unit 1: cellular energetics part i – macromolecules part ii – enzymes part iii – cellular...
TRANSCRIPT
Unit 1: Cellular Energetics
• Part I – Macromolecules
• Part II – Enzymes
• Part III – Cellular Respiration
• Part IV – DNA Replication
• Part V – Protein Synthesis
Part I – Macromolecules
The questions:
• What are monomers? What are polymers?
• How are polymers synthesized (built) and hydrolyzed (broken down)?
Dehydration Synthesis (condensation)
– Reaction that joins molecules together by removing water
– Polymerization = the synthesis of a polymer– Polymers are built from monomers via dehydration
synthesis
• Breaks polymers into their constituent monomers (“building blocks”) by lysing (breaking) bonds through the addition of water.
Hydrolysis
1. Carbohydrates (polysaccharides)• Contain CHO
• General molecular formula = CH2O
• Aldoses and Ketoses vary in location of carbonyl group -C=O– Aldoses have carbonyl on ends (glucose)– Ketoses have carbonyl within molecule (fructose)
Monomer = monosaccharide
Disaccharides (double sugars)
• 2 monosaccharides joined by a glycosidic linkage– Covalent bond formed between two monosaccharides
by dehydration synthesis
Examples of disaccharides• Maltose = glucose + glucose
• Sucrose = glucose + fructose
• Lactose = glucose + galactose
Polysaccharides (many sugars)• Long polymers of many monosaccharides
• Architecture & function determined by position of glycosidic linkages– Alpha linkages are breakable by Eukaryotes
• Starch, glycogen
– Beta linkages are NOT • Cellulose, chitin
Types of Polysaccharides
A. Structural polysaccharides: – Beta glycosidic linkages– Cellulose - plant cell walls, structural molecule– Chitin - exoskeleton in insects, arachnids,
crustaceans
B. Food storage molecules – Alpha glycosidic linkages– Starch- food storage molecules in plants– Glycogen- food storage molecules in animals
2. Lipids
• Group shares one common trait – no affinity for water
• Do NOT consist of monomers → polymers• Highly varied group• Biologically important:
– Fats– Phospholipids– Steriods
A. Fats
• Made of glycerol and 3 fatty acids• Saturated fatty acids (animal fats) are carbon
chains with single bonds only– Ex: Butter, lard; solids at room temp.
• Unsaturated fatty acids (plant fats) have at least one double bond (kinks in chain)– Monounsaturated = only one double bond– Polyunsaturated = many double bonds
• Ex: Vegetable oils; liquid at room temp
“Hydrogenated” fatty acids
• Hydrogen is artificially added to replace double bonds with single bonds.
• Liquids are solidified
• Ex: peanut butter, margarine
B. Phospholipids
• 2 fatty acids (tails) attached to phosphate group “head”
• When placed in water they self assemble into a micelle
C. Steroids
• Lipids characterized by carbon skeletons consisting of four fused rings
• Ex. Cholesterol– Common component of animal cell membranes (this
is why animal meat is higher in cholesterol)– Precursor from which other steroids, including sex
hormones, are synthesized
3. Proteins
• Most diverse of all macromolecules
• Humans have over twenty thousand proteins in their bodies, each performing a specific function
General Categories of Proteins
1) Structural: Spider silk
2) Storage : Egg white
3) Transport: Hemoglobin
4) Hormonal: Insulin
5) Receptor: Transport protein
6) Contractile: Actin & myosin
7) Defensive: Antibodies
8) Enzymatic: Digestive enzymes
Monomers = Amino Acids• 20 total amino acids• 8 “essential” AA’s; must be derived from food• 12 can be synthesized by body• THREE TYPES
– Non-polar (8)– Polar (7)– Electrically charged (acidic, basic) (5)
General structure of amino acid
• All amino acids have a carboxyl group (-COOH) on one end and an amino group (NH
3) on the other
• R group determines their interactions with one another to form secondary, tertiary, and quaternary structure
Polymers = polypeptides
• Formed by dehydration synthesis
• Peptide bonds: bonds between adjacent amino acids
Protein shape determines function
• Primary structure: sequence of amino acids
• Secondary Structure: coiling or folding of polypeptide chain in repeated patterns– Ex: Alpha helices– Ex: Beta pleated sheets
• Tertiary structure: irregular contortions from interactions between side chains (R-groups) with one another– H-bonds– Disulfide bridges– Hydrophobic interactions
• Quaternary structure: 2 or more polypeptide chains aggregated into 1 functional molecule
4. Nucleic Acids
• Nucleic acids are the building blocks of both DNA and RNA– DNA directs its own replication, transmits
genetic information to future offspring, and controls RNA synthesis
– RNA controls protein synthesis
Nucleotides
Monomer = Nucleotides
• Nucleotide - building block of nucleic acids
• Composed of three subunits:
1) Pentose sugar (ribose or deoxyribose)
2) Phosphate groups comprise the “sugar-phosphate” backbone
3) Nitrogenous bases = variable portions of the molecule
DNA vs. RNA
Polymer = polynucleotide• Adjacent nucleotides are
joined by covalent bonds called phosphodiester linkages between the -OH on one nucleotide and the phosphate on the next nucleotide
Complementary Base Pairing• Always a Pyrimidine with a Purine
– Purines are Adenine & Guanine– Pyrimidines are Cytosine, Thymine (DNA only),
and Uracil (RNA only)
Complementary Base Pairing
Why Do Bases Bond This Way?
• Hydrogen bonds:– A and T form two hydrogen bonds
– G and C form three hydrogen bonds
• Therefore, there is no way to bond inappropriately
Base Pairing
A
T
Base Pairing G
C
Macro Structure of DNA
• Double Helix- “Twisted Ladder” of A-T and G-C base pairing
• DNA contains genes (thousands) that code for proteins
• In association with proteins (histones) DNA makes chromosomes (46 in humans)
• Stored in nuclei of Eukaryotic cells