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