Biological molecules: All are organic (based on carbon). Monomers vs. polymers: Monomers refer to the subunits that, when polymerized, make up a larger polymer. Monomers may function on their own in some cases.
Four types of biological molecules Carbohydrates - refer to a large group of biochemicals which in nature include monomers and polymers. Lipids - not considered as monomers/polymers like the others; they all have one PHYSICAL property in common. Proteins - polymers of amino acids with versatile functions. Nucleic acids - polymers of nucleotides, may be DNA or RNA.
Definition: contain carbon, hydrogen, and oxygen (carbo+hydrate), usually in the following ratio: [C(H20)]n
Basic Building Blocks Monosaccharides Three types, each of which contains 6 carbon atoms: glucose (most popular) fructose galactose
Monosaccharides Usually, they exist in nature as a "ring" form, after an ester linkage forms between the #1 carbon and the hydroxyl group of carbon #5 (in the case of monosaccharides with six carbons).
Building on a theme When two monosaccharides are joined together by dehydration synthesis (a glycosidic bond), a DISACCHARIDE results. Disaccharides always contain glucose + one other monosaccharide: Sucrose (common table sugar) = glucose + fructose Lactose ("milk sugar") = glucose + galactose Maltose = glucose + glucose
Other monosaccharides Some have five carbons, like ribose and deoxyribose, the sugars in the nucleotides of DNA and RNA (LATER)
Polysaccharides Usually consist of long chains of glucose or modified glucose monomers, linked by different types of glycosidic bonds and with different branching properties. Starch - plant storage polysaccharide Cellulose - plant structural polysaccharide (beta-1, 4 linkage that animals cannot in general digest) Glycogen - animal storage polysaccharide Chitin - makes up fungal cell walls and arthropod exoskeletons - polymer of N-acetyl glucosamine (NAG) Peptidoglycan - polymer of alternating NAG and NAM (N-acetyl muramic acid) subunits, most bacterial cell walls contain it
Functions of Carbohydrates: Mainly, to provide ENERGY for an organism Structural components of cell walls May be attached to proteins and function as antigens
In nutrition, Mono- and disaccharides are referred to as sugars, or simple carbohydrates. Polysaccharides are referred to as complex carbohydrates.
Definition: biological molecules that are insoluble in water (they are hydrophobic, or non-polar)
Basic Types Triglycerides (fats and oils) Phospholipids Sterols
Triglycerides Triglycerides are formed when three FATTY ACIDS are joined to a molecule of the trialcohol glycerol by dehydration synthesis. Fats are solid at room temperature, because they contain saturated fatty acids. Oils tend to be liquid at room temperature, because they possess at least one point of unsaturation (C=C double bond).
Saturated fatty acids Points of unsaturation (cause double bonds and "kinks" in the molecule)
Phospholipids Are very similar to triglycerides in chemistry: one of the fatty acids is replaced with a phosphate containing group. This causes the molecule to have a "split personality", being partially hydrophobic and partially hydrophilic. Molecules like this are referred to as amphipathic.
Sterols, or steroids Are based on ring structures. Cholesterol is the most popular steroid, although many hormones and other biological compounds are formed from cholesterol (testosterone, estrogen, cortisol, vitamin D).
Functions of LIPIDS: Triglycerides - long term energy storage, cushioning and insulation in multicellular organisms. Phospholipids - structural basis of cell membranes and lipid-transporting lipoproteins (HDL's and LDL's). Steroids - Cholesterol functions in the structure of cell membranes; others are hormones, etc.
Definition: long chains of subunits called AMINO ACIDS joined by PEPTIDE BONDS (dehydration synthesis again) There are 20 different amino acids. Each one contains a central carbon bound to an amino group, a carboxylic acid group, a hydrogen, and an R (variable) group.
AMINO ACIDS
Levels of protein structure Primary - sequential order of amino acids in chains
Levels of protein structure Secondary - local hydrogen bonding interactions between amino and acid groups form structures such as the alpha-helix and the beta-pleated sheet.
Continued Tertiary - hydrogen bonds, electrostatic, and hydrophobic interactions between R groups cause the molecule to fold up in threedimensional space. Quaternary - Sometimes, folded polypeptides associate with each other to form a functional protein (e.g., hemoglobin, antibodies).
Types of non-covalent interactions that create and maintain tertiary structure include: Hydrophobic interactions Hydrogen bonding (between R-groups) Ionic/electrostatic interactions
Functions of PROTEINS are MANY!! Enzymes (catalyze chemical reactions) Hormones Antibodies Structural (mainly in animals - muscle tissue, connective tissue) Famous proteins: hemoglobin, collagen, keratin, insulin Membrane associated transporters and more!!
In nutrition, We ingest proteins mainly to get amino acids for building our own proteins. They do however contain calories, and any excess will be converted to fat. In the process, they become deaminated, forming the metabolic waste urea, which is excreted in the urine.
Definition: long chains of subunits called NUCLEOTIDES joined by PHOSPHODIESTER BONDS. There are two classes of nucleic acids depending upon which type of sugar they contain. The two classes are DNA and RNA.
The nucleotide contains: A five carbon sugar (ribose in RNA or deoxyribose in DNA); A phosphate group; A nitrogen containing base, of which there are four types in DNA.
Continued DNA bases: Guanine Cytosine Adenine Thymine In RNA, thymine is replaced by uracil.
Bonding RULES DNA exists in nature as a double helix, with two nucleotide strands running antiparallel and joined by hydrogen bonding between the bases. A binds with T (2 H-bonds). G binds with C (3 H-bonds, stronger bond). In RNA, A binds with U when applicable.
Functions of NUCLEIC ACIDS DNA makes up the genes, which contain genetic information. RNA functions in various capacities in the process of protein synthesis (i.e., expression of the genetic information).
ATP, a triphosphate form of an RNA nucleotide, also functions as the major energy carrying molecule of the cell! Ribose