BIO 330 Cell Biology
Spring 2011
Lecture Outline
Macromolecules of the Cell
I. Proteins
A. Types of proteins
Enzymes
Structural
Motility
Regulatory
Transport
Hormonal
Receptor
Defensive
Storage
B. Monomers: Amino acids
Basic structure
Groups of amino acids
Hydrophobic
Hydrophilic
Polar
Negatively charged
Positively charged
C. Polymers: Polypeptides and proteins
Peptide bond
N-terminus vs C-terminus (amino vs carboxy)
D. Protein Structure
Primary structure
Amino acid sequence
Secondary structure
Alpha helix
Beta sheet
Motifs – e.g., helix-loop-helix
Depends primarily on hydrogen bonding
Tertiary structure
3-dimensional folding: native conformation
Depends on several types of intermolecular interactions between R groups:
Disulfide bonding
Hydrogen bonding
Categories of tertiary structure:
Globular (e.g., most enzymes)
Fibrous (e.g., collagen)
Domains
Parts of a single polypeptide with distinct functions
BIO 330 Cell Biology
Spring 2011
Lecture Outline
Quaternary structure
Multiple polypeptides joining together to form one functional protein
Multiprotein complex several proteins joined together, all involved in a single
multi-step process – e.g., pyruvate dehydrogenase complex
II. Nucleic Acids
A. Types of nucleic acids
DNA – deoxyribonucleic acid
RNA – ribonucleic acid
(ATP and GTP)
B. Monomers: Nucleotides
Purines: cytosine, thymine, uracil
Pyrimidines: adenine, guanine
Nucleotide = nucleoside + phosphate
Nucleoside = sugar + base
ATP = adenosine triphosphate = sugar + adenine + 3 phosphates
C. Polymers: DNA and RNA
Phosphodiester bonds
Directional
Nucleic acids are built from nucleoside triphosphates
Provide energy needed to build the molecules
III. Carbohydrates (Polysaccharides)
A. Types of carbohydrates
Simple sugars – monosaccharides
E.g., glucose, galactose, fructose
Disaccharides
E.g., sucrose, lactose, maltose
Oligosaccharides
E.g., short (branching) polymers attached to cell surface
Polysaccharides
E.g., starch, cellulose, glycogen
B. Monomers: Monosaccharides
Sugar: an aldehyde or ketone with two or more hydroxyl groups
Aldosugars vs ketosugars
Named according to # of carbons
Triose, tetrose, pentose, hexose, heptose
D-Glucose: C6H12O6 (aldohexose)
Ring vs linear forms
Hydroxyl on C1 can be oriented “up or down”
BIO 330 Cell Biology
Spring 2011
Lecture Outline
Orientation changes the nature of glycosidic bond
Alpha vs beta
C. Polymers: Storage and Structure
Storage polysaccharides
Starch and glycogen
Alpha glycosidic bonds
Branched or unbranched
Starch – amylase vs amylopectin
Structural polysaccharide
Cellulose
Beta glycosidic bonds
Indigestible to mammals
Bacterial cell walls
Glucosamine derivatives
N-acetylglucosamine (GlcNAc)
N-acetylmuramic acid (MurNAc)
Chitin
GlcNAc only
D. Three dimensional structure of polysaccharides
Glycogen & starch
Loosely coiled helices
Cellulose
Rigid linear rods
Aggregate into microfibrils
IV. Lipids
A. Types of lipids
*Common characteristic is hydrophobic nature
Functional categories
Energy storage
Membrane structure
Specific biological functions
Chemical categories
Fatty acids
Tricylglycerols (triglyerides)
Phospholipids
Glycolipids
Steroids
Terpenes
B. Fatty acids
Long unbranched hydrocarbon chain with COOH at one end
BIO 330 Cell Biology
Spring 2011
Lecture Outline
Amphipathic
Even # of carbon atoms (12-20)
Synthesis involves adding 2-C groups
Saturated vs unsaturated vs trans fats
C. Triacylglycerols
Glycerol + 3 fatty acids linked by ester bonds via condensation reactions
Fatty acid chains within a triglyceride are not necessarily identical
Energy storage is primary function
“Oil” = liquid triglyceride (plants)
“Fat” = solid triglyceride (animals)
D. Phospholipids
Similar to triglycerides, with a polar group substituted for one fatty acid chain
Amphipathic – form membranes
Two types
Phosphoglycerides
Phosphatidic acid – precursor to many membrane molecules
Two fatty acyls plus phosphate group attached to glycerol
Phosphoglycerides have an alcohol attached to phosphate
Alcohol: serine, ethanolamine, choline, inositol
Sphingolipids
Sphingosine (an amine alcohol)
Ceramide = sphingosine + fatty acid
“Head groups”
E. Glycolipids
Derivatives of sphingosine containing carbohydrate instead of lipid R group
Amphipathic
Usually in outer leaflet of plasma membrane
F. Steroids
Derivative of 4-ringed hydrocarbon
Cholesterol – amphipathic
Steroid hormones
Estrogen, testosterone, cortisol, aldosterone
G. Terpenes (isoprenoids)
Derivative of isoprene – a 5-C compound
Diverse biological functions
Vitamin A
Carotenoid pigments
Doichols
Coenzyme Q