Lithium has an atomic number of 3 and a mass number of 7. Which of the following is the number of neutrons in a lithium atom?
A. 4
B. 7
C. 12
D. 3
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The atom is identified by the atomic number in the periodic table. The atomic number is equal to the number of protons and mass number is the sum of the number of protons and neutrons in the nucleus of an atom. Thus, to find how many neutrons are in lithium atom we use the formula below.
Mass number = number of protons + number of neutrons.
Letting n be number of neutrons in the lithium atom, we have
7=3+n
Rearranging the above equation
3+n=7
n=7-3
n=4
Thus, lithium atom has 4 neutrons.
Therefore, the Correct Answer is A.
More Questions on Custom TEAS Science Practice Test 1
Question 1:
Which of these organs is not considered an accessory digestive structure?
A. mouth
B. salivary glands
C. pancreas
D. liver
The Correct Answer is A.Accessory organs of the digestive system comprise of organs that empty secretions into the alimentary canal. These organs include salivary glands, liver, gallbladder and pancreas. The mount if path of the alimentary canal.
Question 2:
Which of the following best describes veins?
A. thick walled, small lumens, low pressure, lack valves
B. thin walled, large lumens, low pressure, have valves
C. thin walled, small lumens, high pressure, have valves
D. thick walled, large lumens, high pressure, lack valves
The Correct Answer is B.Question 3:
Which of the following indicates the function of sodium bicarbonate released by the pancreas?
A. Sodium bicarbonate inhibits peristalsis
B. Sodium bicarbonate is a protease that digests carbohydrates
C. Sodium bicarbonate stimulates the pyloric sphincter
D. Sodium bicarbonate neutralizes the acidity of chyme
The Correct Answer is D.Sodium bicarbonate is an alkaline solution, which is released by the pancreas. Chyme is acidic coming from the stomach is neutralized by sodium bicarbonate to protect the duodenum.
Question 4:
Base your answer on the graph and on your knowledge of biology. Which is a true statement about the relationship between pH and enzyme action?
A. All enzymes work best at a neutral pH.
B. Adding more acid does not affect the rate of activity of an enzyme.
C. Enzymes function only in a pH range of 4.0 to 5.5.
D. The activity of an enzyme is affected by pH.
The Correct Answer is D.Question 5:
The Life Cycle of HIV
Which of the following allows the AIDS virus, which contains RNA, to insert viral DNA into the DNA of a host T-cell after the AIDS virus enters the cell?
A. Receptor proteins located on the surface of the virus
B. The protein that makes up the capsid of the virus
C. Reverse transcriptase, an enzyme encoded by the virus
D. The phospholipids found on the envelope of the virus
The Correct Answer is C.The AIDS virus (HIV virus) is Class VI or Group VI in the Baltimore Classification. Based on the Baltimore Classification, this specifically involves the reverse transcriptase enzyme and it is encoded by the virus.
This is the enzyme that will produce DNA molecules from the viral RNA. This is the mechanism involved where it will use the reverse transcriptase enzyme to insert viral DNA into the genetic material of the host cell.
Question 6:
Which of these processes occurs in the mouth?
A. Ingestion
B. Mechanical digestion
C. Chemical digestion
D. All of the above
The Correct Answer is D.All of these processes occur in the mouth. Ingestion involves taking food into the mouth, mechanical digestion includes the physical breakdown of food through chewing and mixing with saliva, and chemical digestion begins with the action of enzymes in saliva, such as amylase, which starts to break down carbohydrates.
Question 7:
Which of the following are used to determine a person’s DNA sequence?
A. Genes
B. Enzymes
C. Hormones
D. Blood types
The Correct Answer is A.A gene is the basic physical and functional unit of heredity and it is the DNA that make up genes. Enzymes are biological catalysts that speed up metabolic and cellular reactions in our bodies. Hormones are responsible for controlling the action of certain cells or organs in our bodies. Blood types are of four types, A, B, AB, and O.
Question 8:
In a certain plant, red flowers are dominant over white flowers.
A plant heterozygous for red flowers and a plant with white flowers are crossed.
Which of the following is the expected proportion of phenotypes in the next generation?
A. 3 red, 1 white
B. 1 white, 3 red
C. 2 red, 2 white
D. 4 white
The Correct Answer is C.2 red, 2 white.
In this cross, the plant heterozygous for red flowers has the genotype Rr (where R represents the dominant red allele and r represents the recessive white allele), while the plant with white flowers has the genotype rr.
The possible offspring from this cross would have the genotypes Rr (red), Rr (red), rr (white), and rr (white), resulting in a 1:1 ratio of red to white flowers.
Question 9:
An atom of lead (Pb) has a mass number of 207. How many neutrons are in the nucleus?
A. 130
B. 125
C. 82
D. 84
The Correct Answer is B.We find the number of neutrons as follows
Number of neutrons
= mass number – atomic number
= 207 – 82
= 125 neutrons
Question 10:
Punnett squares are used by geneticists to determine the probability of different offspring genotypes. In the one shown below, what letter(s) belong in the lower right box?
A. AA
B. Aa
C. aA
D. aa
The Correct Answer is D.From the given Punnett square, we can cross the genotypes of the two parents and established the phenotypes the offspring will have. The Punnett square is filled as:
|
|
A |
a |
|
a |
Aa |
aa |
|
a |
Aa |
aa |
The requested answer is aa.