Nokea
Which type of fiber is insoluble and promotes gut motility?
- A. Pectin
- B. Cellulose
- C. Beta-gluca
- D. Guar gum
Correct Answer: B
Rationale: A) Pectin is a soluble fiber found in fruits and vegetables. It forms a gel-like substance in the gut and can help lower cholesterol levels.
B) Cellulose is an insoluble fiber found in plants, particularly in the cell walls of fruits, vegetables, and whole grains. It adds bulk to the stool and promotes gut motility by aiding in the movement of food through the digestive system.
C) Beta-glucan is a soluble fiber found in oats and barley. It can help lower cholesterol levels and improve blood sugar control.
D) Guar gum is a soluble fiber derived from guar beans. It can help with digestion and may have a role in managing blood sugar levels.
In this case, the question specifically asks for the type of fiber that is insoluble and promotes gut motility, which is characteristic of cellulose.
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How are sister chromatids distinguished from homologous chromosomes in meiosis I?
- A. Sister chromatids share the same centromere, while homologous chromosomes have different centromeres.
- B. Sister chromatids have identical DNA sequences, while homologous chromosomes have slightly different sequences due to crossing over.
- C. Sister chromatids repel each other, while homologous chromosomes attract each other during synapsis.
- D. Sister chromatids separate during anaphase I, while homologous chromosomes separate during anaphase II.
Correct Answer: B
Rationale: In meiosis I, sister chromatids are exact copies of each other, containing identical DNA sequences. On the other hand, homologous chromosomes are pairs of chromosomes, with one inherited from each parent, and they can have different versions of genes due to genetic recombination during crossing over in prophase I. Choice A is incorrect because homologous chromosomes naturally have different centromeres. Choice C is incorrect as sister chromatids and homologous chromosomes do not exhibit repulsion or attraction during synapsis. Choice D is incorrect as sister chromatids separate during anaphase II, not anaphase I, while homologous chromosomes separate during anaphase I.
What is the role of RNA interference in silencing genes?
- A. Increases protein production
- B. Promotes gene mutation
- C. Inhibits the expression of specific genes
- D. Repairs damaged DNA
Correct Answer: C
Rationale: RNA interference (RNAi) is a biological process that involves the silencing of gene expression by inhibiting the translation of mRNA or by degrading mRNA molecules. This mechanism plays a crucial role in regulating gene expression and can be used to selectively silence specific genes. By interfering with the expression of specific genes, RNAi can downregulate protein production from those genes. Therefore, option C, 'Inhibits the expression of specific genes,' is the correct role of RNA interference in silencing genes. Options A, B, and D are incorrect because RNA interference does not increase protein production, promote gene mutation, or repair damaged DNA; its primary function is to inhibit gene expression by degrading or interfering with mRNA.
Which part of the respiratory system is responsible for gas exchange between the blood and inhaled air?
- A. Trachea
- B. Larynx
- C. Alveoli
- D. Pharynx
Correct Answer: C
Rationale: The correct answer is C, Alveoli. The alveoli are tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide takes place between the air we breathe in and the blood. The trachea, larynx, and pharynx are all part of the airway passage but do not directly participate in gas exchange. The trachea serves as the windpipe, the larynx is involved in sound production and protecting the airway during swallowing, and the pharynx helps with swallowing and speech production. Therefore, the alveoli specifically facilitate the critical gas exchange process, making them the correct answer in this context.
Which of the following best describes a balanced force acting on an object?
- A. The object remains at rest
- B. The object moves with constant velocity
- C. The object accelerates
- D. The object's mass changes
Correct Answer: B
Rationale: When a balanced force acts on an object, the net force is zero, resulting in no acceleration. This means that the object will continue to move with a constant velocity if it was already in motion or remain at rest if it was initially stationary. Choice A is incorrect because the object can also move with constant velocity. Choice C is incorrect as acceleration only occurs when an unbalanced force is applied. Choice D is incorrect as the mass of an object is not affected by the balance of forces acting on it.
What happens to the frequency of a wave if its wavelength decreases while the speed remains constant?
- A. Frequency decreases
- B. Frequency increases
- C. Frequency remains constant
- D. Frequency becomes zero
Correct Answer: B
Rationale: The correct answer is B: Frequency increases. Frequency and wavelength are inversely proportional in a wave with a constant speed. When the wavelength decreases while the speed remains constant, the frequency must increase to maintain the constant speed of the wave. This relationship is governed by the equation: speed = frequency x wavelength. Choice A is incorrect as frequency increases when wavelength decreases. Choice C is incorrect as the frequency changes in this scenario. Choice D is incorrect as the frequency does not become zero but increases when the wavelength decreases.