Positive selection of t cells occur in .the thymus
In order for plants to produce energy and maintain cellular function, their cells undergo the highly intricate process of photosynthesis. Critical in this process is the stoma. Stomata (multiple stoma) are located on the outermost cellular layer of leaves, stems, and other plant parts. An open stoma facilitates the process of photosynthesis in three ways. First, it allows light to enter the intercellular matter and trigger the process. Second, it allows for the uptake of carbon dioxide, a key chemical in producing plant energy. Third, it allows for oxygen to be expelled into the outside environment, a byproduct of photosynthesis that is no longer needed by the cell.
Answer:
apex refers to the highest point or vertex of a plant stem or root. The shoot apex is where fresh stems, leaves, and other parts of a plant grow after the old parts fall off or dry up.
Explanation:In experiments conducted plants with the apex grows and its height increase while the height of the plant without the apex does not change.In another experiment plant with the apex grows towards the direction of sunlight which is positive phototropic movement and the plant without the apex does not turn towards light.therefore we can conclude there is an effect of the apex on the growth of a plant.
The question is incomplete as it does not have the options which are:
A. Gram-negative bacilli cannot cause harm to the cell; only Gram-positive bacilli can harm the cell.
B. Gram-negative bacilli release endotoxins that cause cell injury and increased capillary permeability.
C. Gram-negative bacilli excrete elaborate exotoxins that interfere with cellular production of ATP.
D. Gram-negative bacilli enter the cell and disrupt its ability to replicate.
Answer:
B. Gram-negative bacilli release endotoxins that cause cell injury and increased capillary permeability.
Explanation:
Gram-negative bacteria are pathogenic in nature due to the composition of their cell wall. Their cell wall contains an additional layer of a molecule called lipopolysaccharides or LPS.
The LPS layer is toxic in nature and is known as endotoxin and is involved in the pathogenicity of the bacteria as the toxin causes the injury to the Endothelial cell membrane of the host cell.
When the bacteria cell is lysed and the LPS circulates in the blood, then LPS binds the receptors and acts on CD14. This attracts the neutrophils at the site and can cause vascular injury due to increased capillary permeability.
Thus, Option-B is the correct answer.
