Question

1. Nitrogen (N) is more electronegative than hydrogen (H). Which of the following is a correct statement about the atoms in ammonia (NH3)?

A. There are covalent bonds between the hydrogen atoms and polar bonds between each hydrogen atom and the nitrogen atom.

B. Ammonia has an overall negative charge.

C. The nitrogen atom has a partial positive charge; each hydrogen atom has a partial negative charge.

D. Ammonia has an overall positive charge.

E. Each hydrogen atom has a partial positive charge; the nitrogen atom has a partial negative charge.

2. The diploid cells that produce sperm in human males contains 46 chromosomes. If one of these cells undergoes a non-disjunction event in meiosis II, what is the chromosome number in each of the resulting sperm cells?

A. 46, 46, 47, 45

B. 45, 45, 47, 47

C. 22, 22, 24, 24

D. 23, 23, 24, 22

3. Textbooks often refer to oxygen as the "final electron acceptor." What does this statement mean?

A. When oxygen accepts electrons, a cell dies.

B. Oxygen was the last electron acceptor to be discovered.

C. Oxygen is the final acceptor of electrons at the end of the electron transport chain in photosynthesis.

D. Oxygen is the final acceptor of electrons at the end of the electron transport chain in cell respiration.

4. Which of the following is a major difference between prokaryotic cells and eukaryotic cells?

A. Eukaryotic cells are always part of a multicellular organism, while prokaryotic cells are never part of a multicellular organism.

B. Prokaryotic cells have nuclei, while eukaryotes don't.

C. Prokaryotes are not able to carry out aerobic respiration, relying instead on anaerobic metabolism, whereas eukaryotic cells CAN do aerobic respiration.

D. Prokaryotes are generally smaller than eukaryotes

E. two of the above are differences between prokaryotic and eukaryotic cells

5. There is a pond that contains two different kinds of fish-like creatures, one called gumpies and the other called wumpies. Both populations have quite a lot of heritable variation. Gumpies are eaten by a larger kind of aquatic animal called dumpies, that do not eat wumpies. Gumpies and wumpies sometimes eat each other.

Which of the following statements about natural selection and gumpies and wumpies is true?

A. natural selection can act on neither gumpies nor wumpies

B. natural selection can act on wumpies but not gumpies

C. natural selection can act on both gumpies and wumpies

D. natural selection can act on gumpies, but not on wumpies

E. natural selection can act on dumpies but not gumpies or wumpies

6. If a cell with 12 pairs of homologous chromosomes is in the G1 phase of the cell cycle, how many DNA double helices are present in that cell?

A. 48

B. 6

C. 24

D. 12

Answer 1

1) The correct answer is (E)  Each hydrogen atom has a partial positive charge; the nitrogen atom has a partial negative charge.

Partial charges  are created due to the asymmetric distribution of electrons in chemical bonds. Nitrogen is more electronegative than hydrogen and therefore there is a slight shift of electrons of the bond towards nitrogen giving it a negative partial charge and hydrogen a positive charge.

The covalent bonds in ammonia are formed between nitrogen and hydrogen atoms and not between hydrogen atoms. Nitrogen in ammonia has a charge of -3 and the hydrogen atom have +1 and three hydrogen atoms so +3 , which result in the overall neutral charge of the molecule of ammonia.

2) Correct answer is (D) 23, 23, 24, 22.

Nondisjunction  is the failure of homologous chromosomes / sister chromatids to separate properly during cell division.Since here nondisjunction occurs during meiosis II, it means that at least one pair of sister chromatids did not separate. So, two cells will have the normal haploid number (n) of chromosomes. Additionally, one cell will have an extra chromosome (n + 1) and one will be missing a chromosome (n - 1).

Therefore n=23 , n=23 , n+1= 23+1=24 , n-1=23-1 =22.

3) Correct answer is (D) Oxygen is the final acceptor of electrons at the end of the electron transport chain in cell respiration.

  The byproducts of catabolic processes are NADH and FADH2 which are the reduced forms fetch into Electron Transport Chain where the electrons carried by NADH and FADH2 are passed to membrane bound electron carriers which are then passed on to other electron carriers and finally accepted by oxygen resulting in the production of water. Oxygen has the highest (most positive) standard reduction potential which means that is is most likely to accept electrons from other carriers.

4) Correct answer is (D) Prokaryotes are generally smaller than eukaryotes.

Prokaryotic cells are 0.1–5.0 µm in diameter,whereas eukaryotic cells range from 10–100 µm in diameter.

Not all eukaryotic cell come under multicellular. Certain unicellular organisms are also eukaryotic, but prokaryotes are never multicellular.Both the cell have nuclei and are capable of both aerobic and anaerobic respiration.

5) Correct answer is (C)  natural selection can act on both gumpies and wumpies.

Natural selection can occur in both gumpies and wumpies because both of them have to encounter environmental pressures( here in the case is predation ) in order for their survival . Gumpies are prey to dumpies so in order to survive from the predation it need to change . Also wumpies are eaten by gumpies and vice versa leading to the factor that for both of their survival,each other surivival is effected . Changes might need to be adapt by them in order to favour in their natural habitat, thus leading them to natural selection.

6) Correct answer is (B) 6

In G1 phase dna content is 2N OR 2C and here it is mentioned 12 homologous pair,i.e, 2N=12 which implies N=6 . And each chromosome contain one molecule of DNA therefore total DNA double helices present is 6.