Which of the following ions binds to the troponin complex, initiating contraction of a muscle?
A. Potassium.
B. Calcium.
C. Phosphorus.
D. Sodium
Calcium ions play a crucial role in initiating muscle contraction.
When a muscle cell is stimulated to contract by an action potential, calcium channels open in the sarcoplasmic membrane and release calcium into the sarcoplasm.
Some of this calcium attaches to troponin, which causes it to change shape.
This shape change exposes binding sites for myosin on the actin filaments.
Myosin’s binding to actin causes crossbridge formation, and contraction of the muscle begins.
The other ions mentioned in the question do not have this specific role in muscle contraction.
Potassium ions are important for maintaining the resting membrane potential of cells, but they do not bind to the troponin complex.
Phosphorus ions are important for energy metabolism, but they do not bind to the troponin complex.
Sodium ions are important for generating action potentials, but they do not bind to the troponin complex.
Therefore, the Correct Answer is B.
More Questions on TEAS 7 Science
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Q #1: Why is it important for new scientific findings to be published?
A. Scientists will get paid if their findings are published.
B. Publishing findings will help scientists become more biased.
C. Other scientists can validate or disprove the findings
D. This prevents other scientists from performing similar tests
Answer Explanation
Other scientists can validate or disprove the findings.
It is important for new scientific findings to be published so that other scientists can review the research and either validate or disprove the findings.
This process of peer-review helps to ensure the accuracy and reliability of scientific research.
Choice A.
Scientists will get paid if their findings are published is not correct because while some scientists may receive funding or grants for their research, the primary goal of publishing scientific findings is not for financial gain.
Choice B.
Publishing findings will help scientists become more biased is not correct because the goal of publishing scientific findings is to share information and promote transparency, not to promote bias.
Choice D.
This prevents other scientists from performing similar tests is not correct because publishing scientific findings allows other scientists to build upon the research and perform further tests to validate or disprove the findings.
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Q #2: What is the approximate threshold value for mammalian neurons?
A. -55 mV
B. -80 mV
C. +35 mV
D. 0 mV
Answer Explanation
The approximate threshold value for mammalian neurons is -55 mV.
The threshold potential is the critical level to which a membrane potential must be depolarized to initiate an action potential.
Most often, the threshold potential is a membrane potential value between –50 and –55 mV
The membrane potential of a neuron is determined by the distribution of ions across the cell membrane.
At rest, the inside of a neuron is more negative than the outside due to the presence of negatively charged proteins and other molecules.
The movement of ions across the cell membrane can change the membrane potential.
For example, when sodium ions enter the cell, they make the inside of the cell more positive (less negative), causing depolarization.
Choice B is incorrect because -80 mV is below the typical threshold value for mammalian neurons.
Choice C is incorrect because +35 mV is above the typical threshold value for mammalian neurons.
Choice D is incorrect because 0 mV is above the typical threshold value for mammalian neurons.
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Q #3: Nitrogen gas is an extremely stable molecule because of which of the following?
A. Ionic bonds
B. Hydrogen bonds
C. Resonance bonds
D. Triple covalent bonds
Answer Explanation
Triple covalent bonds.
Nitrogen gas (N2) is an extremely stable molecule because it consists of two nitrogen atoms bonded together by a triple covalent bond.
A covalent bond is a type of chemical bond where atoms share electrons to form a molecule.
In a triple covalent bond, three pairs of electrons are shared between the two atoms, resulting in a very strong bond that makes the molecule extremely stable.
Choice A.
Ionic bonds is not correct because ionic bonds involve the transfer of electrons from one atom to another to form ions, which are then attracted to each other due to their opposite charges.
Nitrogen gas does not contain ions and is not held together by ionic bonds.
Choice B.
Hydrogen bonds is not correct because hydrogen bonds are weak electrostatic attractions between molecules that contain hydrogen atoms bonded to highly electronegative atoms such as oxygen or nitrogen.
Nitrogen gas does not contain hydrogen atoms and is not held together by hydrogen bonds.
Choice C.
Resonance bonds is not correct because resonance refers to the delocalization of electrons in a molecule where multiple Lewis structures can be drawn to represent the molecule.
Nitrogen gas has a single Lewis structure and does not exhibit resonance.
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Q #4: Which of the following results in osteoporosis?
A. An increase in osteocyte activity while osteoclast activity continues at expected levels.
B. A decline in osteoclast activity while osteoblast activity continues at expected levels.
C. An increase in osteocyte activity while osteoblast activity reduces.
D. A decline in osteoblast activity while osteoclast activity continues at expected levels.
Answer Explanation
A decline in osteoblast activity while osteoclast activity continues at expected levels results in osteoporosis.
Osteoporosis is caused by an imbalance between the functioning of osteoclast and osteoblast cells.
Osteoblasts are responsible for forming new bone, while osteoclasts break down old bone.
If osteoblast activity declines while osteoclast activity continues at expected levels, this means that more bone is being broken down than is being formed, leading to a loss of bone density and an increased risk of osteoporosis.
Choice A is incorrect because an increase in osteocyte activity would not result in osteoporosis.
Osteocytes are mature bone cells that maintain the mineral concentration of the bone matrix.
Choice B is incorrect because a decline in osteoclast activity would not result in osteoporosis.
Osteoclasts break down old bone, so a decline in their activity would mean that less bone is being broken down.
Choice C is incorrect because an increase in osteocyte activity would not result in osteoporosis.
As mentioned earlier, osteocytes are mature bone cells that maintain the mineral concentration of the bone matrix.
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Q #5: Testosterone is categorized as which of the following types of hormones?
A. Estrogen
B. Progestin
C. Aldosterone
D. Androgen
Answer Explanation
Testosterone is classified as an androgen hormone.
Androgens are a type of sex hormone that primarily regulates the development and maintenance of male characteristics, such as body hair growth, muscle mass, and deepening of the voice.
Testosterone is produced primarily in the testes in males and in smaller amounts in the ovaries and adrenal glands in females.
Option A, estrogen, is a female hormone that regulates the development of female sexual characteristics, such as breast growth and menstruation.
While estrogen and testosterone are both steroid hormones and can be converted to one another in the body, testosterone is not categorized as estrogen.
Option B, progestin, is a synthetic form of the hormone progesterone.
Progesterone is a female hormone that plays a role in the menstrual cycle and pregnancy.
Testosterone and progestin are not related, and testosterone is not categorized as progestin.
Option C, aldosterone, is a mineralocorticoid hormone that regulates salt and water balance in the body.
It is produced in the adrenal gland and plays a role in regulating blood pressure.
Testosterone and aldosterone are not related, and testosterone is not categorized as aldosterone.
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Q #6: Which of the following substances is excreted by sweat glands in response to the breakdown of proteins and the formation of ammonia?
A. Urea
B. Sebum
C. Water
D. Lysozymes
Answer Explanation
Urea is a substance that is excreted by sweat glands in response to the breakdown of proteins and the formation of ammonia.
When proteins are broken down, they produce ammonia, which is a highly toxic compound for the body.
Ammonia is then converted into urea and released out of the body through sweat glands.
Choice B.
Sebum is not correct because it is an oily substance secreted by sebaceous glands to lubricate and protect the skin, but it is not related to the breakdown of proteins or the formation of ammonia.
Choice C.
Water is not correct because while it is a component of sweat, it is not specifically related to the breakdown of proteins or the formation of ammonia.
Choice D.
Lysozymes are not correct because they are enzymes found in tears, saliva and other body fluids that have antibacterial properties, but they are not related to the breakdown of proteins or the formation of ammonia.
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Q #7: Which of the following types of cells produce and release antibodies?
A. Natural killer cells
B. Cytotoxic T-cells
C. Plasma B cells
D. Helper T-cells
Answer Explanation
Plasma B cells.
Antibodies are produced by specialized white blood cells called B lymphocytes (or B cells).
When an antigen binds to the B-cell surface, it stimulates the B cell to divide and mature into a group of identical cells called a clone.
The mature B cells, called plasma cells, secrete millions of antibodies into the bloodstream and lymphatic system.
Choice A, Natural killer cells, is not the correct answer because natural killer cells are a type of white blood cell that play a major role in the host-rejection of both tumors and virally infected cells.
Choice B, Cytotoxic T-cells, is not the correct answer because cytotoxic T-cells are a type of white blood cell that kills cancer cells, cells that are infected (particularly with viruses), or cells that are damaged in other ways.
Choice D, Helper T-cells, is not the correct answer because helper T-cells are a type of white blood cell that play an important role in the immune system by helping other white blood cells fight infections.
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Q #8: Which of the following is the function of a totipotent cell?
A. Fights infectious diseases.
B. Aids in the maturation of sex cells.
C. Carries electrical impulses.
D. Develops into any kind of cell.
Answer Explanation
A totipotent cell can self-renew by dividing and develop into the three primary germ cell layers of the early embryo and into extra-embryonic tissues such as the placenta.
A fertilized egg is a totipotent stem cell and as such can develop into any specialized cell found in the organism.
Choice A is not correct because totipotent cells do not fight infectious diseases.
Choice B is not correct because totipotent cells do not aid in the maturation of sex cells.
Choice C is not correct because totipotent cells do not carry electrical impulses.
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Q #9: A myocardial infarction affects which of the following blood vessels of the heart?
A. Coronary
B. Aorta
C. Pulmonary
D. Vena cava
Answer Explanation
A myocardial infarction affects the coronary blood vessels of the heart.
A myocardial infarction, commonly known as a heart attack, occurs when blood flow decreases or stops in the coronary artery of the heart, causing damage to the heart muscle 1.
Choice B is incorrect because the aorta is not a blood vessel of the heart.
The aorta is the main artery that carries oxygenated blood from the heart to the rest of the body.
Choice C is incorrect because the pulmonary blood vessels are not affected by a myocardial infarction.
The pulmonary blood vessels carry deoxygenated blood from the heart to the lungs.
Choice D is incorrect because the vena cava is not a blood vessel of the heart.
The vena cava is a large vein that carries deoxygenated blood from the body to the heart.
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Q #10: In the following data table of an experiment carried out at 4°C (39.2 F) over 4 hours Solution in bag Solution outside bag Bag mass change (g): water Water -0.2 20% sucrose Water +2.4 , 40% sucrose Water +4.3 , 60% sucrose water +5.8 Which of the following options represents the dependent variable?
A. Duration
B. Temperature
C. Bag mass change
D. Solution used outside
Answer Explanation
Bag mass change is the dependent variable in this experiment.
In an experiment, the dependent variable is the variable that is being measured and is expected to change in response to changes in the independent variable(s).
In this case, the bag mass change is being measured and is expected to change in response to changes in the independent variable (sucrose concentration).
Choice A is incorrect because duration is not a variable in this experiment.
Choice B is incorrect because temperature is not a variable in this experiment.
Choice D is incorrect because sucrose concentration is an independent variable, not a dependent variable.
An independent variable is a variable that is manipulated by the experimenter to see how it affects the dependent
