Chapter 2 Chemical Basis of Life

Report
PowerPoint Lecture Outlines
to accompany
Hole’s Human
Anatomy and Physiology
Tenth Edition
Shier w Butler w Lewis
Chapter 2
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Chapter 2
Chemical Basis of Life
Why study chemistry in an Anatomy and Physiology class?
- body functions depend on cellular functions
- cellular functions result from chemical changes
- biochemistry helps to explain physiological processes,
and develop new drugs and methods for treating
diseases
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Structure of Matter
Matter – anything that takes up space and has weight;
composed of elements
Elements – composed of chemically identical atoms
• bulk elements – required by the body in large
amounts
• trace elements – required by the body in small
amounts
Atoms – smallest particle of an element
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Atomic Structure
Atoms - composed of
subatomic particles:
• protons – carry a
positive charge
• neutrons – carry no
electrical charge
• electrons – carry a
negative charge
Nucleus
• central part of atom
• composed of protons and
neutrons
• electrons move around the
nucleus
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Atomic Number and
Atomic Weight
Atomic Number
• number of protons in the
nucleus of one atom
• each element has a unique
atomic number
• equals the number of
electrons in the atom
Atomic Weight
• the number of protons
plus the number of
neutrons in one atom
• electrons do not
contribute to the weight of
the atom
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Isotopes
Isotopes
• atoms with the same atomic numbers but
with different atomic weights
• atoms with the same number of protons
and electrons but a different number of
neutrons
• oxygen often forms isotopes (O16, O17,
O18)
• unstable isotopes are radioactive; they
emit subatomic particles
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Molecules and Compounds
Molecules – particle formed when two or more atoms
chemically combine
Compound – particle formed when two or more
atoms of different elements chemically combine
Molecular formulas – depict the elements present
and the number of each atom present in the molecule
H2
C6H12O6
H2O
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Electrons
• found in regions of space called electron shells (energy shells)
• each shell can hold a limited number of electrons
• for atoms with atomic numbers of 18 or less, the following rules apply:
• the first shell can hold up to 2 electrons
• the second shell can hold up to 8 electrons
• the third shell can hold up to 8 electrons
• lower shells are filled first
• if the outermost shell is full, the atom is stable
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Ions
Ion
• an atom that has gained or lost an electron(s)
• an electrically charged atom
• atoms form ions to become stable
Cation
• a positively charged
ion
• formed when an atom
loses an electron(s)
Anion
• a negatively charged ion
• formed when an atom gains an
electron(s)
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Ionic Bond
Ionic Bond
• an attraction between a cation and an anion
• formed when electrons are transferred from one atom
to another atom
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Covalent Bond
Formed when atoms share electrons
•Hydrogen atoms form single bonds
•Oxygen atoms form two bonds
•Nitrogen atoms form three bonds
•Carbon atoms form four bonds
H―H
O=O
N≡N
O=C=O
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Structural Formula
Structural formulas show how atoms bond and are
arranged in various molecules
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Polar Molecules
Polar Molecule
• molecule with a slightly negative end and a slightly positive
end
• results when electrons are not shared equally in covalent
bonds
• water is an important polar molecule
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Hydrogen Bonds
Hydrogen Bond
• a weak attraction between the positive end of one polar
molecule and the negative end of another polar molecule
• formed between water molecules
• important for protein and nucleic acid structure
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Chemical Reactions
Chemical reactions occur when chemical bonds form or
break among atoms, ions, or molecules
Reactants are substances being changed by the chemical
reaction
Products are substances formed at the end of the chemical
reaction
NaCl  Na+ + ClReactant
Products
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Types of Chemical Reactions
Synthesis Reaction – chemical bonds are formed
A + B  AB
Decomposition Reaction – chemical bonds are broken
AB  A + B
Exchange Reaction – chemical bonds are broken and formed
AB + CD  AD + CB
Reversible Reaction – the products can change back to
the reactants
A + B n AB
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Acids, Bases, and Salts
Electrolytes – substances that release ions in water
NaCl  Na+ + Cl-
Acids – electrolytes that release hydrogen ions in water
HCl  H+ + Cl-
Bases – substances that release ions that can combine with
hydrogen ions
NaOH  Na+ + OH-
Salts – electrolytes formed by the reaction between an
acid and a base
HCl + NaOH  H2O + NaCl
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Acid and Base Concentrations
pH scale - indicates the
concentration of hydrogen ions in
solution
Neutral – pH 7; indicates
equal concentrations of H+
and OH-
Acidic – pH less than 7;
indicates a greater
concentration of H+
Basic or alkaline – pH
greater than 7;
indicates a greater concentration
of OH-
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Organic Versus Inorganic
Organic molecules
• contain C and H
• usually larger than inorganic molecules
• dissolve in water and organic liquids
• carbohydrates, proteins, lipids, and nucleic acids
Inorganic molecules
• generally do not contain C
• usually smaller than organic molecules
• usually dissolve in water or react with water
to release ions
• water, oxygen, carbon dioxide, and inorganic
salts
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Inorganic Substances
Water
• most abundant compound in living material
• two-thirds of the weight of an adult human
• major component of all body fluids
• medium for most metabolic reactions
• important role in transporting chemicals in the body
• can absorb and transport heat
Oxygen (O2)
• used by organelles to release energy from nutrients
• necessary for survival
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Inorganic Substances
Carbon dioxide (CO2)
• waste product released during metabolic reactions
• must be removed from the body
Inorganic salts
• abundant in body fluids
• sources of necessary ions (Na+, Cl-, K+, Ca2+, etc.)
• play important roles in metabolic processes
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Organic Substances
Carbohydrates
• provide energy to cells
• supply materials to build cell structures
• water-soluble
• contain C, H, and O
• ratio of H to O close to 2:1 (C6H12O6)
• monosaccharides – glucose, fructose
• disaccharides – sucrose, lactose
• polysaccharides – glycogen, cellulose
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Organic Substances
Carbohydrates
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Organic Substances
Lipids
• soluble in organic solvents
• fats (triglycerides)
• used primarily for energy
• contain C, H, and O but less O than carbohydrates (C57H110O6)
• building blocks are 1 glycerol and 3 fatty acids per molecule
• saturated and unsaturated
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Organic Substances
Lipids
• phospholipids
• building blocks are 1 glycerol, 2 fatty acids, and 1 phosphate per
molecule
• hydrophilic and hydrophobic
• major component of cell membranes
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Organic Substances
Lipids
• steroids
• connected rings of carbon
• component of cell membrane
• used to synthesize hormones
• cholesterol
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Organic Substances
Proteins
• structural material
• energy source
• hormones
• receptors
• enzymes
• antibodies
• building blocks are amino acids
• amino acids held
together with
peptide bonds
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Organic Substances
Proteins
Four Levels of Structure
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Organic Substances
Nucleic Acids
• constitute genes
• play role in protein synthesis
• building blocks are nucleotides
• DNA (deoxyribonucleic acid) – double polynucleotide
• RNA (ribonucleic acid) – single polynucleotide
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Organic Substances
Nucleic Acids
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Clinical Applications
Radioactive Isotopes Reveal Physiology
• injected into the body
• different types taken up by different organs
• can be detected in the body using a scintillation
counter
• can be used to destroy specific tissues
• commonly used
• iodine-131 for thyroid function
• thallium-201 for heart function
• gallium-67 and cobalt-60 for cancer
• others used to assess kidney functions, measure hormone
levels and bone density changes
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