Chapter 2: The Chemical Level of Organization Flashcards
1
Q
What is chemistry?
A
The science of the structure and interactions of matter.
2
Q
What is matter?
A
- Anything that occupies space and has mass.
Exists in 3 states:
1. Solid.
2. Liquid.
3. Gas.
3
Q
What is mass?
A
The amount of matter in any object, which does not change.
4
Q
What is weight?
A
Force of gravity acting on matter, which does change.
5
Q
What is a solid state of matter?
A
- Are compact.
- Have a definite shape and volume.
- Example: Bones and teeth.
6
Q
What is a liquid state of matter?
A
- Have a definite volume.
- Assume the shape of their container.
- Example: Blood plasma.
7
Q
What is a gas state of matter?
A
- Have neither a definite shape nor volume.
- Example: Oxygen and carbon dioxide.
8
Q
What is a chemical element?
A
- Each element is a substance that cannot be split into a simpler substance by ordinary chemical means.
- Total of 118 elements.
- 92 occuring naturally on Earth.
9
Q
What is a chemical symbol?
A
- One or two letters of the element name in English, Latin or another language.
- Example: H for hydrogen, C for carbon, O for oxygen, N for nitrogen, Ca for calcium, Na for sodium.
10
Q
How many chemical elements are normally present in your body?
A
- 26 different chemical elements.
- Consists of the major elements, lesser elements and trace elements.
11
Q
What are the major elements in the body?
A
- Constitutes about 96% of the body’s mass.
Consists of 4 elements:
1. Oxygen.
2. Carbon.
3. Hydrogen.
4. Nitrogen.
12
Q
What are the lesser elements in the body?
A
- Contribute about 3.6% of the body’s mass.
Consists of 8 elements:
1. Calcium.
2. Phosphorus.
3. Potassium.
4. Sulfur.
5. Sodium.
6. Chlorine.
7. Magnesium.
8. Iron.
13
Q
What are the trace elements in the body?
A
- Present in tiny amounts.
- Account for remaining body mass, about 0.4%.
Consists of 14 elements:
1. Aluminum.
2. Boron.
3. Chromium.
4. Cobalt.
5. Copper.
6. Fluorine.
7. Iodine.
8. Manganese.
9. Molybdenum.
10. Selenium.
11. Silicon.
12. Tin.
13. Vanadium.
14. Zinc.
14
Q
Define the major element oxygen.
A
- 65% of the total body mass.
- Part of water and many organic (carbon-containing) molecules.
- Used to generate ATP.
15
Q
Define the major element carbon.
A
- 18.5% of the total body mass.
- Forms the backbone chains and rings of all organic molecules; carbohydrates, lipids (fats), proteins, nucleic acids (DNA and RNA).
16
Q
Define the major element hydrogen.
A
- 9.5% of the total body mass.
- Constituent of water and most organic molecules.
- Ionized form (H+) makes body fluids more acidic.
17
Q
Define the major element nitrogen.
A
- 3.2% of the total body mass.
- Component of all proteins and nucleic acids.
18
Q
Define an atom.
A
- Smallest units of matter that retain the properties and characteristics of the element.
- Extremely small.
19
Q
What is a subatomic particle?
A
- A particle that composes an atom.
- Dozens of different subatomic particles, only 3 types important for understanding chemical reactions in human body:
1. Protons.
2. Neutrons.
3. Electrons.
20
Q
What is the nucleus of an atom?
A
- Dense central core, contains positively charged protons and uncharged (neutral) neutrons.
- Tiny, negatively charged electrons move about in a large space surrounding the nucleus.
21
Q
What is an electron shell?
A
- Negatively charged electrons form a negatively charged “cloud” that envelops nucleus.
- Depicted as simple circles around nucleus.
- Each shell can hold a specific number of electrons.
- Fill with electrons in a specific order, beginning with first shell.
22
Q
What is the first electron shell?
A
- Nearest the nucleus.
- Never holds more than 2 electrons.
23
Q
What is the second electron shell?
A
- Holds a maximum of 8 electrons.
24
Q
What is the third electron shell?
A
- Holds a maximum of 18 electrons.
25
Why is an atom **electrically neutral**?
* Number of electrons in an atom of an element always equals number of protons.
* Negatively charged electrons and positively charged protons balance each other.
26
What is the **atomic number** of an atom?
* Number of protons in the nucleus of an atom.
* Atoms of different elements have different atomic numbers because they have different numbers of protons.
27
What is the **mass number** of an atom?
* Number of protons and neutrons in an atom.
28
What is an **isotope**?
* Atoms of an element that have different numbers of neutrons and therefore, different mass numbers.
29
What is a **radioactive isotope (radioisotopes)**?
* Unstable; their nuclei decay into a stable configuration.
* As they decay, atoms emit radiation (either subatomic particles or packets of energy) and in process transform into a different element.
30
Examples of **atomic structures** of stable atoms:
* **Hydrogen (H): 1 proton, 1 electron shell**.
Atomic number = 1
Mass number = 1 or 2
Atomic mass = 1.01
* **Carbon (C): 6 protons, 6 neutrons, 2 electron shell**s.
Atomic number = 6
Mass number = 12 or 13
Atomic mass = 12.01
31
Examples of **atomic structures** of stable atoms:
* **Nitrogen (N): 7 protons, 7 neutrons, 2 electron shells**.
Atomic number = 7
Mass number = 14 or 15
Atomic mass = 14.01
* **Oxygen (O): 8 protons, 8 neutrons, 2 electron shells**.
Atomic number = 8
Mass number = 16, 17 or 18
Atomic mass = 16.00
32
What is the **atomic mass** of an **atom**?
* Average mass of all the naturally occurring isotopes.
* Atomic mass of an element is close to mass number of its most abundant isotope.
33
What is the **half life** of an isotope?
* Time required for half of the radioactive atoms in a sample of that isotope to decay into more stable form.
* As fast as fraction of a second or as slow as millions of years.
34
What is a **dalton**?
* Standard unit for measuring mass of atoms and their subatomic particles.
* Aka an atomic mass unit.
* Neutron has a mass of 1.008 daltons.
* Proton has a mass of 1.007 daltons.
* Electron has a mass of 0.0005 daltos.
35
What is an **ion**?
* Aom that has positive or negative charge because it has unequal numbers of protons and electrons.
* Atom becomes an ion if it either gives up or gains electrons.
36
What is **ionization**?
* Process of giving up or gaining electrons.
* Ion of an atom is symbolized by writing its chemical symbol followed by number of positive or negative charges.
37
What is a **molecule**?
* When two or more atoms share electrons.
* Molecule may consist of two atoms of same kind, such as an oxygen molecule.
38
What is a **compound**?
* Substance that contains atoms of two or more different elements.
* Most atoms in body are joined into compounds.
* Examples: water (H2O) and sodium chloride (NaCl), common table salt, are compounds.
39
What is a **free radical**?
* Atom or group of atoms with an unpaired electron in outermost shell.
* Example: Superoxide (formed by addition of an electron to an oxygen molecule).
* Unpaired electron makes free radical unstable, highly reactive and destructive to nearby molecules.
* Become stable by either giving up unpaired electron to, or taking on an electron from, another molecule.
40
What is a **chemical bond**?
* Forces that hold together the atoms of a molecule or a compound.
* Likelihood that atom will form a chemical bond with another atom depends on number of electrons in its outermost shell.
41
What is a **valence shell**?
* An atoms outermost shell.
* Atom with valence shell holding 8 electrons is chemically stable (unlikely to form chemical bonds with other atoms).
* Most biologically important elements **do not** have 8 electrons in their valence shells.
42
Define the **octet rule**.
* When 2 or more atoms interact in ways that produce chemically stable arrangement of 8 valence electrons for each atom.
43
What is an **ionic bond**?
* Force of attraction that holds together ions with opposite charges.
* Positively and negatively charged ions are attracted to one another.
* Mainly found in teeth and bones.
44
What is a **cation**?
* Positively charged ion.
45
What is an **anion**?
* Negatively charged ion.
46
What is an **electrolyte**?
* Iconic compound, breaks apart into positive and negative ions in solution.
* Most ions in body are dissolved in body fluids as electrolytes.
* Their solutions can conduct an electric current.
47
What are common **ions** found in the body?
**Cations**: Hydrogen (H+), Sodium (Na+), Potassium (K+), Ammonium (NH4+), Magnesium (Mg2+), Calcium (Ca2+), Iron (II) (Fe2+), Iron (III) (Fe3+).
**Anions**: Fluoride (F-), Chloride (Cl-), Iodine (I-), Hydroxide (OH-), Bicarbonate (HCO3-), Oxide (O2-), Sulfate (SO4 2-), Phosphate (PO4 3-).
48
What is a **covalent bond**?
* When 2 or more atoms **share** electrons rather than gaining/losing them.
* Atoms form a covalently bonded molecule by sharing 1, 2 or 3 pairs of valence electrons.
* The larger the number of electron pairs shared between 2 atoms, the stronger the covalent bond.
* Most common chemical bond in body.
* Can form between atoms of same element or different elements.
49
What is a **single covalent bond**?
* When 2 atoms share 1 electron pair.
* Example: Molecule of hydrogen forms when 2 hydrogen atoms share their single valence electrons, which allows both atoms to have a full valence shell at least part of the time.
50
What is a **double covalent bond**?
* Results when 2 atoms share 2 pairs of electrons.
* Example: Oxygen molecule.
51
What is a **triple covalent bond**?
* Results when 2 atoms share 3 pairs of electrons.
* Example: Molecule of nitrogen.
52
What is a **nonpolar covalent bond**?
* Two atoms share the electrons **equally**.
* One atom **does not** attract shared electrons more strongly than other atom.
* Bonds between 2 identical atoms are always nonpolar covalent bonds.
53
What is a **polar covalent bond**?
* Sharing of electrons between two atoms is **unequal**.
* Nucleus of one atom attracts shared electrons more strongly than nucleus of other atom.
* When polar covalent bonds form, resulting molecule has partial negative charge near the atom that attracts electrons more strongly.
* This atom has greater **electronegativity** (power to attract electrons to itself).
54
What is a **hydrogen bond**?
* Forms when a hydrogen atom with partial positive charge attracts the partial negative charge of neighboring electronegative atoms, most often larger oxygen or nitrogen atoms.
* Result from attraction of oppositely charged parts of molecules.
* Weak bonds, cannot bind atoms into molecules.
* Establish important links between molecules or between different parts of a large molecule.
55
What is **surface tension** in hydrogen bonds?
* Hydrogen bonds that link neighboring water molecules give water considerable cohesion.
* Measure of the difficulty of stretching/breaking the surface of a liquid.
* Boundary between water and air, waters surface tension is very high as water molecules are more attracted to one another than to molecules in air.
56
Define a **chemical reaction**.
* Occurs when new bonds form/old bonds break between atoms.
* Foundation of all life processes.
* Interactions of valence electrons are basis of all chemical reactions.
* Starting substances are know as **reactants**.
* Ending substances are known as **products**.
57
Define **metabolism**.
* All the chemical reactions occurring in the body.
58
Define **energy** (in relation to chemical reactions).
* The capacity to do work.
* Consists of 2 principal forms of energy:
1. **Potential energy** (energy stored by matter due to its position).
2. **Kinetic energy** (energy associated with matter in motion).
* Each chemical reaction involves energy changes.
59
What is **chemical energy**?
* Form of potential energy that is stored in the bonds of compounds and molecules.
* Total amount of energy present at beginning and end of a chemical reaction is the same.
60
What is the **law of conservation** of energy?
* Energy can be neither created nor destroyed.
* May be converted from one form to another.
* Generally releases heat, some of which is used to maintain normal body temperature.
61
What is an **exergonic reaction**?
* **Release** more energy than they absorb.
62
What is an **endergonic reaction**?
* **Absorb** more energy than they release.
63
What is **activation energy**?
* Energy needed to break chemical bonds in reactant molecules so reaction can start.
* Particles of matter are continuously moving, colliding with one another.
* Sufficiently forceful collision can disrupt movement of valence electrons, causing an existing chemical bond to break/new one to form.
64
How does the **concentration** affect **activation energy**?
* The more particles of matter present in a confined space, the greater the chance they will collide.
* Concentration increases when more are added to given space or when pressure on the space increases.
65
How does the **temperature** affect **activation energy**?
* As temperature rises, particles of matter move more rapidly.
* Higher the temperature, more forcefully particles collide and greater the chance that a collision will produce a reaction.
66
What is a **catalyst**?
* Chemical compounds that speed up chemical reactions by lowering activation energy needed for reaction.
* Most important catalysts in body are **enzymes**.
* Does not alter difference in potential energy between the reactants and products.
* Lowers amount of energy needed to start the reaction.
* Catalyst is unchanged at end of the reaction.
67
Define a **synthesis reaction - anabolism**.
* When 2 or more atoms, ions or molecules combine to form new and larger molecules.
* All the synthesis reactions in body are collectively referred to as **anabolism**.
* Anabolic reactions are usually **endergonic**, absorb more energy than they release.
68
Define a **decomposition reaction - catabolism**.
* Split up large molecules into smaller atoms, ions or molecules.
* Decomposition reactions that occur in the body are collectively referred to as **catabolism**.
* Usually **exergonic**, release more energy than they absorb.
69
Define **exchange reactions**.
* Consist of both synthesis and decomposition reactions.
70
Define **reversible reactions**.
* The products can revert to the original reactants.
71
What are the two principal classes of **compounds**?
1. Inorganic compounds.
2. Organic compounds.
72
What is an **inorganic compound**?
* Usually lack carbon skeleton.
* Are structurally simple.
* Include water and many salts, acids and bases.
* May have ionic or covalent bonds.
* Water makes up 55-60% of lean adults total body mass.
* All other inorganic compounds combined add 1-2%.
73
What is an **organic compound**?
* Always contain carbon.
* Usually contain hydrogen.
* Always have covalent bonds.
* Most are large molecules, many made up of long carbon atom chains.
* Organic compounds make up remaining 38-43% of human body.
74
Define **water**.
* Most important and abundant inorganic compound in all living systems.
* Nearly all body's chemical reactions occur in a watery medium.
* Versatile solvent because its polar covalent bonds, (electrons are shared unequally) create positive and negative regions.
75
Define **solvent**.
* Usually a liquid substance capable of dissolving or dispersing one or more other substances.
* Usually more solvent than solute in a solution.
76
Define **solution**.
* Liquid mixture in which the minor component (the solute) is **uniformly** distributed within major component (the solvent).
* Solute particles in a solution are very small, a solution looks transparent.
* Solutes do not settle out and accumulate on bottom of a container.
77
Define **solute**.
* Substance that is dissolved in a solution. A solute is usually solid.
78
Define **hydrophilic**.
* Solutes that are charged or contain polar covalent bonds.
* Dissolves easily in water.
* Example: sugar and salt in water.
79
Define **hydrophobic**.
* Molecules that contain mainly nonpolar covalent bonds.
* Not very water-soluble.
* Example: animal fats and vegetable oils.
80
Define **hydrolysis reactions**.
* Decomposition reaction that breaks down large molecules into smaller molecules by addition of water molecules.
81
Define **dehydration synthesis reacions**.
* When two smaller molecules join to form one larger molecule.
* A water molecule is one of products formed from this reaction.
82
Why does water have a high heat **capacity**?
* Due to the large number of hydrogen bonds in water.
* As water absorbs heat, some of energy is used to break hydrogen bonds.
* Less energy is left over to increase motion of water molecules, which would increase the water's temperature.
83
What is a **mixture**?
* A combination of elements or compounds that are physically blended together but not bound by chemical bonds.
84
What are the three common liquid mixtures?
1. **Solutions**
2. **Colloids**
3. **Suspensions**
85
What is a **colloid mixture**?
* Solute particles are large enough to scatter light.
* Translusent or opaque appearance.
* The solutes do not settle out and accumulate on the bottom of a container.
86
What is a **suspension** mixture?
* The suspended material may mix with the liquid or suspending medium for some time, but eventually will settle out.
* Example: Blood.
87
What is the **concentration** of a solution?
* The amount of solute that has been dissolved in a given amount of solvent or solution.
* Expressed by mass per volume percentage (relative mass of a solute found in given volume of solution).
* Concentration in units of mole per liter (also called molarity), which relate to total number of molecules in given volume of solution.
88
What is a **mole (molarity)**?
* Amount of any substance that has a mass in grams equal to the sum of the atomic masses of all its atoms.
* Example: 1 mole of element chlorine (atomic mass = 35.45) is 35.45 grams. A 1 molar (1M) solution = 1 mole of a solute in 1 liter of solution.
89
What is **percentage (mass per volume)**?
* Number of grams of a substance per 100 mililiters (mL) of solution.
* Example: To make a 10% NaCl solution, take 10g of NaCl and add enough water to make a total of 100mL of solution.
90
What is **Avogadro's number**?
* Number of units in one mole of any substance. (6.023 x 10^23).
* Measurements of substances that are stated in moles tell us about numbers of atoms, ions or molecules present.
91
Define **dissociate**.
* The seperation of inorganic acids, bases and salts into ions in a solution.
92
What is an **acid**?
* A substance that dissociates into one or more hydrogen ions (H+) and one or more anions.
* Because H+ is a single proton with one positive charge, an acid is also referred to as a **proton donor**.
93
What is a **base**?
* Removes H+ from a solution, is a proton acceptor.
* Many bases dissociate into one or more hydroxide ions and one or more cations.
94
Define the **pH scale**.
* A solutions acidity or alkalinity, which extends from 0 to 14.
* Based on the concentration of H+ in moles per liter.
* Midpoint of pH scale is 7, where concentrations of H+ and OH- are equal (pure water).
pH below 7 = **acidic**
pH above 7 = **basic (alkaline)**
95
What is an **acidic solution**?
* A solution that has more H+ than OH- and has a pH below 7.
* A ph of 6 denotes 10 times **more** H+ than a pH of 7.
96
What is a **basic (alkaline) solution**?
* A solution that has more OH- than H+ and has a pH above 7.
* A pH of 8 indicates 10 times **fewer** H+ than a pH of 7 and 100 times **fewer** H+ than a pH of 6.
97
What is the pH of **blood**?
* 7.35 - 7.45, slightly more basic than pure water.
98
What is a **buffer system**?
* Systems which function to convert strong acids or bases into weak acids or bases.
* Strong acids (or bases) ionize easily and contribute many H+ (or OH-) to a solution.
99
What are **buffers**?
* Chemical compounds that can convert strong acids or bases into weak ones.
* Remove or adding protons (H+).
* One important buffer system in body is carbonic acid-bicarbonate buffer system.
100
What is the **carbonic acid-bicarbonate buffer system**?
* Carbonic acid (H2CO3) can act as weak acid and bicarbonate ion (HCO3-) can act as weak base.
* This buffer system can compensate for either an excess or shortage of H+,
101
What is a **macromolecule**?
* When small organic molecules comine into very large molecules.
* Are usually polymers.
102
What is a **polymer**?
* Large molecule formed by covalent bonding of many identical or similar small builiding-block molecules called **monomers**.
* Reaction that joins 2 monomers is usually dehydration synthesis.
103
What is an **isomer**?
* Molecules that have same molecular formula but different structures.
* Example: molecular formulas for sugars glucose and fructose are both C6H12O6.
* Individual atoms are positioned differently along carbon skeleton, giving sugars different chemical properties.
104
What are **carbohydrates**?
* Includes sugars, glycogen, starches and cellulose.
* Large and diverse group of organic compounds.
* Source of chemical energy for generating ATP needed to drive metabolic reactions.
* Elements found in carbohydrates: carbon, hydrogen and oxygen.
* Have 2:1 ratio of hydrogen to oxygen.
105
Define a **monosaccharide**.
* Simple sugars, the monomers of carbohydrates.
* Contain from 3-7 carbon atoms.
* Soluble in water.
* Monosaccharides with 3 carbons = **trioses**.
* Monosaccharides with 4 carbons = **tetroses**.
* Monosaccharides with 5 carbons = **pentoses**.
* Monosaccharides with 6 carbons = **hexoses**.
* Monosaccharides with 7 carbons = **heptoses**.
* Cells break down the hexose glucose to produce ATP.
106
Define a **disaccharide**.
* Molecule formed from combination of 2 monosaccharides by dehydrate synthesis.
* Example: molecules of monosaccharides glucose and fructose combine to form molecule of the disaccharide sucrose (table sugar).
Glucose and fructose are **isomers**.
Can be split into smaller, simpler molecules by **hydrolysis**.
* Soluble in water.
107
Define a **polysaccharide**.
* Third major group of carbohydrates.
* Each polysaccharide molecule contains tens/hundreds of monosaccharides joined through dehydration synthesis.
* Usually insoluble in water, do not taste sweet.
* Main polysaccharide in the human body is glycogen.
108
What are **starches**?
* Polysaccharides formed from glucose by plants.
* Found in foods (pasta and potatoes).
* The major carbohydrates in the diet.
109
What is **glycogen**?
* Main polysaccharide in human body.
* Made entirely of glucose monomers linked to one another in branching chains.
* Limited amount of carbohydrates is stored as glycogen in liver and skeletal muscles.
110
What are **organic compouonds**?
* **Carbohydrates**.
* **Lipids**.
* **Proteins**.
* **Nucleic Acids**.
* **Adenosine triphosphate (ATP)**.
111
Define **lipids**.
* Second important group of organic compounds.
* Make up 18-25% of body mass in lean adults.
* Contain **carbon**, **hydrogen** and **oxygen**.
* **Do not** have 2:1 ratio of hydrogen to oxygen.
* Most insoluble in polar solvents such as water; are hydrophobic.
* Only smallest lipids (some fatty acids) can disolve in watery blood plasma.
112
What is a **lipoprotein**?
* Lipoproteins are soluble because proteins are on outside and lipids are on inside.
* When other lipid molecules join with hydrophilic protein molecules, resulting in a lipid-protein complexes.
113
What do **lipids** include?
* **Fatty acids**.
* **Triglycerides** (fats and oils).
* **Phospholipids** (lipids that contain phosphorus).
* **Steroids** (lipids that contain rings of carbon atoms).
* **Eicosanoids** (20-carbon lipids).
* Variety of other substances, including fat-soluble vitamins (vitamims A, D, E and K) and lipoproteins.
114
What are **fatty acids**?
* Among simplest lipids.
* Used to synthesize triglycerides and phospholipids.
* Can be catabolized to generate adenosine triphosphate (ATP).
* Fatty acid consists of a carboxyl group and a hydrocarbon chain.
* Can be either **saturated** or **unsaturated**.
115
Describe a **saturated fatty acid**.
* Contains only single covalent bonds between carbon atoms of hydrocarbon chain.
* Lack double bonds, each carbon atoms of the hydrocarbon chain is **saturated** with hydrogen atoms.
116
Describe an **unsaturated fatty acid**.
* Contains one or more double covalent bonds between carbon atoms of hydrocarbon chain.
* Fatty acid is **not** completely saturated with hydrogen atoms.
117
What are **tyiglycerides**?
* Most plentiful lipids in body and diet.
* Also known as triacylglycerols.
* Consists of two types of building blocks; a single glycerol molecule and three fatty acid molecules.
* Three-carbon glycerol molecule forms backbone of a tyiglyceride.
* Can be solid or liquid at room temperature.
* Body's most highly concentrated form of chemical energy.
118
What is a **fat**?
* Triglyceride that is solid at room temperature.
* Fatty acids of a fat are mostly saturated.
* Lack double bonds in their hydrocarbon chains, can closely pack together and solidify at room temperature.
119
What is a **saturated fat**?
* Fat that mainly consists of saturated fatty acids.
* Mostly in meats (red meats) and non-skim dairy products (whole milk, cheese, and butter).
* Found in few plant products (cocoa butter, palm oil, coconut oil).
* Diets that contain large amounts of saturated fats are associated with heart disease and colorectal cancer.
120
What is an **oil**?
* Tyiglyceride that is liquid at room temperature.
* Fatty acids of an oil are mostly unsaturated.
* Contain one or more double bonds in their hydrocarbon chains.
* Fatty acids of an oil can be monounsaturated or polyunsaturated.
121
What is a **monounsaturated fat**?
* Tyiglycerides, mostly consist of monounsaturated fatty acids.
* Olive oil, peanut oil, canola oil, most nuts and avocados are rich in triglycerides with monounsaturated fatty acids.
* Decrease the risk of heart disease.
122
What is a **polyunsaturated fat**?
* Triglycerides, mostly consist of poly-unsaturated fatty acids.
* Corn oil, saff lower oil, sunflower oil, soybean oil and fatty fish (salmon, tuna, mackerel) contain high percentage of polyunsaturated fatty acids.
* Decrease the risk of heart disease.
123
Describe **triglycerides** as energy.
* Provide more than twice as much energy per gram as carbohydrates and proteins.
* Capacity to store triglycerides in adipose (fat) tissue is unlimited for all practical purposes.
124
What are **phospholipids**?
* Have glycerol back-bone and two fatty acid chains attached to first two carbons.
* In third position, phosphate group (PO43-) links a small charged group that usually contains nitrogen (N) to backbone.
* This portion of molecule (head) is polar, can form hydrogen bonds with water molecules.
* The two fatty acids (tails) are non polar, can interact with other lipids.
125
What does **amphipathic** mean?
* When molecules have both polar and nonpolar parts.
* Amphipathic phospholipids line up tail-to-tail in double row to make up much of a membrate that surrounds each cell.
126
What are **steroids**?
* Have four rings of carbon atoms.
* Body cells synthesize other steroids from cholesterol, which has a large nonpolar region consisting of four rings and hydrocarbon tail.
* Body, commonly encountered steroids, (cholesterol, estrogens, testosterone, cortisol, bile salts and vitamin D).
* Known as sterols, have at least one hydroxyl (alcohol) group.
* The polar hydroxyl groups make sterols weakly **amphipathic**.
127
What are **eicosanoids**?
* Lipids derived from 20-carbon fatty acid called arachidonic acid.
Two principal subclasses of eicosanoids:
* **Prostaglandins**.
* **Leukotrienes**.
128
What are **prostaglandins**?
* Wide variety of functions.
* Modify responses to hormones.
* Contribute to inflammatory response.
* Prevent stomach ulcers.
* Dilate airways to lungs.
* Regulate body temperature.
* Influence formation of blood clots.
129
What are **leukotrienes**?
* Participates in allergic and inflammatory responses.
130
What are **other lipids**?
* **Fat-soluble vitamins** (beta-carotenes).
* **Vitamins D, E, and K**.
* **Lipoproteins**.
131
What are **proteins**?
* Large molecules, contain carbon, hydrogen, oxygen and nitrogen.
* Some contain sulfur.
* Normal lean adult body is 12-18% protein.
* More complex in structure than carbohydrates or lipids.
* Many roles in body, largely ressponsible for structure of body tissues.
132
What are the different types of **proteins**?
* **Structural**.
* **Regulatory**.
* **Contractile**.
* **Immunological**.
* **Transport**.
* **Catalytic**.
133
Describe the function of **structural proteins**.
* Form structural framework of various parts of body.
* Examples: collagen in bone and connective tissues; keratin in skin, hair, and fingernails.
134
Describe the function of **regulatory proteins**.
* As hormones that regulate various physiological processes; control growth and development.
* As neurotransmitters, medicate responses of nervous system.
* Examples: hormone insulin. Neurotransmitter known as substance P (medicates sensation of pain in nervous system).
135
Describe the function of **contractile proteins**.
* Allow shortening of muscle cells, which produces movement.
* Examples: myosin; actin.
136
Describe the function of **immunological proteins**.
* Aid responses that protect body against foreign substances and invading pathogens.
* Examples: antibiotdies; interleukins.
137
Describe the function of **transport proteins**.
* Carry vital substances throughout body.
* Example: hemoglobin (transports most oxygen and some carbon dioxide in blood).
138
Describe the function of **catalytic proteins**.
* Act as enzymes that regulate biochemical reactions.
* Examples: salivary amylase; sucrase; ATPase.
139
What is an **amino acid**?
* Monomers used to build proteins.
Each of 20 different amino acids has a hydrogen (H) atom and 3 important functional groups attached to a central carbon atom:
1. An amino group (-NH2).
2. An acidic carboxyl group (-COOH).
3. A side chain (r group).
* At normal pH of body fluids, both amino group and carboxyl group are **ionized**.
* Different side chains give each amino acid its distenctive chemical identity.
140
What is a **peptide bond** and how is it formed?
* Covalent bond joining each pair of amino acids.
* Protein is synthesized in stepwise fashion - one amino acid is joined to a second, a third is then added to the first two, ect.
* Forms between carbon of the carboxyl group (-COOH) of one amino acid and nitrogen of the amino group (-NH2) of another.
* As peptide bond formed, a molecule of water is removed, (dehydration synthesis reaction).
* Breaking peptide bond, (digestion of dietary proteins), is hydrolysis reaction.
* **Dipeptide**: 2 amino acids combine.
* **Tripeptide**: 3 amino acids combine.
* Further adding of amino acids result in formation of chainlike **peptide** (4-9 amino acids) or **polypeptide** (10-2000 or more amino acids).
141
Define **denaturation**.
* Protein unravels, loses characteristic shape (secondary, tertiary and quaternary structure).
* Usually caused by altered environment.
* Proteins that are denatured are no longer functional, although can be reversed in some cases. (Frying an egg).
142
What are the 2 parts of some **enzymes**?
* Protein portion called the **apoenzyme** .
* Nonprotein portion called a **cofactor** (may be metal ion, such as iron, magnesium, zinc or calcium)) or organic molecule called a coenzyme).
143
What are the 3 **important properties of enzymes**?
1. Are highly specific.
2. Are very efficient.
3. Are subject to a variety of cellular controls.
144
Explain how **enzymes are highly specific**.
* Each enzyme binds only to specific substrates (reactant molecules on which enzyme acts).
* Part of enzyme that catalyzes reaction (active site), thought to fit substrate like a key.
* Active site can also change its shape to fit snugly around substrate once the substrate enters active site (induced fit).
145
Explain how **enzymes are very efficient**.
* Can catalyze reactions at rates 100 million-10 billion x more rapid than similar reactions without enzymes.
* Number of substrate molecules that single enzyme molecule can convert to product molecules in one second, between 1-10,000 and high as 600,000.
146
Explain how **enzymes are subject to a variety of cellular controls**.
* Rate of synthesis and concentration at any given time are under control of cell's genes.
* Substances within cell may enhance or inhibit activity of given enzyme.
* Many enzymes have active and inactive forms in cells.
* Rate at which inactive form becomes active or vice versa is determined by chemical environment inside cell.
147
Describe how an **enzyme works**.
1. Substrates make contact with active site on surface of enzyme molecule, forming temporary intermediate compound called **enzyme-substrate complex**.
2. Substrate molecules transformed by rearrangement of existing atoms, breakdown of substrate molecule/combination of several substrate molecules into products of the reaction.
3. After reaction is completed and reaction products move away from enzyme, unchanged enzyme is free to attach to other substrate molecules.
* Sometimes, single enzyme may catalyze reversible reaction in either direction.
148
Define **nucleic acids**.
* Huge organic molecules that contain carbon, hydrogen, oxygen, nitrogen and phosphorus.
Consist of 2 varieties:
1. **Deoxyribonucleic acid** (DNA).
2. **Ribonucleic acid** (RNA).
149
What is **DNA** (deoxyribonucleic acid)?
* Forms inherited genetic material inside human cells.
* In humans, each gene is a segment of DNA molecule.
* Genes control protein synthesis, regulate most of the activities that take place in body cells.
* Self-replicating.
* Encodes information for making proteins.
Consists of 2 kinds:
1. **Nuclear**.
2. **Mitochondrial**.
150
What is **RNA** (ribonucleic acid)?
* Second type of nucleic acid.
* Relays instructions from genes to guide each cell's synthesis of proteins from amino acids.
* Single-stranded in humans.
* Sugar in RNA is pentose ribose.
* Contains the pyrimidine base **uracil** (U) instead of **thymine**.
* Made using DNA as blueprint. Carries genetic code and assists in making proteins.
3 different kinds of RNA:
1. **Messenger RNA**.
2. **Ribosomal RNA**.
3. **Transfer RNA**.
151
What is a **nucleic acid**?
* A chain of repeating monomers called neucleotides.
152
What are the 3 parts of **nucleotide of DNA**?
1. **Nitrogenous base**. Contains 4 different nitrogenous bases, which contain atoms of C, H, O and N. In DNA, 4 nitrogenous bases are **adenine** (A), **thymine** (T), **cytosine** (C) and **guanine** (G).
2. **Pentose sugar**. 5-carbon sugar called deoxyribose attaches to each base in DNA.
3. **Phosphate group**. Alternate with pentose sugars to form "backbone" of DNA strand; bases project inward from backbone chain.
153
What is the **double helix model**?
* DNA resembles a spiral ladder.
* 2 strands of alternating phosphate groups and deoxyribose sugars form uprights of ladder.
* Paired bases, held tigether by hydrogen bonds, form rungs.
* Adenine pairs with thymine.
* Cytosine pairs with guanine.
* When DNA is copied, 2 strands unwind and each serves as template/mold on which to construct new second strand.
154
Define **mutation** of DNA.
* Any change that occurs in base sequence of a DNA strand.
* Some mutations result in death of cell, cause cancer, or produce genetic defects in future generations.
155
What is **ATP** (adenosine triphosphate)?
* "Energy currency" of living systems.
* ATP transfers energy liberated in exergonic catabolic reactions to power cellular activities that require energy (**endergonic reactions**).
* Examples: muscular contractions, movement of chromosomes during cell division, movement of structures within cells, transport of substances across cell membranes, synthesis of larger molecules for smaller ones.
* Consists of 3 phosphate groups attached to adenosine, a unit composed of adenine and the 5 carbon sugar ribsoe.
156
Where does the cell get the **energy required to produce ATP**?
* Energy needed to attach a phosphate group to ADP, supplied mainly by catabolism of glucose in process called callular respiration.
Cellular respiration has 2 phases:
1. **Anaerobic**.
2. **Aerobic**.
157
Describe the **anaerobic phase** of cellular respiration.
* Series of reactions that do not require oxygen.
* Glucose partially broken down by series of catabolic reactions into pyruvic acid.
* Each glucose molecule that is converted into pyruvic acid molecule yields 2 molecules of ATP.
158
Describe the **aerobic** phase of cellular respiration.
* In presence of oxygen, glucose is completely broken down into carbon dioxide and water.
* These reactions generate heat and 30 or 32 ATP molecules
