p.p1 growth. 4. Explain the term glycolysis. The

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1. Trace the digestion of protein.
The digestion of proteins begins in the mouth with chewing. The food is broken up into smaller pieces to allow it to be swallowed. Saliva aids in swallowing, however, it does not begin the process of breaking down the protein. Once it reaches the stomach, hydrochloric acid and the enzyme Pepsin commences the breakdown of the macronutrient. The acidity of the stomach assists in the unfolding of the proteins, while the Pepsin disassembles the protein chains into shorter and shorter chains. The contractions of the stomach then digest the macronutrient into a more homogenous mixture known as chyme, which is then emptied into the small intestine. The protein is then broken down further by pancreatic juice, the two major protein-digesting enzymes contained in it being chymotrypsin and trypsin. The small fragments are then broken down into individual amino acids by enzymes released by the small intestine, which are then pushed to absorption sites. In the lower sections of the small intestine, adenosine triphosphate (ATP) is required for the amino acids to be transported from the intestinal lumen to the intestinal cells in the blood. Once in the blood, the amino acids are transported to the liver, which break the amino acids into ammonia, which is then transformed into Urea to be expelled in urine. 

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2. Explain the concept of protein complementing.
Protein complementing is the combining of incomplete proteins to form a complete protein. A food is considered an incomplete protein when it does not contain one or more of the essential amino acids that are required to build cells. For example, beans and rice are complementary proteins.

3. Describe the diseases that result from inadequate intake of protein and protein-energy.
Protein deficiency is most common in the elderly and individuals who maintain a vegetarian or vegan diet. If an individual is deficient in protein it can lead to a wasting and shrinkage of muscle tissue, oedema (build up of fluids) and anaemia (lack of red blood cells or haemoglobin in the blood). Regularly getting sick may also be a sign that an individual is protein deficient, as immune cells are made from proteins. If children are deprived of adequate protein it may result in slow and stunted growth. 

4. Explain the term glycolysis.
The process of glycolysis extracts energy from glucose. By the end of the ten steps the glucose is divided into two three-carbon molecules know as pyruvates. 

5. Outline how and where the macronutrients enter the TCA cycle.
Glucose, fatty acids, glycerol and amino acids enter the TCA or Kreb cycle in slightly different ways. Firstly, units of the macronutrients are broken down to their atom components of carbon, hydrogen, oxygen and nitrogen. During metabolism, 2 compounds are produced which begin the TCA cycle. They are pyruvate and acetyl coenzyme A. Fatty acids enter the energy production cycle at the point of acetyl CoA. Ketogenic amino acids are converted directly to acetyl CoA, while glycogenic amino acids can enter the Kreb cycle directly. Glycolysis