Organ, in biology, a group of tissues in a living organism that have been adapted to perform a specific function. In higher animals, organs are grouped into organ systems; e.g., the esophagus, stomach, and liver are organs of the digestive system.
3) is active transport because active transport requires energy.
Answer:
The correct answer is: C. Active Transport.
Explanation:
Because Na+ and K+ are ions, which makes them <em>charged molecules</em>, they can only diffuse through the cell membrane when using specialized protein channels. This is called <u>facilitated diffusion</u> and is a form of passive transport because sodium and potassium move <em>following their gradients</em>, which are made of the difference in concentration between the inside of the cell and the outside of the cell. For example, potassium is highly concentrated inside the cell and poorly concentrated outside the cell, so potassium diffuses from the inside to the outside to even the concentrations.
But the question asks in which process Na+ and K+ move in and out of the cell SIMULTANEOUSLY, so the answer is actually <u>active transport</u>. Active transport is the opposite of passive transport. While passive transport occurs naturally and doesn't need ATP (energy) to happen, active transport needs ATP because it moves molecules AGAINST their gradient. One of the most famous and important structures involved in active transport is the Na+/K+ pump, which consists of a <em>specialized protein using energy to enter 2 potassium ions and take out 3 sodium ions at the same time</em>. This Na+/K+ is fundamental to maintain the gradients, which are important for the correct functioning of many cells.
<h3>
Most railroad tracks are built from pieces of steel supported by wooden ties, and laid with a gap between the ends. </h3>
Explanation:
The reasons are:
Firstly , the thermal expansion of solid at higher temperatures.
During the summer season, the steel tracks may expand due to thermal expansion and if gaps are not laid the tracks will bend and lead to accidents.
Secondly, imbibition of water during rainy season.
During the rainy season the wooden tracks will imbibe water and swell. If gaps are not provided, this may result irregular levels of railway track. This may prove very dangerous and lead to railway accident.
Answer:
Oswald Avery, Colin MacLeod, and Maclyn McCarty showed that DNA (not proteins) can transform the properties of cells, clarifying the chemical nature of genes. Avery, MacLeod and McCarty identified DNA as the "transforming principle" while studying Streptococcus pneumoniae, bacteria that can cause pneumonia.
Explanation:
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