Biology Molecule Essay Example For Students

Biology Molecule Essay Unit 1 -man is high 50s to 60% water -distribution in body divided into 3compartments: 1) intracellular 28 litres 2) intercellular/interstitial fluid 11 litres 80% 3) blood plasma 3 litres 20% -women contain less water thanmen -organisms can contain 60-80% water -bacteria have lots of water -fat cellshave little -waters properties result from its structure and molecularinteractions -water is polar -polar covalent bonds and asymmetrical shape giveit opposite charges on opposite sides -electrons spend more time around O givingH a slight positive charge -hydrogen bonds form between the oxygen of onemolecule and the hydrogen of another -cohesion: substance being held together byhydrogen bonds -hydrogen bonds are transient yet enough is always held togetherto give water more structure than almost any other liquid -beads and meniscusformed by cohesion (also helps upward transport of water in plants) -adhesioncounteracts downward pull of gravity -water has greater surface tension thanmo st liquids -surface molecules are hydrogen bonded to molecules below andaround them -surface tension can hinder life (i.e. beading in the alveoli oflungs) -makes water unwettable -surfactants used to counteract this -waterhas a high specific heat which allows it to resist extreme temperature changes-has a high heat of vaporization that causes it to require alot of energy tochange states -when sweating, heat energy is utilized to change states fromliquid to gas, causing a drop in temperature -as a solid water is less densethan as a liquid and will float -charged regions of molecules have an electricalattraction to charged ions -water surrounds ions separating and shielding themfrom one another -polar compounds are generally soluble -charged regions ofwater are attracted to oppositely charged regions of other polar molecules-polar molecules are miscible in other polar liquids -most water moleculesdont dissociate (~ 1/554 million do) -hydrogen atom in hydrogen bond betweenthe two water molecules may shift from the oxygen atom it is covalently bondedto the unshared orbitals of the oxygen that it is hydrogen bonded to -hydrogenion is transferred creating a hydronium ion and leaving a hydroxide ion -thesolvent is water itself -at equilibrium water is not dissociated -at equilibriumin pure water at 25oC = -pH of this solution is 7 (neutral) -high pH= low acidity -acids are substances that increase the relative and removeOH- because it tends to combine with H+ to form water if * , it isacidic and has a pH between 0 and 7 -bases are substances that reduce therelative in a solution -it may increase the -if * , it isbasic and has a pH greater than 7 -buffers are important in the body to keep thepH range between 6 and 8 -pH of blood is between 7.34 and 7.44 -mustnt shiftbelow 7.2 or acidosis will occur -some body zones may have a pH as low as 0.5 oras high as 10 -buffers minimize sudden changes and are a combo of hydrogendonors and hydrogen acceptors -ions are a ccepted when in excess and donated whenin short supply -in biological systems an example is the bicarbonate buffer -inresponse to a rise in pH, the carbonic acid dissociates to form a carbonate ionand a hydrogen proton -if there is a drop, it is reversed (pH up = to right, pHdown = to left) -equilibrium is established but it is always moving to the leftor the right -a balance is the optimum pH -other body buffers include proteinmolecules which donate and accept amino acids to stabilize pH -most of the restof organisms is made up of carbon based compounds like carbs, lipids, proteins,nucleic acids -carbon compounds are known as organic -vitalism is the belief ina life force outside the control of chemical laws -this has been disproved aswater, ammonia, hydrogen and methane have been combined in a lab to form organicsubstances -C+O+H = carbohydrates -C+H+N = amino acids, urea, proteins, lipids-carbon atoms are the most versatile building blocks -each has 4 valences wherebonds can form -carbon chains form the skeleton of most organic molecules -maybe straight or branched, long or short, or in closed rings -hydrocarbons containonly hydrogen and carbon -they form when organic matter decomposes andfunctional groups break off leaving a skeleton -hydrocarbon chains, branches,and rings can be modified by other elements which are joined on in a particularmatter -these are components of organic molecules that are often involved inchemical reactions -they replace 1 or more hydrogens in a hydrocarbonCarbohydrates: -sugars and starches -nonsugars: plant starch, animal starch,cellulose, chitin -come from pasta, rice, flour, fruit, syrups -important sourceof energy, can be oxidized to release energy, improves your mood -contain C, H,and O, with generally 2 times as much H as O -sugar names usually end with -ose,and are named depending on the number of carbons in them (e.g. triose, pentose)-6 carbon sugars, hexoses, are most important -general formula is C6H12O6, andin living systems, the state is aqueous -solids exist in chains, and liquids asrings -the molecular formula is the same for different hexoses, but thestructural formula differs -other isomers of glucose can be reorganized by cellsinto alpha glucose, and then oxidized -glucose is the major nutrient for cellsand its carbon skeleton is raw material for the synthesis of other organicsDisaccharides: -2 hexose sugars-most common are: sucrose, lactose and maltose-glucose + glucose = maltose + water -glucose + fructose = sucrose + water-glucose + galactose = lactose + water -this process is known as condensation ordehydration synthesis -synthesis of disaccharides doesnt happen in the humanbody, but usually they are eaten and digested, through a process known ashydrolysis or disaccharidases Polysaccharides: -these are macromolecules thatare made by condensation when monosaccharides are joined -general molecularformula isC6H12O5 -common polysaccharides are amylose, amylopectin (plantstarch), glycogen ( animal starch), cellulose (cell wall material), chitin(leathery covering of invertebrates) -plants use glucose to grow, and extra isstored in the roots in a soluble form which is then reactivated in the spring this reactivates the growing process year after year -animal starch is stored inspecial cells (average person has a 24 hour supply) and can readily be convertedinto glucose for use -cellulose and chitin are structural carbohydrates -amyloseis formed when glucose molecules join in a 1-4 linkage pattern -first carbon ofone glucose links to the fourth carbon of another -this is a covalent bond or aglycosiolic link -bond is angular and forms a spiral called an alpha helix -ifit branches, amylopectin is formed -cellulose is a 1-4 linkage of beta glucose-this creates a straight strand and not a helix -these bonds are rigid andrequire special enzymes (cellulase) to break them -the position of the betaglucose molecules alternates Lipids: -humans rarely eat pure lipids -cellmembranes a re primarily lipid and lipids can easily enter cells, carrying afoods flavor with them -a diet should have less than 30% fat, 55-65% carbs,and 10-15% protein -lipids are important as a source of energy, insulation(adipose tissue), cushions for the internal organs, as a lubricant, as anemulsifying agent (cholesterol in bile), as a structural component of cells (1/6of brain is fat), cholesterol as a precursor molecule for vitamin D, cortisone,testosterone, progesterone, and estrogen -lipids are simplest biologicalmolecules and are composed mostly of C, H and a few Os -they are energy richbecause of the high C to H ratio -fat consists of a glycerol molecule connectedby ester bonds to a 3 fatty acid molecule (this is a tryglyceride) -if the bondsbetween the carbons are single bonds, the fatty acid is saturated (fat formed isa saturate) -if they have multiple bonds, it is an unsaturated fat -apolysaturate is more than one fatty acid held together by single bonds -multiplebonds can be bro ken and extra hydrogens added through hydrogenation -shortchained fats of unsaturated fatty acids are soft with a low b.p. -long chainedfats of saturated fatty acids are harder with a high b.p. -length of chainsaffects boiling point the most -to make an oil from a solid, you musthydrogenate it Steroids: -saturated fatty acids can be converted to the steroidcholesterol -triglycerides are monitored more closely in the blood thancholesterol -the amount of saturates converted to cholesterol is genetic-abnormal genes can cause excessive production (1 gene = severe heart disease, 2= shortened life span) -liver produces cholesterol -steroids have a 5 ring shape-examples are androgens, estrogens, and cortisone Proteins: -there are 20 aminoacids, 8 of which are essential and can be converted into any of the other 12-protein rich foods are digested into amino acids and the body absorbs them tomake their own proteins -liver cells convert them into absent aminos =transaminofication -proteins ar e synthesized on ribosomes in the cytoplasms ofcells or on polysomes (ribosome chains0 -DNA codes proteins by copying its infoonto a shorter strand known as mRNA (m = a message to synthesize a protein) -themessage is received and a protein is synthesized -for synthesis all 20 arerequired -number, sequence and type of amino acids making up the protein is theprimary structure this is determined by DNA -secondary structure is thecoiling or pleating of amino acid chains, caused by rigid peptide bonds whichare bent by strong intermolecular attraction between hydrogens and oxygens ofevery fourth amino this results in a regular, repeating twist or an alphahelix-chains lie parallel to one another and form hydrogen bonds between themselves this is a beta sheet but is not very common -secondary structure is determinedby intermolecular bonds -tertiary structure refers to the folds in the coiledchain -this is called by a thiol called cysteine this can form a bridge whenit meets another cyste ine -when 2 cysteines meet, a disulfide link is formed-insulin has 6 cysteine amino acids and forms 3 bridges and a slightly globularprotein -the more cysteine amino acids there are, the more folds or joints thatresult and the more globular the protein is -globular proteins are thedoers that function because they have a particular shape due to thecysteine-cysteine sulfur bridges -some proteins may be a bunch of polypeptidechains close together -this is quaternary structure, which very few proteinshave -all proteins have a primary and secondary structure, but few have atertiary structure, and even fewer a quaternary -proteins can be 50-50,000 aminoacids long -amino acids are joined by peptide bonds, a covalent bond between theC of one amino acid and the N of a neighbour -a polypeptide chain is a string ofaminos not long enough to be a protein -amino acids are so named because oftheir two functional groups, the amine group and the carboxylic acid groupNucleic Acids: -all living cells contain DNA and RNA -these carry instructionsfor making proteins and specify the sequence in which amino acids should belinked together -DNA and RNA are polynucleotides, polymers of nucleotides-nucleotides consist of a phosphate group + a pentose + a nitrogenous base -theycan be linked together by condensation to form a polynucleotide -if a nucleotidecontains ribose, it becomes Ribo Nucleic Acid -these are always just a singlestrand, but may be looped into 3 dimensional shapes -if the nucleotide containsdeoxyribose, Deoxyribo Nucleic Acid results -DNA molecules are far longer thanRNA molecules, and can never contain Uracil -4 possible bases are adenine,guanine, cytosine, and thymine -DNA molecules contain two polynucleotidestrands, held together by hydrogen bonds between the bases -hydrogen bonds canonly be formed between specific base pairs: Adenine Thymine Cytosine Guanine-a sense strand is a sequence of bases that tells the order in which to stringtogether the amino acids -a le ngth of DNA coding the sequence for a polypeptideis called a gene -three bases, a codon, specify an amino acid -there are 64possible arrangements of bases in a codon -polypeptides are made when 2 strandsof DNA split up and an RNA molecule builds up against the sense strand -basesequence of RNA must match that of the DNA molecule -a complete RNA moleculethen peels off and travels to the location where polypeptides are made -sequenceof bases on a DNA molecule is the same for a human or a bacteria OtherNucleotides: -a slightly different version of one of the nucleotides that formsRNA is ATP -ATP contains ribose, adenine and 3 phosphate groups instead of 1-phosphate groups may be lost one at a time to make ADP (di) or AMP (mono) -allliving cells make ATP as an energy currency, it is produced constantly -ATPmolecules usually last less than a minute before being broken down -~40 kg isproduced in a day -if a cell needs energy, it hydrolyses ATP and releases energyin small packets NAD: -con tains ribose sugar, adenine and 2 nucleotides -onenucleotide does not contain any of the 5 bases, but instead a nicotinamide ring-they can accept hydrogens and become NADH -hydrogens are accepted or passed onduring respiration or photosynthesis. 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