Answer:
B. The membrane lets certain substances move across it freely, while others must move through a “gate”.
Explanation:
Selective permeability is a property of cellular membranes that only allows certain molecules to enter or exit the cell. This is important for the cell to maintain its internal order irrespective of the changes to the environment. For example, water, ions, glucose and carbon dioxide may need to be imported or exported from the cell depending on its metabolic activity. Similarly, signaling molecules may need to enter the cell and proteins may need to be released into the extracellular matrix. The presence of a selectively permeable membrane allows the cell to exercise control over the quantum, timing and rate of movement of these molecules.
Answer:
The correct answer would be D) tissue.
In biology, the level of organisation from simplest to complex level can be summarized as:
Organelles → cells → tissues → organs → organ systems → organisms → populations →communities → ecosystem → biosphere.
It is clear that tissue is organization level that exists between cells and organs.
When similar cells are assembled together to perform specific function, the assembly or this organization is said to be the tissue.
There can be different types of tissues such as muscle tissue, nerve tissue et cetera.
Similarly, tissues arrange themselves to carry out specific function in the form of organ.
For example, heart is made up of cardiac tissue.
Answer:
a. insulation
Explanation:
The myelin sheath provides increased cell isolation (increased membrane resistance) because there are no membrane leakage channels in which there is myelin.
In addition to no membrane leakage channels, there is also virtually no type of membrane channel when there is myelin sheath (eg sodium and potassium pumps), which causes the cell a lower need for protein synthesis, or that is, less energy expenditure.
Answer:
The correct answer is option - d. Production of primary spermatocytes.
Explanation:
The accessory cells or supporting cells present within the seminiferous tubules of reproductive system termed as the Sertoli cells. They play various roles in the body and reproductive system.
Sertoli cells make blood-testis barrier in adjacent Sertoli cells in the seminiferous tubules. These cells secrete different types of enzymes and hormones such as inhibin which are also secreted by ovary and placenta in females. Sertoli cells produce seminiferous tubular fluid to provide nutrition to the sperm. Apoptotic germ cells are timely eliminated by these cells.
Thus, the correct answer is option D. Production of primary spermatocytes.
Answer:
amphibians because it is a cold blooded vertebrate and has aquatic gill breathing larvea
Explanation:
