The Chemical Basis of Life All the chemistry you need to know.
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Transcript of The Chemical Basis of Life All the chemistry you need to know.
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The Chemical Basis of Life
All the chemistry you need to know
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Matter is anything that occupies space and has mass.
Energy is the capacity to do work, or put mass into motion.
Potential (stored) energy
Kinetic energy (energy of motion)
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Some forms of energy:• Radiant energy - energy that travels in
waves
• Electrical energy – flow of charged particles
• Heat – kinetic energy of molecules
• Chemical energy - potential energy, the way living things store energy
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Elements are substances which cannot be splitinto simpler substances by ordinary chemical reactions.
Each element has a one or two letter chemicalsymbol.
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C
O
H
N
Ca
Cl
Na
K
Carbon
Oxygen
Hydrogen
Nitrogen
Calcium
Chlorine
Sodium
Potassium
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O, C, H, N = 96 % of body weight
Add
Ca and P = 98.5 % of body weight
Add
K, S, Cl, Na and Mg = 99.9.% of body weight
“Bulk Elements”
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Atoms are the smallest unit of an element that still has the chemical properties of that element.Atoms:Have a central nucleus
Protons (+)Neutrons (0)
Orbitals on the outside that hold
Electrons (-)
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The number of electrons in the outermost shell determines how each atom interacts with other atoms.
Atomic number = the number of protons in the atom.
Atomic weight (or Mass number) = the total number of protons and neutrons.
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Isotopes are atoms of an element that all have the same number of protons, but have different numbers of neutrons.
The time it takes for half of a radioactive substance to decay is called its half-life.
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When two or more atoms combine in a chemical reaction, a molecule is formed. This molecule may have very different properties than the elements that formed it.
When a molecule contains two or more atoms of different elements, it is called a compound.
CO2 H2O NaCl C12H22O11
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• Atoms are most stable when their outermost shell contains eight electrons. They may accept, give up or share electrons with another atom to do this.
• The outer most shell is the valence shell and the number of electrons that must be gained or lost to fill or empty that shell is called the valence number.
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Atoms are held together by forces of attraction called chemical bonds, which are forms of potential energy.
Ionic bonds
Covalent bonds
Hydrogen bonds
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In an ionic bond electrons are transferred from one atom to another. Opposing charges hold the atoms together.
An ion is a charged particle (atom or molecule).
Na+ Ca++ positive charge - cations Cl- HCO3
- negative charge – anions
Substances that breaks into positively and negatively charged ions in solution are called electrolytes.
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Covalent bonds are formed when atoms share electrons. These are the strongest bonds. C - C
Double covalent bonds C=C
Triple covalent bonds N≡N
(atmospheric nitrogen)
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• Electronegativity – electron “hog”
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When one end of molecule has a positive charge and the other has a negative charge, the molecule is polar.
When molecules have a more uniform distribution of charges they are called nonpolar molecules.
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Polar molecules are hydrophilic .“water loving”
Nonpolar molecules are hydrophobic.“water fearing”
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Hydrogen bonds are weak but important bonds. They do not bind atoms into molecules, but are important in giving large molecules their shape.
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Chemical reactions involve making and breaking bonds.
Making bonds requires the input of energy.
Energy is stored in molecules in the chemical bonds.
Breaking bonds usually releases energy.
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Water• Water is denser as a liquid than a solid
– Ice floats
• Water has a high heat capacity– Allows for heat loss by sweating or panting
• Water is cohesive– Water strider = good– Lungs = bad – Surfactant reduces the surface tension of
water
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Water cont.
• Water clings to surfaces – adhesion– This is how plants bring water up to their
leaves
• Water is a good solvent– Substances dissolved in water are solutes– Many important biological molecules are
amphipathic – (both – feeling) hydrophilic and hydrophobic ends
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Water participates in chemical reactions:
dehydration synthesis - combines atoms with the removal of water
hydrolysis – breaks apart molecules with the addition of water.
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Water breaks up into hydrogen ions (H+)
and hydroxide ions (OH-)
Chemical equilibrium = balance
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pH
• The negative log of the hydrogen ion concentration. The more hydrogen ion a solution has, the lower its pH is.
• “power of hydrogen”
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In water:
Acids - one or more hydrogen ions (H+) and one or more anions.
Bases - hydroxide ion (OH-) and one or more cations.
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A salt ionizes into anions and cations, neither H+ nor OH-
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pH regulation (homeostatsis)
• 7.35 – 7.45
• CO2 + H2O ↔ H2CO3 ↔ HCO3- + H+
• Buffer systems
• Respiratory system
• Excretion by kidney