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1CHEMICAL LEVEL OF ORGANIZATION BIO 168CHEMICAL LEVEL OF ORGANIZATIONCHAPTER 2created by Dr. C. Morgan
2TOPICSIntroductionAtoms, Molecules, and BondsChemical NotationChemical ReactionsInorganic CompoundsOrganic CompoundsChemicals and Living Cells
3Introduction Objectives Discuss the composition of matter.Learn why you need to understand some basic chemistry.Learn about the relationship between chemical reactions and living systems.
4IntroductionFor all practical purposes, we may say that everything is composed of chemicals—atoms and molecules.Therefore, to understand living systems, you must understand some basic chemistry.The structure and function of living systems is a constant interplay of finely tuned chemical reactions.You will learn about the nature of chemicals, how they react, and their role in the structure and function of living things.
5TOPICSIntroductionAtoms, Molecules, and BondsChemical NotationChemical ReactionsInorganic CompoundsOrganic CompoundsChemicals and Living Cells
6Atoms and Molecules Objectives Define matter and know its three statesLearn the structure of an atomDistinguish between atomic number, atomic weight, and molecular weightDefine isotopeUnderstand that electrons have energy and are in motionLearn the importance of electrons in chemical reactionsUnderstand the formation of chemical bonds
7Atoms and MoleculesMatterBy definition, matter is anything that occupies a space and has mass (on earth mass = weight).Matter exists in 3 states, gas, liquid, or solid.Matter is made up of materials that are known as elements which cannot be further broken down by ordinary means.Appendix II shows the Periodic Chart of the Elements (many should be familiar to you).TABLE 1 in your text lists the main elements in your body along with their abbreviation and significance.O, C, H, N, Ca are the 5 body elements in greatest %.
8Atoms and Molecules (cont) Atomic StructureNucleusProtons + NeutronsProtons & neutrons have mass+++ElectronsIn motionElectrons have almost zero masselectron cloudFig. 2 b
9Atoms and Molecules (cont) The atomic number of an atom = its number of protons.The mass number = number of protons + neutrons.The atomic weight = average number of protons + neutrons in atoms of an element including isotopes.An isotope is an element that has atoms with a different number of neutrons from the most commonly occurring type of that atom under consideration.For example: carbon (C) usually has 6 neutrons but some isotopes of carbon have 7 or 8 neutrons making the atomic weight of carbon
10Atoms and Molecules (cont) Electrons and electron shells Remember forever, only electrons enter into chemical reactions.Atoms are electrically neutral because they have the same number of protons (+) and electrons (–).Electrons have energy and are in motion in specific orbitals or electron shells around the nucleus.Atoms” try” to become stable but can do so only if they have a full outermost electron shell.It is the outermost shell electrons that react and determine the chemical properties of an atom.
11Atoms and Molecules (cont) Electrons and electron shells (cont)Fig. 2
12Atoms and Molecules (cont) Electrons and electron shells (cont)The first shell holds 2 electrons, the second 8, and the outermost shell holds 8.Atoms with full outer shells are inert (do not react).Atoms lose, gain, or share electrons in order to become stable with a full outermost electron shell.This process of atoms losing, gaining, or sharing electrons causes chemical reactions.When atoms lose or gain electrons, their electrical charge balance is upset causing an atom to have more positive or negative charge.
13Atoms and Molecules (cont) Electrons and electron shells (cont) +Is this atom stable?+
14Atoms and Molecules (cont) Electrons and electron shells (cont) Is this atom stable?Fig. 2 d
15Atoms and Molecules (cont) Chemical bondingThe energy and electrical charges associated with electrons that participate in chemical reactions produces relationships between atoms known as chemical bonds.Chemical bonds contain energy.A molecule consists of of a chemical structure containing more than one atom.Its molecular weight = its atomic weight of all atoms expressed in grams.A compound consists of a molecule with more than one kind of atom and new properties (i.e., water).
16Atoms and Molecules (cont) Ionic chemical bondsAtoms that have a net positive or negative charge are called ions which are highly reactive.Cations have a net positive charge.Anions have a net negative charge.Ions present in body fluids are very important in cell function and water balance.Atoms (or molecules) with positive and negative charges are attracted to each other and will stay together to form an ionic bond which is strong.For example: table salt is sodium chloride formed by ionic bonds between adjacent sodium and chloride atoms (ions).
17Atoms and Molecules (cont) Ionic chemical bonds (cont) ? To become stable, Na must ____ one electron.? To become stable, Cl must ____ one electron.NaClFig. 3 a
18Atoms and Molecules (cont) Ionic chemical bonds (cont) NaClFig. 3 b
19Atoms and Molecules (cont) Chemical covalent bonds Sharing electrons is another option for atoms to complete their outermost electron shell.At any moment in time, each atom may “claim” the electron(s) belonging to the other atom because shared electrons spend time orbiting around both nuclei.If sharing is equal, this forms a nonpolar covalent bond between participating atoms.If only one electron pair is shared between two atoms, it is a single covalent bond; two pairs shared = double covalent bond; three pairs shared = triple bond.Covalent bonds are strong bonds.
20Atoms and Molecules (cont) Covalent bonds (cont)free radicals are highly reactiveFig. 4free radical
21Atoms and Molecules (cont) Polar covalent bondsSometimes shared electrons spend more time around one atom’s nucleus than around the other one(s) nucleus (unequal sharing).This causes a slight charge to be established on the atoms participating in the covalent bonds.The atom where shared electrons spend relatively more time becomes slightly negative; the atom(s) deprived of their electrons for relatively more time become slightly positive.This produces a polar covalent bond.There are positive and negative poles on the “polar” molecule.
22WATER Atoms and Molecules (cont) Polar covalent bonds (cont) the most famous polar moleculeFig. 5
23Atoms and Molecules (cont) Hydrogen bondsThere are several weaker chemical bonds that help hold adjacent molecules together.Hydrogen bonds are the most important weak bonds.To test the strength of hydrogen bonds, you may see a needle float horizontally on the surface of water.However, the needle tip may easily pierce the surface.The unique properties of water are associated with the hydrogen bonds between adjacent water molecules.Water is the most abundant molecule in the body.
24Atoms and Molecules (cont) Hydrogen bonds (cont)surface tensionneedleTry this!Fig. 6
25TOPICSIntroductionAtoms, Molecules, and BondsChemical NotationChemical ReactionsInorganic CompoundsOrganic CompoundsChemicals and Living Cells
26Chemical Notation Objectives Learn the rules pertaining to chemical notationLearn how to write formulae in chemical notationRecognize a balanced chemical equationDistinguish between reactants and products of a chemical reaction written in chemical notationRecognize ionic forms of atoms written in chemical notation
27Chemical NotationTABLE 2 (focus) gives the rules of chemical notation.Abbreviations: H = one atom of hydrogen2 H = two individual atoms of hydrogenH2 = a molecule of hydrogen (H–H)Reactants 2H + O H2O Products Atoms on the left = atoms on the right A Balanced Chemical EquationNa+ = sodium ion that lost one electron Cl– = chlorine ion that gained one electron Ca2+ = calcium ion that lost two electrons
28TOPICSIntroductionAtoms, Molecules, and BondsChemical NotationChemical ReactionsInorganic CompoundsOrganic CompoundsChemicals and Living Cells
29Chemical Reactions Objectives Relate chemical reactions with metabolismDefine work and define energyDistinguish between kinetic and potential energyRecognize the types of chemical reactionsDistinguish between catabolism and anabolismLearn the importance of reversible reactionsDiscuss the role of enzymes in metabolic reactionsDistinguish between acids and basesDefine pH; learn the pH scale and normal blood pHLearn about the role of buffers in maintaining pH
30Chemical ReactionsEvery living cell has thousands of chemical reactions occurring simultaneously at all times.Some reactions are breaking molecules while others are building molecules.In chemical reactions, atoms are rearranged.The sum of all chemical reactions that sustain life is called metabolism.Because energy is associated with electrons which form chemical bonds, metabolism involves releasing, storing, and using energy.
31Chemical Reactions (cont) Energy conceptsWork is movement or events that cause a change in the physical structure of matter.Energy is the capacity to do work.Kinetic energy is the energy associated with motion.Potential energy is stored (i.e., water behind a dam).Energy may be changed from potential to kinetic as when chemical energy is used to contract muscle fibers.Conversions are not 100% efficient so some energy is lost as heat.
32Chemical Reactions (cont) Types of Chemical Reactions Decomposition reactions: AB A + BCatabolic reactions are metabolic reactions that breakdown molecules to harvest the potential energy in their chemical bonds.Synthesis reactions: A + B ABAnabolic reactions are metabolic reactions that make new complex molecules from small molecular units such as assembling hair protein from individual amino acids.Exchange reactions: AB + CD AD + BCExergonic reactions release energy; endergonic reactions require an input of energy to make them happen.
33Chemical Reactions (cont) Types of Chemical Reactions (cont) Reversible reactions: A + B ABNotice that both decomposition and synthesis occur.Usually these reactions occur at rates that represent an equilibrium or balance.However, if the product is continuously used up by a cell, in which direction will the reaction proceed?Many important reactions in the body are reversible such as hemoglobin loading oxygen in the lungs and then giving it up for cellular use.
34Chemical Reactions (cont) Enzymes and Chemical Reactions Atoms and molecules are in constant motion in a liquid.In order to react, atoms or molecules must make contact.In living systems, without the help of special proteins called enzymes, reactions would proceed too slowly to sustain life.An enzyme decreases the amount of energy (= activation energy) that is needed to get a reaction to occur.Enzymes cause reactions to proceed faster.Metabolic pathways utilize a specific enzyme for each step (chemical reaction) in the pathway.A B C Denzyme 1enzyme 2enzyme 3
35Chemical Reactions (cont) Enzymes and Chemical Reactions (cont) activation energy decreases in presence of enzymeA + B ABenzymeFig. 7
36TOPICSIntroductionAtoms, Molecules, and BondsChemical NotationChemical ReactionsInorganic CompoundsOrganic CompoundsChemicals and Living Cells
37Inorganic Compounds Objectives Distinguish between inorganic and organic compounds.Describe nutrients and metabolitesList the three most important inorganic compounds in the body.Learn why water is important in the human body.Define a solution and the ionization process.Discuss pH, the pH scale, and buffering.Learn some inorganic acids found in the body.Define a salt and an electrolyte; learn about importance of electrolytes in body fluids.
38Inorganic CompoundsNutrients are the essential chemical materials that you normally obtain from your diet.Metabolites include all molecules synthesized or broken down during the chemical reactions in your body.Nutrients and metabolites fall into two broad categories, inorganic and organic compounds.The minerals your body needs are inorganic compounds.The energy sources and vitamins your body needs are organic compounds.
39Inorganic Compounds (cont) Inorganic compounds are small molecules that do not contain C and H atoms as the main ones with one exception, carbon dioxide (CO2) which is considered to be inorganic.CO2 is plentiful in the body because it is a waste product of cellular respiration, a process that makes a widely utilizable form of energy for cellular work.You get rid of CO2 when you exhale air from your lungs.The most plentiful inorganic substances in the body besides CO2 are oxygen, water, some acids and bases, and some salts.
40Inorganic Compounds (cont) In contrast to inorganic compounds, organic compounds have carbon as their main atom, often occurring as chains of carbon atoms.Organic compounds are usually larger and more complex than inorganic compounds.Carbon dioxide and oxygen are inorganic substances that exist as gases in the body.What kind of chemical bonds hold the atoms of these molecules together?
41Inorganic Compounds (cont) WaterWater, the most important inorganic substance in your body, makes up about 2/3 of your weight and its balance is critically important.The polar covalent bond of water makes each molecule have a slight negative charge on the oxygen side and a slight positive charge on the hydrogen side.Water is a polar molecule and will react with other molecules that are polar or charged.Ionic compounds often break apart when placed in water, a process called ionization because ions are formed (like dissolving table salt in water).
42Inorganic Compounds (cont) Water (cont)Table salt releases Na+ and Cl– which represent the largest number of ion types in body fluids bathing cells.Also, when ionized, salts will conduct an electrical current so they are called electrolytes.Every heart beat, every nerve impulse, and every muscle contraction in your body depends on the presence of certain electrolytes, especially K+ and Na+.TABLE 3 lists the most important electrolytes in the body.
43Inorganic Compounds (cont) Water (cont)Many organic substances have polar covalent bonds so they will also dissolve in water.Substances that readily react with water are hydrophilic.Substances that do not react with water are hydrophobic.Oil and water do not mix because oil is hydrophobic.Oils and fats are nonpolar (lack polar covalent bonds) so hydration spheres do not form to dissolve them.Several more characteristics of water are due to its polarity and hydrogen bonding.
44Inorganic Compounds (cont) Water (cont)(1) Water is an excellent solvent because it dissolves many kinds of inorganic and organic substances.HydrationMany substances release ions when they dissolve.Ions form bonds with water molecules.Fig. 8
45Inorganic Compounds (cont) Water (cont)(2) Metabolic reactions occur in water as water is added during catabolic reactions (hydrolysis) and is removed during dehydration synthesis.(3) Water also resists changes in temperature or in other words, it has a high heat capacity.Body temperature may be maintained at minimal energy costs and chemical reactions will occur at predictable rates in the cells and body fluids.(4) Water is a good lubricant.
46Inorganic Compounds (cont) Water (cont)A solution consists of a solvent (such as water) and solute(s) which are molecules or atoms of substances that are dissolved in the solvent.Solute concentrations of important electrolytes are closely followed in ill patients.Concentrations are usually reported in moles per liter (m / l) or millimoles per liter (mm / l) of solution.Other concentration expressions are also used.A mole is a sample that has the weight in grams equal to the elements atomic or molecular weight of a substance.g/l, g/dl, mg/l, mg/dl are used to express concentration.
47Inorganic Compounds (cont) Water (cont)Body fluids are mostly water.Fluids in tissues, blood, lymph, and within cells contain large amounts of protein or other large molecules.This solution is called a colloid.Liquid gelatin is a colloid.A suspension consists of particles large enough to settle out due to gravity.Blood is a suspension because red blood cells will settle out of the plasma (liquid portion) if the clotting factors are removed.
48Inorganic Compounds (cont) Hydrogen ions and pHBecause H+ are so reactive and we have many of them in our body fluids, their concentration is of special concern and must be regulated.The concentration of H+ is measured in pH units, each a 10X difference in concentration.The pH values range from 0 to14 with 0 being the most acidic and 14 the least acidic (most basic).pH 7 is considered neutral (blood is about 7.4)pHs above 7 are basic and those below are acidic.If the pH of body fluids is not maintained within a narrow range, cells will not function properly and will die which may eventually lead to organismic death.
49Inorganic Compounds (cont) pH scalebasic or alkalineacidicFig. 949
50Inorganic Compounds (cont) Buffers and pH controlThe body maintains pH by the use of buffers which are substances that may donate or remove H+ from fluids.All body fluids contains some buffers.Most body buffers participate in reversible reactions.They may take up or supply H+ to solution.You may take an antacid tablet or liquid to settle an overly acidic stomach to relieve “heartburn”.The antacids remove excess H+ from stomach fluid so they are acting as a buffer.
51Inorganic Compounds (cont) Acids, Bases, and SaltsA substance that releases hydrogen ions (H+) into a solution is an acid. Ex. HCl H+ + Cl–A substance that removes hydrogen ions from solution is a base.Substances that supply OH– (hydroxide ions) are good bases because the hydroxide ions quickly combine with H+ thereby removing them from solution.Ex. H+ + OH– H2OYour stomach contains HCl, a strong acid.Strong acids dissociate completely.
52Inorganic Compounds (cont) Acids, Bases, and Salts (cont) Besides HCl in the stomach, there are other important inorganic acids and bases in the body, especially carbonic acid which is part of a buffer system.Carbonic acid is a weak acid which means that is does not dissociate completely into CO2 and H2O.H2CO3 CO2 + H2OBases in your body are all weak meaning there are always some undissociated molecules present.Salts are inorganic compounds that release cations and anions when they are dissolved but the cations are not H+ and the anions are not OH–.
53TOPICSIntroductionAtoms, Molecules, and BondsChemical NotationChemical ReactionsInorganic CompoundsOrganic CompoundsChemicals and Living Cells
54Organic Compounds Objectives Learn the chemical characteristics of the four main classes of organic compounds: carbohydrates, lipids, proteins, and nucleic acids.Understand the importance of each class of organic compound in the human body.Distinguish between dehydration synthesis and hydrolysis.Understand the role of enzymes in chemical reactions.Learn the structure and use of ATP, a high-energy compound.
55General considerations Organic CompoundsGeneral considerationsMost organic compounds are built around a carbon skeleton with the carbon atoms covalently bonded to each other in a linear or ring fashion.H and O usually presentCarbon shares 4 electrons (atomic # =6)Fig. 10
56General considerations Organic CompoundsGeneral considerationsFunctional groups: certain atomic groupings are common as part of organic molecules and they confer particular properties on those molecules.Carboxyl group – COOH (acts as an acid by releasing H+Amino group – NH2 (acts as a acid or a base by releasing or accepting an H+ depending on the pH)Hydroxyl group – OH (may combine with H+ to form H2O; participates in dehydration synthesis)Phosphate group – PO4 (links molecules to form macromolecules (DNA, RNA); high energy molecules)TABLE 4 shows the important functional groups.
57Organic Compounds (cont) CarbohydratesC : H : O1 : 2 : 1Know shape of glucoseGlucose =C6H12O6Fig. 10linearring
58Organic Compounds (cont) Carbohydrates (cont)A monosaccharide is a small carbohydrate with 3 to 7 carbons (i.e., glucose, fructose; energy sources).A disaccharide is two monosaccharides joined (i.e., sucrose or table sugar, lactose; energy sources).A polysaccharide is a chain of monosaccharides joined to form a large molecule.Glycogen is a polysaccharide of glucose (energy source) and some polysaccharides are structural molecules.Starch is the storage form of glucose in plants.TABLE 5 concerns carbohydrates.
59Organic Compounds (cont) Building molecules—dehydration synthesis Fig. 11 aMultiple unit molecules are made by dehydration synthesis, the removal water.New covalent bonds form between adjacent units.The resulting disaccharide above is a new molecule with different properties from either monosaccharide.
60Organic Compounds (cont) Breaking molecules—hydrolysis Large molecules are broken into their component units by adding water back in, a process called hydrolysis.New covalent bonds form to yield small units, each with its own chemical characteristics.Hydrolysis is the reverse of dehydration synthesis and vice-versa.Fig. 11 b
61Organic Compounds (cont) GlycogenWhich process builds glycogen?Fig. 12A branched polysaccharide of glucose
63Dehydration synthesis of a triglyceride or fat Organic Compounds (cont)Lipids (cont)C = CDehydration synthesis of a triglyceride or fatFig. 15
64Lipids (cont)Lipids include oils, waxes, and fats.Lipids are not soluble in water.Lipids are carried in the blood attached to proteins which then makes them temporarily water soluble.Fats are important energy storage molecules since when broken down, a gram of fat yields 2X the amount of energy as a gram of carbohydrate or protein.Triglycerides also provide insulation and protection of internal organs.TABLE 6 concerns lipids.
65Organic Compounds (cont) Lipids (cont)Lipids may also be ring shaped molecules—these are steroids.Fig. 16
66Organic Compounds (cont) Lipids (cont)Eicosanoids are essential fatty acids which must be derived from your diet.Prostaglandins and leukotrienes are two types of eicosanoids.These act as local hormones which coordinate responses and events in cells, a tissue region, or an organ.Prostaglandins also have a ring structure.Fig. 14
67Organic Compounds (cont) Lipids (cont)Fatty acid chains may be combined with other chemical groups to form different types of molecules.H2O soluble endPhospholipidCell membranes are made of double layered phospholipidsInsoluble endFig. 17 a
68Organic Compounds (cont) Lipids (cont)Phospholipid heads will orient toward water while tails will orient away from water.Micelles will move into the intestinal cells.carbohydrateFig. 17 c
69Organic Compounds (cont) Proteins—functionsYou have more types of proteins (100,000+) than any other kind of molecule in your body.They have structural and functional roles.Structural proteins examples:* hair and nails,* connective tissue fibers that form the substance of spongy tissues (liver, spleen)* connective tissue fibers that form muscle fibers, tendons, ligaments, and bone.
70Organic Compounds (cont) Proteins—functions (cont) Functional protein examples:* transport proteins such as hemoglobin that carries oxygen to cells* cell membrane channels that transport substances into and out of cells* buffers that help maintain pH* enzymes that control chemical reactions* hormones that control expression of genetic information * blood clotting enzymes and proteins* immune system components and cell markers.
71Organic Compounds (cont) Proteins—structureAmino acid unit structureBufferingAmino gp may accept an H+BufferingH may be donated as H+ to solutionH20 amino acids differ in R group onlyFig. 18
72Organic Compounds (cont) Proteins—structure (cont) Peptides are chains of amino acids each linked to the next by a peptide bond (covalent).Av.=1,000 a.a.sFig. 19
73Organic Compounds (cont) Proteins—structure (cont) Proteins have four levels of structural complexity.The primary structure of a protein is the sequence of amino acids in the polypeptide chain.Fig. 20 a
74Organic Compounds (cont) Proteins—structure (cont) Folds and helices established by weak bonds between repeating sequences along the polypeptide chain forms the secondary structure.Fig. 20 bThe alpha helix and pleated sheet are common secondary structures.
75Organic Compounds (cont) Proteins—structure (cont) Tertiary structure3D shapeFig. 20 cBonds between side groups cause complex folding of the peptide chain (note embedded secondary helix).
76Organic Compounds (cont) Proteins—structure (cont) functional proteinstructural proteinhairnailsskintendonsligamentsFig. 20 dQuaternary structure: more than 1 polypeptide chain
77Organic Compounds (cont) Proteins—structure (cont) Shape is the key to protein function.Complex shape is maintained by weak bonds including hydrogen bonds and S–S (disulfide) bonds.Weak bonds are broken by increasing temperature or altering the chemical environment (pH).A protein that has lost its shape is no longer functional and is said to be denatured.Body temperature and pH must be maintained so functional proteins are not denatured.
78Organic Compounds (cont) Proteins—enzymesEnzymes are proteins that speed up chemical reactions in cells.Many different synthetic and hydrolytic enzymes exist.Without enzymes, reactions in cells would be too slow to sustain life.Again, it is the three dimensional shape of each enzyme that is the key to its function.An enzyme lowers the activation energy for a reaction.Enzymes make it easier to for a reaction to begin.Enzymes are needed for all types of metabolic reactions.
79Organic Compounds (cont) How enzymes work—Specific enzyme for each reactionEnzyme does not enter reactionEnzyme may be reusedSome require cofactorsFig. 21
80Organic Compounds (cont) Proteins—enzymes (cont) Basic characteristics of enzymes:Specificity: specific enzyme for each reactionSaturation limits: depends on number of enzyme molecules present; limits speed of a reactionRegulation: enzyme reactions may be controlled by the presence of inorganic cofactors such as ions (Ca2+ and Mg2+) or organic coenzymes.Binding of these factors changes the shape of the enzyme to make it functional.Vitamins function as coenzymes.TABLE 7 concerns proteins.
81Nucleic acids—functions Organic Compounds (cont)Nucleic acids—functionsDNA stores genetic information for making proteins and duplicating the cell’s genes.Genetic information is contained in the sequence of bases along the length of the nucleic acid molecule.BasesTABLE 8RNADNAFig. 23
82Organic Compounds (cont) Nucleic acids--structure The bases are nitrogen containing rings.Purine bases have a double ring structure.Pyrimidine bases have a single ring structure.Thymine is unique to DNA.Uracil is unique to RNA.Fig. 2282
83Organic Compounds (cont) Nucleic acids--structure DNASugar-phosphate chains with bases attached.Forms a double helixComplementary bases held together by hydrogen bonds in DNA.G pairs with CA pairs with TRNA helps make protein.Fig. 23b83
84Organic Compounds (cont) ATP (adenosine triphosphate) Note the nucleotide structure—what does it resemble?Terminal phosphate bond is easily broken and yields much energy for all types of cellular work.Fig. 24
85Organic Compounds (cont) ATP (cont)When the terminal phosphate bond is broken to provide energy for cellular work, ADP remains.ADP is recharged by adding back a terminal phosphate to again make ATP.ATP ADP + phosphate group + energyATPenergy in from energy outnutrients + P ADP for work
86TOPICSIntroductionAtoms, Molecules, and BondsChemical NotationChemical ReactionsInorganic CompoundsOrganic CompoundsChemicals and Living Cells
87Chemicals and Living Cells Objectives By analogy, compare a cell with a factoryDiscuss the importance of compartmentationReview the role of various organic compoundsDiscuss metabolic turnover.Reinforce why you need to understand basic chemical principles in order to understand anatomy and physiology.
88Chemicals and Living Cells Each living cell has all the working components to sustain its life as if it were a single cell organism.Cells have compartments which allows for various cellular activities to be occurring simultaneously.A cell is a bit like a factory with various rooms, assembly lines, and one or more products produced.Some products are used within the room or factory while others are delivered for use elsewhere outside the factory.
89Chemicals and Living Cells (cont) The cellular factory must be supplied with raw materials, energy, and must have a stable environment.Energy is supplied primarily by ATP made within the cell from nutrients (glucose).Phospholipids form the walls and partitions of the factory to create compartments or rooms.Proteins form the hardware (machines), internal structure, and supply the enzymes (workers) to help carry out the chemical reactions.Nucleic acids contain the computer code that directs all the activities within the cellular factory.
90Chemicals and Living Cells (cont) The chemical composition of a cell is constantly changing as materials are taken in or removed during the metabolic processes.Organic molecules are replaced as needed.The turnover rate is the time between cellular synthesis and recycling of the molecule.The turnover rate varies with the kind of molecule and metabolic activity of the tissue.Liver protein is 5-6 days; triglycerides are 20 days, phospholipids last 200 days.TABLE 10 lists some turnover rates.
91Chemicals and Living Cells (cont) The activities that occur within the cell are all chemical in nature.Likewise, the activities that occur in tissues, organs, systems, and the organism are chemical in nature.Therefore, to understand physiology, one must know some elements of basic chemistry.That is why you must work hard to understand the materials presented in this chapter.Since anatomy and physiology are linked, the basis for understand both isCHEMISTRY CHEMISTRY CHEMISTRY