Carbohydrates Overview Quiz

Carbohydrates

• Carbohydrates include sugars and polymers of sugars.
• Contain a carbonyl group and many hydroxyl groups.
• Made up of carbon, hydrogen, and oxygen.
• Monosaccharides are simple sugars with molecular formulas that are multiples of the unit CH2O.
• Glucose is the most common monosaccharide.
• Glucose is a nutrient and fuel for cells used in cellular respiration.
• Monosaccharides can serve as building blocks for amino acids or as monomers for di- and polysaccharides.
• Disaccharides are two monosaccharides joined together by covalent bonds.
• Sucrose is the most common disaccharide.
• The monomers of sucrose are glucose and fructose.
• Plants transfer carbohydrates from roots to leaves in the form of sucrose.
• Polysaccharides are polymers with many sugars joined via dehydration reactions.
• Starch is a storage polysaccharide.
• Plants store starch, which is a polymer of glucose monomers.
• Starch allows plants to store excess glucose.
• Glycogen is a storage polysaccharide that is a polymer of glucose that is stored in liver and muscle cells.
• Cellulose is a structural polysaccharide that forms tough plant cell walls.
• Chitin is a structural polysaccharide that forms the exoskeletons of arthropods.

Proteins

• Proteins are molecules consisting of polypeptides (polymers of amino acids) folded into a three-dimensional shape.
• Proteins are comprised of carbon, hydrogen, oxygen, nitrogen, and sulfur.
• The shape of a protein determines its function.
• Amino acids are molecules with an amino group and a carboxyl group.
• There are 20 different amino acids.
• Each amino acid has a unique side chain.
• Different aspects of the amino acid are based on the side chain’s physical and chemical properties.
• Side chains can be grouped as nonpolar (hydrophobic), polar (hydrophilic), or charged/ionic (hydrophilic).
• Interactions between side chains determine the shape and function of a protein.
• To form a peptide bond the carboxyl group of one amino acid must be positioned next to the amino group of another amino acid.
• This bond is formed via a dehydration reaction.
• Polypeptides are chains of many amino acids linked by peptide bonds.
• Each polypeptide has a unique sequence of amino acids and directionality.
• One end of a polypeptide is a free amino group (N-terminus) and the other is a free carboxyl end (C-terminus).
• The sequence of amino acids determines the 3D shape of a polypeptide.
• When a polypeptide twists and folds due to amino acid interactions, it forms a protein.
• Unique sequences of AAs for polypeptides are determined by genes.
• Proteins function as antibodies, enzymes, messengers, structural elements, and transport/storage molecules.
• Antibodies help to protect the body from disease.
• Enzymes carry out chemical reactions or assist in creating new molecules.
• Messengers transmit signals such as hormones.
• Structural proteins provide structure and support.
• Transport/storage proteins bind to and carry small atoms and molecules through the body.

Levels of Protein Structure

• The primary structure of a protein is the linear chain of amino acids.
• The primary structure is determined by the genes and dictates the secondary and tertiary structures.
• The secondary structure of a protein is the coils and folds due to hydrogen bonding within the polypeptide backbone.
• Two forms of secondary protein structure are the alpha helix and the beta pleated sheet.
• The tertiary structure of a protein is the 3D folding due to interactions between the side chains of the amino acids.
• Tertiary protein structure is reinforced by hydrophobic interactions and disulfide bridges.
• The quaternary structure of a protein is the association of two or more polypeptides.
• Quaternary structure is only found in some proteins.

Nucleic Acids

• Nucleic acids are polymers made up of nucleotide monomers.
• Nucleic acids store, transmit, and express hereditary information.
• There are two basic forms of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).

Components of Nucleic Acids

• Nucleotides are the monomers of nucleic acids.
• Polynucleotides are polymers of nucleotides.
• Nucleic acids are comprised of nucleotides.

Nucleotides

• A nucleotide contains a nitrogenous base, a five-carbon sugar (pentose), and a phosphate group.
• In a polynucleotide, each monomer only has one phosphate group.

Nitrogenous Bases

• There are two types of nitrogenous bases: pyrimidines and purines.
• Pyrimidines have one six-atom ring.
• Pyrimidines include cytosine, thymine, and uracil.
• Thymine is only found in DNA, while uracil is only found in RNA.
• Purines have one six-atom ring bonded to one five-atom ring.
• Purines include adenine and guanine.

Five-Carbon Sugar

• A sugar is bonded to the base.
• In DNA, the sugar is deoxyribose.
• In RNA, the sugar is ribose.

Phosphate Group

• A phosphate group is added to the 5’ carbon of the sugar (which is attached to the base) to form a nucleotide
• A nucleoside is the portion of the nucleotide without the phosphate group.

Polynucleotides

• Phosphate groups link adjacent nucleotides via a phosphodiester linkage.
• Polynucleotides have directionality.
• The 5' end has a phosphate group, while the 3' end has a hydroxyl group.
• The sequence of bases along the DNA or mRNA is unique for each gene.
• This sequence dictates the amino acid sequence which, in turn, dictates the primary structure of a protein.
• The primary structure of a protein dictates the 3D structure of a protein.

DNA

• DNA consists of two polynucleotides that form a double helix.
• The strands are antiparallel.
• The strands are held together by hydrogen bonds between bases.
• Cytosine binds to guanine.
• Adenine binds to thymine.

RNA

• RNA is a single-stranded polynucleotide.
• RNA is variable in shape due to base pairing within the molecule.
• Adenine bonds to uracil.
• Cytosine bonds to guanine.

Lipids

• Lipids are a class of molecules that are not considered to be true polymers.
• Lipids are generally small in size and are not considered to be macromolecules.
• Lipids are nonpolar and hydrophobic.
• The three main types of lipids are fats, phospholipids, and steroids.

Fats

• Fats are composed of glycerol and fatty acids.
• Glycerol is an alcohol with hydroxyl groups.
• Fatty acids are long carbon chains with a carboxyl group at one end.
• Three fatty acids join to a glycerol via an ester linkage, which forms a bond between a hydroxyl and carboxyl group.
• Fatty acids are classified as saturated or unsaturated.
• Saturated fatty acids have no double bonds between carbons in the carbon chain. This means they are saturated with hydrogen.
• Unsaturated fatty acids contain one or more double bonds in the carbon chain.

Phospholipids

• Phospholipids are a major component of cell membranes.
• Phospholipids have two fatty acids attached to a glycerol and a phosphate group.
• Phospholipids assemble as a bilayer in water.
• The tails of phospholipids are hydrophobic, while the heads are hydrophilic.

Steroids

• Steroids are lipids with four fused rings.
• Unique groups attached to the rings determine the type of steroid.
• Testosterone is an example of a steroid.