Chemical Level of Organization Flashcards
Discern between matter and mass.
Matter is anything that takes up space and has mass.
Mass is the quantity of matter in an object.
The more matter, the greater the mass.
The two are not equivalent: In orbit beyond Earth’s gravity, you would be weightless, but your mass would remain unchanged.
Define an atom and describe the properties of its subatomic particles.
Atoms are the smallest stable unit of matter, composed of subatomic particles, only three of which are important for understanding the basic chemical properties of matter.
Describe an atom and how atomic structure affects the mass number and atomic weight of the various chemical elements.
Define: atomic number, mass number, element, isotope, atomic mass, atomic weight
Atoms can be subdivided into the nucleus (protons & neutrons) and the electron cloud (electrons), and they interact by means of their electrons to produce more complex structures.
Atomic number is the number of protons in an atom. Atoms usually contain the same amount of protons and electrons; thus, they are electrically neutral.
Mass number is the total number of both protons and neutrons in an atom.
An element is a pure substance consisting of only atoms with the same atomic number.
Atoms of a single element can differ in the number of neutrons in the nucleus. These are called isotopes, and they have essentially identical chemical properites, and are only distinguishable on the basis of mass. (e.g., mass number)
Atomic mass is the actual mass of an atom of a specific isotope, and is expressed using the atomic mass unit (amu), or dalton. By convention, 1 amu is equal to 1/12 of the mass of a carbon-12 atom, the most common form of the element carbon.
Atomic weight of an element is an average of the different atomic masses and proportions of its different isotopes. For example, the mass number of the most common isotope of hydrogen is 1, but the atomic weight of hydrogen is 1.0079, primarily because some hydrogen atoms (0.015%) have a mass number of 2, and even fewer have a mass number of 3.
Explain the relationship between electrons and energy levels.
Within the electron cloud, electrons occupy an orderly series of energy levels.
The number of electrons in the outermost energy level determines the atom’s ability to participate in chemical reactions.
Compare the ways in which atoms combine to form molecules and compounds.
Discern between molecules and compounds.
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Ionic bonds
- Created by the electrical attraction between cations and anions.
- Involves the transfer of one or more electrons from an atom that can lose them to achieve stability, to another atom that can gain them to achieve stability.
- E.g., Sodium chloride (table salt).
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Covalent bonds
- Created by sharing electrons between atoms.
- E.g., Carbon dioxide (CO2)
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Molecules
- A chemical structure consisting of atoms of one or more elements held together by covalent bonds.
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Compound
- A chemical substance made up of atoms of two or more different elements in a fixed proportion, regardless of the type of bond joining them.
- E.g., Table salt is a compound and not a molecule because there are no covalent bonds in its structure.
Describe the three states of matter and the importance of hydrogen bonds in liquid water.
- Solids maintain their volume and shape at ordinary temperatures and pressures. The particles of a solid are held tightly together.
- Liquids have a constant volume but no fixed shape. Its shape is determined by the shape of the container. The particles of a liquid are held loosely together.
- Gases have neither a constant volume nor a fixed shape. They can be compressed or expanded, and will fill a container of any size. The particles of a gas are independent of each other.
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Water is the only substance that occurs as a solid (ice), a liquid (water), and a gas (water vapour) at temperatures compatible with life. It exists as a liquid over a broad range primarily because of hydrogen bonding among the water molecules.
- The polar charge on water molecules gives water the ability to disrupt the ionic bonds of a variety of inorganic compounds and cause them to dissolve.
- Almost all naturally occuring elements are found in seawater, and at least 29 elements are dissolved in our body fluids.
- At the water surface, the hydrogen bonds between water molecules slow the rate of evaporation and form surface tension, which acts as a barrier that keeps allows small objects (e.g., water striders) to walk across the surface of a pond and prevents dust particles from touching the surface of the eye.
- The polar charge on water molecules gives water the ability to disrupt the ionic bonds of a variety of inorganic compounds and cause them to dissolve.
Define metabolism.
All of the reactions underway in the cells and tissues of the body at any given moment make up its metabolism.
In effect, each cell is a chemical factory. Growth, maintenance and repair, secretion, and contraction all involve complex chemical reactions. Cells also use chemical reactions to provide the energy they neecd to maintain homeostasis and to perform essential functions.
Distinguish between work, kinetic energy, and potential energy.
- Work is the movement of an object or a change in the physical structure of matter. (e.g., walking, molecule synthesis, evaporation)
- Energy is the capacity to perform work.
- Kinetic energy is the energy of motion, energy that can be transferred to another object and do work.
- Potential energy is stored energy, energy that has the potential to do work.
- E.g., The cells of a skeletal muscle at rest contain potential energy in the form of the positions of protein filaments and the covalent bonds between molecules within the cells. When the muscle contracts, it performs work, and potential energy is converted into kinetic energy and heat. The amount of heat is proportional to the amount of work done, which is why exercise increases body temperature.
Distinguish among the major types of chemical reactions that are important for studying physiology.
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Decomposition reactions
- Breaks a molecule into smaller fragments (e.g., within the digestive tract)
- Simple decomposition: AB → A + B
- Those involving water are important in the breakdown of complex molecules in the body and is referred to as hydrolysis. In hydrolysis, one of the bonds in a complex molecule is broken, and the components of a water molecule are added to the resulting fragments.
- AB + H2O → AH + BOH
- Decomposition reactions of complex molecules within the body’s cells and tissues are referred to collectively as catabolism.
- When a covalent bond (i.e., potential energy) is broken, it releases kinetic energy that can perform work. By harnessing the energy released in this way, cells carry out vital functions such as growth, movement, and reproduction.
- CD → C + D + ENERGY
- Breaks a molecule into smaller fragments (e.g., within the digestive tract)
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Synthesis reactions
- The opposite of decomposition; the assembly of smaller molecules into larger molecules by formation of new chemical bonds.
- Simple synthetic reaction: A + B → AB
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Dehydration synthesis (a.k.a. condensation reaction) is the opposite of hydrolysis; it forms a complex molecule by removing a water molecule.
- AH + BOH → AB + H2O
- Synthesis of new molecules within the body’s cells and tissues is known collectively as anabolism, which takes energy since chemical bonds require energy to form
- C + D + ENERGY → CD
- The opposite of decomposition; the assembly of smaller molecules into larger molecules by formation of new chemical bonds.
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Exchange reactions
- Parts of reacting molecules are shuffled around to produce new products.
- A simple exchange: AB + CD → AD + CB
- In an exchange reaction, the reactant molecules must break apart via a decomposition reaction before they can interact with each other to form the product molecules via a synthesis reaction.
- Parts of reacting molecules are shuffled around to produce new products.
Describe the crucial role of enzymes in metabolism.
- Enzymes catalyze chemical reactions by lowering the activation energy required.
- Enzymatic reactions proceed until equilibrium.
- Reactions that release energy are exergonic and those that require energy are endergonic.
- Enzymatic reactions are essential for the processing of metabolites (e.g., nutrients and inorganic compounds like oxygen)
Describe four important properties of water and their significance in the body.
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Lubricant
- Water is an effective lubricant because there is little friction between water molecules. Even a thin layer of water between two opposing surfaces will greatly reduce friction between them.
- E.g., within joints and body cavities
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Chemical reactant
- Chemical reactions in the human body occur in water, and water molecules also participate in some reactions (i.e., hydrolysis and dehydration synthesis)
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High heat capacity
- Water has an unusually high heat capacity (the quantity of heat required to raise its temperature by 1ºC) because water molecules in the solid and liquid state are attracted to one another through hydrogen bonding. Benefits of this high heat capacity include:
- Large mass of water changes temperature very slowly (i.e., thermal inertia)
- Water carries heat away when it changes from a liquid to a gas, explaining the cooling effects of perspiration on the skin.
- Water temperature must be really high for water molecules to develop enough kinetic energy to break hydrogen bonds to become vapour.
- Water has an unusually high heat capacity (the quantity of heat required to raise its temperature by 1ºC) because water molecules in the solid and liquid state are attracted to one another through hydrogen bonding. Benefits of this high heat capacity include:
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Solvent
- A remarkable number of inorganic and organic molecules will dissolve in water.
Explain how the chemical properties of water affect the solubility of inorganic and organic molecules.
- An ionic compound will dissociate (i.e., ionize) as water molecules break them apart in solution.
- Anions are surrounded by the positive poles of water molecules.
- Catons are surrounded by the negative poles of water molecules.
- The sheath of water molecules around an ion in solution is called an hydration sphere.
- An aqueous solution containing ions will conduct an electric current. These soluble inorganic substances are called electrolytes. Small electrical currents carried by ions are essential to muscle contraction and nerve function.
- Hydration spheres can also form around organic molecules containing polar covalent bonds (e.g., glucose).
- Molecules that interact readily with water molecules in this way are called hydrophilic.
- A solution containing dispersed proteins or other large molecules is called a colloid.
- These dispersed particles will remain in solution indefinitely. (e.g., jello)
- A solution containing dispersed particles which settle out of solution over time due to gravity are called suspensions. (e.g., whole blood suspended in blood plasma)
- Many organic molecules are nonpolar.
- Hydration spheres will not form, and these molecules will not dissolve.
- These molecules that do not readily interact with water are called hydrophobic. (e.g., fats and oils)
Discuss the importance of pH and the role of buffers in body fluids.
- Abnormal fluctuations in pH can damage cells and tissues by breaking chemical bonds, since hydrogen ions are extremely reactive in solution.
- An acid is any solute that dissociates in solution and releases hydrogen ions, therby lowering pH.
- Hydrochloric acid (HCl) is a strong acid: HCl → H+ + Cl-
- A base is any solute that dissociates in solution and removes hydrogen ions, thereby raising pH.
- Sodium hydroxide (NaOH) is a strong base: NaOH → Na+ + OH-
- A weak acid/base fails to dissociate completely and have a lesser impact on pH compared to strong acids/bases.
- A salt is an ionic compound consisting of any cation except a hydrogen ion and any anion except a hydroxide ion.
- Salts dissociate completely, releasing cations and anions, but do not change the local concentration of hydrogen/hydroxide, so they are neutral.
- A buffer is a compound which stabilizes the pH of a solution by removing or replacing hydrogen ions.
- Buffer systems typically involve a weak acid and its related salt, which functions as a weak base.
- E.g., the body’s carbonic acid - bicarbonate buffer system
- Buffers and buffer systems help to maintain homeostasis of pH.
Describe the common elements of organic compounds and how functional groups modify the properites of organic compounds.
- Organic compounds always contain the elements carbon and hydrogen, and generally oxygen as well.
- Made up of long hydrocarbon chains connected covalently.
- Many are soluble in water.
- Functional groups greatly influence the chemical (acid/base) and physical (solubility) properties of any molecule in which they occur.
Discuss the structures and functions of carbohydrates.
- A carbohydrate is an organic molecule that contains carbon, hydrogen, and oxygen in a ratio near 1:2:1.
- Monosaccharide (simple sugars)
- Glucose, fructose (isomers)
- Energy source
- Disaccharide
- Sucrose, lactose, maltose
- Energy source
- Polysaccharides
- Glycogen (animal starch), starches
- Glucose storage
Discuss the structures and functions of lipids.
- Lipids contain carbon, hydrogen, and oxygen, and the carbon to hydrogen ratio is near 1:2, however, lipids contain much less oxygen. (e.g., fats, oils, waxes)
- Most lipids are insoluble in water.
- Fatty acids are long carbon chains with hydrogen attached. One end (the head) is attached to a carboxyl group: -COOH
- In a saturated fatty acid each carbon has four single covalent bonds.
- In an unsaturated fatty acid, one or more of the single covalent bonds has been replaced by a double covalent bond.
Discuss protein structure and the essential functions of proteins within the body.
- Amino acids are simple organic compounds that combind to form proteins.
- All contain carbon, hydrogen, oxygen, and nitrogen. Sulfur is present in cysteine and methionine.
- The carboxyl group can act as an acid.
- The amino group can act as a base.
- The molecule has positive and negative charge, but no net charge (i.e., a zwitterion.
- Two amino acids are linked together via a dehydration synthesis.
- Primary structure: results from the sequence of amino acids bonded together in a linear chain.
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Secondary structure: results from bonds between atoms at different parts of the polypeptide chain.
- Alpha helix; a simple spiral
- Beta-pleated sheets: flat pleated sheets
- Tertiary structure: results from the complex coiling and folding that gives a protein its 3D structure.
- Quarternary structure: results from interaction between multiple polypeptide chains to form a complex (e.g., hemoglobin contains four subunits)
Discuss the structure and function of high-energy compounds.
- High-energy compounds contain high-energy bonds, covalent bonds whose breakdown releases energy under controlled conditions.
- E.g., adenosine triphosphate (ATP), pyrophosphate
- The hydrolytic breakdown of ATP requires an enzyme called adenosine triphosphatase (ATPase)
What are the 13 most abundant elements found in the human body?
What are trace elements?
- Oxygen
- Carbon
- Hydrogen
- Nitrogen
- Calcium
- Phosphorus
- Potassium
- Sodium
- Chlorine
- Magnesium
- Sulfer
- Iron
- Iodine
The human body also contains atoms of another 14 elements that are present in very small amounds. These are trace elements.
Why are some elements reactive and others inert?
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Reactive elements
- Electrons in the valence shell of an atom can be transferred or shared with another atom.
- Atoms with unfilled energy levels, (e.g., hydrogen, lithium) will react with other atoms in ways that provide them a full valence shell.
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Noble gases a.k.a. inert elements
- Inert elements (e.g., helium, neon) do not readily participate in chemical processes since they have filled outermost energy levels, and their atoms neither react with one another nor combine with atoms of other elements.
How does a reactive element become stable?
By gaining, or losing, or sharing electrons to fill their outermost energy level.
When this occurs, atoms are no longer electronically neutral, and they become ions.
Atoms that lose electrons from the outer energy level have more protons than electrons; they have a net positive charge and are called cations.
Atoms that gain electrons to fill their outer energy level have more electrons than protons; they have a net negative charge and are called anions.
The interactions that stabilize the outer energy levels of atoms often result in chemical bonds which hold the participating atoms together when the reaction has ended.
Compare polar and non-polar molecules.
- Non-polar molecules have atoms which share their electrons equally, resulting in no electrical charge. (e.g., an oxygen or carbon dioxide molecule)
- Polar molecules have atoms which share their electrons unequally, resulting in a dipole moment. (e.g., a water molecule)
