are the small sacs that are the site of gas exchange in the lungs. In addition to being an airway, the is the location of the human vocal cords. Cilia in cells along the trachea and nasal passages secrete which traps dirt and particles from the air. Air is only approximately 21% oxygen. The majority of air is . The medulla oblongata controls the contraction and relaxation of the , causing the lungs to inflate and deflate during breathing. Explain the process of breathing. Begin with inhalation and describe the route that the air takes to the lungs, and what happens when the air reaches the lungs. Include in your description the terms: mouth, nose, pharynx, larynx, trachea, bronchi, lungs, alveoli, carbon dioxide, oxygen, and capillaries.

6. in the dna double helix, how are the two strands of dna held together? a. chemical bonds between base pairs hold the two strands of dna together. b. hydrogen bonds between the base pairs hold the two strands of dna together. c. hydrogen bonds between sugar groups and phosphate groups hold the two strands of dna together. d. chemical bonds between sugar groups and phosphate groups hold the two strands of dna together.

Considering the yellow and green pea color phenotypes studied by gregor mendel: a. what is the biochemical function of the protein that is specified by the gene responsible for the pea color phenotype? (1 point) b. a null allele of a gene is an allele that does not specify (or encode) any of the biochemical function that the gene normally provides (in other words, either no protein at all or only non-functional protein is produced from it). of the two alleles, y and y, which is more likely to be a null allele? (1 point) c. in terms of the underlying biochemistry, why is the y allele dominant to the y allele? (2 points) d. why are peas that are yy homozygotes green? (1 point) e. the amount of protein produced from a gene is roughly proportional to the number of functional copies of the gene carried by a cell or individual. what do the phenotypes of yy homozygotes, yy heterozygotes, and yy homozygotes tell us about the amount of sgr enzyme needed to produce a yellow color? explain your reasoning. (2 points)

What do all macromolecules have in common with each other? oa. they all are formed from the same elements.ob. they all have major roles in cell membranesoc. they all act as catalysts in the body.od. they all have peptide bonds between carbon atoms.