Lipids are hydrophobic macromolecules
The normal membrane potential inside the axon of nerve cells is –70mV, and since this potential can change in nerve cells it is called the resting potential. When a stimulus is applied a brief reversal of the membrane potential, lasting about a millisecond, occurs. This brief reversal is called the action potential
<span>A stimulus can cause the membrane potential to change a little. The voltage-gated ion channels can detect this change, and when the potential reaches –30mV the sodium channels open for 0.5ms. The causes sodium ions to rush in, making the inside of the cell more positive. This phase is referred to as a depolarisation since the normal voltage polarity (negative inside) is reversed (becomes positive inside). </span>
<span>Repolarisation. At a certain point, the depolarisation of the membrane causes the sodium channels to close. As a result the potassium channels open for 0.5ms, causing potassium ions to rush out, making the inside more negative again. Since this restores the original polarity, it is called repolarisation. As the polarity becomes restored, there is a slight ‘overshoot’ in the movement of potassium ions (called hyperpolarisation). The resting membrane potential is restored by the Na+K+ATPase pump.</span>
Answer: W = 6.4x10⁻²¹J
Explanation: <u>Work</u> is the energy transferred to or from an object due to the application of a force along a displacement.
The ion Na is gaining energy to move from a lower potential to a higher one.
For this to happen, the work done is calculated as
in which
W is work in Joules (J)
q is charge in Coulomb (C)
is potential difference in Volts (V)
The ion Na has one positive charge. In coulombs, the charge is
q = 1.6x10⁻¹⁹C
The potential difference in Volts is
= 40x10⁻³ or 4x10⁻²V
Calculating
W = 1.6x10⁻¹⁹. 4x10⁻²
W = 6.4 x 10⁻²¹ J
The work done to move an ion of sodium from the exterior to the interior is 6.4 x 10⁻²¹ J.
Answer:
True
Explanation:
lungs are responsible for the excretion of gaseous wastes, primarily carbon dioxide from cellular respiration in cells throughout the body.
Answer:
Agriculture negatively impacts coral reefs. Chemicals used by farmers, such as pesticides and fertilizers, runs off the land when it rains.
Coastal waters suffer from huge amounts of a variety of agricultural and industrial chemicals that are released into them. Fertilizers and pesticides used in agricul-tural development projects are discharged into the sea and might lead to coral reef destruction.