C HAPTER 6--- C HEMISTRY IN B IOLOGY Miss Queen S ECTION 6.1 Atoms, Elements, Compounds.
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Transcript of C HAPTER 6--- C HEMISTRY IN B IOLOGY Miss Queen S ECTION 6.1 Atoms, Elements, Compounds.
CHAPTER 6--- CHEMISTRY IN BIOLOGY
Miss Queen
SECTION 6.1 Atoms, Elements, Compounds
COMPOSITION OF MATTER Matter - Everything in
universe is composed of matter Matter is anything that occupies
space or has massMass – quantity of matter an object has
Weight – pull of gravity on an object
Atom – the smallest unit of matter “indivisible”
Heliumatom
ATOMS
The simplest particle of an element that retains all the properties of that element
Properties of atoms determine the structure and properties of the matter they compose
Our understanding of the structure of atoms based on scientific models, not observation
STRUCTURE OF AN ATOM--THE NUCLEUS
Central coreConsists of
positive charged protons and neutral neutrons
Positively charged
Contains most of the mass of the atom
THE PROTONS
All atoms of a given element have the same number of protons
Number of protons called the atomic number
Number of protons balanced by an equal number of negatively charged electrons
THE NEUTRONSThe number varies slightly among
atoms of the same elementDifferent number of neutrons
produces isotopes of the same element
ELEMENTSPure substances that cannot be
broken down chemically into simpler kinds of matter
More than 100 elements (92 naturally occurring)
90% of the mass of an organism is composed of 4 elements (oxygen, carbon, hydrogen and nitrogen)
Each element unique chemical symbol Consists of 1-2 letters First letter is always capitalized
ATOMIC MASS
Protons & neutrons are found in the nucleus of an atom
Protons and neutrons each have a mass of 1 amu (atomic mass unit)
The atomic mass of an atom is found by adding the number of protons & neutrons in an atom
THE ELECTRONSNegatively charged high energy
particles with little or no massTravel at very high speeds at
various distances (energy levels) from the nucleus
ENERGY LEVELS Atoms have 7 energy levels The levels are K (closest to the
nucleus), L, M, N, O, P, Q (furthest from the nucleus)
The K level can only hold 2 electrons Levels L – Q can hold 8 electrons (octet
rule)
ATOMIC STRUCTURE
Electrons are arranged in Energy Levels
or Shells around the nucleus of an atom.
• first shell a maximum of 2 electrons
• second shell a maximum of 8
electrons
• third shell a maximum of 8
electrons
SUMMARY
1. The Atomic Number of an atom = number of
protons in the nucleus.
2. The Atomic Mass of an atom = number of
Protons + Neutrons in the nucleus.
3. The number of Protons = Number of Electrons.
4. Electrons orbit the nucleus in shells.
5. Each shell can only carry a set number of electrons.
PERIODIC TABLE Elements are arranged by their atomic
number on the Periodic Table The horizontal rows are called Periods &
tell the number of energy levels Vertical groups are called Families & tell
the outermost number of electrons
COMPOUNDSMost
elements do not exist by themselves
Readily combine with other elements in a predictable fashion
A compound is a pure substance made up of atoms of two or more elements The proportion of atoms
are always fixedChemical formula
shows the kind and proportion of atoms of each element that occurs in a particular compound
Molecules are the simplest part of a substance that retains all of the properties of the substance and exists in a free state
Some molecules are large and complex
CHEMICAL FORMULAS Subscript after a
symbol tell the number of atoms of each element
H20 has 2 atoms of hydrogen & 1 atom of oxygen
Coefficients before a formula tell the number of molecules
3O2 represents 3 molecules of oxygen or (3x2) or 6 atoms of oxygen
PROPERTIES
The physical and chemical properties of a compound differ from the physical and chemical properties of the individual elements that compose it
The tendency of elements to combine and form compounds depends on the number and arrangement of electrons in their outermost energy level
Atoms are most stable when their outer most energy level is filled
Most atoms are not stable in their natural state
Tend to react (combine) with other atoms in order to become more stable (undergo chemical reactions)
In chemical reactions bonds are broken; atoms rearranged and new chemical bonds are formed that store energy
COVALENT BONDSFormed when two atoms share
one or more pairs of electrons
IONIC BONDSSome atoms become stable by
losing or gaining electronsAtoms that lose electrons are
called positive ions
Atoms that gain electrons are called negative ions
Because positive and negative electrical charges attract each other ionic bonds form
SECTION 6.2Chemical Reactions, Enzymes
ENERGY AND CHEMICAL REACTIONS Living things undergo thousands of
chemical reactions as part of the life process
Chemical reaction is the process by which atoms or groups of atoms in substances are reorganized into different substances.
CHEMICAL EQUATIONS
represent chemical reactionsReactants are shown on the left side
of the equationProducts are shown on the right
side
The number of each kind of atom must be the same on either side of the arrow (equation must be balanced)
Bonds may be broken or made forming new compounds
Activation Energy is the minimum amount of energy needed to form products in a chemical reaction.
Enzymes are an important class of catalysts in living organisms
Catalyst is a substance that lowers the activation energy needed to start a chemical reaction. Mostly protein Thousands of different kinds Each specific for a different chemical reaction
ENZYME STRUCTURE
Enzymes work on substances called substrates
Substrates must fit into a place on an enzyme called the active site
Enzymes are reusable!
SECTION 6.3Water and Solutions
WATERA water molecule (H2O), is made up of three atoms --- one oxygen and two hydrogen.
H
HO
WATER: THE FACTS
Water is possibly the most important compound in living organisms.
Water consists of 1 atom of oxygen combined with 2 atoms of hydrogen.
Water makes up 70 to 95 percent of most organisms.
- water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.
SOLUTIONS
A solution is a mixture in which 2 or more substances are uniformly distributed in another substance
Solute is the substance dissolved in the solution Particles may be
ions, atoms, or molecules
Solvent is the substance in which the solute is dissolved
Water is the universal solvent
SOLUTIONS Solutions can be
composed of varying proportions of a given solute in a given solvent --- vary in concentration (measurement of the amount of solute)
A saturated solution is one in which no more solute can be dissolved
Aqueous solution (water) are universally important to living things
ACIDS AND BASESOne of the most important aspects
of a living system is the degree of acidity or alkalinity
ACIDS
Number of hydronium ions in solutions is greater than the number of hydroxide ions
HCl H+ + Cl-
BASESNumber of hydroxide ions in
solution is greater than the number of hydronium ions
NaOH Na+ + OH-
PH SCALE logarithmic scale
for comparing the relative concentrations of hydronium ions and hydroxide ions in a solution
ranges from 0 to 14
Each pH is 10X stronger than next
e.g. ph 1 is 10 times stronger than ph 2
the lower the pH the stronger the acid
the higher the pH the stronger the base
pH 7.0 is neutral
BUFFERS
Control of pH is very important
Most enzymes function only within a very narrow pH
Control is accomplished with buffers made by the body
Buffers keep a neutral pH (pH 7)
Buffers neutralize small amounts of either an acid or base added to a solution
Complex buffering systems maintain the pH values of your body’s many fluids at normal and safe levels
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ORGANIC COMPOUNDS
Compounds that contain CARBON are called organic.
Macromolecules are large organic molecules.
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MACROMOLECULES
Large organic molecules.Also called POLYMERS.Made up of smaller “building
blocks” called MONOMERS.Examples:
1. Carbohydrates2. Lipids3. Proteins4. Nucleic acids (DNA and RNA)
50
CARBOHYDRATES
Small sugar molecules to large sugar molecules.
Examples:A. monosaccharideB. disaccharideC. polysaccharide
51
CARBOHYDRATES
Monosaccharide: one sugar unit
Examples: glucose (C6H12O6)
deoxyriboseriboseFructoseGalactose
glucose
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CARBOHYDRATES
Disaccharide: two sugar unit
Examples: Sucrose (glucose+fructose)
Lactose (glucose+galactose)
Maltose (glucose+glucose)glucoseglucose
copyright cmassengale
53
CARBOHYDRATES
Polysaccharide: many sugar units
Examples: starch (bread, potatoes)
glycogen (beef muscle)
cellulose (lettuce, corn)
glucoseglucose
glucoseglucose
glucoseglucose
glucoseglucose
cellulose
54
LIPIDSGeneral term for compounds which are
not soluble in water.Lipids are soluble in hydrophobic solvents.Remember: “stores the most energy”Examples: 1. Fats
2. Phospholipids3. Oils4. Waxes5. Steroid hormones6. Triglycerides
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LIPIDS
Six functions of lipids:1. Long term energy storage2. Protection against heat loss (insulation)3. Protection against physical shock4. Protection against water loss5. Chemical messengers (hormones)6. Major component of membranes (phospholipids)
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LIPIDS
Triglycerides:composed of 1 glycerol and 3 fatty acids.
H
H-C----O
H-C----O
H-C----O
H
glycerol
O
C-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3
=
fatty acids
O
C-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3
=
O
C-CH2-CH2-CH2-CH =CH-CH2 -CH
2 -CH2 -CH
2 -CH3
=
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FATTY ACIDSThere are two kinds of fatty acids you may see these on
food labels:
1. Saturated fatty acids: no double bonds (bad)
2. Unsaturated fatty acids: double bonds (good)O
C-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3
=
saturated
O
C-CH2-CH2-CH2-CH=CH-CH2 -CH
2-CH2 -CH
2 -CH3
=
unsaturated
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PROTEINS (POLYPEPTIDES) Amino acids (20 different kinds of aa) bonded
together by peptide bonds (polypeptides).
Six functions of proteins:1. Storage: albumin (egg white)2. Transport: hemoglobin3. Regulatory: hormones4. Movement: muscles5. Structural: membranes, hair, nails6. Enzymes: cellular reactions
copyright cmassengale
59
PRIMARY STRUCTURE
Amino acids bonded together by peptide bonds (straight chains)
aa1 aa2 aa3 aa4 aa5 aa6
Peptide Bonds
Amino Acids (aa)
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NUCLEIC ACIDSNucleotides include:
phosphate grouppentose sugar (5-carbon)nitrogenous bases:
adenine (A)thymine (T) DNA onlyuracil (U) RNA onlycytosine (C)guanine (G)
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NUCLEOTIDE
OO=P-O O
Phosphate Group
NNitrogenous base (A, G, C, or T)
CH2
O
C1C4
C3 C2
5
Sugar(deoxyribose)