17. Which polysaccharide is an important component in the structure of many animals and fungi?
(A) chitin
(B) cellulose
(C) amylopectin
(D) amylose
(E) starch

13. A localized group of organisms that belong to the same species is called a_______. (A) community (B) family (C) ecosystem (D) population (E) Biosphere

14. How many electrons are involved in a triple covalent bond? (A) 3 (B) 6 (C) 9 (D) 12 (E)15

15. What is the hydroxyl ion (OH-) concentration of a solution of pH 8? (A) 8M (B) 8 x 10-6 M (C)10-6 M (D) 10-8 M (E) 8 x 10-8 M

16. Use the following figure to answer the question. The figure shows the structures of glucose and fructose. These two molecules are________.(A) isotopes (B) cis-trans isomers (C) enantiomers (D) epimers (E) structural isomers

18._________is a regulatory mechanism in which the end product of a metabolic pathway inhibits an enzyme that catalyzes an early step in the pathway. (A) Allosteric inhibition (B) Cooperative inhibition (C) Feedback inhibition (D) Metabolic inhibition (E) Competitive inhibition

19.Which of the following is the most common pathway taken by a newly synthesized protein that will be secreted by a cell? (A) rough ER→ Golgi → transport vesicle →  nucleus (B) Golgi→  rough ER lysosome →  transport vesicle →  plasma membrane (C) rough ER → lysosome →  transport vesicle →  plasma membrane (D) rough ER →  Golgi → transport vesicle→  plasma membrane (E) nucleus → endosome →  Golgi →  transport vesicle→  plasma membrane

20. In some cells, there are many ion electrochemical gradients across the plasma membrane even though there are usually only one or two proton pumps present in the membrane. The gradients of the other ions are most likely accounted for by ________.(A) osmosis (B)ion channels (C) pores in the plasma membrane (D) passive diffusion across the plasma membrane (E) cotransport proteins

21. One of the major categories of receptors in the plasma membrane functions by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this? (A) G protein-coupled receptors (B) receptor tyrosine kinases (C) steroid receptors (D) ligand-gated ion channels (E) glycolipid

22. Which electron carrier(s) function in the citric acid cycle? (A) NAD+ only (B) ADP and ATP (C)  the electron transport chain (D) NADH and FADH2 (E) Glucose

23. Which of the following sequences correctly represents the flow of electrons during photosynthesis? (A) NADPH →O2 →CO2 (B) NADPH→ chlorophyll→ Calvin cycle (C) H2O→ NADPH → Calvin cycle (D) NADPH→ electron transport chain→ O2 (E) Pyruvate → ATP Calvin cycle