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Spring 2022 Final Exam Solutions on Digestion – Tufts University

The following are accurate digestion exam solutions for an assessment done at Tufts University in spring 2022. The solutions are mainly based on macronutrients. We can also do your nutrition exams in case you’re stuck with one of a similar kind. Our website hosts brilliant biology exam solvers from the best universities worldwide.

Briefly Analyze Popular Mysteries of Digestion

On the one hand, the process of digestion is entirely elementary, the hollow tube of the digestive system stores food temporarily, prepares it for absorption, absorbs what is absorbable, and rejects the rest as feces. On the other hand, such simplicity has challenging riddles within it. How is it that the gut can digest meat without digesting itself? How does it consume tripe, or the gut wall used as casing for some sausages, or even bone, without the cannibalistic self-destruction of its tissues? The stomach contains hydrochloric acid, and in quite a concentration (gastric juice is about 0.6% HCI). The popular appraisal of its strength is that a stomach's contents could burn a hole in the carpet. So why does the stomach not burn a hole within itself? And how can glands of living tissue manufacture such a corrosive substance as hydrochloric acid?

There are further problems. The human being, traditionally called an omnivore, can indeed eat a bewilderment of foods; yet he can starve to death with remarkable ease. The human system cannot cope with plants, trees, mosses, and most of the botanical world; it can cope best with botanical end-products, such as fruits, seeds, and nuts. The few plants known as vegetables are exceptions. The plant world, so suitable for all the herbivores and consumed so avidly by well over half of the world's animal species, is virtually forbidden to man. Forbidden too, despite our digestive ability to break down so many chemical compounds, are a few substances that have the power to poison us, destroy our lives, or merely affect our well-being disastrously. Eating earth or leaves or old newspapers will not do us good, and may do us harm, but poisons are in a different category. A substance is said to be a poison if less than 2 oz. of it - about 50 gms.- will either kill us or be seriously harmful. (Everything is harmful if consumed to excess, even bread, and water. Poisons are harmful if consumed minutely.)

Proteins are a further complexity. The body must have these within the diet and certainly absorbs them, but the body is normally resentful of foreign proteins and brings its powers of immunity to bear upon any such invasions by amassing anti- bodies counter the antigens. However, foreign proteins taken into the gut are customarily absorbed, transformed, and utilized without any disturbance whatsoever.

Also, what is hunger, and what is thirst? In general, we eat what we need in that we stay reasonably constant in weight. We drink without too much thought of the need for liquid, and yet do not dehydrate ourselves. We say 'enough', and scarcely pause to marvel at such precise comprehension of our various requirements.

A final conundrum, more perplexing to the chemist than the ordinary consumer, is that the body performs with speed and precision large numbers of chemical reactions that would normally take far, far longer if carried out in a laboratory at the same temperature and pressure. Anyone who has ever wielded a test-tube or a frying pan will know that chemistry happens faster when things are hotter; yet the body breaks down molecules, combusts them with oxygen, and builds up the molecules at the modest 98°F (36-7°C) temperature of the human frame. This is less than the temperature of bath-water, and the chemistry both of cooking and the test tube would be immeasurably slow if confined to such heat. A partial answer to the body's abilities is the profusion of enzymes, the natural catalysts which assist and promote biochemical reactions and are not used up in the process; but to define a catalytic enzyme is one thing. To explain how it achieves its remarkable role of initiating or accelerating any reaction, without being unduly involved, is quite another.

Explain The Structure of Proteins and How They’re Digested

Proteins (after the Greek word for primary or fundamental) are large molecules made up of chains of amino-acids. These amino- acids are joined together by what is called the peptide linkage, whereby the coach-amino-group (NH) is attached to a carboxyl group (COOH).

Some enzymes can break the linkage, and can add a molecule of water at the same time - hence the action called hydrolysis. Some links, as might be expected, are easier to break than others; so the long protein molecules become broken, firstly, into shorter lengths (polypeptides), then into very short lengths consisting of three amino-acids (tripeptides) or two amino-acids (dipeptides). Finally, there will just be the single amino-acids.

Traditionally called the body's building blocks the twenty different kinds of amino-acid which go to build up protein are true when fully digested and broken down into single units, the raw material for the manufacture of the body's tissues. The human apart from its bone and its fat is rich in protein, a fact appreciated by the occasional carnivore; but all proteins have to be broken down into their amino-acids before they can be built up again into useful protein. Digestion does the breaking down.

Elabrate the Structure And Digestion Of Carbohydrates

Carbohydrates (after the Latin for coal and the Greek for water) are compounds of carbon, hydrogen, and oxygen (but they lack the nitrogen crucial to protein). These three are joined together to form the three kinds of monosaccharides, namely glucose, fructose, and galactose, and all carbohydrates are built up of monosaccharide units. Once again the problem of digestion is breaking down big molecules into smaller ones. The big poly- saccharides, often called starches, have to be broken down.

They too have linkages, called glucosidic linkages, and the big poly- Saccharides are attached by enzymes at their linkages until they form disaccharides (two units) and monosaccharides (one unit). Unlike proteins, which are all big and which all have to be broken down, some carbohydrates are small. Glucose is just composed of single monosaccharide units, but glucose has to be made artificially.

There are two disaccharides present in food: Sucrose - found in cane sugar, and lactose found in milk, - Whether artificial or natural such carbohydrates need little or no breaking down, and therefore next to no time is necessary for their digestion; hence their use for those with disrupted digestions or the need for instant energy.

Explain The Structure And Digestion Of Fats

Fats (an Anglo-Saxon word) are, like proteins and carbo- hydrates, combinations of simpler units. These units are glycerol (or glycerin) and fatty acids, such as stearic acid, palmitic acid, and oleic acid. All such fats are, like carbohydrates, made up of carbon, hydrogen, and oxygen, but in different proportions- the fats have very little oxygen. A typical carbohydrate has equal amounts of carbon and oxygen and twice as much hydrogen. A typical fat has twice as much hydrogen as carbon, being made up principally of CH2 units, but only an atom or two of oxygen at one end of the molecule.

Another major difference between fats, carbohydrates, and proteins is that fats can easily be stored. The body's available stores both of protein and carbohydrate are very limited, but the body's willingness to store up supplies of fat bedevils large portions of the population. The fact that honey (a carbohydrate) lasts and so does biltong (a protein), while butter (a fat) goes rancid does not destroy the generalization that fat is easier and better to store. Weight for weight, fat has twice the fuel value of either protein or carbohydrate.

Whaich Major Enzymes Are Involved In Digestion And What Do They Do?

The all-important and all-skillful digestive enzymes, which act so effectively upon the casual assortment of foods consumed by the average human, make a long list. Their names and their products also tend to be lengthy. Nevertheless, the most crucial enzymes in digestion ought to be mentioned. Their products follow in parentheses.

From the salivary glands: Salivary amylase (maltose - a disaccharide) (Maltase glucose)

From the stomach: Pepsin (peptides) Rennin (casein-a milk protein)

from the pancreas: Trypsin (peptides) Lipase (glycerol and fatty acids) Amylase (maltose) Ribonuclease (nucleotides – proteins of cell nucleus) Deoxyribonuclease (nucleotides)

From the intestine: Carboxypeptidase (amino-acids) Aminopeptidase (amino-acids) Enterokinase (trypsin - same as the pancreatic enzyme) Maltase (glucose) Sucrase (glucose, fructose) Lactase (glucose, galactose)

Those from the salivary glands work best in neutral conditions, those from the stomach work best in acid, and those from the intestinal glands work best in neutral or alkaline conditions. The stomach's acidity is partly neutralized by an intestinal secretion of sodium bicarbonate, the same chemical which so many people pour, with such enthusiasm, into their stomachs.

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