Answer:
Those capillaries that have endothelial cells tightly attached have an increase in cell-to-cell junctions, such as desmosomal junctions that are poorly permeable to substances.
These capillaries generally function as conductors or collectors and not as permeabilizers like the pulmonary capillaries that are fenestrated and allow a high passage of substances and gases.
The capillaries are waterproof and prevent the passage of substances or fluids such as in the blood-brain barrier that is very selective
Explanation:
The blood-brain barrier is too selective since it is not favorable for the organism that many fluids, drugs, substances or chemical compounds enter the brain space.
This is the reason why the vessels are waterproof and why pharmacology was challenged to invent drugs that could cross this barrier since it was considered impossible.
An example is dopamine, which in parkynson's disease the levo group is added to dopamine, thus forming levodopamine as a product, this is the only way that the drug crosses the blood-brain barrier and can pass the impermeable barrier generated by capillaries with endothelial cells that are close to each other or closely linked
D)Heat within Earth
Explanation:
The heat from within the earth is as a result of plate tectonics. Plates on the earth are driven by heat within the earth through convection currents.
- Plate tectonics suggests that the earth are broken into slabs that moves on the weak and ductile material called asthenosphere.
- Heat from within the earth causes the melting of asthenosphere.
- The riding lithosphere which is cold will sink into the asthenoshpere.
- Hot mantle materials will move to the surface thereby setting up a convection current.
- Heat from within the earth rises to the surface due to plate movement.
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Answer:
B- Photosynthesis
Explanation:
Chloroplasts are <em>chlorophyll-containing, eukaryotic cell structures</em> that function in photosynthesis by absorbing energy from sunlight, combining this energy with water and CO2 to convert them to sugars . This cell structure is known as a plastid. The sugars produced, are important for the survival of the plant.
Chloroplasts reproduce on their own, independent of the whole cell because they contain their own DNA. Plant chloroplasts are located in guard cells in plant leaves. Closely linked to these guard cells are tiny pores called stomata, which allow gas exchange required for photosynthesis.
Photosynthesis occurs in two stages:
- The light reaction stage
- The dark reaction stage
The Light reaction stage takes place in the presence of light. Clorophyll converts light into chemical energy in the form of ATP and NADPH. Both molecules produced, are used in the dark stage to produce sugar.
In the dark reaction stage, the stroma, containing enzymes, facilitates reactions leading to the production of sugars from ATP and NADPH. This process is also called the carbon fixation stage. The sugar produced can be stored in the form of starch for other processes such as respiration.
They are thus known as the "supporting cells" of the nervous system. The four main functions of glial cells are: to surround neurons and hold them in place, to supply nutrients and oxygen to neurons, to insulate one neuron from another, and to destroy and remove the carcasses of dead neurons (clean up).
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