Answer:
The mechanisms of transport across the cell membrane are as follow: 1- simple diffusion, 2- facilitated diffusion, 3- primary active transport and 4-secondary active transport
Explanation:
The cell membrane is a selectively permeable structure capable of transporting substances by different mechanisms. Simple diffusion is a type of passive transport (i.e. does not require energy) where non-polar molecules (e.g. O2, CO2) pass across the membrane by a process that does not require energy from the cell. Facilitated diffusion is another type of passive transport where larger polar molecules (e.g., glucose and amino acids) pass across the membrane by using specific transmembrane integral proteins. On the other hand, primary active transport is a type of active transport that uses chemical energy (e.g., ATP) to move substances such as metal ions (Na+, K+, Ca2+) across the cell membrane against their concentration gradient. Finally, secondary active transport is another type of active transport where transporter proteins are used to couple the movement of ions (e.g., H+ protons) down their electrochemical gradient to the transport of another ions/solutes against their concentration/ electrochemical gradient.
Before a cell can enter cell division, it needs to take in nutrients. All of the preparations are done during interphase.<span> Interphase is a series of changes that takes place in a newly formed cell and its nucleus, before it becomes capable of division again. It is also called preparatory phase or intermitosis.</span>
Answer:
Electron Transport Chain
In the third stage, electrons from the NADH and FADH2 molecules move to the electron transport chain (ETC). These electrons generate the required power to move protons through the mitochondria into the space between membranes. In the final stage of cellular respiration, oxygen combines with the electrons and protons to form water.
Answer:
Deleterious alleles appear sporadically in a population
Explanation:
A population with a deleterious allele will have no or few individuals that have the ability to pass along these traits. These alleles appear less in a population because of selective pressure but they are not always absent. The alleles appear less often but are are not always passed on and the others that are genetically fit are able to pass along their genes. The reason the population equilibrium is not zero is because these alleles do appear but they are not necessarily passed along. These individuals may not be able to reproduce or reach the age of reproduction.
Deleterious alleles appear more often, making individuals less fit genetically, i.e. they pass fewer copies of their genes to future generations. Put another way, natural selection purges the deleterious alleles.
