Molecules of Life ICHAPTER 3Molecules of Life ICHAPTER 3
Carbon/Organic Chemistry• Bonding in hydrocarbons
• Functional groups
• Monomers and Polymers, Linking and Breaking
Carbohydrates• Monosaccharides
• Disaccharides
• Polysaccharides
Lipids• Fats and Oils
• Steroids
• Phospholipids
Relevance of Biomolecules in Everyday Life
completely
Organic Molecules
• A cell is mostly water.
– The rest of the cell consists mostly of carbon-based molecules.
– Organic chemistry is the study of carbon compounds.
• Carbon is a versatile atom.
– It has four electrons in an outer shell that holds eight.
– Carbon can share its electrons with other atoms to form up to four covalent bonds.
• Carbon can use its bonds to:
– Attach to other carbons.
– Form an endless diversity of carbon skeletons.
Figure 3.2
Each Carbon Atom Makes Four Covalent Bonds to Other Atoms
Figure 3.3
Carbon Connects With Hydrogens to Form Hydrocarbons
Methane (CH4) is the simplest hydrocarbon
Figure 3.4
Other Hydrocarbons in Our Lives
Molecules of Life ICHAPTER 3Molecules of Life ICHAPTER 3
Carbon/Organic Chemistry• Bonding in hydrocarbons
• Functional groups
• Monomers and Polymers, Linking and Breaking
Carbohydrates• Monosaccharides
• Disaccharides
• Polysaccharides
Lipids• Fats and Oils
• Steroids
• Phospholipids
• Each type of organic molecule has a unique three-dimensional shape that defines its function in an organism.
– The molecules of your body recognize one another based on their shapes.
– Even slight differences in molecular arrangement effects the chemical behavior of a molecule
– Certain groups of atoms confer chemical reactivity to a molecule (functional groups)
Structure Gives Rise to Function
Isomers
Figure 3.5
Functional Groups That Contribute to Molecular Behavior
Molecules of Life ICHAPTER 3Molecules of Life ICHAPTER 3
Carbon/Organic Chemistry• Bonding in hydrocarbons
• Functional groups
• Monomers and Polymers, Linking and Breaking
Carbohydrates• Monosaccharides
• Disaccharides
• Polysaccharides
Lipids• Fats and Oils
• Steroids
• Phospholipids
Giant Molecules from Smaller Building Blocks
• On a molecular scale, many of life’s molecules are gigantic.
– Biologists call them macromolecules.
– Examples: DNA, carbohydrates
• Most macromolecules are polymers.
– Polymers are made by stringing together many smaller molecules called monomers.
– Cells link monomers by dehydration reactions.
monomers polymer
Figure 3.6a
Dehydration/Condensation Synthesis of a Polymer
Figure 3.6b
Hydrolytic Breakdown of a Polymer
Biological Molecules
• There are four categories of large molecules in cells:
– Carbohydrates
– Lipids
– Proteins
– Nucleic acids
Molecules of Life ICHAPTER 3Molecules of Life ICHAPTER 3
Carbon/Organic Chemistry• Bonding in hydrocarbons
• Functional groups
• Monomers and Polymers, Linking and Breaking
Carbohydrates• Monosaccharides
• Disaccharides
• Polysaccharides
Lipids• Fats and Oils
• Steroids
• Phospholipids
Carbohydrates
• Carbohydrates are composed of:
– Simple sugars (monosaccharides) found in table sugar, fruit, and soft drinks.
– Complex sugars (polysaccharides) found in pasta and potatoes as well as the cells of plants
Simple Sugars: Monosaccharides
• Monosaccharides are simple sugars.
– Glucose is found in sports drinks.
– Fructose is found in fruit.
• Honey contains both glucose and fructose.
Glucose and Fructose are Structural Isomers
Same molecular formula but different structural formulas
Carbonyl functional
groups makes these
sugars reactive
(can lose electrons)
Hydroxyl groups make these
sugars polar and
water soluble
Glucose
Fructose
Simple Sugars Usually “Round up” into Rings
Straight chain form Ring form
Disaccharides
• A disaccharide is a double sugar.
– It is constructed from two monosaccharides.
• Disaccharides are joined through a dehydration reaction.
Disaccharides
Figure 3.11
Lactose is a disaccharide that some people cannot digest as adults
Table Sugar (Sucrose) is a Disaccharide
Polysaccharides
• Complex carbohydrates are called polysaccharides.
– They are long chains of sugar units.
– They are polymers of monosaccharides.
• Polysaccharides can be classified by function
– Energy storage polysaccharides
– Structural support polysaccharides
Polysaccharides
Figure 3.13
Three Polysaccharides
Energy storage
Energy storage
Structural support in plants
Cellulose Cannot Be Broken into Glucose Monosaccharides By Mammals
Plant-eaters have resident bacteria and protozoa that break the cellulose into glucose within their digestive system
Molecules of Life ICHAPTER 3Molecules of Life ICHAPTER 3
Carbon/Organic Chemistry• Bonding in hydrocarbons
• Functional groups
• Monomers and Polymers, Linking and Breaking
Carbohydrates• Monosaccharides
• Disaccharides
• Polysaccharides
Lipids• Fats and Oils
• Steroids
• Phospholipids
Lipids
• Lipids are not water soluble (hydrophobic)
– Lipids are mostly composed of hydrocarbon chains or rings
– They do not mix with water.
• Important lipid polymers that we will study are:
– Fats and Oils
– Phospholipids
– Steroids
Fats and Oils (Triglycerides)
• A fat or oil consists of a four part chain of hydrocarbons (a triglyceride)
– Triglyceride is a combination of glycerol and three fatty acids.
• Fats perform essential functions in the human body:
– Energy storage
– Cushioning
– Insulation
A Fat or Oil is Made From Three Fatty Acids and One Glycerol
Dehydration reactions
Fats
• Unsaturated fatty acids (One or more C=C bonds)
– Have less than the maximum number of hydrogens bonded to the carbons.
– Tend to be solid at room temperature, e.g.. butter
• Saturated fatty acids (Only C-C bonds)
– Have the maximum number of hydrogens bonded to the carbons.
– Tend to be liquid at room temperature, e.g. corn oil
Saturated and Unsaturated Fats (Triglycerides)
• Not all fats are unhealthy.
– Some fats perform important functions in the body and are essential to a healthy diet.
– Many unsaturated fats and cis-fats are good for you
Healthy Triglycerides
Steroids
• Steroids are very different from fats in structure and function.
– The carbon skeleton is bent to form four fused rings.
• Cholesterol is the “base steroid” from which your body produces other steroids.
– Example: sex hormones
Steroids Consist of Four Joined Rings
Biological role: Helps keep cell wrappers (membranes) fluid
and flexible
Biological role: Act as
chemical messengers
(hormones) to stimulate
certain body parts
Phospholipids: Barrier-forming molecules
Phospholipids organize into
double-layered spheres in water
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
Molecules of Life ICHAPTER 3Molecules of Life ICHAPTER 3
Carbon/Organic Chemistry• Bonding in hydrocarbons
• Functional groups
• Monomers and Polymers, Linking and Breaking
Carbohydrates• Monosaccharides
• Disaccharides
• Polysaccharides
Lipids Proteins and Nucleic Acids
• Fats and Oils will be discussed next time
• Steroids
• Phospholipids