Matter takes up space and has mass Everything composed of matter Any biological process, function or...
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Transcript of Matter takes up space and has mass Everything composed of matter Any biological process, function or...
Matter takes up space and has mass Everything composed of matter
Any biological process, function or structure can be broken down to it’s chemical level -> molecules/atoms
Atoms and Molecules Element-substance that cannot be broken down
chemically to simpler substances with different properties
There are 92 naturally occurring elements, 25 of which are essential to life
O - 65% C - 18.5 % H - 9.5 % N - 3.3 %
C, H, O found in carbs, proteins, lipids and nucleic acids
N found in proteins, nucleic acids P found in nucleic acids S
Ca, P, K, S, Na, Cl, Mg = ~4 %
Few elements exist pure (alone) in nature - they are part of compounds
Compounds-substance containing two or more elements in a fixed ratio
Atomic structure Protons and
neutrons located in the nucleus at the center of the atom
Electrons found outside nucleus in orbitals, electron shells, or energy levels
Atomic number - the # of protons in an element, gives it it’s unique properties - all atoms of a particular element have the same # of protons
Atomic mass =
Atomic Symbols Each element represented by unique atomic symbol
One or two letters First letter capitalized Superscripted number before:
• Represents mass number
•
Subscripted number before• Represents to atomic number
• Number of protons in nucleus
MassMassNumberNumber
AtomicAtomicNumberNumber
AtomicAtomicSymbolSymbol
126
Carbon
C
Periodic Table Elements grouped in periodic table based on
characteristics Horizontal rows = periods; larger and larger
1
H1.008
3
Li6.941
11
Na22.99
19
K39.10
4
Be9.012
12
Mg24.31
20
Ca40.08
5
B10.81
13
Al26.98
21
Ga69.72
6
C12.01
14
Si28.09
22
Ge72.59
7
N14.01
15
P30.97
23
As74.92
8
O16.00
16
S32.07
24
Se78.96
9
F19.00
17
Cl35.45
25
Br79.90
10
Ne20.18
18
Ar39.95
26
Kr83.60
2
He4.003
II
IIII IIIIII IVIV VV VIVI VIIVII
VIIIVIII
11
22
33
44
Groups
Periods
Isotopes
Isotope - same # of protons (same element), different # of neutrons (different atomic mass)
Radioactive isotopes (radioisotopes) -
Radioisotopes
Tracers-monitor fate of atoms Useful in medical diagnosis (PETscans) Exposure to high levels can damage
molecules (DNA) harming organisms and causing cancer
Electrons and Bonding
Electrons determine how atoms behave when contacting other atoms-this is the single most important factor in the chemistry of living things
The # of electrons in the outermost shell (valence) determines chemical properties of atoms
Atoms with incomplete outer shells tend to interact with other atoms
Atoms want to have their outermost energy level filled
They can fill it by sharing electrons, or by giving electrons to or receiving electrons from another atom
Compounds and Molecules
When atoms of two or more elements chemically bond together, a compound is formed
The shapes of molecules are important in the structural and functional roles they play in living things
Chemical Bonds Sharing of
electrons forms a covalent bond
Giving and receiving electrons form ionic bonds
Covalent bond between atoms form molecules
Ionic bond
One atom (Na) gives (donates) an electron
The other atom (Cl) receives an electron
The atom that gives up an electron becomes a positive ion
The atom that receives an electron becomes a negative ion
Opposite charges attract each other (electrostatic attraction) to form am an ionic bond
Electrons and energy levels
Excited state - when an electron absorbs additional energy to move up to the next energy level. Electrons return to original ground state by emitting extra energy
Plants use this brief energy increase (10-8 sec) during photosynthesis
Biologically Important Weak Bonds
Organisms need to be able to change to maintain homeostasis (chemical balance) to meet changing environment
Covalent bonds are too strong and cannot be broken easily and changed
Weak bonds of biological importance include: ionic bonds, hydrogen bonds, van der Waals interactions
Hydrogen Bonds
Electrostatic attraction between oppositely charged portions of nearby molecules
Hydrogen bonds form between molecules that have no net overall electrical charge (are neutral)
Ionic bonds form between oppositely charge atoms
Weak bonds play crucial role in stabilizing shape of large molecules like DNA, proteins
Covalent bonds = 50-110 kcal/mole
Ionic bonds = 10 kcal/mole
Hydrogen bonds = 4-5 kcal/mole
van der Walls = 1-2 kcal/mole