Transcript Chemistry for Changing Times 11th Edition Hill and Kolb

Biochemistry
Biochemistry is the chemistry of
living things and life processes.
• I. CARBOHYDRATES
• II. LIPIDS
• III. PROTEINS
• IV. NUCLEIC ACIDS
Energy in Biological Systems
Green plants contain chloroplasts which are capable of
taking the radiant energy of the sun and storing it as
chemical energy in glucose molecules.
6 CO2 + 6 H2O → C6H12O6 + 6 O2
Plant cells can also convert carbohydrate molecules to
fat molecules and some are even capable of converting
them to proteins.
Animals cannot produce their own energy. They must
obtain such energy by eating plants or other animals that
eat plants.
Energy in Biological Systems
Metabolism is defined as the series of
chemical reactions that keep a cell alive.
Metabolic reactions are divided into two
categories:
Catabolism: the process of breaking down
molecules to produce energy.
Anabolism: the process of synthesizing molecules.
CARBOHYDRATES
Carbohydrates are the most abundant organic compound
in plants and animals.
- the storehouse of chemical energy (glucose,
starch)
- component of supportive structures in plants
(cellose) and bacterial cell walls (mucopoly
saccharides)
- essential component of nucleic acids (D-ribose)
- A, B and O blood types are determined by
specific membrane - bound carbohydrates.
CARBOHYDRATES
Carbohydrates
- starch
- sugars
- cellose
function groups which identifies this classification H
C O where the H:O is always 2:1
Sugars - monosarchaide - glucose can be written
either cyclic -real or straight chain - fisher
projections - do not show stereo chemistry
- sugars have many different isomers which
determine different physical & chemical properties
like sweetness
CARBOHYDRATES
Carbohydrates are composed of polyhydroxy aldehydes
or ketones,
O
O
||
||
HO - R - C - H
R - C - R - OH
and contain two functional groups:
hydroxyl (-OH) and carbonyl (C=O).
Carbohydrates are also called SACCHARIDES due to
the sweet taste of the simple members of this family:
CN(H2O)M
- monosaccharides
- oligosaccharides
- polysaccharides
3 to 9 carbons
2 to 10 units
10 or more units
Carbohydrates
Monosaccharides: carbohydrates that cannot
be hydrolyzed into simpler compounds.
Carbohydrates
Most monosaccharides actually exist in
cyclic form.
Carbohydrates
Disaccharides consist of molecules that can be
hydrolyzed into two monosaccharide units.
GLUCOSE
- Important sugar for humans
- dextrose, grape sugar, blood sugar
- (glucose) controlled by hormones
(insulin & glucagon)
- (gluc) = 100 - 120 mg/100mL,
insulin stimulates uptake of excess glucose
Low glucose count = light headed, shaky
Glucagon stimulates liver to release
glucose to establish normal levels.
LACTOSE (MILK SUGAR)
- B - D - galactose + D - glucose
- C1 hydroxyl group of galactose bonds to C4 hydroxyl
group of glucose
- B (14) glycosidic bond
- sugar in mammalian milk
- used by body as energy source, hydrolized to glucose
and galactose (reverse RX)
- lactose intolerence: unable to hydrolyze lactose since
the enzyme “lactase” is not produced (undigested lactose
remains in intestinal tract causing cramping and diarrhea
and dehydration.
- galactosemia: enzyme missing, galactose toxic
Carbohydrates
Polysaccharides are composed of large
molecules that can be hydrolyzed into
many monosaccharide units. Examples
include starch, cellulose, and glycogen.
Carbohydrates
Both starch and
cellulose are polymers
of glucose. The
linkages between
glucose molecules in
starch are alpha (α)
linkages, whereas in
cellulose they are beta
(β) linkages.
Fats and Other Lipids
Lipids are biological molecules that are
insoluble in water but are soluble in
nonpolar organic solvents.
Fats are esters of long-chain fatty acids
and glycerol. Fats are often called
triglycerides or triacylglycerols.
LIPIDS
- Classified by solubility product; lipids are insoluble in
water (non polar)
-
Five major types
1. Fats & oils (triglycerides)
2. Phospholipids (cell membranes)
3. Fat soluble vitamins
4. Steroids
5. Waxes
- Each lipid type has a distinct structure
1. Fats & oils = fatty acids & glycerol
2. Phospholipids = fatty acids, phosphate and amino
alcohol
3. Fat soluble vitamins =
4. Steroids = a fused structure of three cyclohexanes
& a cyclopentane
5. Waxes = fatty acids and long chain alcohol
Fats and Other Lipids
Triglycerides
are triesters of
glycerol and
fatty acids.
Fats and Other Lipids
Saturated fatty acids have no carbon-tocarbon double bonds.
Monounsaturated fatty acids have one
carbon-to-carbon double bond.
Polyunsaturated fatty acids have two or
more carbon-to-carbon double bonds.
Fats and Other Lipids
Solid fats have a high proportion of saturated
fatty acids.
Liquid oils have only unsaturated fatty acids.
Iodine number is a measure of the degree of
unsaturation of a fat or oil. Iodine number is the
number of grams of I2 that are consumed by 100
g of a fat or oil.
FATS AND OILS
I.
Nearly all fatty acids have even number
of carbon atoms in an unbranched chain. R =
12 to 20
II. As the number of carbon atoms in a
saturated fatty acid increases, it’s melting
point increases.
III. Unsaturated fatty acids have lower
melting points than saturated fats.
IV. The greater the degree of unsaturation,
the lower the melting point.
HYDROGENATION
Hydrogenation of an oil leads to a
saturated oil (a fat).
Partially hydrogenated oils contain
more saturated fatty acids than the
original oil but they contain no
cholesterol, unlike similar products
from butter or lard.
Proteins
Proteins are a vital
component of all
living things.
Proteins
Plants can synthesize proteins from carbon
dioxide, water, and minerals like nitrates or
sulfates.
Animals must consume proteins as part of their
diet.
Humans can synthesize some amino acids, but
must obtain essential amino acids in a normal
diet.
Proteins
Proteins are polymers
of amino acids.
Amino acids contain
both an amine and
carboxylate group
attached to the same
carbon called the
alpha carbon.
The Peptide Bond
Amino acids are linked to each other to form
proteins by an amide linkage between the
amine of one amino acid to the carboxylate of
another amino acid. This amide linkage is
known as the peptide bond.
The Peptide Bond
Dipeptide is formed when two amino
acids are joined.
Tripeptides contain three amino acid
units.
Polypeptides contain 10 or more amino
acid units.
Proteins may contain 10,000 or more
amino acid units.
The Peptide Bond
The sequence of the amino acids in a protein is
critical. The sequence is always denoted from
the free amino group (N-terminal) to the free
carboxyl group (C-terminal).
Structure of Proteins
Enzymes
Enzymes are biological catalysts. Most are
proteins. Many are highly specific, only
catalyzing a single reaction or related group of
reactions. The substrate is the reactant
molecule whose reaction the enzyme catalyzes.
Enzymes
The activity of many enzymes can be explained
by the induced fit model. According to the
induced fit model, the substrate molecule bonds
to the enzyme at the active site, forming an
enzyme-substrate complex. This complex can
then catalyze the reaction of the substrate and
form products.
Enzyme + Substrate → Enzyme-substrate complex ↔ Enzyme + Products
Enzymes
Induced Fit Model
Enzymes
Inhibition
The action of enzymes can be inhibited.
One mechanism of enzyme inhibition has
a molecule bonding to the enzyme protein
at another site other than the active site.
This changes the shape of the protein and
prevents the substrate from bonding at the
active site. This mechanism is used to
control the action of certain enzymes.
Enzymes
Inhibition
Enzymes
Cofactors: Some enzymes require another
molecule to be present for proper functioning of
the enzyme. Cofactors can be inorganic ions
(Zn2+, Mg2+, …) or organic molecules.
Coenzyme: A cofactor that is a nonprotein
organic molecule.
Apoenzyme: Pure protein part of an enzyme.
Enzymes in Medicine
Diabetic test strips use two enzymes to measure blood
sugar. One enzyme catalyzes the oxidation of glucose,
producing hydrogen peroxide as a by-product. The other
enzyme catalyzes the breakdown of hydrogen peroxide
and oxidizes a dye to produce a color change.
Enzymes can be monitored to diagnose liver damage or
heart damage.
Enzymes can also be used to break up clots after a heart
attack or to increase clotting to treat hemophelia.
Enzymes in Industry
Enzymes have many industrial
applications including the production of
baby foods, beer, sweeteners for soft
drinks, animal feeds, and blue jeans.
Enzymes in Everyday Life
Enzymes are used in stain removers and
meat tenderizers. Those that are lactoseintolerant can also take enzymes to
reduce the discomfort caused by ingesting
dairy foods. Worldwide production of
enzymes is worth more than $1 billion per
year.
Nucleic Acids
Nucleic acids serve as the information
and control centers of the cell. They are in
two major forms: deoxyribonucleic acid
(DNA) and ribonucleic acid (RNA). Both
consist of long chains called nucleotides.
Each nucleotide is composed of a sugar
unit, phosphate unit, and a heterocyclic
amine base.
Nucleic Acids
Nucleic Acids
Nucleotides are
composed of a sugar,
phosphate, and an
amine base.