| Course | NS105 Fundamentals of Nutrition |
|---|---|
| Unit | Unit 2 |
| Paper type | Digestion and absorption summary |
| Length | About 1,170 words, 7 pages double-spaced |
| Format | APA 7 student paper |
| School | Purdue University Global |
| Program | BS in Nutrition Science |
| Updated | October 2026 |
Free sample paper for NS105 Unit 2
A Turkey Sandwich, an Apple and a Glass of Milk, Organ by Organ: A Unit 2 Digestion and Absorption Summary
[Student Name]
Purdue University Global
NS105: Fundamentals of Nutrition
Unit 2 Digestion and Absorption Summary
[Instructor Name]
[Date]
The lunch and its composition are composite, with values rounded from standard food composition tables; the physiology sources cited are real.
The Lunch
The meal contains, approximately:
1. Two slices of whole-wheat bread: starch and some fiber, about 24 grams of carbohydrate and 4 grams of fiber, plus about 7 grams of protein.
2. Three ounces of sliced turkey: about 18 grams of protein and 3 grams of fat.
3. One slice of cheese and a teaspoon of mayonnaise: about 9 grams of fat and 5 grams of protein.
4. One medium apple: about 25 grams of carbohydrate, mostly fructose and glucose, and about 4 grams of fiber, much of it pectin.
5. One cup of 2 percent milk: about 12 grams of lactose, 8 grams of protein and 5 grams of fat.
Each nutrient is followed below as the meal moves through the digestive tract.
The Mouth
Chewing breaks the sandwich and apple into smaller pieces and mixes them with saliva. Salivary amylase begins breaking starch from the bread into shorter chains. Lingual lipase, secreted by glands in the tongue, begins work on fat, though its role in adults is small. Protein, lactose and fiber pass through the mouth essentially unchanged. The food leaves as a soft mass, a bolus, swallowed into the esophagus (Goodman, 2010).
The Stomach
In the stomach, strong acid stops salivary amylase and unfolds proteins, making them easier to digest. Pepsin, activated by the acid, begins breaking the turkey, bread, cheese and milk proteins into smaller pieces called polypeptides. Gastric lipase continues a small amount of fat digestion. Starch digestion pauses, since amylase does not work in acid. Lactose and fiber pass through unchanged.
The stomach also controls the pace. Churning mixes the meal into a semi-liquid called chyme, released into the small intestine a little at a time. Because this lunch contains fat and protein, stomach emptying is slower than it would be for the apple alone, which helps explain why a mixed meal keeps a person fuller longer.
The Small Intestine
Most digestion and nearly all absorption take place in the small intestine.
Starch. Pancreatic amylase, released into the first part of the small intestine, finishes breaking starch into small sugars. Enzymes on the intestinal lining split those into glucose, which is absorbed into the blood.
Sugars in the apple. Glucose is absorbed directly. Fructose is absorbed by a separate transport route, more slowly.
Lactose. Lactase, an enzyme on the intestinal lining, splits lactose into glucose and galactose, which are absorbed. In many adults, lactase production declines after childhood. In those people, some lactose passes undigested into the large intestine, where bacteria ferment it; whether this causes symptoms such as bloating depends on the dose, the amount of lactase remaining and the gut bacteria (Misselwitz et al., 2019). A single cup of milk is often tolerated even by people with reduced lactase.
Protein. Pancreatic enzymes, including trypsin and chymotrypsin, continue breaking polypeptides into smaller pieces, and enzymes on the intestinal lining finish the job. Amino acids and small peptides are absorbed into the blood.
Fat. Bile from the liver, stored in the gallbladder, emulsifies the fat from the turkey, cheese, mayonnaise and milk into small droplets. Pancreatic lipase then breaks triglycerides into fatty acids and monoglycerides, which form tiny clusters called micelles with bile salts. These carry the products to the intestinal lining, where they are absorbed, reassembled into triglycerides and packaged into chylomicrons, which enter the lymph rather than the blood (Goodman, 2010).
Fiber. Neither the bread's fiber nor the apple's pectin is broken down by human enzymes; dietary fiber is defined in the reference intakes as carbohydrate the human gut cannot digest (Institute of Medicine, 2005). Both pass on.
By the end of the small intestine, nearly all of the lunch's starch, sugars, protein and fat have been absorbed, and what moves on to the colon is mainly the fiber from the bread and apple, any lactose the person could not digest and water.
What Controls the Pace
Digestion is regulated rather than automatic. Hormones released by the stomach and small intestine respond to the meal's contents: when fat and protein from the turkey, cheese and milk reach the small intestine, the hormone cholecystokinin signals the gallbladder to release bile and the pancreas to release enzymes, and it slows stomach emptying so the intestine is not overwhelmed. Secretin, released in response to acid, prompts the pancreas to release bicarbonate, which neutralizes the acid arriving from the stomach so that pancreatic enzymes can work. Nerves linking the gut and brain contribute too, which is why the sight and smell of food can start saliva and stomach acid flowing before the first bite. These signals explain why a mixed lunch is handled differently from a sugary drink: the meal's own composition sets the pace of its digestion.
The Large Intestine
In the colon, bacteria ferment much of the apple's pectin and some of the bread's fiber, producing short-chain fatty acids that the colon cells use for fuel, along with gas. Insoluble fiber from the whole wheat adds bulk. Water and electrolytes are reclaimed, and the remaining material forms stool. The trip from mouth to elimination for a mixed meal usually takes a day or more, varying widely between people.
Absorbed Nutrients After Absorption
Glucose, galactose, fructose and amino acids travel in the blood through the portal vein to the liver, which handles them first, before anything is passed to other tissues. The liver converts galactose and most fructose to glucose or to stored forms. Fat, packaged in chylomicrons, bypasses the liver at first, entering the lymph and then the bloodstream, where it delivers fatty acids to muscle and fat tissue.
Summary Table in Words
1. Starch: begins in the mouth, pauses in the stomach, finishes in the small intestine; absorbed as glucose.
2. Protein: begins in the stomach, finishes in the small intestine; absorbed as amino acids and small peptides.
3. Fat: barely begins in the mouth and stomach; digested mainly in the small intestine with bile and lipase; absorbed and sent into the lymph.
4. Lactose: digested in the small intestine by lactase if present; otherwise fermented in the colon.
5. Fiber: not digested by human enzymes; partly fermented by bacteria in the colon.
Why the Order Matters
Following one meal shows that digestion is not a single event but a sequence in which each organ prepares the meal for the next. Fat and protein slow the stomach, so the sandwich and milk shape how quickly the apple's sugars reach the blood. Lactose depends on an enzyme that varies between people, and fiber depends on bacteria rather than the body's own enzymes. A summary organized by nutrient as well as by organ makes those differences visible.
References
Goodman, B. E. (2010). Insights into digestion and absorption of major nutrients in humans. Advances in Physiology Education, 34(2), 44-53. https://doi.org/10.1152/advan.00094.2009
Institute of Medicine. (2005). Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids. National Academies Press. https://doi.org/10.17226/10490
Misselwitz, B., Butter, M., Verbeke, K., & Fox, M. R. (2019). Update on lactose malabsorption and intolerance: Pathogenesis, diagnosis and clinical management. Gut, 68(11), 2080-2091. https://doi.org/10.1136/gutjnl-2019-318404
NS105 Unit 2 instructions, in plain terms
The digestion unit asks students to explain how the body breaks down and absorbs nutrients, usually by following a meal through the digestive tract. Prompts typically expect each organ described in order, the main enzymes and secretions named, absorption explained for each macronutrient and what happens to the nutrients afterward. Choose a realistic meal with starch, protein, fat, a sugar such as lactose and fiber, so every process has something to act on. Name enzymes at the level your text uses. Explain why fat needs bile and travels through the lymph. Address lactose and fiber, which behave differently from other nutrients. Mention how hormones and nerves regulate the process. Cite a physiology source. Four to five pages is typical.
How this NS105 Unit 2 example is built
A numbered list breaks the lunch into its components with approximate nutrient amounts. Separate sections follow the mouth, stomach and small intestine, each saying what happens to starch, protein, fat, lactose and fiber, with lactase decline explained and fat's route through bile, micelles and chylomicrons traced. The highlighted sentence summarizes what is left by the end of the small intestine. A section explains the hormones that control the pace, then the colon's fermentation of fiber. Another describes where absorbed nutrients go next. A five-line summary by nutrient follows, and a closing section explains why tracing one meal reveals each organ readying food for the next.
Reading the NS105 Unit 2 grading rubric
NS105 digestion summaries are usually scored on accuracy above all: correct organs, enzymes, sites of absorption and routes into the body. Completeness is a second criterion, covering all macronutrients the meal contains, including lactose and fiber. Points go to organization that a reader can follow, whether by organ, by nutrient or both. Explaining regulation, such as hormones that slow the stomach, earns credit for depth. Use of a credible physiology source and correct terminology count under evidence. The remaining marks reward plain prose and correct APA. A summary that treats digestion as a list of organs, or that sends fat into the blood the same way as glucose, typically loses accuracy points.
NS105 Unit 2 help: mistakes that cost points
Digestion summaries often describe each organ in general terms without saying what happens to specific nutrients there. Another frequent error is placing most digestion in the stomach, when the small intestine does most of the work. Students forget that salivary amylase stops in stomach acid or that fat needs bile before lipase can act. Fat's absorption into the lymph is commonly missed. Fiber is sometimes said to be digested, or left out entirely. Regulation is rarely mentioned. If your assigned meal is chosen and you are unsure where each nutrient goes, write down what the meal contains, and a writer can help you trace each component through the tract.
Get an NS105 Unit 2 example written to your instructions
Share the meal your Unit 2 prompt names, or the one you actually ate where the prompt lets you pick, with the instructions and rubric. The summary follows that meal stop by stop, with a table if the rubric asks for one, and is back in 24-48h. There is no charge for a first sample written this way. The paper above is an original model document written by our desk, not a submitted student paper and not an official Purdue University Global document.
More NS105 papers and BS in Nutrition Science samples
- NS105 Unit 1: Nutrient Definition Post
- NS105 Unit 3: Energy Calculation Set
- NS105 Unit 4: Carbohydrate Profile
- NS105 Unit 5: Fat and Protein Comparison
- NS105 Unit 6: Seminar Reflection
- NS105 Unit 7: Three Day Food Record
- NS105 Unit 8: Nutrient Density Comparison
- NS105 Unit 9: Dietary Guidance Analysis
- NS105 Unit 10: Nutrition Case Summary
NS105 Unit 2 questions, answered
Do I need to name every enzyme?
Name the ones your text names at this level, usually salivary amylase, pepsin, the pancreatic enzymes as a group and lactase at the intestinal lining. A summary that lists twenty enzymes without saying what each acts on reads as copied. It is better to name fewer and attach each one to the part of the meal it works on.
How long does a meal take to pass through?
It varies with the meal, which is why a careful summary gives a range and cites it. Fat and protein slow stomach emptying, while a mostly liquid meal leaves sooner. Whole-tract transit is usually described in days rather than hours. Giving a single precise figure, unless your text gives one, tends to draw a query from the grader.
Should the summary include the large intestine?
Yes, if the meal contains fiber, and nearly every realistic meal does. The colon is where water is reclaimed and where gut bacteria ferment part of the fiber into short-chain fatty acids, some of which the colon lining uses for fuel. Stopping at the small intestine leaves the fiber unexplained, and graders notice the gap.
Where can I find a free NS105 Unit 2 sample paper?
This page presents a complete Unit 2 digestion and absorption summary following a turkey sandwich, apple and milk lunch organ by organ, with margin notes and APA references.
Why does fat travel through the lymph instead of the blood?
After absorption, fatty acids are reassembled into triglycerides and packed into chylomicrons, which are too large to enter blood capillaries directly. They enter the lymph and reach the bloodstream later.