What is the difference between isotonic and isometric muscle contractions?
Isotonic contractions produce no movement while isometric contractions produce movement.
Isotonic contractions produce movement while isometric contractions produce no movement.
Isotonic contractions generate tension in the muscle while isometric contractions involve shortening of the muscle fibers.
Isotonic contractions involve contraction of individual muscle fibers while isometric contractions involve the entire muscle.
Correct Answer : B
Isotonic and isometric contractions are two types of muscle contractions that differ in the amount of force produced and the movement of the muscle. In isotonic contractions, the muscle changes length and produces movement, such as lifting a weight. The force generated by the muscle remains constant throughout the movement. Isotonic contractions can be further classified as concentric contractions, in which the muscle shortens as it contracts, and eccentric contractions, in which the muscle lengthens as it contracts.
In contrast, isometric contractions occur when the muscle generates force without changing its length or producing movement. For example, holding a weight in a fixed position without moving it requires an isometric contraction. In an isometric contraction, the force generated by the muscle increases up to a maximum and then remains constant. Isometric contractions can be used to build strength and endurance in the muscle, but they do not produce movement.
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Correct Answer is A
Explanation
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The other options refer to different structures:
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- D. Ureter: Carries urine from the kidneys to the bladder, also not related to blood drainage.
Correct Answer is C
Explanation
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- Sebaceous glands are found near hair follicles and are primarily responsible for acne when they become clogged.
The other options are not related to acne:
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- D. Ceruminous glands: These are found in the ear canal and produce earwax, not involved in facial skin health.
Correct Answer is C
Explanation
Down syndrome is a genetic disorder caused by the presence of an extra copy of chromosome 21. It is also known as trisomy 21, because affected individuals have three copies of chromosome 21 instead of the normal two.
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Correct Answer is A
Explanation
Electrons are subatomic particles that possess a very small mass compared to protons and neutrons. The mass of an electron is approximately 11836of the mass of a proton or neutron, making it negligible when calculating the atomic mass of an atom.
In atomic mass calculations, protons and neutrons are considered because they make up the bulk of the atom's mass:
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- Neutron: Neutral charge, with a mass also close to 1 amu.
- Electron: Negligible mass, contributing very little to the atomic mass, which is why the atomic mass number is typically determined by the number of protons and neutrons.
Quarks are the fundamental constituents of protons and neutrons but are not typically referred to in terms of atomic mass.
Correct Answer is A
Explanation
The three germ layers that form during embryonic development are the ectoderm, mesoderm, and endoderm. The ectoderm is the outermost layer, and it gives rise to the skin, hair, nails, and nervous system. The nervous system develops from a specialized region of the ectoderm called the neural plate, which invaginates to form the neural tube. The neural tube ultimately gives rise to the brain and spinal cord, which make up the central nervous system, as well as the peripheral nervous system. The endoderm gives rise to the lining of the digestive and respiratory tracts, while the mesoderm gives rise to the musculoskeletal system, circulatory system, and several other organs. The exoderm is not a germ layer and does not exist during embryonic development.
Correct Answer is A
Explanation
The data collected by the researcher on the number of cars passing through a busy intersection at different times of the day for a month would be most useful to analyze traffic paterns during rush hour.
Correct Answer is C
Explanation
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- Parotid glands are located just in front of your ears.
- Sublingual glands are located below either side of your tongue, under the floor of your mouth.
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Correct Answer is A
Explanation
Transfer RNA (tRNA) is responsible for carrying amino acids to ribosomes during protein synthesis. Each tRNA molecule has a specific anticodon that matches a codon on the messenger RNA (mRNA) molecule. The tRNA molecule binds to the mRNA codon and brings the corresponding amino acid to the ribosome, where it is added to the growing polypeptide chain.
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Correct Answer is A
Explanation
The scientific method is a systematic approach used to answer questions or test hypotheses about the natural world. The steps involved in the scientific method are:
- Observation: This is the first step in the scientific method. It involves observing a phenomenon or a problem and gathering information about it.
- Hypothesis: After making an observation, a scientist forms a hypothesis, which is a tentative explanation for the phenomenon or problem.
- Prediction: Based on the hypothesis, the scientist makes a prediction about what will happen in an experiment or what they will observe.
- Experimentation: The scientist designs and conducts an experiment to test the hypothesis and prediction.
- Analysis: The data collected from the experiment are analyzed to determine if they support or refute the hypothesis.
- Conclusion: Based on the analysis of the data, the scientist draws a conclusion about whether the hypothesis is supported or refuted.
Option b) is incorrect because it starts with hypothesis before observation. Option c) is incorrect because prediction comes before experimentation. Option d) is incorrect because hypothesis comes after observation and data collection.
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Correct Answer is C
Explanation
Water molecules primarily enter cells through the process of facilitated diffusion, specifically via aquaporins, which are specialized channel proteins that facilitate the rapid transport of water across the cell membrane. This process does not require energy (ATP) as it relies on the concentration gradient of water, allowing water to move from areas of higher concentration to lower concentration.
Here’s why the other options are not correct in the context of water transport:
- A. Gated channels: While aquaporins can be gated, this term generally refers to channels that open and close in response to specific signals, which is not the primary mechanism for water transport in most cells.
- B. Electrochemical gradients: This term relates to the combined effect of electrical and chemical gradients across a membrane, typically for ions rather than water molecules directly. Water movement can be influenced by osmotic gradients but is not solely dependent on electrochemical gradients.
- D. Proton pumps: These are involved in transporting protons (H⁺ ions) across membranes, primarily for establishing an electrochemical gradient, not for the transport of water.
Thus, water molecules enter cells mainly by facilitated diffusion through aquaporins.
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