UNIT II - BIOCHEMISTRY
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Transcript of UNIT II - BIOCHEMISTRY
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UNIT II - BIOCHEMISTRYBig Campbell ~ Ch 2-5
Baby Campbell ~ Ch 2-3
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I. CHEMICAL BASIS OF LIFE
• Elementso Cannot be broken down without losing characteristic
propertieso Six elements in greatest concentration in living things are
Sulfur Phosphorus Oxygen Nitrogen Carbon Hydrogen
o Defined by Atomic # which is = #of protons and the #of electrons in most cases
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I. CHEMICAL BASIS OF LIFE, cont
• Atomso Smallest unit of matter
that retains properties of that element Protons (+); found in
nucleus Neutrons (neutral);
found in nucleus Electrons (-); found in
electron clouds.
o Atomic Mass = p + no Isotopes – when an
atom has a different atomic mass, Ex: C12, C13, C14
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I. CHEMICAL BASIS OF LIFE, cont• Chemical Bonds
o Chemical behavior of atom determined by valence electronso Atoms interact with other atoms to complete their valence shells,
either by transferring or sharing electrons
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I. CHEMICAL BASIS OF LIFE, cont
• Types of Chemical Bondso Ionic – Results when one atom has a much stronger
attraction for electrons than another; one atom has a greater electronegativity. Electron(s) are transferred resulting in formation of ions. Bond forms due to charge attraction. Strength is dependent on environment
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I. CHEMICAL BASIS OF LIFE, conto Covalent Bonds – More stable;
results from sharing a pair of valence electrons. Forms a molecule. One pair of electrons shared = single covalent bond; two pair of electrons shared = double covalent bond.Non-polar covalent bond –
formed when electronegativity of atoms is the same
Polar covalent bond – formed when one atom is more electronegative; unequal sharing of electrons results in slight charges at either end of molecule
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II. WATER• Properties of Water Due to its
Polarityo Hydrogen “bonds”
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II. WATERo “Stickiness”
Cohesion Surface Tension
AdhesionCapillary Action
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II. WATER, conto Regulation of Temperature
High specific heat High heat of vaporization
o Density of “solid” water _<_ density of liquid water
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II. WATER, conto Solvent of Life
Hydrophilic “Water-loving” Polar molecules
“pull apart” ionic compounds & other polar molecules
Hydrophobic “Water-hating” Non-ionic and non-
polar substances are repelled by water
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II. WATER, cont
• Dissociation of Watero Rare, but measurable phenomenono (2)H2O → H3O+ + OH- → H+ + OH-
o In aqueous solution at 25˚C, total conc of [H+] [OH-] = 1x10-14
Neutral solution → [H+] = [OH-]; therefore [H+] = 1 x 10-7
o pH = Provides a means for a compressed measurement of [H+] -log10[H+]
o Acid – Substance that dissolves in water to __increase_ [H+] [H+] _>___ 1 x 10-7; pH __<__ 7
o Base - Substance that dissolves in water to _decrease_ [H+] [H+] _<___ 1 x 10-7; pH _>_ 7
o pH of Water = 7
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II. WATER, cont
o Buffers Maintain a constant pH by donating, accepting H+
Bicarbonate Buffer System Very important buffer system in blood pH of blood = _7.4_
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III. ORGANIC CHEMISTRY – THE STUDY OF CARBON
• Atomic Structure of Co Atomic Number of C = 6
6 protons 6 electrons __4___ valence electrons
o Hydrocarbon – composed on only C-H; impt in fossil fuels. Hydrophobic
o Isomer – compounds with the same #of elements/atoms, but a different structural arrangement. See Ex…
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Four Ways Carbon skeletons can vary
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III. ORGANIC CHEMISTRY, contFunctional Group Structure Characteristics
Hydroxyl-OH may be written as HO-
Very polar; forms “ –ols” (alcohols)
Carbonyl
C=O, also written -CO Ketone – if carbonyl group is within the carbon skeleton
Aldehydes – if carbonyl group is at the end of the carbon skeleton.
Carboxyl-COOH; c alled carboxylic acids
Acts as an acid; donates H+ to solution
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III. ORGANIC CHEMISTRY, cont
Functional Group Structure Characteristics
Amino-NH2; called amines Acts as a base; removes H+
from solution
Sulfhydryl-SH; called thiols Important in stabilizing protein
structure; forms disulfide bridges
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Phosphate-OPO3; known as organic phosphates
Gives molecule negative charge; react with water to release energy
Methyl-CH3 Affects the expression of
DNA
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IV. THE BIOMOLECULES
• Most are polymers made up of single units called monomers
• Four Main Groups CARBOHYDRATES
LIPIDS
PROTEINS
NUCLEIC ACIDS
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IV. BIOMOLECULES, cont• Dehydration Synthesis
o Also called _CONDENSATION REACTION__o Reaction that occurs to build polymerso Forms __COVALENT_ bond between 2 monomerso _WATER_lost as waste producto Requires energy input, enzymes
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IV. BIOMOLECULES, cont• Hydrolysis
o “__WATER BREAKING/SPLITTING_”o Covalent bonds between monomers broken Releases energy;
reaction accelerated with enzymes
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V. CARBOHYDRATES
• Provide fuel, act as building material• Generally, formula is a multiple of CH2O
• Contain carbonyl group & multiple hydroxyl groups• Monomer = monosaccharides• Monosaccharides – usually found as ringed structures
o PentosesRibose
Deoxyribose
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V. CARBOHYDRATES, conto Hexoses
GlucoseFructoseGalactose
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V. CARBOHYDRATES, cont• Disaccharides
o 2 monosaccharides covalently bonded together through dehydration synthesis
o ExampleSucroseLactoseMaltose
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V. CARBOHYDRATES, cont• Polysaccharides
o Many monosaccharides covalently bonded together through dehydration synthesis
o Two main groups Energy Storage Polysaccharides
Starch – Plants store glucose as starch in cell structures called plastids. Humans have enzymes to hydrolyze starch to glucose monomers.
Glycogen – Storage form of glucose in animals. More highly-branched than starch. In humans, found mainly in liver, muscle cells
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V. CARBOHYDRATES, cont Structural polysaccharides
Cellulose – polymer of glucose. Every other glucose is upside down – forms parallel strands of glucose molecules held together with H-bonds
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V. CARBOHYDRATES, contStructural polysaccharides• Chitin – found in arthropod
exoskeleton, cell walls of fungi
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VI. LIPIDS• Very diverse group• Non-polar, hydrophobic molecules• Hydro_phobic__• Not true polymers• Four groups
Fats & oils phospholipids steroids waxes
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VI. LIPIDS, cont
• Fats& Oilso Composed of
glycerol + 3 fatty acids
o Glycerol = 3-C alcohol
o Fatty acids – long hydrocarbon chains ending with carboxyl group
o AKA triglycerideso Used for energy
storage
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VI. LIPIDS, cont
Saturated fats – “Saturated with hydrogens”; contain all single bonds. Typically from animal source, solid at room temp. Associated with greater health risk.
Unsaturated fats – Contain double bonds, fewer H-atoms. Results in “kinked” hydrocarbon chain. Typically from plant source, liquid at room temp.
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Fats, cont.
• Saturated fat • Unsaturated fat
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VI. LIPIDS, cont
• Phospholipids 2 fatty acids
attached first 2-carboxyl groups of glycerol.
Negatively-charged phosphate group is attached to 3rd carboxyl
Partially polar and partially non-polar
Found in all cell membranes.
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Phospholipid, cont.
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VI. LIPIDS, cont• Waxes – One fatty acid attached to an alcohol. Very
hydrophobic. Used as coating, lubricant• Steroids – Consist of 4-rings with different functional
groups attached. o Cholesterol – steroid found in animal cell membranes;
precursor for sex hormones
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Steroids, cont.
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VII. PROTEINS
• Important part of virtually all cell structures, processes, reactions
• Amino Acids – Proteins are large polymers made up of amino acid monomers. All amino acids have the same basic structure:
o Amino groupo Carboxyl groupo Carbon, known as alpha carbono R group → variable component; gives each amino acid its unique
properties. Determines whether amino acid is classified as polar, non-polar, acidic, or basic.
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VII. PROTEINS, cont
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VII. PROTEINS, cont
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VII. PROTEINS, cont
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VII. PROTEINS, cont
• Amino Acid → Proteino Dehydration synthesis results in formation of a peptide bondo Polypeptide – many amino acids covalently bonded together
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VII. PROTEINS, cont
• Protein Conformation o Protein’s shape is related to its function. Generally, a
protein must recognize/bind to another molecule to carry out its function.
o Denaturation - A change in a protein’s shape. Results in a loss of protein’s ability to carry out function.
o Four levels of protein structurePrimarySecondaryTertiaryQuaternary
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VII. PROTEINS, cont
Primary – Sequence of amino acids
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VII. PROTEINS, cont Secondary – Coiling of polypeptide chain due to formation of H-bonds
between H of amino end of one aa and OH of carboxyl end of another aa Alpha helix – created from H-bonds forming within one pp chain Beta pleated sheet – H-bonds form between aa in parallel pp chains
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VII. PROTEINS, cont Tertiary - Involves
interactions between R groups of amino acids. Helps to give each protein its unique shape.
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VII. PROTEINS, cont
Quaternary – Proteins that are formed from interactions between 2 or more polypeptide chains folded together. Examples include hemoglobin, collagen, chlorophyll
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VII. PROTEINS, cont• Enzymes
o Biological catalysts that act by lowering activation energy; that is, the amount of energy needed to get the reaction going
o Only catalyze reactions that would normally occuro Recycled – not used up or changed by the reactiono Temperature and pH sensitiveo Substrate specific
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VII. PROTEINS, cont
o Induced fit – As enzyme envelops substrate, a slight change takes place in bond angles, orientation of atoms. Allows chemical rxns to occur more readily
o Inhibition of Enzyme Function Competitive inhibitor – mimics
normal substrate Non-competitive inhibitor –
attaches to another part of enzyme; changes shape of active site
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VII. PROTEINS, conto Regulation of enzyme
function Allosteric Regulation –
binding of a molecule to enzyme that affects function of protein at another site
Feedback Inhibition – as end product is synthesized and accumulates, enzyme is inactivated → switches off metabolic pathway
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VIII. NUCLEIC ACIDS
• Nucleic acid group includes DNA, RNA, ATP
• Monomers = _NUCLEOTIDES_ Composed of
Pentose deoxyribose (DNA) ribose (RNA)
Phosphate group Nitrogen base
• Polymers formed through _dehydration synthesis__ Phosphate group of one
nucleotide covalently binds to sugar of next
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VIII. NUCLEIC ACIDS, cont Nitrogen Bases
Pyrimidines – Single-ringed structure
Thymine Cytosine Uracil
Purines – Double-ringed structure
Adenine Guanine
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VIII. NUCLEIC ACIDS, cont• DNA