Biology Chapter 3 Study Guide

Identify the different functional groups in a complex molecule.

functional groups in biological molecules include: hydroxyl, methyl, carbonyl, carboxyl, amino, phosphate, and sulfhydryl groups. These groups play an important role in the formation of molecules like DNA, proteins, carbohydrates, and lipids.

Explain how a peptide bond forms between two amino acids.

. This is a dehydration synthesis reaction, and usually occurs between amino acids.

List and describe the four major components of amino acid. Explain how amino acids may be grouped according to the physical and chemical properties of the R group.

Amino group Carboxyl Group Hydrogen Atom R Group: determines quality (polar, non-polar)

Briefly describe the three-dimensional structure of DNA

Chromosomal DNA consists of two DNA polymers that make up a 3-dimensional (3D) structure called a double helix. In a double helix structure, the strands of DNA run antiparallel, meaning the 5' end of one DNA strand is parallel with the 3' end of the other DNA strand.

Describe the structure, and biological importance of fats, phospholipids, and steroids.

Fats consist of glycerol plus 3 fatty acids, 16-20 carbons in fat chains, some double bonds. Used for energy storage. Phospholipids consist of a phosphate plus 2 fatty acids and are found in cell membranes. Steroids consist of 4 fused rings and are found in hormones and cholesterol.

Explain how carbon's electron configuration accounts for its ability to form large, complex, and diverse organic molecules

In organic molecules, carbon usually forms single or double covalent bonds. Each carbon atom acts as an intersection point from which a molecule can branch off in as many as four directions. This enables carbon to form large, complex molecules.

Distinguish between monomers and polymers.

Monomers are the small molecules that make up a Polymer. A Polymer is a long chain consisting of monomers that are connected by covalent bonds.

List the major components of a nucleotide and describe how these monomers are linked to form a nucleic acid.

Pentose sugar, a phosphate group, and a nitrogenous base. The phosphate group of one nucleotide bonds with the pentose sugar of another nucleotide to form nucleic acids.

Name the principal energy storage molecules of plants and animals.

Plants: starch stores the energy Animals: glycogen(made in your liver) store the energy

Distinguish among the three types of isomers: structural, cis-trans (geometric), and enantiomer (optical isomer).

Structural isomers differ in the covalent arrangements of their atoms. In cis-trans isomers, carbons have covalent bonds to the same atoms, but these atoms differ in their spatial arrangements due to the inflexibility of double bonds. Enantiomers are isomers that are mirror images of each other and that differ in shape due to the presence of an asymmetric carbon, one that is attached to four different atoms or groups of atoms.

Distinguish between a protein and a polypeptide.

The bond between amino acids is called a peptide bond, so a polymer of amino acids is called a polypeptide. A protein is a biologically functional molecule made up of one or more polypeptides folded and coiled into a specific three-dimensional structure.

Distinguish between saturated and unsaturated fats.

The difference between saturated and unsaturated fat lies in the number of double bonds in the fatty acid chain. Saturated fatty acids lack double bonds between the individual carbon atoms, while in unsaturated fatty acids there is at least one double bond in the fatty acid chain.

List the four major classes of macromolecules.

The four major classes or macromolecules are carbohydrates, lipids, nucleic acids and proteins.

Distinguish between the glycosidic linkages found in starch and cellulose. Explain why the difference is biologically important.

The glycosidic linkages in starch and cellulose are different due to their slightly different ring structures for glucose. In starch, the glucose monomers are arranged in an alpha configuration. In cellulose, the monomers are in a beta configuration. The structures are essentially flip flopped from each other.

Explain how weak interactions and disulfide bridges contribute to the tertiary protein structure.

The hydrogen bonds maintain this structure by repeating constituents of the polypeptide backbone. Explain how weak interactions and disulfide bridges contribute to tertiary protein structure. The weak interactions between the side chains contribute to tertiary protein structure.

Name two types of secondary protein structure. Explain the role of hydrogen bonds in maintaining secondary structure.

The most common types of secondary structures are the α helix and the β pleated sheet. Both structures are held in shape by hydrogen bonds, which form between the carbonyl O of one amino acid and the amino H of another. Images showing hydrogen bonding patterns in beta pleated sheets and alpha helices.

Name the major functional groups found in organic molecules. Describe the basic structure of each functional group and outline the chemical properties of the organic molecules in which they occur.

The seven functional groups that are most important in the chemistry of life: -Hydroxyl group: In a hydroxyl group (—OH), a hydrogen atom is bonded to an oxygen atom, which in turn is bonded to the carbon skeleton of the organic molecule. -Carbonyl group: The carbonyl group ( CO) consists of a carbon atom joined to an oxygen atom by a double bond. -Carboxyl group: When an oxygen atom is double-bonded to a carbon atom that is also bonded to an —OH group, the entire assembly of atoms is called a carboxyl group (COOH). -Amino group: The amino group (NH2) consists of a nitrogen atom bonded to two hydrogen atoms and to the carbon skeleton. -Sulfhydryl group: The sulfhydryl group consists of a sulfur atom bonded to an atom of hydrogen; resembles a hydroxyl group in shape. -Phosphate group: In a phosphate group, a phosphorus atom is bonded to four oxygen atoms; one oxygen is bonded to the carbon skeleton; two oxygen carry negative charges. The phosphate group (OPO32, abbreviated) is an ionized form of a phosphoric acid group (OPO3H2; note the two hydrogens). -Methyl group: A methyl group consists of a carbon bonded to three hydrogen atoms. The methyl group may be attached to a carbon or to a different atom.

Describe how carbon skeletons may vary and explain how this variation contributes to the diversity and complexity of organic molecules.

The skeletons vary in length and may be straight, branched, or arranged in closed rings. Some carbon skeletons have double bonds, which vary in number and location. Such variation in carbon skeletons is one important source of the molecular complexity and diversity that characterize living matter

List the different types of polysaccharides used by plants and animals for energy storage and for structure.

Three important polysaccharides, starch, glycogen, and cellulose, are composed of glucose. Starch and glycogen serve as short-term energy stores in plants and animals, respectively.

Describe the formation of a glycosidic linkage.

a glycosidic linkage, a covalent bond formed between two monosaccharides by a dehydration reaction

Distinguish between: a. pyrimidine and purine c. ribose and deoxyribose d. 5' end and 3' end of a nucleotide

a. The main difference between purines and pyrimidines is that purines contain a six-membered nitrogen-containing ring fused to an imidazole ring whereas pyrimidines contain only a six-membered nitrogen-containing ring. b. The pentose sugar in DNA is called deoxyribose, and in RNA, the sugar is ribose. The difference between the sugars in the presence of the hydroxyl group on the 2' carbon of the ribose and its absence on the 2' carbon of the deoxyribose. c. Atoms in each DNA nucleotide can be identified by specific numbers. ... One end of the chain carries a free phosphate group attached to the 5'-carbon atom; this is called the 5' end of the molecule. The other end has a free hydroxyl (-OH) group at the 3'-carbon and is called the 3' end of the molecule.

Explain what determines protein conformation and why it is important.

it is the amino acid sequence of each polypeptide that determines what three-dimensional structure the protein will have under normal cellular conditions.

Describe the basic structure of a hydrocarbon and explain why these molecules are hydrophobic.

organic molecules consisting of only carbon and hydrogen.

List four conditions under which proteins may be denatured.

pH, salt concentration, temperature, or alteration of other aspects of the environment.

Explain how the primary structure of a protein is determined.

the primary structure of a protein is determined by the gene corresponding to the protein. A specific sequence of nucleotides in DNA is transcribed into mRNA, which is read by the ribosome in a process called translation.