Atoms, Molecules and Macromolecules

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Atoms, Molecules and Macromolecules

• Building Complex Molecules That Comprise Living
  Things

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Comparison of Terms
Element Substance that cannot be broken down to another substance with different properties
Atom Smallest unit that has characteristic properties of the element
Molecule Two or more atoms joined by chemical bonds
Macromolecule Large polymer made of monomer units
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Composition of an Atom

• Nucleus
• Proton positively charged particle ()
• Neutron uncharged particle (n or )
• Number of protons Number of neutrons Atomic
  mass
• Number of protons Atomic number

• Electrons negatively charged particles
• Number of electrons Number of protons

Each electron circles the nucleus in an
orbitrepresenting a specific energy level.
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Atomic Models
ElectronShell
Nucleus
Hydrogen (H)
Helium (He)
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Different Kinds of Atoms
Innermostelectron shell
Max 2e-
2e-2n 2p
6e-6n 6p
4p
Helium
Carbon
4n
4e-
2p
2n
2e-
15e-16n 15p
8e-8n 8p
20e-20n 20p
7p
8n
7e-
5p
4n
Max 8e-
Oxygen
Phosphorus
Calcium
5e-
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Applying Your Knowledge
Magnesium Chlorine
Atomic Number 12 17
Atomic Mass 24 35
Number of Protons
Number of Neutrons
Number of Electrons
12
17
18
12
12
17
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Electron Energy Levels
Energy Level Capacity for Electrons
1 2
2 8
3 8
In forming molecules, atoms combine to fill
their outer energy levels.
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Applying Your Knowledge
Magnesium Chlorine
Total Number of Electrons 12 17
Number of Electrons in First Electron Shell
Number Electrons in Second Electron Shell
Number of Electrons In Third Electron Shell
2
2
8
8
2
7
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Chemical Bonds
Bond Characteristics
Ionic One atom loses an electron, another gains an electron
Covalent Atoms share electrons
Polar Covalent Electrons are shared unequally
Hydrogen Covalently-bound hydrogen is attracted to another atom
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Ionic Bonding in NaCl
Positivecharge
Sodium ion ep-1
Negativecharge
Chlorineion ep1
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Ionic Bonding in NaCl

• Ion charged atom with unequal numbers of protons
  and electrons.
• Ions of opposite charges attract.
• Sodium ions nestle between chlorine ions.
• Perfectly cubical crystals form.

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Applying Your Knowledge

• What would be the chemical formula if magnesium
  and chlorine united to form a molecule?
  (Mgmagnesium Clchlorine)
• Which electrons from each atom are involved in
  forming the bond(s)?

MgCl2
One electron from outer shell of Mg is donated to
one Cl and the other electron from Mg is donated
to the other Cl.
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Covalent Bonding
Oxygen Atom
Oxygen Atom
Oxygen Molecule (O2)
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In Water, Polar Covalent Bonds Join Oxygen and
Hydrogen
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Hydrogen Bonds Join Water Molecules
Water molecules carry slight charges Electrons
favor O over H
Hydrogen bonds form between O of one water
molecule and H of another


O
H

H

O
H

HydrogenBonds

H

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Due to hydrogen bonding, ionic and polar
substances dissolve in water
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Organic Molecules Contain Carbon
Each carbon atom can make four covalent bonds
with other types of atoms or additional carbons.

Hydrophobic Not attracted to waterNon-polar substances
Hydrophilic Attracted to waterPolar and Ionic substances
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Chemical Properties of Carbon

• Question How many electrons does carbon
  need to fill its outer energy level?

• Answer Four

Each carbon atom can make four covalent bonds
with other types of atoms or additional carbons.

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Macromolecules Polymers Made of Repeating
Monomers
Macromolecule Monomer Unit
Carbohydrates Sugars
Lipids Fatty acids
Proteins Amino acids
Nucleic Acids Nucleotides
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Synthesis and Breakdown of Macromolecules
Condensation Synthesis Removal of water to add monomer units
Hydrolysis Addition of OH and H groups of water to break a bond between monomers
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Dehydration Synthesis / Hydrolysis
Dehydration Synthesis
Hydrolysis
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Carbohydrates Structure

• Simple
• Monosaccharides one sugar unit

Glucose blood sugar All cells use glucose for
energy
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Carbohydrates Structure

• Simple
• Disaccharides two sugar units
• Examples sucrose, lactose, maltose

Sucrose Water
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Carbohydrates Structure

• Complex
• Polysaccharides many sugar units
• Starch -- storage in plants
• Glycogen -- storage in animals
• Cellulose -- plant cell walls, indigestible

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Carbohydrates Structure

• Complex
• Polysaccharides many sugar units

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Carbohydrates Functions

• Energy source
• Structural component
• Cell-cell communication

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Applying Your Knowledge

1. Monosaccharide
2. Polysaccharide
3. Disaccharide

1. Which molecule consists of two sugar units?
2. Which choice best describes glycogen?
3. Which type of molecule provides the basic energy
   for your cells?
4. Which type of molecule is found in milk?

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Lipids Structure

• Triglyceridepredominant form in diet
• One molecule of glycerol
• Three fatty acids

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Lipids Structure

• Types of Fatty Acids
• Saturated 2H per internal carbon
• Unsaturated -- lt2H per internal carbon
  ?one or more double bonds
• Monounsaturated one double bond
• Polyunsaturated more than one double bond

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Which Is a Source of Unsaturated Fatty Acids?
Linseed Oil
Beef Fat
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TriglycerideFormation
Triglyceride
Glycerol
RemoveTheseWaters
Add 3FattyAcids
3 Waters
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Lipids Structure

• Phospholipidcomponent of cell membranes

PolarHead
Glycerol
Fatty Acid Tails
Hydrophobic
Hydrophilic
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Lipids Structure

• Steroids
• Linked carbon rings
• Used to produce
• Hormones
• Cholesterol
• Vitamin D2

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Lipids Functions

• Concentrated energy source
• Structural components of cell membranes
• Phospholipids
• Cholesterol
• Communication
• Steroid Hormones
• Metabolism
• Fat-soluble vitamins
• Insulation
• Protection from water
• Waxes

Cholesterol
Phospholipids
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Applying Your Knowledge

1. Polyunsaturated fatty acid
2. Cholesterol
3. Monounsaturated fatty acid
4. Saturated fatty acid

1. Which molecule is made of a series of carbon
   rings?
2. Which molecule has more than one double bond?
3. Which molecule has 2H for each internal carbon?
4. Which molecule has one double bond?

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Macronutrients As Energy Sources