Upload
others
View
4
Download
0
Embed Size (px)
Citation preview
Biol 219Lec 3Fall2016
1
BiomoleculesBiomolecules
• Carbohydratesmonosaccharides polysaccharides
• Lipids fattyacids triglycerides
• Proteins aminoacids polypeptides
• NucleicAcids nucleotides DNA,RNA
Monomers Polymers
Carbohydrates
• containcarbon,hydrogen,&oxygen,usuallyina1:2:1ratio
• generalformula:(CH2O)xn;n=#ofCatoms
• highlypolarmolecules:many–OHgroups→watersoluble
• simplecarbohydratesaresugars(mono- anddisaccharides)
• glucose(C6H12O6) isamajorenergysourceforcells
Carbohydrates– 3categories
Polysaccharides
Function: Glucose storageFig. 2.2
Carbohydrates
hexoses - 6 carbons (C6H12O6)
Monosaccharides (simple sugars)
pentoses - 5 carbons (C5H10O5)
Biol 219Lec 3Fall2016
2
Dehydration (condensation) reactions build up polymers from monomers.
A-OH + H-B → A–B + H2O
Hydrolysis reactions breakdown polymers into monomers.
A–B +H2O → A-OH +H-B
a watermolecule isremoved toformthenewcovalentbond
a watermolecule isaddedtosplitthecovalent bond
DehydrationSynthesisexample
Lipids
• Mostlynon-polar molecules, rich inC-H bonds
• Mostlyinsoluble in H2O
• Functions:
• cellmembrane (phospholipids, cholesterol)
• energyreserves(triglycerides ~2x asmuch as carbspergram)
• signalingmolecules (steroid hormones andeicosanoids)
10
Classes of Lipids:1. Fatty acids2. Triglycerides3. Phospholipids4. Steroids5. Eicosanoids
Lipids
Fatty acids - building blocks (monomers) of most lipids
carboxyl group
Hydrocarbon “tail’
Lipids
- long carbonchains with Hatomsattached (“hydrocarbon tail”)- oneendhas acarboxylgroup (-COOH)
Saturated- each C atom in the “tail” has 4 single
covalent bonds• 2 bonds to 2 adjacent C atoms• 2 bonds to 2 H atoms
Lipids
Fatty acids may be:
“saturated” with hydrogen atoms
monounsaturated – 1 DBpolyunsaturated – 2 or more DBs
Unsaturated- 1 or more DOUBLE covalent bonds
between C atoms• forms a “kink” in the tail
Biol 219Lec 3Fall2016
3
FattyAcids
15
Lipids Fatty acids
Partially hydrogenated oils and “trans fats” – chemically modified unsaturated fats; solidified with H
• hydrogenation – adding H to fatty acids: unsaturated → saturated• “trans” double bonded fatty acids produced as a byproduct• produced in manufacturing of some margarines & vegetable shortening• increase risk of heart disease • lowers HDL (“good” cholesterol); raises LDL ( “bad” cholesterol)• U.S. FDA now requires labeling of trans fats
On July 25, 2008, California became the first state to ban trans fats in restaurants effective January 1, 2010.
FYI: not on test
Lipids
Mostlipidsarehydrophobic,whichmeanstheyareinsolubleinaqueoussolutionsbutsolubleinorganicsolvents.
Mostlipidsaremadefromtwokindsofmolecules:glycerol andfattyacids joinedbydehydrationsynthesis.
Lipids
Triglycerides
Mainfunction:Energystorage inadipose tissue, liverandmusclecells
Alsopaddingandprotectionforsomeorgans
18
Phospholipids phosphate group links together:
• diglyceride (2 fatty acids + glycerol) and a nonlipid groupamphipathic molecules - non-polar “tail” & polar “head”
Lipids
+
-
Biol 219Lec 3Fall2016
4
19
LipidsPhospholipidse.g. phosopholipid bilayer – cell membrane hydrophilic heads face water
• H2O inside cell & H2O outside cell• hydrophobic tails face each other
e.g. micelles – droplets formed in H2O• hydrophilic heads face water
Hydrophobic
ICF
ECF
20
Steroids – 4 hydrocarbon ringsTypes:
• Cholesterol - component of cell membranes; - precursor to other steroids
• Steroid hormones- e.g., estrogen and testosterone (sex hormones)- other steroid hormones are important in
metabolism and mineral balancee.g., cortisol, aldosterone
Lipids
Eicosanoids - modified fatty acids with a 5 C ring,- many function as paracrine substances (“local hormones” )
- direct local cellular activity (vs. true hormones which are released into the bloodstream and travel throughout the body)
Types: • prostaglandins• prostacyclins
• thromboxanes
LipidsProteins
23
Amino Acids – building blocks of protein• central carbon atom• hydrogen atom• amino group (-NH2)• carboxyl group (-COOH)• variable R group
• can be polar,non-polar,acidic (-) orbasic (+)
Proteins
Biol 219Lec 3Fall2016
5
Peptides – combination of two or more amino acids
Peptide bond – links adjacent aa’s (carboxyl group & amino group)
Fig.2.3 Fig.2.3
• Duetohydrogenbonding
• α-helix• β-pleatedsheet• β-turns
Fig.2.3
Disulfide bonds and weak bonds stabilize the tertiary structure of proteins.
Biol 219Lec 3Fall2016
6
31
Tertiary structure – 3-dimensional folding from: 1) R group interactions mostly determine tertiary structure2) interactions between polypeptide & surrounding H2O or lipid molecules3) inner R group interactions
Quaternary structure – interaction among 2 or more protein subunitse.g. globular (hemoglobin) or fibrous (collagen or keratin)
Fig.2.3
ProteinStructure• Fibrousproteins
• Pleatedsheetsorchainsofhelices• Insolubleinwater• Importantstructuralfunction(collagen,keratin)
• Globularproteins• Complextertiarystructure• Solubleinwater• Lipidcarriersinblood,enzymes
35
Protein Denaturation - unfolding of proteins due to drop in pH and/or increased temperature à causes hydrogen bonds to break (= shape change)
Can be reversible (mild changes) or irreversible (extreme changes)
Nucleic Acids
Biol 219Lec 3Fall2016
7
NucleicAcids
Deoxyribonucleicacid (DNA)formsthegeneticcodeinsideeachcellandregulatesmostoftheactivitiesthattakeplace inourcellsthroughoutalifetime.
Ribonucleicacid (RNA)relaysinstructionsfromthegenesinthecell’snucleustoguideeachcell’sassemblyofaminoacidsintoproteinsbytheribosomesinthecytoplasm.
38
Nucleotides have 3 molecular parts: 1. pentose sugar (ribose or deoxyribose)2. phosphate group3. nitrogenous base (5 types: A, G, T, C, U)
Nucleic Acids
Nucleotides are thebuilding blocks (monomers) ofDNAandRNA
Fig. 2.440
Purines – double ringAdenine (A)Guanine (G)
The Nitrogenous BasesPyrimidines – single ring
Cytosine (C)Thymine (T) DNA only
Uracil (U) RNA only
41
• located in cell’s nucleus• stores genetic information • sugar is deoxyribose• sugar + phosphate form “backbone”• nitrogenous bases point inwardà Forming:
• double stranded• double helix structure
Deoxyribonucleic acid (DNA)DNA
Biol 219Lec 3Fall2016
8
43
DNA
DNA strands are held together by hydrogen bondsbetween complementary nitrogenous bases
Complementary base pairs – shape and polarity of bases only allows formation of H bonds between:
• adenine (A) thymine (T)
• guanine (G) cytosine (C)
---------------
44
Ribonucleic Acid (RNA)
• sugar is ribose• mostly single stranded (also 2º and 3º structures
in tRNA and rRNA)• base pairing: A...U, G...C
Classes of RNA• messenger (mRNA)• transfer (tRNA)• ribosomal (rRNA)
. . .. . .. . .
RNA relays instructions fromthegenes in thecell’s nucleus toguide eachcell’s assembly ofamino acids into proteins by the ribosomes in thecytoplasm.
45
DNA vs. RNA
(1) Sugar:DNA = deoxyriboseRNA = ribose
(2) Nitrogenous bases:DNA = A G C TRNA = A G C U
(3) Strands:DNA = double strandedRNA = mostly single stranded
Adenosine Triphosphate (ATP) –a high-energy nucleotide
ATPis the“energycurrency”moleculeofthecellPhosphorylation - additionahigh-energyphosphategrouptoADPtoformATP