Lecture 3: water chemistry Flashcards
Life can be boiled down to chemistry:
life is carbon based. cast array of different kinds of chemical compounds with carbons that make life possible. carbohydrates, lipids, proteins, nucleic acids. the structure of these chemicals turns out to be important: behave differently, perform different cellular duties. These biological molecules developed over 400,000,000 years.
chemical composition of a body:
25 of the naturally occurring elements are essential to people. 4 make up ~96% of the weight of the body. 1. oxygen. 2. carbon. 3. hydrogen. 4. nitrogen. trace elements are required only in very small amounts: iodine, fluorine, magnesium, etc.
element consists of a single kind of atom
atom: smallest unit of matter that still retains properties of an element. electrons: (-) orbit around a nucleus. Protons (+) and neutrons (no charge): packed tightly into the nucleus
atomic structure:
electrons orbit around the nucleus in a surrounding shell. the protons in a nucleus neutralize electron charge- net neutral charge
more electrons mean more shells
the outer most electron shell has electrons with highest energy.
Matter: anything that occupies space and mass
92 naturally occurring elements. elements have a symbol derived from English/latin/German name. organized into the periodic table by atomic number
the atomic mass of an atom:
atomic mass indicates how much matter it contains (essentially protons+neutrons) don’t confuse with the atomic number (# of protons alone)
isotopes:
element with two or more forms of atoms. contain the same number of protons and electrons, but the number of neutrons varies. radioisotopes break down and emit radiation.a radioactive isotope is one in which the nucleus decays spontaneously. radiation from decaying isotopes can damage cellular molecules and pose serious health risks. Natural sources of radiation can also pose a threat. radon, a radioactive gad, is a carcinogen that can cause lung cancer. Radon testing is a standard procedure before a house is bought or sold
molecules:
2 or more atoms linked together
compound:
type of molecule with 2 or more elements in a fixed ratio. common compounds: NaCl (salt) H2O (water) C6H12O6( glucose)
chemical bonding and molecules:
only electrons are directly involved in chemical bonds. The number of electrons in an atom determines its chemical properties/bonds. chemical reactions enable atoms to transfer/share electrons. thus atoms are held together by attractions called chemical bonds.
chemical reactions:
all about rearranging matter. but cannot create or destroy matter. Chemical reactions include reactants (the starting products) and products (the end products). cells constantly rearrange molecules by breaking existing chemical bonds, and forming new ones. example: making ATP: energy molecule, break a chemical bond: phosphate group broken off to release energy, chemical arrangement changes but matter as a whole is the same.
ionic bonds:
When an atom loses or gains electrons, it becomes electrically charged. Ions are atoms or molecules that are electrically charged as a result of gaining or losing electrons. Ionic bonds are formed between oppositely charged ions.
covalent bonds:
a covalent bond forms when two atoms share one or more pairs of electrons. covalent bonds are the strongest of the various bonds and hold atoms together in a molecule
Hydrogen Bonds:
understand how water properties make life happen, water has a particular set of skills. the polarity of water results in weak electrical attractions between water molecules. these weak attractions are called hydrogen bonds. readily formed and broken, while individually weak, hydrogen bonds are strong when present in large numbers
water molecules:
a molecule of water (H2O), 2 hydrogens bound to 1 oxygen, covalent bonds, electrons are not shared equally between the oxygen and hydrogen atoms. This causes water to be a polar molecule, one with an uneven distribution of charge.
water polarity:
different distribution of charge inside the molecule. Partially negative charge on this side, partially positive charge on this side
structure/function of water:
the polarity of water molecules and the hydrogen bonding that results explain most of water’s life sustaining properties. large part of an organisms mass is water. water is important and internal constituent and environmental factor
unique properties of water:
lower density with freezing, excellent solvent for polar molecules, high surface tension/cohesive, high specific heat, high heat of vaporization, water exists as solid, gas, or liquid, hydrogen bonds are formed or broken as water changes states.
- the cohesion of water:
water molecules stick together as result of hydrogen bonding. this tendency of molecules of the same kind to stick together is called cohesion and is much stronger for water than most other liquids.
- water moderates temperature
earth’s giant water supply enables temperatures on the planet to stay within limits that permit life by storing a huge amount of heat from the sun during warm periods, giving off heat that warms the air during cold periods. our own bodies, evaporative cooling occurs when a substance evaporates and the surface of the liquid remaining behind cools down
- biological significance of ice floating:
when water molecules get cold enough, they move apart, forming ice. a chunk of ice floats because it is less dense than the liquid water it is floating in. if ice did not float, ponds, lakes, and oceans would freeze solid. ice layer forms above a deep body of water, the floating ice acts as an insulating “blanket” over the liquid water. allowing life to persist under the frozen surface.
- versatility of water as a solvent:
water facilitates chemical reactions. solvent: substances that dissolves another compound. solute: the compound that gets dissolved. aqueous solution: water + dissolved solute
not all compounds will dissolve in water:
hydrophilic substances: interact with water readily (ie NaCl) Hydrophobic substances: does not interact easily. not disrupted or dissolved by water (oil) hugely important in membrane formation in cells.
