Download Section 1 Metabolic Processes Cell Structure and Process

Section 1
Metabolic Processes
Cell Structure and Process
electronegativity: a substance’s ability to attract electrons usually, electronegativity increases from
left to right and from bottom to top in a periodic table
if the electronegativity difference of a bond is greater than or equal to 1.7, that bond is ionic
if it is less than 1.7, it is polar covalent
polarity of a molecule is dependent on the electronegativity of the constituent elements and the
molecule’s shape
bonding:
ionic: usually between metals and nonmetals; metals lose 1 or more electrons to
nonmetals; when dissolved in water, they lose their crystalline structure, ex. NaCl
covalent: compounds form by sharing electrons between neighbouring atoms. A single
†
dash in a structural diagram indicates 1 pair electrons being shared,
2 dashes mean a
double bond (4 electrons shared), etc.
intermolecular forces:
bonds between molecules
determine the physical state of a substance at a given temperature and pressure
weaker than the bonds that hold the molecule together
hydrogen bonds are the strongest intermolecular force. They form between an
electropositive hydrogen of one polar molecule and the electronegative N, O or F of a
neighbouring molecule. These bonds are easily broken and very important biologically, as
they determine the shape and thus the function of molecules
acids, bases and buffers:
acids: substances that increase the concentration of H 3O+ (hydronium) ions when
dissolved in water
† of OH - (hydroxide) ions when dissolved
bases: substances that increase the concentration
in water
† maintain this, cells use buffers.
most cells work best at a pH of approx. 7. To
buffers are usually conjugate acid-base pairs in equilibrium and sometimes buffers are
proteins
the most common buffer (biologically) is carbonic acid and bicarbonate
pH<7.35 is acidosis and pH>7.35 is alkalosis. 7.35 is normal.
organic compounds:
compounds containing carbon
organized according to properties and molecular structure
functional groups:
specific groups of atoms attached to an organic molecule
react with other functional groups
influence physical and chemical properties
organic (carboxylic) acids contain: -COOH
polar
weak acid
†
amines (amino-) contain: -NH 2
weak base
found in†proteins
alcohols contain: -OH
polar, forms hydrogen bonds
†
water
soluble
aldehydes and ketones (carboxyls) contain: = O
if the “ = O ” is on a terminal carbon, the molecule is an aldehyde
† after drinking alcohol
aldehydes are exhaled
† if the “ = O ” is on a mid chain carbon, the molecule is a ketone
ketones are expelled in urine if eating a high-fat diet
† aldehydes and ketones are water-soluble, common in sugars
phosphates contain:
found in ADP and ATP
sulfhydryls contain: -SH
macromolecules
†
large molecules
of repeating subunits
four major classes:
carbohydrates (CHOs)
lipids (made of fatty acids and glycerol)
proteins (made of amino acids)
nucleic acids (made of nucleotides)
condensation reactions
aka anabolic reactions or dehydration synthesis reactions
form larger molecules
a molecule of water is removed, which comes from a H - from one functional group and
a -OH from another one are removed
these reactions absorb energy
†
†
hydrolysis reactions:
aka catabolic reactions
water is added to break a large molecule into smaller molecules
produces energy
enzymes are usually required
carbohydrates
general formula: (CH 2O) n , where “n” is some number
three general groups:
monosaccharides (single sugars) ex. glucose
†
monosaccharides are a single chain or ring of carbon atoms to which
hydroxyl groups are attached.
CH 2OH
H
O
O
C
H
H
H C OH †
H
†
†HO C H
†
OH
H C †
OH
† H
OH
OH
H C OH †
H C OH
†
†
H †
H
ex:
† OH
(solid and dissolved glucose, C6 H12O6 molecules)
†
†
†
†
†
†
oligosaccharides
(double sugars) ex. sucrose
†
2 or more simple sugars attached by glycosidic linkages
+
Æ
ex: glucose + glucose Æ maltose + H 2O
†
†
†
†
+ H 2O
polysaccharides (many sugars) ex. cellulose, starch
complex carbohydrates with 100-1000 simple sugars
there are two kinds:
energy sources and
polysaccharides
isomers: molecules with the same chemical formula, but a different arrangement of atoms, ex.
glucose and galactose
glycosidic linkages:
1-4 glycosidic linkage
1-6 glycosidic linkage, see page 31
lipids:
usually hydrophobic
composed of C, H and O, but has more C-H than O-H bonds
used for storing energy, building membranes and chemical signals
four families: fats, phospholipids, steroids, waxes
carry more energy than proteins or CHOs, can act as insulation
triglycerides (most common fat) are composed of 3 fatty acids attached to 1 molecule of
glycerol (
)
fatty acid: long hydrocarbon chains with -COOH at the end
saturated fatty acids have no double bonds (solid @ room temp.)
† multiple bonds (liquid @ room temp.)
unsaturated fatty acids have
ester linkages are formed by condensation reactions between fatty acids and glycerol
(
), called esterification
steroids (sterols) are hydrophobic molecules containing four fused hydrocarbon rings and
other functional groups
phospholipids are glycerol +2 fatty acids +1 polar phosphate group
waxes contain long-chain fatty acids linked to alcohols or carbon rings
waxes are hydrophobic, firm, pliable
amino acids:
general structure:
proteins:
can be biological catalysts
transport molecules, in haemoglobin, keratin, etc
can be shown as ionized:
amino acid monomers are called peptides
peptides are synthesized in cytoplasm through ‘protein synthesis’
bonds between amino acid monomers are called peptide bonds, formed by condensation
reactions. These bonds are called amide linkages
+
Æ
DNA specifies
† the order of the amino acids when they are assembled
for review questions see p. 50# 19, 20, 23, 24, 25, 26, pp. 86-87# 1-15