The Journey of a cheese sandwich

Food Groups

Carbohydrates- are the starches and sugars that provide the energy our bodies need to function and grow. Almost all of the carbohydrates we consume come from the plant source. They produce glucose as well. Glucose gives us quick energy, but our body cells can't use heaps of it all at once so it saves some in our liver and muscles, when it's called glycogen. Good sources are cereals, bread, pasta, rice and potatoes.

Minerals- We needed it in small amounts to maintain health. Found in Salt, milk (for calcium) and liver (for iron). It gives us strong teeth and bones as well.

Fibre- Fibre is indigestible. It also provides other health benefits such as lowering the risk of diabetes and heart disease. It also controls the blood sugar levels. It aids in weight loss. It’s in vegetables, bran e.t.c.

Protein- Foods such as meat, eggs, and beans contains protein. Our body nerves, tissues, bones all are made up of proteins. So proteins become very necessary for us to grow and repair. Another function of protein is that it produces antibodies which fight with the bacteria, viruses and many foreign substances that are harmful for the body.

Fats- It’s provide energy. It keeps skin and hair healthy. Fat is stored as back up energy and insulate it against cold. Butter, oils, nut contain fats.

Vitamins- We need it in small amounts to maintain health. But it can’t be stored in the body. It also gives good eye sight. Dairy foods, fruit, vegetables are some example.

Water- Water protects our organs and body parts and holds them together. Water is essential for our body cells, it gives them strength. Water is used to transport nutrients, waste matter, hormones and other things in our body. It keeps the body hydrated. Found in fruit juice, milk e.t.c.

Why the body needs food?

The human body is incredibly complex. Every second, millions of physiological and chemical reactions take place in order to maintain good health. The body both creates things (e.g. heat, muscle, proteins, RNA, hair, nails, enzymes, fat tissue, bones) and breaks things down (food, stored fat, etc.). These anabolic and catabolic processes, along with all organs and systems, need fuel to enable them to function. The fuel or energy that the body uses comes from the food and drink that we consume in our diet. In a nutshell, food is human gasoline.

Organs of the digestive ...

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Why the body needs food?

Organs of the digestive system

Let's say I've picked up a cheese sandwich for lunch. Before I even take a bite, my nose it and signals the , which sends word to the controlling my mouth's salivary (spit) glands. Once the glands have their cue, they get busy secreting juices, making my mouth water. When I bite into the sandwich, the salivary glands get even more excited and secrete more saliva, making the moister and easier to swallow.

Then the cheese sandwich's journey begins when it is taken into the mouth, this process is ingestion. Whilst in the mouth, my teeth make the large particles broken down into much smaller particles, by chewing, which also mixes the food with saliva which contains a carbohydrase enzyme. This amylase digests the starch in the sandwich to glucose. The saliva is produced in the three salivary glands. These are called, parotid, sublingual and submandibular.

Before the sandwich even leaves my mouth, an enzyme in my saliva called amylase begins to break down the carbohydrates in the bread. When I swallow, the sandwich pieces slide down my pharynx, also known as the throat. They then come to a fork in the road: One pathway is the esophagus, which leads to the stomach, and the other follows the trachea, which leads to the . When the sandwich is swallowed, the food reaches the esophagus. The reason why the food goes down the oesophagus rather than the windpipe is that a flap called the epiglottis drops over the windpipe stopping the sandwich particles from getting into the lungs.

The oesophagus links the mouth and the stomach together, so the particles of the cheese sandwich enter the stomach organ next, where the food mixes with a protease enzyme which digests protein. The carbohydrates which were digested in the mouth were used in the human body for energy. There is high of starch content in the bread of the cheese sandwich. The carbohydrates are like a body fuel. Professional sportsmen and women need a diet high in carbohydrates because they are active and need energy. Protein, on the other hand which will be found in cheese is used for building cells. Proteins are vital for growth and to repair damaged areas of the human body. Hydrochloric acid is present in the stomach to kill bacteria. It has a low pH, and the enzymes produced by the stomach work best in acidic conditions.

The food empties from the stomach into the duodenum where it is mixed with enzymes and salts produced by the liver and enzymes made in the pancreas. The pancreas secretes three main enzyme types: protease enzymes, carbohydrase enzymes and also lipase enzymes run into the duodenum at the top the small intestine, where it continues its journey. The fats in the sandwich, which are in the butter and the cheese, are also used for energy. Fats act as a store of energy, which are used only when the carbohydrates run out. If there is too much fat it will store up and become obvious to other people that too much are stored. Bile is also alkaline to give the correct pH for the enzymes in the small intestine. The small intestine produces more enzymes to further digest proteins, fats and carbohydrates.

Around the oesophagus and throughout the small intestine (duodenum and the 20ft long ileum) are circular muscles which press the sandwich particles along in a contacting and relaxing motion, so the food gets pressed along. This contracting and relaxing motion is called peristalsis. The muscles responsible for peristalsis need to be regularly exercised. The way these muscles get exercised is not just by normal foods going down and the muscles pressing the particles along. They become stronger by fibre going down and because fibre is difficult to digest the muscles have to press hard and like any other muscles in the human body, they become stronger when they are worked on.

In the small intestine there are millions of villi. These are small, but visible to the human eye, finger like structures which line the small intestine and are perfect for absorbing the food. The main reason why villi are so good at absorbing food is that they have a thin layer of outer cells, which act as a cell, called micro-villi. Whilst villi are structures, micro-villi are tiny cells outside the villi. The villi also have a high blood supply and provide a big surface area for absorption. In the small intestine the food is absorbed through the gut wall into the blood, which takes it around the body to wherever the particles are needed. The job of the enzymes in the small intestine is also to break down the foods.

Chemical digestion, under the control of enzymes throughout the digestive system, takes up to twenty four hours to complete, depending on what the is being digested. Ultimately this is very thorough. Mechanical digestion on the other hand is done mostly in the mouth (where the teeth are biting down the cheese sandwich into much smaller pieces), but also in the stomach which churns food through muscular action. Mechanical digestion happens quickly but is less thorough at breaking down food. Only particles which have been chemically digested are able to pass through into the blood through the cell wall.

The next part of the digestive system is the large intestine. Here the water is absorbed so it is not wasted and passed out with the faeces. Water plays a major part in digestion as 75% of our body is made up of water. The rectum stores the waste products and non-digestible food and completes the re-absorption of water. Finally, when convenient, the waste faeces are passed out of the body through the anus. This is called egestion.

Peer Reviews

Here's what a star student thought of this essay

skatealexia

3rd of Jul 2012

Quality of writing

Minor grammatical errors in places. Spelling and punctuation appear fine. The candidate uses a conversational tone to describe the science behind the cheese sandwich but this is a path I would avoid. The candidate could have made the journey clearer using concise subheadings to show each body system and bullet points to make the information easier to read.

Level of analysis

Whilst the general properties of the seven different types of nutrients are mentioned, they are only outlined in basic scientific detail. To gain higher marks this would go into greater scientific depth. I also do not think this directly answers the question of a journey of a cheese sandwich as I would focus on the contents of a basic cheese sandwich directly and their different journey rather than focus on generic nutrients. The candidate under the heading why does the body need food uses too many words and the scientific information is waffly and not concise or in depth enough. The actual journey itself of the cheese sandwich is described in baseline depth. However the depth of information and the synthesis of different organ systems to gain a larger picture is very good for this level of candidate. The candidate does not mention the action of the pancreas or liver which would further boost their grade.

Response to question

Overall response to the question is good. The candidate addresses a number of different body systems and enzymes although the level of science used is quite basic. The language used can be simplistic in places.

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