Use the following information to answer questions 18 through 20. despite its name, the pacific sea horse is actually a type of fish. its horse-shaped head gives it its name. this creature lives in the pacific waters off the west coast of the americas, from peru to southern california. like many other ocean fish, sea horses face the constant challenge of losing water to their saltier environment. 18) when a pacific sea horse’s body loses water to its environment, which process is responsible? a) exocytosis b) facilitated diffusion c) osmosis 19) when the sea horse eats a meal, its body breaks down organic molecules in the food. some of those molecules enter cellular respiration, which ultimately produces the molecule atp. in which part of the sea horse’s cells is atp produced? a) golgi apparatus b) vacuoles c) mitochondria 20) when a sea horse sees a predator, its nervous system kicks into high gear. a charge reversal wave will travel the length of the nerve cell. when the impulse reaches the end of one nerve cell it must travel across the synapse to the next cell. neurotransmitters exit one cell and enter another via a method of active transport called, exocytosis. which structure is responsible for transmitting signals from one nerve cell to the next via this process? a) ribosome b) cell membrane c) nucleus

The hypotonic cells lose water through OSMOSIS. MITOCHONDRIA produces ATP needed to accomplish other cell functions. Through the CELL MEMBRANE, a neuron sends signals to another one. 18)C / 19)C / 20B.  

18) The sea horse’s body loses water to its environment through OSMOSIS

In this example, the cell is hypotonic, while the sea is hypertonic.

The hypertonic solution has a higher concentration of solute than the interior of the cell.  

Osmosis is the phenomenon that occurs when two dilutions of different concentrations -for instance, the interior of the cell and the seawater- are separated by a semipermeable membrane.

The membrane allows the pass of water but not solute. Hence, water can move from the most diluted side (the cell) to the less diluted one (the sea).  

Water tends to go from the hypotonic solution to the hypertonic one and keeps doing so until concentrations on both sides get equal.

19) The sea horse’s cells produce ATP in the MITOCHONDRIA

Mitochondria are one of the biggest organelles in the cell and are in charge of cellular respiration.

Through this process, the organelles degrade organic molecules, releasing chemical energy from their bindings.

Through this process they consume oxygen.  

The released energy is stored as ATP and then is used in other cellular activities.  

Mitochondria are more grouped in areas or tissues with higher energetical requirements.

20) The CELL MEMBRANE is responsible for transmitting signals from one nerve cell to the next via exocytosis.

The central nervous system generates an action potential that travels to the target activating the calcium channels.

Calcium triggers vesicles fusion to the presynaptic membrane releasing a neurotransmitter into the synaptic space.

Once there, the molecule binds to its receptors on the postsynaptic membrane, causing ion channels to open.

The activation of different receptors cause a change in the postsynaptic membrane modifying the cell activity.  

The correct answers are:

18) C. Osmosis

19) C. Mitochondria

20) B. Cell Membrane

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18.

The correct answer is option C) Osmosis.

The transport of the water molecules takes place through the process of osmosis. Osmosis is the movement of the water molecules down the concentration gradient through a semipermeable membrane.

19.

The correct answer option C) Mitochondria.

In the eukaryotic cells, the mitochondria is the site of the ATP synthesis, that is why, it is also referred as powerhouse of the cell.

20.

The correct answer is option B) Cell Membrane .

During the excitation of the cells, depolarization of the cell membranes takes place by the exchange of the ions. Hence, the cell membrane are responsible for the transmission of the signals propulsion.