Matter and Energy in the Web of Life Chapter 4

What Are Atoms? 1) Smallest particles that retain properties of an element 1) Smallest particles that retain properties of an element 2) Made up of subatomic particles: 2) Made up of subatomic particles: a) Protons (+) a) Protons (+) b) Electrons (-) b) Electrons (-) c) Neutrons (no charge)` c) Neutrons (no charge)`

Atomic Particles

Atomic Number 1) Number of protons 1) Number of protons a) All atoms of an element have the same atomic number a) All atoms of an element have the same atomic number 1. Atomic number of hydrogen = 1 1. Atomic number of hydrogen = 1 2. Atomic number of carbon = 6` 2. Atomic number of carbon = 6`

Mass Number Number of protons + Number of neutrons Isotopes vary in mass number

Mass Number

Isotopes 1) Atoms of an element with different numbers of neutrons (different mass numbers) 1) Atoms of an element with different numbers of neutrons (different mass numbers) a) Carbon 12 has 6 protons, 6 neutrons a) Carbon 12 has 6 protons, 6 neutrons b) Carbon 14 has 6 protons, 8 neutrons` b) Carbon 14 has 6 protons, 8 neutrons`

Radioisotopes 1) Have an unstable nucleus that emits energy and particles 1) Have an unstable nucleus that emits energy and particles 2) Radioactive decay transforms radioisotope into a different element 2) Radioactive decay transforms radioisotope into a different element a) Decay occurs at a fixed rate` a) Decay occurs at a fixed rate`

Radioisotopes as Tracers 1) A Tracer is a substance with a radioisotope attached to it 1) A Tracer is a substance with a radioisotope attached to it a) Emissions from the tracer can be detected with special devices a) Emissions from the tracer can be detected with special devices b) Following movement of tracers is useful in many areas of biology` b) Following movement of tracers is useful in many areas of biology`

Thyroid Scan Thyroid Scan 1) Measures health of thyroid by detecting radioactive iodine taken up by thyroid gland` 1) Measures health of thyroid by detecting radioactive iodine taken up by thyroid gland` normal thyroidenlargedcancerous

PET Scan

What Determines Whether Atoms Will Interact? The number and arrangement of their electrons

Electron Orbitals Electron Orbitals 1) Orbitals can hold up to two electrons 1) Orbitals can hold up to two electrons a) Atoms differ in the number of occupied orbitals a) Atoms differ in the number of occupied orbitals 2) Orbitals closest to nucleus are lower energy and are filled first` 2) Orbitals closest to nucleus are lower energy and are filled first`

Shell Model 1) First shell 1) First shell a) Lowest energy a) Lowest energy b) Holds 1 orbital with up to 2 electrons b) Holds 1 orbital with up to 2 electrons 2) Second shell 2) Second shell a) 4 orbitals hold up to 8 electrons` a) 4 orbitals hold up to 8 electrons` CALCIUM 20p+, 20e -

Shell Model

Shells

Chemical Bonds, Molecules, & Compounds 1) Bond is union between electron structures of atoms 1) Bond is union between electron structures of atoms a) Atoms bond to form molecules a) Atoms bond to form molecules 1. Molecules may contain atoms of only one element 1. Molecules may contain atoms of only one element a. O 2 a. O 2 2. Molecules of compounds contain more than one element 2. Molecules of compounds contain more than one element a. H 2 O` a. H 2 O`

Chemical Bookkeeping 1) Use symbols for elements when writing formulas 1) Use symbols for elements when writing formulas a) Formula for glucose is C 6 H 12 O 6 a) Formula for glucose is C 6 H 12 O 6 a) 6 carbons a) 6 carbons b) 12 hydrogens b) 12 hydrogens c) 6 oxygens` c) 6 oxygens`

Chemical Bookkeeping 1) Chemical equation shows reaction 1) Chemical equation shows reaction Reactants ---> Products 2) Equation for photosynthesis: 2) Equation for photosynthesis: 6CO 2 + 6H 2 O ---> + C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O ---> + C 6 H 12 O 6 + 6O 2

Chemical Equation

Important Bonds in Biological Molecules Ionic Bonds Covalent Bonds Hydrogen Bonds

Ion Formation 1) Atom has equal number of electrons and protons - no net charge 1) Atom has equal number of electrons and protons - no net charge 2) Atom loses electron(s), becomes positively charged ion 2) Atom loses electron(s), becomes positively charged ion 3) Atom gains electron(s), becomes negatively charged ion` 3) Atom gains electron(s), becomes negatively charged ion`

Ionic Bonding Ionic Bonding 1) One atom loses electrons, becomes positively charged ion 1) One atom loses electrons, becomes positively charged ion 2) Another atom gains these electrons, becomes negatively charged ion 2) Another atom gains these electrons, becomes negatively charged ion 3) Charge difference attracts the two ions to each other` 3) Charge difference attracts the two ions to each other`

Ionic Bond

Covalent Bonding 1) Atoms share a pair or pairs of electrons to fill outermost shell Single covalent bond Double covalent bond Triple covalent bond`

Hydrogen Bonding 1) Molecule held together by polar covalent bonds has no NET charge 1) Molecule held together by polar covalent bonds has no NET charge a) However, atoms of the molecule carry different charges a) However, atoms of the molecule carry different charges b) Atom in one polar covalent molecule can be attracted to oppositely charged atom in another such molecule` b) Atom in one polar covalent molecule can be attracted to oppositely charged atom in another such molecule`

Hydrogen Bonding

Hydrogen Bond Stability

Properties of Water PolarityTemperature-StabilizingCohesiveSolvent

Water Is a Polar Covalent Molecule 1) Molecule has no net charge 1) Molecule has no net charge 2) Oxygen end has a slight negative charge 2) Oxygen end has a slight negative charge 3) Hydrogen end has a slight positive charge` 3) Hydrogen end has a slight positive charge` O HH

Water Polarity

Hydrophilic & Hydrophobic Substances 1) Hydrophilic substances 1) Hydrophilic substances a) Polar a) Polar b) Hydrogen bond with water b) Hydrogen bond with water 1. Example: sugar 1. Example: sugar 2) Hydrophobic substances 2) Hydrophobic substances a) Nonpolar a) Nonpolar b) Repelled by water b) Repelled by water 1. Example: oil` 1. Example: oil`

Temperature-Stabilizing Effects Temperature-Stabilizing Effects 1) Liquid water can absorb much heat before its temperature rises 1) Liquid water can absorb much heat before its temperature rises a) Why? a) Why? 2) Much of the added energy disrupts hydrogen bonding rather than increasing the movement of molecules` 2) Much of the added energy disrupts hydrogen bonding rather than increasing the movement of molecules`

Why Ice Floats 1) In ice, hydrogen bonds lock molecules in a lattice 1) In ice, hydrogen bonds lock molecules in a lattice a) Water molecules in lattice are spaced farther apart then those in liquid water a) Water molecules in lattice are spaced farther apart then those in liquid water b) Ice is less dense than water` b) Ice is less dense than water`

Water Is a Good Solvent

The pH Scale 1) Measures H + concentration of fluid 1) Measures H + concentration of fluid 2) Change of 1 on scale means 10X change in H + concentration` 2) Change of 1 on scale means 10X change in H + concentration`