19. Which of the following components and conditions increases membrane fluidity?
(A) phospholipids with long, saturated fatty acyl chains
(B) phospholipids with short, unsaturated fatty acyl chains
(C) lower temperatures
(D) cholesterol at the usual concentrations found in biomembranes
(E) lipid rafts

15. Humans cannot survive at sea by drinking salt water. However, marine vertebrates such as sea turtles and various sea birds can survive by drinking salt water. What DO they have that humans DO NOT? (A) kidneys that are extremely good at producing a concentrated urine. (B) body fluid concentrations that are similar to or greater than those of seawater. (C) the ability to secrete salts and wastes into their intestinal contents like an insect. (D) They use ammonia as their primary nitrogenous waste. (E) salt glands.

16. Which of the following is NOT a feature of apoptosis? (A) formation of apoptotic body (B) DNA fragmentation (C) cell swelling (D) activation of caspases (E) release of cytochrome C from mitochondria

17. A nonsense suppressor tRNA may have the anticodon (A) 5'-CAU-3' (B) 5'-UAA-3' (C) 5'-UUA-3' (D) 5'-CCC-3' (E) 5'-UAG-3'

18. Which of the following accurately gives the distribution of phenotypes produced from a cross of purple dwarf pea plants that are heterozygous for flower color and plant height? (A) 27 purple dwarf; 28 purple tall; 31 white dwarf; 29 white tall (B) 63 purple dwarf; 28 purple tall; 27 white dwarf; 7 white tall (C) 132 purple dwarf; 138 white tall (D) 54 purple dwarf; 6 white tall (E) 100% purple dwarf

20. A 400-bp covalently closed circular DNA with a linking number of 35 has 5 negative supercoils. When the linking number of this DNA is changed to 38 by a topoisomerase, this DNA will have (A) 3 positive supercoils. (B) 3 negative supercoils. (C) 2 positive supercoil. (D) 2 negative supercoils. (E) relaxed.

21. When a cell releases a signal molecule into the environment and a number of cells in the immediate vicinity respond, this type of signaling is (A) typical of hormones. (B) autocrine signaling. (C) paracrine signaling. (D) endocrine signaling. (E) synaptic signaling.

22. Which structure is NOT part of the endomembrane system? (A) nuclear envelope (B) chloroplast (C) Golgi apparatus (D) plasma membrane (E) ER

23. What is a genome? (A) An ordered display of chromosomes arranged from largest to smallest. (B) A specific set of polypeptides within each cell. (C) A specialized polymer of four different kinds of monomers. (D) A specific segment of DNA that is found within a prokaryotic chromosome. (E) The complete complement of an organism's genes.

24. Why are cattle able to survive on a diet consisting almost entirely of plant material? (A) They are autotrophic. (B) Cattle, like the rabbit, reingest their feces. (C) They manufacture all 15 amino acids out of sugars in the liver. (D) Cattle saliva has enzymes capable of digesting cellulose. (E) They have cellulose-digesting, symbiotic microorganisms in chambers of their stomachs.

25. Which one of the following, if present in a urine sample, would likely be caused by trauma? (A) amino acids (B) glucose (C) salts (D) erythrocytes (E) vitamins