active transport. The movement of ions or molecules across a cell membrane in the direction opposite that of diffusion, that is, from an area of lower concentration to one of higher concentration. Active transport requires the assistance of a type of protein called a carrier protein, using energy supplied by ATP.
Fuel cells can make an electricity from a simple electrochemical
reaction in which oxygen and hydrogen combine to form water. There are several
different types of fuel cell but they are all based around a central design
which consists of two electrodes, a negative anode and a positive cathode.
These are separated by a solid or liquid electrolyte that carries electrically
charged particles between the two electrodes. A catalyst, such as platinum, is
often used to speed up the reactions at the electrodes. Fuel cells are
classified according to the nature of the electrolyte. Every type needs
particular materials and fuels and is suitable for any applications. The
article below uses the proton exchange membrane fuel cell to illustrate the
science and technology behind the fuel cell concept but the characteristics and
applications of the other main designs are also discussed. Proton Exchange Membrane Fuel Cells (PEMFC)
The hydrogen ions permeate across the electrolyte to the
cathode, while the electrons flow through an external circuit and provide
power. Oxygen, in the form of air, is supplied to the cathode and this combines
with the electrons and the hydrogen ions to produce water. These reactions at
the electrodes are as follows:
Anode: 2H24H+ + 4e-
Cathode: O2 + 4H+ + 4e- 2H2O
Overall: 2H2 + O22H2O + energy
PEM cells operate at a temperature of around 80°C. At this
low temperature the electrochemical reactions would normally occur very slowly
so they are catalysed by a thin layer of platinum on each electrode.
Answer:
First law of thermodynamics is the conservation of energy states that energy is not created and not destroyed but only can be stored.
Thermodynamics second law states that total entropy of a system increases from lower to higher system and some of the energy is always wasted during the work done.
In the food chain plants are the producers which accept light energy and stored in the form of chemical energy and energy flow to the herbivores and higher trophic levels in the chemical form only and no new energy is created in between the chain (Fisrt law of thermodynamics). Heat is generated during respiration by plants and animals (wasted energy) and entropy also increases with the increase in level of the pyramid of energy (Second law of thermodynamics).
Inferior mesenteric artery
The part of the colon located distal to the left colic flexure is derived from the hindgut is supplied by the inferior mesenteric artery. The distal part (lower third of the rectum) is supplied by the internal iliac artery. The ileocolic artery supplying the cecum is a branch of the superior mesenteric artery.
