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).
Points of unsaturation (cause double bonds and
"kinks" in the molecule) Saturated fatty acids
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
• Secondary - local hydrogen bonding interactions between amino and acid groups form
structures such as the alpha-helix and the beta-pleated sheet.
Levels of protein structure
Continued
• Tertiary - hydrogen bonds, electrostatic, and hydrophobic
interactions
between R groups cause the molecule to fold up in three- dimensional 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
