Transcript Fundamentals of Anatomy and Physiology, Second Edition

Chapter 2
THE CHEMISTRY OF LIFE
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Introduction
• Cells, tissues and organs composed of
chemicals
• Chemical reactions important for function
• Chemistry is the study of:
– Elements, compounds, chemical reactions,
molecular structure
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ATOMIC STRUCTURE
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Atomic Structure (cont’d.)
• Atoms
– Smallest particles of elements
– Maintain all characteristics of element
– Nucleus contains protons and neutrons
– Electrons orbit nucleus in shells
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ELEMENTS, ISOTOPES, COMPOUNDS
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Elements, Isotopes, Compounds
(cont’d.)
• Element: atoms contain same numbers of
protons and electrons
• Compound: contains two or more elements
• Isotope: number of neutrons varies
• Periodic table of the elements
– Arranges elements by increasing atomic
number
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Elements, Isotopes, Compounds
(cont’d.)
• Orbital: area where electron is found
• Energy levels: grouping of orbitals
– Represented as concentric circles surrounding
nucleus
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BONDS AND ENERGY
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Bonds and Energy (cont’d.)
• Ionic: one atom gains and one atom loses
electrons
• Covalent: atoms share electrons
• Hydrogen: weak bonds, hold water
molecules together
• Electron donors vs. acceptors vs. carriers
• Bonds are energy containing
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Bonds and Energy (cont’d.)
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Bonds and Energy (cont’d.)
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COMMON SUBSTANCES IN LIVING SYSTEMS
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Water
•
•
•
•
•
Most abundant substance in cells
Universal solvent
Transport of materials
Absorbs and reduces heat
Protects body structures
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Carbon Dioxide
• Waste product of cellular respiration
• Used in photosynthesis to produce usable
energy sources
• Must be removed quickly from cells
• Carbon in molecules comes from carbon
dioxide gas
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Molecular Oxygen
• Formed from covalent bond of two oxygen
atoms
• Required by all organisms that breathe air
• Necessary to convert food into ATP
• Level in atmosphere is 21%
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Ammonia
• By-product of amino acid breakdown
– Amino acids are building blocks of proteins
– Amino acids contain nitrogen
• Converted to urea in the liver
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Mineral Salts
• Composed of small ions
• Calcium: muscle contraction and strong
bones
• Phosphate - ATP synthesis
• Sodium, potassium, and chloride are
necessary for muscle contraction and
nervous transmission
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Carbohydrates
• 1:2:1 ratio of carbon, hydrogen and oxygen
• Five- and six-carbon simple sugars are
smallest
– Five-carbon: deoxyribose and ribose
– Six-carbon: glucose and fructose
• Functions: energy storage and cell structure
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Lipids
• Insoluble in water
• 95% of fats in body are triacylglycerols
• Saturated fat: fatty acids have single
covalent bonds
• Unsaturated fat: fatty acids have one or
more double covalent bonds
• Functions: energy, insulation and protection
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Proteins
• Contain carbon, oxygen, hydrogen,
nitrogen and sulfur
• Amino acids are building blocks of proteins
• Functions: energy and structure
• Enzymes: protein catalysts for chemical
reactions
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Proteins (cont’d.)
• Structure
– Primary: amino acid sequence
– Secondary: determined by hydrogen bonds
– Tertiary: folding caused by interactions within
peptide bonds and sulfur atoms
– Quaternary: determined by spatial relationships
between units
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Nucleic Acids
• Deoxyribonucleic acid: genetic material of
the cell
• Ribonucleic acid: protein synthesis
– Messenger RNA
– Transfer RNA
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Nucleic Acids (cont’d.)
• Structure
– DNA: double helical chain
– RNA: single chain
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Nucleic Acids (cont’d.)
• Nucleic acids are made up of chains of
nucleotides
– Nucleotide: nitrogen base, sugar and
phosphate group
– Nitrogen bases: purines (two) and pyrimidines
(three)
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Adenosine Triphosphate
• Fuel for cell function and maintenance
• Molecule consists of sugar, adenine, and
three phosphates
– Energy is stored in the second and third
phosphates
• Breakdown of glucose provides energy to
make ATP
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MOVEMENT OF MATERIALS INTO AND OUT OF
CELLS
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Introduction
• Plasma membrane is selectively permeable
– Only selected materials can enter and exit
– This is because of chemical structure
– Water can enter and exit with ease
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Diffusion
• Movement of molecules from area of high
concentration to low concentration
• Brownian movement: random collision of
diffusing molecules
• Accelerated by increased temperature
• O2 - CO2 exchange is an example of
diffusion
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Osmosis
• Movement of water through semipermeable
membrane from high concentration to low
concentration
– Isotonic solution: salt concentration is the same
outside the cell as inside
– Hypotonic solution: salt concentration inside
cell is higher than outside cell
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Osmosis
• Movement of water through semipermeable
membrane from high concentration to low
concentration
– Hypertonic solution: salt concentration higher
outside the cell than inside
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Osmosis (cont’d.)
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Osmosis (cont’d.)
• Active transport
– Used by cells to obtain sugars, amino acids,
larger proteins and fats
– Needs energy in the form of ATP
– Molecules move from areas of low
concentration to areas of high concentration
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pH
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pH (cont’d.)
• Negative logarithm of hydrogen ion
concentration
• Acids: pH values below 7
• Bases: pH values above 7
• Buffers: help maintain pH levels
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pH (cont’d.)
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Summary
• Discussed basic chemical concepts such
as bonds and energy and how they apply to
living systems
• Discussed specific chemical substances
and how they are used in living systems
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Summary (cont’d.)
• Described three ways that substances
move into and out of cells
• Introduced pH and acids/bases
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