Enzymes & Digestion - The Digestive System (GCSE Biology)
The Digestive System
The Human Digestive System
Key Terms
The digestive system is involved in the digestion and absorption of food.
Digestion is the breakdown of food from large, insoluble molecules, to small, soluble molecules. Absorption involves these small, soluble molecules being taken into the bloodstream through the wall of the intestine. Food moves through the gut by peristalsis.
Ingestion is the intake of substance into the body via the mouth e.g. through eating and drinking.
Assimilation is the movement of digested food molecules into the cells where they are used.
Egestion is the passing of undigested food as faeces through the anus.
Loss of watery faeces is known as diarrhoea and oral rehydration therapy can be used to treat it in order to replace the lost fluid. A cause of this can be cholera in which a bacterium produces a toxin that causes movement of chloride ions into the small intestine and thus, water follows due to osmosis. This leads to diarrhoea, dehydration and loss of
salts from the blood.
Breaking Down Food
The human digestive system is responsible for the break down of food and absorption of nutrients. Large, insoluble molecules cannot be absorbed into the bloodstream. The digestive enzymes hydrolyse them into small soluble molecules that can be absorbed. In simple terms, the food is broken down into small pieces, which can cross cell membranes in the small intestine (where food is absorbed).
Mechanical Digestion
- There is physical breakdown of food via mechanical digestion (e.g. teeth, stomach churning) and no chemical changes.
Teeth
- The teeth play an important part in mechanical digestion.
There are different types of teeth with different functions:- Incisors – are sharp for biting and cutting
- Canines – are sharp for tearing and gripping
- Premolars – are flat for crushing and tearing
- Molars – are flat for grinding and crushing
- The structure of human teeth.
- Pulp – soft tissue with blood vessels and nerves
- Dentine – are soft and forms a significant amount of the tooth
- Enamel – outer layer of the tooth that is hard
- Cement – similar to bone around tooth to hold it in place
- Bone – the tooth is rooted here and held in place
- Gum – soft tissue surrounding the tissue and bone to protect
them
- Teeth can decay. Bacteria together with sugars from food can coat your teeth and when the bacteria respire and produce acid which dissolves the enamel and dentine.
- Proper care must be taken of your teeth. This includes a good diet with a sugar restriction and regular brushing to clear the coat of bacteria.
Chemical Digestion
- Mechanical digestion alone is not enough. Mechanical digestion is not enough to allow for food to be absorbed. Just chewing your food into small pieces is not enough to allow cells of the digestive system to absorb much needed nutrients.
- Enzyme-driven breakdown is via chemical digestion (e.g. lipase enzymes) to breakdown large insoluble molecules to smaller soluble molecules that can be absorbed.
Absorption
- The small intestine is the area for absorption of digested food. Water is absorbed both in the small intestine and colon but most occurs in the small intestine.
- The small intestine has villi and microvilli. These are finger-like projections that increase the surface area over which molecules are absorbed.
- Microvilli are associated with a network of capillaries. This allows for efficient absorption.
- Microvilli are also associated with lacteals. These aid in the absorption of fats after digestion. Lacteals carry a fluid called lymph and fats are transported through this to blood vessels.
Digestive Organs
Overview of The Digestive System
The digestive system involves many organs. Digestion can be a complicated topic, so we will begin by giving you a summary of the role of each digestive organ part of the alimentary canal.
Products of Digestion
The products of digestion are absorbed into the bloodstream in the small intestine. When they enter the bloodstream, they can be used for several things, including:
- Building carbohydrates – the simple sugars absorbed (maltose, fructose, glucose) can be used to build new carbohydrates. For example, glucose can be stored as glycogen in the liver.
- Building proteins – the amino acids absorbed can be used for building protein. For example, bodybuilders often eat lots of protein to increase the number of amino acids for muscle synthesis.
- Building lipids – the fatty acid and glycerol molecules absorbed can be used to store fat. For example, if you eat lots of high-lipid foods, you are likely to build up more and more fat stores.
- Respiration – some of the glucose from carbohydrate digestion is used to release energy via respiration. This is why food is so important for daily function and especially for exercise.
FAQs
Enzymes are biological catalysts that speed up chemical reactions in the body. They are made of proteins and are found in every living cell.
Enzymes play a crucial role in digestion by breaking down large molecules of food into smaller, more manageable molecules that the body can absorb and use for energy. Different enzymes are responsible for breaking down different types of food, such as carbohydrates, proteins, and fats.
The human digestive system is the organ system responsible for breaking down food into small molecules that can be absorbed and used by the body for energy, growth, and repair. The main organs of the digestive system include the mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus.
In GCSE biology, students learn about the different organs of the digestive system and their functions, as well as the process of digestion, which involves mechanical and chemical digestion. Mechanical digestion occurs when food is physically broken down into smaller pieces, while chemical digestion involves the use of enzymes to break down food molecules into simpler forms.
The Digestive System works by breaking down food and absorbing its nutrients through a series of processes that begin in the mouth and end in the rectum. Food is mechanically broken down in the mouth through chewing and mixed with saliva, which contains the enzyme amylase to begin breaking down carbohydrates. The food then travels down the esophagus into the stomach where it is mixed with digestive juices and further broken down. From the stomach, the partially digested food moves into the small intestine where it is mixed with digestive enzymes from the pancreas and bile from the liver. This mixture further breaks down the food, allowing the small intestine to absorb the nutrients. The remaining waste products move into the large intestine, where water and electrolytes are absorbed before being eliminated from the body.
There are several organs involved in the digestive system, including:
Mouth: where food is ingested and mechanically broken down by teeth and tongue.
Pharynx: the back of the throat which connects the mouth to the esophagus.
Esophagus: a muscular tube that connects the pharynx to the stomach.
Stomach: a muscular sac that mixes food with digestive juices and breaks it down into a liquid mixture.
Small intestine: a long, narrow tube where most of the nutrients from the broken-down food are absorbed into the bloodstream.
Large intestine: a wider tube where water and electrolytes are absorbed and the remaining waste material is stored until it is eliminated.
Rectum: the lower part of the large intestine where feces are stored.
Anus: the opening at the end of the digestive tract where feces are eliminated from the body.
There are also several accessory organs that help with digestion, including the liver, pancreas, and gallbladder. These organs produce and release substances that aid in the digestion and absorption of nutrients.
The Digestive System is important because it allows the body to break down food and absorb its nutrients. Without the Digestive System, the body would not be able to get the energy and nutrients it needs to function properly.
There are two main types of digestion in the digestive system: mechanical digestion and chemical digestion.
Mechanical Digestion: It is the physical breakdown of food into smaller pieces, making it easier to swallow, move through the digestive tract, and ultimately, absorb the nutrients. This type of digestion begins in the mouth with the action of the teeth and tongue, which break down the food into smaller pieces.
Chemical Digestion: It is the process of breaking down food into simpler chemical compounds through the use of enzymes and other digestive secretions. This type of digestion occurs mainly in the stomach and small intestine. The digestive enzymes break down proteins, carbohydrates, and fats into their basic building blocks, such as amino acids, simple sugars, and fatty acids.
Both types of digestion work together to ensure that food is properly broken down and nutrients are extracted and absorbed into the body.
The products of digestion depend on the type of food that is being digested. Carbohydrates, proteins, and fats are broken down into their basic building blocks, which can then be absorbed into the bloodstream and used by the body for various functions. Here are some examples of the products of digestion:
Carbohydrates: Carbohydrates are broken down into simple sugars, such as glucose, fructose, and galactose.
Proteins: Proteins are broken down into amino acids.
Fats: Fats are broken down into fatty acids and glycerol.
Other products of digestion may include vitamins, minerals, and water. These nutrients are also absorbed into the bloodstream and transported to various organs and tissues throughout the body. The digestive system plays a critical role in breaking down food and extracting the nutrients that the body needs to function properly.
The products of digestion can be used for various functions in the body. Here are some examples:
Carbohydrates: Glucose is the main source of energy for the body’s cells. It is used to fuel cellular processes and activities.
Proteins: Amino acids are used to build and repair tissues in the body, such as muscle tissue, skin, and hair. They are also used to make enzymes, hormones, and other important molecules.
Fats: Fatty acids and glycerol are used to make cell membranes, hormones, and other molecules. They are also stored in adipose tissue and can be used for energy when glucose levels are low.
Vitamins and minerals: These nutrients are used for various functions in the body, such as maintaining healthy bones, supporting immune function, and promoting wound healing.
Overall, the products of digestion provide the body with the nutrients it needs to function properly and maintain good health.
Yes, enzymes can be affected by changes in temperature or pH. Enzymes work best at a specific temperature and pH, and any changes outside of that range can cause the enzyme to denature, or stop working.
The Human Digestive System can be affected by diseases or conditions, such as acid reflux, ulcerative colitis, or Crohn’s disease. These conditions can cause inflammation, pain, and other symptoms that can impact the ability of the Digestive System to function properly.
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