Comparison of Macromolecules

Protein Structure and Amino Acids

• Amino acids are the fundamental components of proteins.
• The R-group is the portion of an amino acid that distinguishes it from others.
• A peptide bond forms between an amino group and a carboxyl group.
• An example of an amino acid featuring a nonpolar side chain is valine.
• Aspartic acid is an amino acid that has negatively charged side chain at physiological pH.
• Cysteine is the amino acid capable of forming disulfide bonds.
• Proline is the amino acid with an R-group that creates a ring structure with its amino group.
• The primary structure of a protein is its amino acid sequence.
• Peptide bonds stabilize the primary structure of proteins.
• An alpha-helix is a type of secondary protein.
• Beta-pleated sheets have a zigzag arrangement of polypeptide chains.
• The overall three-dimensional shape of a protein signifies its tertiary structure.
• A protein domain is a distinct structural unit of a polypeptide.
• Peptide bonds are not involved in stabilizing tertiary structure.
• The quaternary structure refers to the arrangement of subunits.

Protein Function and Synthesis

• Enzymes catalyze biological reactions.
• Energy storage is not a function of proteins.
• Hemoglobin functions as a transport protein.
• Transcription synthesizes RNA from a DNA template.
• In eukaryotes, transcription occurs in the nucleus.
• RNA splicing is a post-transcriptional modification in eukaryotes.
• Introns are non-coding sequences within a gene.
• The 5' cap and 3' poly-A tail enhance eukaryotic mRNA stability and translation.
• Translation synthesizes a polypeptide chain from mRNA.
• Translation occurs at the ribosome.
• A codon on mRNA specifies an amino acid.
• A codon comprises three nucleotides.
• Methionine is coded for by the start codon AUG.
• Incoming aminoacyl-tRNA binds to the A-site on the ribosome.
• The tRNA that carries the expanding polypeptide chain is located at the P-site.
• Translation terminates when a stop codon occupies the A-site.

Protein Mutations and Misfolding

• A missense mutation changes a single nucleotide, leading to a different amino acid.
• Sickle cell anemia results from a mutation in the beta-globin gene.
• Chaperones are proteins that aid in the folding process of other proteins.
• Protein denaturation is the unfolding and disorganization of a protein's structure.

Carbohydrate Structure and Classification

• Monosaccharides compose carbohydrates.
• Glucose is a monosaccharide.
• Sucrose is a disaccharide.
• Starch and glycogen are polysaccharides.
• A glycosidic bond links monosaccharides.

Carbohydrate Digestion and Metabolism

• Carbohydrate digestion starts in the mouth.
• Salivary amylase (ptyalin) starts carbohydrate digestion in the mouth.
• Most carbohydrate digestion occurs in the small intestine.
• The intestinal brush border facilitates the final digestion of carbohydrates into monosaccharides.
• Facilitated diffusion and active transport absorb the glucose into enterocytes.
• Catabolic reactions break down molecules, releasing energy.
• Glycolysis is the breakdown of glucose into pyruvate.
• Lactate is what pyruvate is converted to under anaerobic conditions.
• The liver is the primary site of gluconeogenesis.

Lipid Structure and Function

• Fatty acids are the primary components of lipids.
• Energy storage is a major function of lipids.
• Triacylglycerols consist of glycerol and three fatty acids.
• Phospholipids consist of glycerol, two fatty acids, a phosphate group, and a polar head.
• Cholesterol synthesizes bile salts.

Lipid Digestion and Metabolism

• Lipid digestion primarily occurs in the small intestine.
• Bile salts accomplish the emulsification of lipids.
• Lipase digests triacylglycerols.
• Monoglycerides and fatty acids are the products of triacylglycerol digestion.
• The lymphatic system absorbs long-chain fatty acids.
• Lipolysis is the breakdown of stored triglycerides.