The food conducting tissue in plants, phloem, is composed of which type of cells?
A. Fibers and sclereids
B. Guard cells and subsidiary cells
C. Sieve tubes and companion cells
D. Tracheids and vessels
Answer: Option C
Solution (By JKExamLibrary)
Phloem is composed of sieve tube elements, companion cells, phloem parenchyma, and phloem fibers. Sieve tubes are living cells that transport organic solutes; companion cells assist in loading and unloading. Tracheids and vessels are xylem elements. Fibers and sclereids are sclerenchyma cells. Guard cells regulate stomatal movement.
Explanation:
ATP (adenosine triphosphate) is the immediate energy currency for cellular processes. Hydrolysis of its high-energy phosphate bonds releases energy. Glucose and acetyl CoA are fuels, NADPH is an electron donor for biosynthesis. ATP is generated by substrate-level phosphorylation and oxidative phosphorylation.
Explanation:
The medulla oblongata contains centers for heart rate, breathing, and blood pressure. Hypothalamus controls temperature and hunger, cerebrum intelligence and memory, cerebellum coordination.
Explanation:
The first heart sound 'lub' is caused by the closure of the atrioventricular valves (mitral and tricuspid) at the beginning of ventricular systole. The second sound 'dub' is due to closure of semilunar valves (aortic and pulmonary) at the end of systole. Abnormal sounds (murmurs) indicate valve defects. This is due to turbulence, but the sound specifically is produced by valve closure.
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