ORGANIC MOLECULES FOUR MAIN CATEGORIES:
carbohydrates: fuel & building material
lipids: fats & oils
proteins: perform most cell functions
nucleic acids: information storage
ORGANIC vs. INORGANIC Carbon based molecules are called organic molecules.
Non-carbon based molecules—water, oxygen, and ammonia are inorganic molecules.
Atomic Structure of Carbon
Carbon atoms can form four bonds
Connecting point for other atoms in four directions
Can produce endless variety of carbon skeletons that can bond with carbon or with other elements
CARBON BACKBONES Types of carbon backbones:
- straight chain
- branched chain
- can form double bonds
- can form ring structures
FUNCTIONAL GROUPS Group of atoms within molecules—
determine properties of organic molecules
React in predictable ways with other molecules
Hydrophilic molecules: molecules that are attracted water
Hydrophobic molecules: molecules that do not mix with water
FUNCTIONAL GROUPS 4 most common functional groups:
1) hydroxyl group: (OH)
2) carbonyl group: (C=O)
3) carboxyl group: (O=C-OH)
4) amino group: (H-N-H)
HYDROCARBONS Organic molecules composed only of carbon and hydrogen
Many are important fuels
Methane found in natural gas is used to heat homes.
MONOMERS & POLYMERS Most biological molecules are large and are made up of smaller subunits
Monomer: molecular subunit that is building block of a larger molecule
Polymer: long chain of monomers
DEHYDRATION REACTION Also called condensation reaction Links monomers together forming
polymers or making polymer chains longer
Water molecule is removed in forming a polymer or making it longer
Same type of reaction occurs regardless of type of monomers being linked or type of polymer produced
HYDROLYSIS REACTION Chemical reaction where polymers
are broken down to their monomers
Large polymers must be broken down to make monomers available to cells
Hydrolysis breaks the chemical bonds in polymers by adding water molecules reverse of dehydration/condensation
DEHYDRATION vs. HYDROLYSIS Summary:
Dehydration: water is removed to build a polymer
Hydrolysis: Water is added to break down a polymer
CARBOHYDRATES ARE MADE UP OF SUGAR MOLECULES
Sugars contain carbon, hydrogen, and oxygen in the following ratio:
1 carbon : 2 hydrogen : 1 oxygen
Molecular formula of any carbohydrate is a multiple of the basic formula CH2O
HOW CELLS USE SUGARS Main fuel supply for cellular work
Other uses: - Provide raw material to make other organic molecules such as fats
- Used to make energy stockpiles
- Serve as building materials
MONOSACCHARIDES Sugars that contain just one sugar unit or monomer
Carbohydrate Monomer Unit monosaccharides
Examples: - glucose - fructose - galactose
DISACCHARIDES “double sugars”
Produced in dehydration reactions from two monosaccharides
Most common disaccharide is sucrose – table sugar—formed by linking glucose and fructose molecules
POLYSACCHARIDES 3 common types all glucose polymers:
Starch: found in plant cells—glucose storage molecule
Glycogen: found in animal cells—glucose storage—abundant in muscle and liver cells
Cellulose: used by plant cells for building material—makes up cell walls—not digestible by humans forms “bulk” in our diet
LIPIDS Commonly known as fats and oils Are hydrophobic do not mix with water Lipid Base Unit
Glycerol
Simplest fats are triglycerides Chain of 3 fatty acids (hydrocarbon molecules)
bonded to a glycerol molecule
Lipids Are Not Polymers
Polymer: repeating monomer
Macromolecule: The lipid base unit is not a monomer
FUNCTIONS OF LIPIDS Act as a boundary—they are a major
component of cell membranes
Circulate in the body acting as chemical signals to cells—some are hormones
Used to store energy in the body
Act to cushion and insulate the body
SATURATED FATS All the carbon atoms in fatty acid chains contain only single bonds
Include animal fats such as butter
Solids at room temperature
UNSATURATED FATS Have at least one double bond between the carbon atoms in one of the fatty acid chains
Found in fruits, vegetables, fish, corn oil, olive oil, and other vegetable oils
Liquids at room temperature
STEROIDS Carbon skeleton forms four fused
rings
Classified as lipids are hydrophobic
Some act as chemical signals or hormones estrogen and testosterone
Some form structural components of cells cholesterol
CHOLESTEROL Essential molecule found in all cell membranes
Serves as base molecule from which other steroids are produced
Has bad reputation cholesterol containing substances in blood are linked to cardiovascular disease
FUNCTIONS OF PROTEINS Form structures—hair, fur, muscles
Provide long-term nutrient storage
Circulate and defend the body against microorganisms (antibodies)
Act as chemical signals—hormones
Help control chemical reactions in cells--enzymes
PROTEIN STRUCTURE Polymers formed from monomers
called amino acids
Amino acids bond together to form chains called a polypeptides
Sequence of amino acids makes each polypeptide unique
Each protein is composed of one or more polypeptides
AMINO ACID STRUCTURE
Figure 5-12: All amino acids consist of a central carbon bonded to an amino group, a carboxyl group, and a hydrogen atom. The fourth bond is with a unique side group – called the “R” group. Differences in side groups convey different properties to each amino acid.
PROTEIN SHAPE Functional proteins consist of
precisely twisted, coiled, and shaped polypeptides
Proteins cannot function correctly if shape is altered
Sequence and types of amino acids in the polypeptides affect protein shape
Surrounding environment—usually aqueous—plays a role in protein shape
DENATURATION Denaturation: loss of normal protein shape
Changes in temperature, pH, or other environmental conditions may cause proteins to become denatured
If the protein shape is changed, protein cannot function normally
ENZYMES Provide a way for reactions to occur at cell’s normal temperature
Enzymes lower energy requirement for a chemical reactions in cells so they can occur at normal cell temperatures
Enzymes are highly selective catalysts
ACTIVATION ENERGY Activation energy: minimum energy
required to start chemical reaction
Chemical bonds in reactants must be weakened to start most reactions
Catalysts: compounds that speed up chemical reactions without getting involved in the reaction.
HOW ENZYMES WORK Substrate: specific reactant acted on by an enzyme
Active site: specific region of the enzyme that the substrate fits into
Substrate binds to enzyme’s active site where the substrate undergoes a change
HOW ENZYMES WORK Shape of an enzyme fits the shape
of only specific reactant molecules
As substrate enters, active site of enzyme changes slightly to form snug attachment
Attachment weakens chemical bonds in substrate lowering activation energy required for reaction to proceed
HOW ENZYMES WORK Once products of chemical reaction
are released, enzyme’s active site is ready to accept another reactant molecule
Recycling is a key characteristic of enzymes—they are not “used up” catalyzing a single reaction
Nucleic Acids
Nucleic acids are molecules that store information for cellular growth and reproduction
There are two types of nucleic acids:
- deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) These are polymers consisting of long chains of monomers
called nucleotides A nucleotide consists of a nitrogenous base, a pentose sugar
and a phosphate group:
Nitrogen Bases
The nitrogen bases in nucleotides consist of two general types:
-Purines: adenine (A) and guanine (G)
-Pyrimidines: cytosine (C), thymine (T) and Uracil (U)
Phosphodiester Bond
Nucleotides are linked together in a nucleic acid by a strong covalent bond called a phosphodiester bond.
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