does it all sit in one spot?
o Diffusion is the net movement of particles from an area of higher concentration to an area
of lower concentration
 The direction of movement is called a concentration gradient
o When the number of particles is equally balanced, the particles will still move back and
forth, but at an equal rate
 This rate is called dynamic equilibrium
o Diffusion is what allows many biological functions to occur.
 Nerve conduction
 Muscle contraction
 Medicines in the bloodstream
 Oxygen into the bloodstream
 Carbon Dioxide out of the bloodstream
 How you tone your muscles
 How you distribute your fat storage evenly
Carbon
o Carbon atoms are very small, very stable, and can bond with up to 4 other molecules
o Carbon can form rings, chains, or branched structures
o This results in billions of different molecules able to be formed, all of which are one of four
types of molecules
 Proteins, Carbohydrates, Lipids, Proteins
o Each of these molecules is made up of monomers and polymers
 Monomer: A single puzzle piece or link in a chain
 Polymer: A completed puzzle or multiple links in a chain.
Condensation/Dehydration
o Monomers and polymers use water to attach to each other and break apart.
o Each monomer contains a hydrogen (H) on one end and a hydroxyl (OH) on another end.
o Monomers attach due to a condensation reaction
 Remove the hydrogen off one monomer and the hydroxyl off another.
 Attach the two monomers in their place
 The hydrogen and hydroxyl form an H2O—hence, condensation.
Hydrolysis
o Lysis means “to split”. Hence, hydrolysis is “splitting water.”
o Hydrolysis is the exact reverse of condensation.
 When breaking a polymer into separate monomers, water is required.
 Split the H2O into a hydrogen (H) and a hydroxyl (OH)
 Break the polymer into two monomers and attach the hydrogen and hydroxyl to
plug the gap
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This is also one reason why you should drink water if you’re trying to burn
fat
Biomolecule #1: Carbohydrates
o All carbohydrates have a chemical equation that is a multiple of CH2O
 Example: Glucose is C6H12O6
o Carbohydrates are used by cells as short-term energy sources
o Carbohydrates are built from sugars called saccharides
 A single carbohydrate, such as glucose or fructose, is called a monosaccharide
 (These are the monomers)
 The polymers of carbohydrates are called disaccharides (two monosaccharides) or
polysaccharides (3 or more monosaccharides)
 Disaccharide examples: Sucrose, Maltose, Lactose
 Polysaccharide examples: Starch, Glycogen, Cellulose
Biomolecule #2: Lipids
o Lipids are large biomolecules consisting almost entirely of chains of carbon and hydrogen
o Lipids are not attracted to water molecules and, thus, are not soluble (cannot dissolve in
water)
o Lipids are used by cells as long-term energy storage (fat), insulation and protective coverings
(cell membranes)
o Examples of lipids:
 Butter, Fats, Oils
o Monomers of lipids are called “fatty acids”.
o A saturated fat is a lipid with the most possible Hydrogen atoms in it’s chain
o An unsaturated fat is a lipid missing at least one Hydrogen atom due to a double bond.
 The double bond creates a kink in the chain
o The polymers are 3 fatty acids called triglycerides
Biomolecule #3: Proteins
o Proteins are made of monomers called amino acids
o Amino acids have a Nitrogen (amine), a pair of oxygens (carboxylic acid), a central carbon,
and a special group that changes depending on which amino acid you have
 This special group is called an “R” group
o Each amino acid (a.a.) is connected by attaching the amine from one a.a. to the carboxylic
acid of another a.a.
o The R groups, though, can get in the way.
o So instead of one long chain, the protein has to wrap around itself into a 3-D shape
o Enzymes
 Enzymes are proteins that help speed up chemical reactions
 Each enzyme only reacts with one specific molecule called a substrate.
 This molecule fits perfectly with the enzyme because of the enzyme’s unique 3-d
shape
 Just like a lock-and-key, the enzyme’s reaction can only react with the right
molecule, or key
o Enzymes work by lowering the activation energy of a reaction.
o Activation energy is the minimum amount of energy required to perform a task. Enzymes
reduce this amount to very low levels.
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This allows enzymes to perform their specific task fast and efficiently.
 Digest food, synthesizing hormones, transmit messages through nerves, store
energy for exercise
Biomolecule #4: Nucleic Acids
o DNA and RNA
o Nucleic Acids have one function: store and transport genetic information
o Nucleic acids are made up of chains of nucleotides.
o Each nucleotide has one ribose sugar and a special base.
o Each nucleotide is attached to a phosphate, which is used to connect nucleotides to each
other.
o The different bases are codes. The sequence of the bases tells the cell what type of protein,
carbohydrate, lipid, or nucleic acid to make AND where it should go
o DNA is always located inside the nucleus of the cell so that it is never lost
o RNA is used by the cell to copy the DNA code and transport this message throughout the cell
Conclusion
o Because water is involved in nearly every reaction on the planet, we study atoms and
elements and how they react with water.
o Atoms interact in different ways to form different elements
o Different elements interact with each other to form the four types of biomolecules
o These biomolecules are rearranged and interact with each other in billions of different ways
o All these differences create the diversity of life on our planet.