2. Amino acids can be distinguished from one another by __________.
(A) the number of R groups found on the amino acid molecules.
(B) the chemical properties of their R groups.
(C)the type of bond between the R group and the rest of the amino acid molecule.
(D) the chemical properties of their amino and carboxyl groups.
(E)All of the choices are correct.

174.Đề phòng Động vật(A)O(B)X

175.Người đi xe đạp ra hiệu sắp rẽ trái(A)O(B)X

176.Người đi xe đạp ra hiệu sắp rẽ phải(A)O(B)X

1. ______ is the major constituent of cellular membrane. (A)triglyceride(B) phospholipid (C)steroids (D) fatty acid (E)cholesterol

3. Every subunit (nucleotide) of a polynucleotide contains ______ negative charge(s). (A)0(B) 1 (C)2 (D) 3 (E)4

4. Considering the following statements about active transport, which of these statements are true? I. Facilitated diffusion is a special kind of active transport that does not require energy. II. Active transport requires energy, usually in the form of ATP hydrolysis. III. Active transport moves substances down their concentration gradients. IV. All proteins involved in active transport are carrier proteins V. Ion channels facilitate the active transport of ions (A)II and IV(B) I, II, III and IV (C)II, IV and V (D) I, II and IV (E)All

5. How do the reaction centers of photosystem I, and II differ? (A)chlorophyll a is found in photosystem I, and chlorophyll b in photosystem II.(B) They preferentially absorb slightly different wavelengths of light. (C)One is located in the thylakoid membrane, and the other in the stroma. (D) Only photosystem I is found in the thylakoid membranes. (E)None of the above.

6. Which one of the following statements is NOT true?(A)Receptor tyrosine kinases generally activate a single transduction pathway. (B) RTKs transfers a phosphate group from ATP to the tyrosine of a substrate protein. (C) The cytoplasmic tail of an RTK has multiple tyrosines. (D) Dimerization or formation of large clusters of RTKs happen when they are activated. (E) All of the above.

7. Who discovered the citric acid cycle? (A)Albert Einstein(B) Membrane proteins (C)Hans Krebs (D) Albert Lehninger (E)Melvin Calvin

8. Which one of the following statements is NOT true for apoptosis?(A)Signals that trigger apoptosis can come from outside or inside the cells.(B) In apoptotic cells, organelles, but not DNA, are fragmented. (C)The cell's parts are packaged up in vesicles that are engulfed and digested by specialized scavenger cells.(D) Cell shrinks and becomes lobed. (E)None of the above.