UNIT 1 Chapter 3: Water & the Fitness of Life Chapter 5: The Structure & Function of Macromolecules

The Nature of Water Water’s chemical properties make life possible on Earth: – water is a polar molecule – organisms depend on the cohesion of water molecules – water moderates temperatures on Earth – solid water (ice) floats – water is an ALMOST universal solvent

Water is a Polar Molecule Oxygen is a VERY electronegative atom – region around oxygen is has a slight negative charge; region around hydrogens has a slight positive charge One water molecule can hydrogen bond with up to 4 other water molecules

Organisms Depends on the Cohesion of Water Molecules Hydrogen bonds are constantly being broken and reformed – the phenomenon of cohesion describes how water molecules are held to one another Water molecules also adhere to other substances/surfaces Surface tension makes water behave as if covered by a film

Water Moderates Temperatures on Earth Definitions: – kinetic energy – heat – temperature Heat is measured in units called calories (cal) – amount of heat necessary to raise one gram of water by 1°C

The specific heat of a substance is the amount of heat that needs to be gained/lost to raise/lower it’s temperature by 1°C – water = 1 – ethyl alcohol = 0.6 – iron = 0.1 Bodies of water act to moderate air temperatures – ocean temperatures and coastal areas are more stable than inland

Water requires a lot of heat to vaporize – 580 calories required to vaporize 1g of water – hydrogen bonds must be broken first Evaporative cooling prevents water from vaporizing too much or too quickly

Solid Water (ice) Floats Ice is less dense than liquid water – a volume of water expands ~109% as it freezes

Water is an ALMOST Universal Solvent The polarity of water makes it able to form hydrogen bonds with charged and other polar molecules

Water can interact with molecules that are ionic or polar – hydrophilic Non-polar molecules are insoluble in water and will not dissolve – hydrophobic (ex. oil) END

Most Macromolecules are Polymers Three of the four macromolecules (Carbohydrates, proteins, and nucleic acids…not lipids) form chainlike structures called polymers Three of the four macromolecules (Carbohydrates, proteins, and nucleic acids…not lipids) form chainlike structures called polymers Individual pieces, monomers, are joined to create polymers Individual pieces, monomers, are joined to create polymers Monomers joined by dehydration (condensation) reaction Monomers joined by dehydration (condensation) reaction Polymers disassembled by hydrolysis Polymers disassembled by hydrolysis

Dehydration & Hydrolysis Dehydration: one monomer provides a hydrogen, the other provides a hydroxyl Dehydration: one monomer provides a hydrogen, the other provides a hydroxyl

Hydrolysis: water is used to “restore” a hydrogen to one monomer and a hydroxyl to the other Hydrolysis: water is used to “restore” a hydrogen to one monomer and a hydroxyl to the other Common to the digestive process Common to the digestive process

Carbohydrates Carbohydrates exist as monomers, dimers, and polymers Carbohydrates exist as monomers, dimers, and polymers Special names: monosaccharide, disaccharide, polysaccharide Special names: monosaccharide, disaccharide, polysaccharide

Monosaccharides are joined by dehydration reactions Monosaccharides are joined by dehydration reactions Bond created: glycosidic linkage Bond created: glycosidic linkage Polysaccharides are monosaccharides joined by many glycosidic linkages Polysaccharides are monosaccharides joined by many glycosidic linkages

Polysaccharides perform storage and structural roles Polysaccharides perform storage and structural roles Starch is composed entirely of glucose monomers Starch is composed entirely of glucose monomers Plants store starch in plastids Plants store starch in plastids

Cellulose is stored in plants’ cell walls Cellulose is stored in plants’ cell walls

Animals store glucose in the form of glycogen Animals store glucose in the form of glycogen Highly branched like amylopectin Highly branched like amylopectin Chitin is found in exoskeletons of arthropods and cell walls of many fungi Chitin is found in exoskeletons of arthropods and cell walls of many fungi

Lipids Lipids (fats) are not constructed of monomers Lipids (fats) are not constructed of monomers Created from glycerol and fatty acids Created from glycerol and fatty acids

Fatty acids are joined to glycerol by an ester linkage Fatty acids are joined to glycerol by an ester linkage 3 fatty acids + 1 glycerol = triglyceride 3 fatty acids + 1 glycerol = triglyceride

Fatty acids vary in the number of carbons and the number of double bonds present between carbons Fatty acids vary in the number of carbons and the number of double bonds present between carbons No double bonds = saturated No double bonds = saturated One double bond = unsaturated One double bond = unsaturated More than one double bond = polyunsaturated More than one double bond = polyunsaturated

Phospholipids contain two fatty acids and a phosphate group Phospholipids contain two fatty acids and a phosphate group END

Proteins Proteins are instrumental in virtually everything an organism does Proteins are instrumental in virtually everything an organism does They are polymers constructed of amino acid monomers They are polymers constructed of amino acid monomers Combinations of 20 amino acids are joined to form polypeptides Combinations of 20 amino acids are joined to form polypeptides

Amino acids are categorized based on their properties Amino acids are categorized based on their properties

Amino acids are joined by dehydration reactions and form peptide bonds Amino acids are joined by dehydration reactions and form peptide bonds Polypeptide orientation: Polypeptide orientation: Amino end = N-terminus Amino end = N-terminus Carboxyl end = C-terminus Carboxyl end = C-terminus

Protein function is based on it’s 3-D shape, or conformation Protein function is based on it’s 3-D shape, or conformation Protein conformation has four levels Protein conformation has four levels Primary: linear sequence of amino acids Primary: linear sequence of amino acids Secondary:  helices  and  pleated  sheets, created by hydrogen bonding among polypeptide backbone Secondary:  helices  and  pleated  sheets, created by hydrogen bonding among polypeptide backbone Tertiary: marked by hydrogen, ionic, and covalent bonding between R-groups of amino acids Tertiary: marked by hydrogen, ionic, and covalent bonding between R-groups of amino acids Quaternary: occurs only when a protein is constructed of more than one polypeptide Quaternary: occurs only when a protein is constructed of more than one polypeptide

Primary Primary Secondary Secondary Tertiary Tertiary Quaternary Quaternary

Nucleic Acids Nucleic acids, DNA (DeoxyriboNucleic Acid) and RNA (RiboNucleic Acid), store and transmit genetic information Nucleic acids, DNA (DeoxyriboNucleic Acid) and RNA (RiboNucleic Acid), store and transmit genetic information DNA has the ability to replicate itself as well as the ability to create RNA DNA has the ability to replicate itself as well as the ability to create RNA RNA used to create proteins RNA used to create proteins Central Dogma: DNA  RNA  proteins Central Dogma: DNA  RNA  proteins

Nucleic acids are polymers of monomers called nucleotides Nucleic acids are polymers of monomers called nucleotides Nucleotides = nitrogenous base + phosphate group + pentose (5 carbon) sugar Nucleotides = nitrogenous base + phosphate group + pentose (5 carbon) sugar Nucleotides are joined by phosphodiester link Nucleotides are joined by phosphodiester link END