<span>The plasma membrane is both a barrier and gateway between the cytoplasm and ECF. It is selectively permeable—it allows some things through, such as nutrients and wastes, but usually prevents other things, such as proteins and phosphates, from entering or leaving the cell.</span><span>The methods of moving substances through the membrane can be classified in two overlapping ways: as passive or active mechanisms and as carrier-mediated or not. Passive mechanisms require no energy (ATP) expenditure by the cell. In most cases, the random molecular motion of the particles themselves provides the necessary energy. Passive mechanisms include filtration, diffusion, and osmosis. Active mechanisms, however, consume ATP. These include active transport and vesicular transport. Carrier-mediated mechanisms use a membrane protein to transport substances from one side of the membrane to the other. We will first consider the mechanisms that are not carrier-mediated (filtration, simple diffusion, and osmosis) and then the carrier-mediated mechanisms (facilitated diffusion and active transport).</span>
Answer:
The overall strategy employed in the catabolism of the carbon skeletons of the 20 amino acids is conversion to citric acid intermediates such as acetyl-CoA
Explanation:
The breakdown of the different carbon skeletons of the 20 amino acids is strategically channelled towards the citric acid cycle. Six major products are obtained in the catabolism of the carbon chain of amino acids and these products all enter the citrc acid cycle. The six major products are acetyl-CoA, α-ketoglutarate, succinyl-CoA, fumarate, oxaloacetate and pyruvate.
The amino acids that are broken down completely into acetoacetyl-CoA and/or acetyl-CoA are said to be ketogenic since they yield ketone bodies in the liver.
The amino acids that are broken down into α-ketoglutarate, succinyl-CoA, fumarate, oxaloacetate and pyruvate can be converted to glucose and glycogen and are said to be glucogenic. Pyruvate can further be converted to either acetyl-CoA or oxaloacetate. Some amino acids though are both ketogenic and glucogenic, e.g. tryptophan, threonine.
Carbohydrate macromolecules, or Polysaccharides
Chromosomes and autosomal or somatic cells
Formation of the Earth's Atmosphere. The early Earth was very different from our Earth today. The early Earth experienced frequent impacts from asteroids and meteorites and had much more frequent volcanic eruptions. There was no life on Earth for the first billion years because the atmosphere was not suitable for life.
