Biochemistry. Biochemistry is the chemistry of living things and life processes. I. CARBOHYDRATES II. LIPIDS III. PROTEINS IV. NUCLEIC ACIDS. Energy in Biological Systems.
Biochemistry is the chemistry of living things and life processes.
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.
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 are the most abundant organic compound
in plants and animals.
- the storehouse of chemical energy (glucose,
- component of supportive structures in plants
(cellose) and bacterial cell walls (mucopoly
- essential component of nucleic acids (D-ribose)
- A, B and O blood types are determined by
specific membrane - bound carbohydrates.
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 are composed of polyhydroxy aldehydes or ketones,
HO - R - C - HR - 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:
- monosaccharides 3 to 9 carbons
- oligosaccharides 2 to 10 units
- polysaccharides 10 or more units
Monosaccharides: carbohydrates that cannot be hydrolyzed into simpler compounds.
Most monosaccharides actually exist in cyclic form.
Disaccharides consist of molecules that can be hydrolyzed into two monosaccharide units.
- 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.
- B - D - galactose + D - glucose
- C1 hydroxyl group of galactose bonds to C4 hydroxyl group of glucose
- B (14) 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
Polysaccharides are composed of large molecules that can be hydrolyzed into many monosaccharide units. Examples include starch, cellulose, and glycogen.
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.
Saturated fatty acids have no carbon-to-carbon double bonds.
Monounsaturated fatty acids have one carbon-to-carbon double bond.
Polyunsaturated fatty acids have two or more carbon-to-carbon double bonds.
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.
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 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.
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.
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.
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 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).
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.
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
Induced Fit Model
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.
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.
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 have many industrial applications including the production of baby foods, beer, sweeteners for soft drinks, animal feeds, and blue jeans.
Enzymes are used in stain removers and meat tenderizers. Those that are lactose-intolerant 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 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.