Bio- Ch 2 Chem Composition Of Life

Front 1

element

Back 1

cannot be broken down into similar substance by chem reactions - 92 naturally occurring

Front 2

compound

Back 2

2 or more element in fixed ratio

Front 3

example of emergent property in elements

Back 3

change chars when combined into compounds

Front 4

elements necessary for life

Back 4

25/92

Front 5

most common elements

Back 5

96 percent of human life=
carbon (C), oxygen (O), hydrogen (H), and nitrogen (N)—make up 96% of living matter.
Most of the remaining 4% of an organism’s weight consists of phosphorus (P), sulfur (S), calcium (Ca), and potassium (K).
Trace elements are required by an organism but only in minute quantities

Front 6

atom

Back 6

smallest unit of matter with the properties of the element

Front 7

what keeps the electrons around the nucleus?

Back 7

attraction of negative to positive charge

Front 8

dalton

Back 8

unit used to measure mass for atoms and subatom particles
-prot and neut each about 1 dalton

Front 9

atomic number

Back 9

number of protons in nuclei... all atoms of element have the same number
- subscript in front of symbol

Front 10

mass number

Back 10

sum of protons and neutrons
- used to calculate atomic weight (atomic weight in daltons)
- superscript

Front 11

isotopes

Back 11

same element different # of neutrons

Front 12

radioactive isotopes

Back 12

unstable isotopes, decay spontaneously emitting particles and energy
ex 14c, when it decays a neutron converts to a proton and an electron, turning into 14n a different element
- many applications in biological research such as fossil dating. tracing atoms and pet scans
- if a substance with a known quantaty of radioactive isotope is injected into the blood its rate of excretion in urine can be measured
- energy emitted is hazardous to life
- destroy molecules in living cells

Front 13

structure of an atom

Back 13

mostly empty space, small ucleus and electrons

Front 14

subatomic particles in chem reactions

Back 14

electron config effects chemical behavior of the atom... nuclei do not come close enough to contact

Front 15

energy

Back 15

ability to do work

Front 16

energy in electrons

Back 16

potential energy because of position relative to nucleus, farther away= more pot energy
- changes in pot energy only occur in fixed amounts (must absorb or release energy that matches the diff in pot energy between levels)

Front 17

elements ion the periodic table

Back 17

same rows fill the same shells with electrons. moving left to right each element adds one electron

Front 18

electrons in outer shell

Back 18

valence electrons

Front 19

same number of valence electrons=

Back 19

similar chemical behaviors

Front 20

electron orbitals

Back 20

-complex 3d space where electron is found 90% of the time
- can hold a max of 2 electrons
- first shell= 1s orbital
- second shell= 2s and 3 2p (dumbell shaped)

Front 21

electron positioning

Back 21

occupy separate orbitals within the valence shell until forced to share
unpaired electrons make the atom reactive and are involved in chem reactions

Front 22

chemical bonds

Back 22

atoms are attracted close together after chem reactions
- covalent and ionic are the strongest

Front 23

covalent bond

Back 23

sharing of a pair of valence electrons-- both atoms count both electrons

Front 24

molecule

Back 24

2 or more atoms held together by covalent bonds
structural formula = H-H
molecular formula= h2

Front 25

atom's valence

Back 25

its bonding capacity (number of unpaired electrons)

Front 26

electronegativity

Back 26

attraction of an atom for the shared electrons of a covalent bond
- strong electroneg atoms pull electrons towards themselves

Front 27

nonpolar/polar covanlent bond

Back 27

nonpolar= shared equally (similar or same electronegativities) (CH4)

polar- differ in electroneg (h20) partial negative charge near the strong electroneg atom and partial positive near the weaker

Front 28

ionic bond

Back 28

2 atoms are so unequal in attraction for valence electrons that one strips electron away
- strength depends on environment

Front 29

ions

Back 29

after ionic bond atoms are not neutral
cations- positive
anions- negative
---- atoms in ionic bond can have charges that are not caused by transfered with each other

can also be charged molecules

Front 30

ionic compunds

Back 30

formed by ionic bonds, salts, like nacl

Front 31

weak bonds

Back 31

ionic bonds in water, hydrogen bonds, and van der wals interactions play important roles in chemistry of life

Front 32

hydrogen bonds

Back 32

hydrogen atom covalently bonded to strongly electroneg atom is attracted to another strongly electroneg atom
-- occur because of the partial neg and pos charges

Front 33

van der waals interactions

Back 33

temproary regions of partial neg and positive charge because electrons are always in motion. when they accumulate by chance in one area it chreates changing reagions of partial negative and pos charges and molecules in close proximity can be attracted

Front 34

shape of a molecule

Back 34

determines the function
- determined by the positions of electron orbitals shared by the atoms involved in the bond
- moleccular shape is how biological molecules recognize and interact with one another

Front 35

covalent bonds and molecule shape

Back 35

orbitals in valence shell rearrange
for electrons in s and p, bond makes 4 new orbitals in tetrahedrals shape

Front 36

example of molecular shape dictating function

Back 36

signal molecules from a transmitting cell bind to receptor molecules from a receiving cell
te temporary attachment of the receptor and signal molecule stimulates activity in the receptor cell
molecules with similar shapes have same biological effects ie heroin shaped like endorphins

Front 37

starting molecules in chem reaction? final molecules?

Back 37

reactants and products

Front 38

photosynthesis

Back 38

carbon dioxide and water --> sugar and oxygyn
powered by sunlight
6c02+6h20= c6h1206+6O2

Front 39

reversible reactions

Back 39

when reactant concentrations are high they collide requently to make products and as the products build up they collide to reform reactants.
eventually the rate of formation of products is the same as the rate of breakdown== chemical equilibrium
concentrations stabilized at a particular ratio.