Post on 26-Apr-2018
Biology – Kevin Dees
Small molecules (like water and NaCl) have certain properties that arise from the bonds which hold atoms together in a particular arrangement.
Many of the molecules that compose the cells in a living thing are huge and are often termed macromolecules.
very large molecules - some proteins for examples contain
thousands of covalently bonded carbon atoms
Biology – Kevin Dees
There are four categories of biological macromolecules:
1. Carbohydrates * 2. Lipids 3. Proteins* 4. Nucleic Acids* * these three categories are composed
of molecules that are formed as polymers
Biology – Kevin Dees
Polymers
• Polymers are long molecules consisting of many similar or identical building blocks linked by covalent bonds.
• These basic units (or building blocks) are known as monomers.
• As we will see, the monomers of each of the three different macromolecules are different , but the chemical mechanism to build polymers from these monomers is very similar.
Biology – Kevin Dees
Synthesis and breakdown of polymers
• Each monomer molecule will be connected to an adjacent monomer by a chemical reaction known as dehydration synthesis
• When a covalent bond forms between the two monomers, each monomer contributes a part of a water molecule
• the H+ (hydrogen ion) • OH- (hydroxide group)
Biology – Kevin Dees
• These reactions are building reactions (anabolic reactions) and require the input of energy.
• Enzymes are used to help speed up these
reactions by lowering the activation energy of the reaction.
Biology – Kevin Dees
• Polymers may also be broken down into smaller units by a catabolic reaction.
• This process requires the addition of water and is known as hydrolysis. – Split with water – The reverse of dehydration synthesis – Also requires enzymes to activate
Biology – Kevin Dees
1. Carbohydrates
• Functions: – Quick energy source (fuel) – Structural building materials
• Sugars (monosaccharides) form the basic monomers of polysaccharides.
Biology – Kevin Dees
monosaccharides • Glucose is the most common
(most sugar names end in –ose)
• Glucose is important in the cellular respiration reaction
• “easy to catabolize”
Biology – Kevin Dees
Glycosidic linkages • Covalent bonds formed by dehydration
synthesis linking monosaccharides
Glucose Fructose Sucrose – a disaccharide
Other disaccharides:
maltose – found in beer
Lactose – found in milk
Biology – Kevin Dees
Large polysaccharides
• Macromolecules of a few hundred to a few thousand monosaccharides.
• Used for storage – may be catabolized by hydrolysis to create monosaccharides for fuel.
• Used for building materials for cells
Biology – Kevin Dees
Polysaccharide examples
• Starch – storage polysaccharide in plants – Glucose bank for plants – Most animals have enzymes that can hydrolyze starch
• Glycogen – storage polysaccharide in
animals – Stored in liver and muscle tissue – Used when demand for sugar increases; only a day’s
worth of stored energy
Biology – Kevin Dees
• Cellulose - the most abundant organic compound on earth – Structural polysaccharide –
found only in plants – Found in the cell wall of
plant cells – Very strong – Forms long fibers – Most animals do not have
enzymes to hydrolyze cellulose
• Termites and cows use symbiotic microorganisms
Biology – Kevin Dees
• Chitin – structural polysaccharide found in arthropods – Insects, crustaceans, arachnids – Composes the exoskeleton – Also found in some fungi – Used to make surgical thread – very thin, very
strong and decomposes easily.
Biology – Kevin Dees
2. Lipids
• Do not consist of polymers • Grouped together because they are
hydrophobic – little or no affinity for water • Classes of lipids:
– Fats – Phospholipids – Steroids
Biology – Kevin Dees
Fats • Consist of a glycerol and fatty acids • Are formed by dehydration synthesis • Function - energy storage (2X sugar)
- insulation in adipose tissue
Biology – Kevin Dees
• Saturated fats – fatty acid tail does not have double bonds in the hydrocarbon chains – This makes them very stable and more difficult to
break down – Solid at room temperature – Most animal fats – lard, butter
• increased risk of CV disease • atherosclerosis
• Unsaturated fats – fatty acid tails have double bonds in hydrocarbon chains – Most plant oils – olive oil – Liquid at room temperature
Biology – Kevin Dees
Phospholipids
• Similar to fat but only has two fatty acid tails attached to glycerol and has a phosphate group (PO4) as well.
• Amphipathic -
hydrophobic and hydrophilic properties
Biology – Kevin Dees
Steroids
• Cholesterol – fond in animal cells • Some hormones – estrogen, testosterone
Biology – Kevin Dees
3. Proteins • Very diverse group with many functions • Monomers are amino acids – 20 naturally
occurring – Amino group – α carbon – Carboxyl group – R group (variable)
Biology – Kevin Dees
Functions of proteins
• Enzymes – catalysts in reactions – Digestive enzymes
• Structural proteins – physical support – Collagen
• Storage proteins – stores amino acids – Casein milk protein
• Transport proteins – aid in transport in organs or cells – Hemoglobin
• Hormonal proteins – coordinates body activities – Insulin
• Receptor proteins – cell’s response to stimuli – Acteylcholine binding sites
• Contractile proteins – contraction for movement – Actin and myosin
• Defense proteins – protection against disease – antibodies
Biology – Kevin Dees
Protein function is determined by shape
• There are four levels of protein structure – Primary structure – sequence of amino acids
Biology – Kevin Dees
• Secondary structure – Hydrogen bonding along backbone causes
the polypeptide chain to : • coil (α helix) • fold (ß pleated sheet)
Biology – Kevin Dees
• Tertiary structure – interactions among side (R groups) chains causes additional folding and produces a truly three-dimensional molecule
Biology – Kevin Dees
•Protein are very large 3-D molecules and their shape is crucial to their function. When proteins change their shape they change their function If the shape change is dramatic the protein may become denatured and lose its functionality
Biology – Kevin Dees
4. Nucleic Acids • Nucleic acids store and transmit hereditary
information – Hereditary information
• Primary structure of a protein is determined by the sequence of amino acids.
• This sequence of amino acids is ultimately programmed by the units of inheritance called genes
• Genes consist of molecules of DNA
• Deoxyribonucleic Acid –DNA • Ribonucleic Acid - RNA
Biology – Kevin Dees
Nucleic acids as polymers
• Composed of monomers called nucleotides – Three components of
a nucleotide • Nitrogenous base
– Adenine, cytosine, thymine, guanine, uracil
• Phosphate • Pentose sugar
– Ribose or deoxyribose
Biology – Kevin Dees
• The nucleotides are joined by the bonding of the phosphate group from one nucleotide to the pentose sugar from the next
• Forming the phosphate – sugar backbone
• This also makes these chains directional
• 3’ and 5’ ends
Biology – Kevin Dees
DNA structure
• Two complementary strands of nucleotides
• Formed by the hydrogen bonding of complementary base pairs A—T and G—C
• double helix – Discovered by Watson
and Crick
Biology – Kevin Dees
• The structure of DNA allows DNA to carry genetic information (in the sequences of the bases) and to self-replicate (make a copy of itself).
• The strands are directional – 3’ and 5’ ends – antiparallel
Biology – Kevin Dees
RNA
• Single stranded • Made from DNA template • Uracil replaces thymine in RNA (pairs with
Adenine) • Several types:
– mRNA –messenger RNA – tRNA – transfer RNA – Used to build polypeptides