Answer:
peptide antigens by MHC class II molecules
Explanation:
Helper T cells are activated by peptide antigens by MHC class II molecules. These antigens express on the surface of antigen-presenting cells (APCs). After activation, the T helper cells divide and secrete cytokines to assist the immune response.
None of the provided options are reasonable. <span>comparing nutrient concentrations between the photic zone and the benthic zone can not tell you whether differences in concentrations between the photic and benthic zone are due to uptake by phytoplankton or because nutrients are sinking to the sea bottom and ocean stratification is preventing mixing. The approach of c</span><span>ontrasting nutrient uptake by autotrophs at different locations under different temperatures would not provide useful information on limiting nutrients. but rather uptake rates at different temperatures. It is likely that e</span>xperimentally enriching some areas of the ocean and compare their productivity to that of untreated areas can provide an indication of limiting nutrients, but this is not advisable, as it would have to be done on a large scale, and one cannot be sure of the ecological consequences. Also, because it would not be a controlled experiment, other factors could create 'noise' in the data. The last option, <span>observe antarctic ocean productivity from year to year to see if it changes, also does not help, as there is no correlation between nutrient concentrations using this approach. The best approaches would be either the last approach, but with the additional monitoring of nutrient concentrations, or under a controlled laboratory experiment.</span>
The cell goes in a "dormant phase". A good example is the neuron. Neurons are very metabolically active but they don't divide so they go into a phase that doesn't include growth or replication of genetic material.
Answer:
False. Bone can be classified as a connective tissue because it provides support and structure to the body.
Explanation:
Connective tissue is those tissues that fill spaces between organs and other tissues, and also provide support to the organism. It is characterized by the presence of different types of cells separated by intercellular material synthesized by them.
The bony tissue is the principal structural and supportive connective tissue that differs from the other connective tissues because its extracellular matrix is mineralized, which makes it possible to accomplish its support and protection function due to its rigidity and hardness. The mineral that deposits in the osteoid matrix is the calcium phosphate, composing hydroxyapatite crystals. The bony tissue is a storage site of calcium and phosphate, which are available for maintaining constant the calcium blood levels according to the individual physiological needs.
Answer:
Viruses can use energy of living cells that they infect.
Explanation:
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