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Chapter 5: The Structure and Function of Large Biological Molecules -…
Chapter 5: The Structure and Function of Large Biological Molecules
Carbohydrates
A sugar (monosaccharide) or one its dimer (disaccharide) or polymers (polysaccharides)
Must be consumed to be replenished
Glycosidic Linkage
The covalent bond between two monomers is a glycosidic linkage
The enzyme Amylase can break Glycosidic bonds
Structure
A geometric shape (Hexagon, Pentagon, etc.)
Polysaccharide
A polymer of many monosaccharides, formed by dehydration reactions
Have storage and structural roles
Ex: Starch, Glycogen, Cellulose, and Chitin
Starch
A storage polysaccharide of plants, consists of glucose monomers
Glycogen
A storage polysaccharide in animals
Cellulose
A major component of the tough wall of plant cells
The cellulose in human food passes through the digestive track as "insoluble fiber"
Chitin
Structural polysaccharide is found in the exoskeleton of arthropods
Also provides structural support for the cell walls of many fungi
Disaccharide
A double sugar, consisting of two monosaccharides joined by a glycosidic linkage formed by a dehydration reaction
Dehydration Reaction
When two monomers bond together through the loss of a water molecule
Is a catabolic reaction
Monosaccharide
The simplest carbohydrate, active alone or serving as a monomer for disaccharides and polysaccharides
Have the molecular formula that are usually multiples of CH2O
Always in a 1:2:1 ratio
Ex: Glucose (C6H12O6), the most common monosaccharide
Classification
Location of Carbonyl Group
Aldose
A type of sugar characterized by the presence of a carbonyl group at the end of its carbon chain, forming an aldehyde group
Ex: Glucose and Rlbose
Ketone
A type of organic compound characterized by the presence of a carbonyl group located within the carbon chain
Ex: Acetone
Size of Carbon Skeleton
Hexoses
Characterized by having six carbon atoms in their structure
Ex: Glucose and Fructose
Trioses
Characterized by having three carbon atoms in their structure
Pentoses
Characterized by having five carbon atoms in their structure
Lipids
Any of a group of large biological molecules, including fats, phospholipids, and steroids, that mix poorly, if at all, with water
Must be consumed
The one class of large biological molecules that doesn't include true polymers
Only biological molecule to be hydrophobic
Ester Bonds
A covalent bond formed during a dehydration synthesis
The enzyme Lipase breaks down Ester Bonds
Fats
Are constructed from two types of smaller molecules: glycerol and fatty acids
Glycerol
A three-carbon alcohol with a hydroxyl group attached to each carbon
Fatty Acids
A carboxyl groups attached to a long carbon skeleton
Triacylglycerol
In a fat, three fatty acids are joined to glycerol by an ester linkage
Saturated Fats
A type of fatty acids where the hydrocarbon chains have no double bonds between carbon atoms
Structure
Have straight hydrocarbons chains due to the absence of double bonds
Typically solid at room temperature
Ex: Lard and Butter
Unsaturated Fats
A type of fatty acids where their are one or more double bonds in their hydrocarbon chains
Structure
Contains one or more double bonds, usually in a cis configuration, causing bends or kinks in the chain
Typically liquid at room temperature
Ex: Olive Oil
Trans-Fat
A type of unsaturated fat that have been artificially altered through a process called hydrogenation
Hydrogenation
The process of converting unsaturated fats to saturated dats by adding hydrogen
May contribute more than saturated fats to cardiovascular diease
Major function of fats is energy storage and insulation
Phospholipids
A lipid made up of glycerol joined to two fatty acids and phosphate group
Hydrophobic Tails
The hydrocarbon tails are hydrophobic and are excluded from water
Hydrophilic Heads
The phosphate group and its attachments form a hydrophilic head that has an affinity of water
Function
Major constituents of cell membranes
Phospholipid Bilayer
A fundamental component of cellular membranes, crucial for maintaining the structure and function of cells
Phospholipid
Molecules that have a hydrophilic head and hydrophobic tails
Bilayer
In an aqueous environment, phospholipids self-assemble into a bilayer
The hydrophilic heads face the water on both sides, while the hydrophobic tails point inward, away from the water, creating a stable barrier
Steroids
A type of lipid characterized by a carbon skeleton consisting of four fused rings with various chemical groups attached
Ex: Cholestorol
A type of steroid, a component in animal cell membranes and a precursor from which other steroids are synthesized
Proteins
A biologically functional molecule consisting of one or more polypeptides folded and coiled into a specific three-dimensional structure
Must be consumed
Peptide Bond
The covalent bond that links amino acids
The enzyme Peptidase can break the peptide bond
Amino Acids
An organic molecule possessing both a carboxyl and an amino group
Serves as the monomers of proteins
R-Groups
Also known as a side chain; Is a component of an amino acid that varies among the 20 standard amino acids
Amino acids differ in their properties due to differing side chains, R-Group
20 different types of amino acids
Polypeptides
Unbranched polymers built from these amino acids
Protein Structures
Primary Structure
Its sequence of amino acids
Determined by inherited genetic information
Structure
A linear line
Secondary Structure
The segments of polypeptide chains that repeatedly coiled or folded in patterns that contribute to the protein's overall shape
The coils and folds result from hydrogen bonds between repeating constituents of the polypeptide backbone
Structure
Alpha Helix
A delicate coil held together by hydrogen bonding between every fourth amino acid
Beta Pleated Sheet
Two or more segments of the polypeptide chain lying side by side are connected by hydrogen bonds between parts of the two parallel segments
Tertiary Structure
The overall shape of a polypeptide, results from interactions between R-Groups, rather h=than interactions between backbone constituents
Interactions
Hydrogen Bonds
Ionic Bonds
Hydrogen Interactions
These interactions occur between atoms of the polypeptide backbone, not the side chains, and are responsible for forming alpha helices and beta pleated sheets
Van der Waals Interaction
Weak forces that occur between molecules or atoms when they are very close together
Disulfide Bridges
Strong covalent bonds that form between two sulfhydryl groups (--SH) on cysteine amino acids within a protein
These may reinforce the protein's structure
Quaternary Structure
The overall protein structure that results from the aggregation of these polypeptide subunits
Results when two or more polypeptide chains form one macromolecule
Ex: Collagen and Hemoglobin
Collagen
A fibrous protein consisting of three polypeptide chains from one macromolecule
Hemoglobin
a globular protein consisting of four polypeptides: two alpha helix and two beta pleated sheets subunits
Nucleic Acid
A polymer consisting of many nucleotide monomers
Serves as a blueprint for proteins and, through the actions of proteins, for all cellular activities
Phosphodiester Bonds
The covalent bonds between two nucleotides to form the sugar-phosphate backbone of DNA and RNA
The enzyme Nuclease breaks down Phosphodiester Bonds
Components
Nucleotides
Each polynucleotide is made of monomers
Consists of a nitrogenous base, a pentose sugar, and one or more phosphate groups
Families of Nitrogenous Base
Pyrimidines have a single six-membered ring
Cytosine, Thymine, and Uracil
Purines have a six-membered ring fused to a five-membered ring
Adenine and Guanine
Nucleoside
The portion of a nucleotide without the phosphate group
Polynucleotides
A polymer consisting of many nucleotide monomers in a chain
Condensation Reaction
A chemical process where two molecules combine to form a larger molecule, releasing a small molecule as a byproduct
Often involves the loss of a water molecule, known as a dehydration reaction
Types
Deoxyribonucleic Acid (DNA)
Has a double helix structure
Antiparallel
Referring to the arrangement of the sugar-phosphate backbones in a DNA double helix
Ribonucleic Acid (RNA)
A single strand
Gene Expression
Gene
The amino acid sequence of a polypeptide is programmed by a unit of inheritance
DNA provides directions for its own replication
DNA directs synthesis of messenger RNA
Messenger RNA (mRNA)
Conveys genetic instructions from DNA in the nucleus to ribosomes in the cytoplasm, where proteins are synthesized
Complementary to its DNA template
Transfer RNA (tRNA)
Acts as a translator, converting mRNA codons into amino acids, which are the building blocks of proteins
Each tRNA molecule carries a specific amino acid and has an anticodon that pairs with a complementary mRNA codon