BIO130 Section One Guide (2)

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26 Apr 2011
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Chapter 2 Cell Chemistry and Biosynethsis
(pg. 51-64)
Water Is the Most Abundant Substance in Cells
-Water accounts for about 70% of a cells weight
-DNA, RNA, sugars, and most proteins are all hydrophilic
-Uncharged Molecules of long hydrocarbon tails that are hydrophobic can be
exploited to construct membranes
Four Types of Noncovalent Attractions Help Bring Molecules Together in Cells
-In aqueous solution, covalent bonds are 10-100x stronger than other attractions
between atoms
-There are three three noncovalent chemical bonds that are much weaker:
oIonic (electrostatic attraction) forms permanent dipoles
Polar water molecules cluster around both fully charged ions to reduce
the electron affinity of both oppositely charged atoms
oHydrogen bonds where an electropositive H atom is partially shared by
two electronegative atoms
a proton that has partially dissociated from a donor atom, allowing it
to be shared by a second acceptor atom highly directional
ovan der Waals attractions the electron cloud around any nonpolar atom
will fluctuate, producing a flickering dipole
ohydrophobic force caused by a pushing of nonpolar surfaces out of the H-
H bonded water network, where they would otherwise interfere with the
highly favourable interactions between water molecules
bringing any two nonpolar surfaces together reduces their contact
with water
central to the proper folding of protein molecules
A Cell Is Formed from Carbon Compounds
-carbon is outstanding among all the elements in its ability to form large molecules
(silicon is a poor second)
-C-C covalent bonds are highly stable no upper limit to their size
Cells Contain Four Major Families of Small Organic Molecules
-Sugars, fatty acids, amino acids, nucleotides
Sugars Provide an Energy Source for Cells and Are the Subunits of
Polysaccharides
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