Chapter 2 -A. Food and Digestive system(ICO8).docx

chapter 2 ========= structure and function of the body of living things =================================================== A. **Food and Digestive System** **[Food]** 1. **The Role of Food for the Body** Needing food or nutrients is one of the characteristics of living things. Eating is one...

chapter 2 ========= structure and function of the body of living things =================================================== A. **Food and Digestive System** **[Food]** 1. **The Role of Food for the Body** Needing food or nutrients is one of the characteristics of living things. Eating is one way living beings sustain their lives. Food contains substances that the body needs to grow and develop. It also provides energy for living beings to carry out their activities. Walking, running, playing, and other activities are possible because of energy. When food is converted into energy, the released energy is measured in calories. Calories in the food you eat provide energy as heat to help your body function. Without calories, your organs cannot work properly. The calorie needs of each person vary based on factors like gender, age, activity level, weight, and health condition. If someone consumes more calories than needed, it can lead to weight gain and even obesity. Generally, men need around 2,500 calories per day, while women need around 2,000 calories per day. 2. **Nutrients** Food entering the body is digested by the digestive system, breaking it down into nutrients. Nutrients are organic and inorganic chemicals in food that the body needs to function. Nutrients are divided into six categories: carbohydrates, proteins, fats, vitamins, minerals, and water. **a. Carbohydrates** Functions of Carbohydrates for the Body: 1. As an energy source. Each gram of carbohydrate produces 4.1 calories. 2. Maintaining the body\'s acid-base balance. 3. Important in metabolic processes. 4. Forming cell structures by binding proteins and fats. Types of Carbohydrates: - **Simple Carbohydrates**: Small molecule chains, often called \"sugars.\" They include monosaccharides (like glucose, fructose, and galactose) and disaccharides (like maltose, lactose, and sucrose). Simple carbs provide short-term energy but are quickly digested, leading to rapid increases in blood sugar and making you feel hungry again. Examples: Cakes, fruit juice, fruit concentrate, and sugar. - **Complex Carbohydrates**: Longer molecule chains that take more time to digest, providing sustained energy and making you feel full longer. Examples: Starch (found in sago, bread, cassava, rice, corn, and sweet potatoes) and fiber (found in vegetables and fruits). Fiber aids digestion but is not a nutrient since it can\'t be digested by the body. **b. Proteins** Functions of Proteins for the Body: 1. As an energy source, with each gram producing 4.1 calories. 2. Maintaining acid-base balance. 3. Building body cells and tissues. 4. Repairing damaged cells and tissues. 5. Creating essential substances like enzymes and hormones. Proteins are made of amino acids, classified into essential (not produced by the body, must come from food) and non-essential (produced by the body). Proteins can be obtained from animals (e.g., eggs, fish, meat) or plants (e.g., soybeans, long beans, green beans). **c. Fats** Functions of Fats for the Body: 1. As an energy source, with each gram producing 9.3 calories. 2. Dissolving vitamins A, D, E, and K. 3. Protecting internal organs from impact. 4. Insulating the body from cold. 5. Storing energy under the skin. 6. Being part of certain cell components, like cell membranes. Types of Fats: **- Saturated Fats:** Found in meats, coconut milk, and dairy products. They can raise bad cholesterol (LDL), increasing heart disease and diabetes risk. **- Unsaturated Fats:** Found in avocados, nuts, and olive oil. They help control cholesterol, insulin, and blood sugar levels, and stabilize heart rhythm. **- Trans Fats:** Found in fried foods, they increase heart disease risk by raising cholesterol levels. **d. Vitamins** Vitamins are organic nutrients needed in small amounts to help the body function. They don\'t provide energy but are essential for speeding up biochemical and metabolic processes. Lack of vitamins can cause deficiency diseases. Types of Vitamins: \- **Water-Soluble Vitamins**: Include vitamins B and C, which can\'t be stored in the body and need to be consumed daily. \- **Fat-Soluble Vitamins:** Include vitamins A, D, E, and K, which can be stored in the body\'s fat tissues. **e. Minerals** Minerals cannot be produced by the body and must come from food. They help maintain acid-base and ion balance, form tissues, and are components of hormones and enzymes. Types of Minerals: \- **Macro Elements:** Needed in large amounts (e.g., sodium, chloride, potassium, calcium, phosphorus, magnesium, sulfur). **f. Water** Water is the most important nutrient as 70% of our body is made up of water. It helps regulate body temperature and removes waste. It\'s recommended to drink 2 liters of water daily to keep your body functioning properly. 3. **Food Additives** Food additives are substances added to food to enhance flavor, color, preservation, aroma, and texture. Here are some common types of food additives: **a. Sweeteners** Sweeteners are used to add sweetness to food. Natural sweeteners include table sugar, palm sugar, and coconut sugar. Artificial sweeteners, such as aspartame, sorbitol, and cyclamate, are found in candies and sodas. Consuming too many sweeteners can lead to health issues like diabetes. **b. Color Additives** Color additives make food look more appealing. Natural color additives include turmeric, butterfly pea flowers, dragon fruit, and suji leaves, which are safe to consume. However, synthetic color additives, especially those meant for fabrics, can be harmful and cause diseases like cancer. **c. Flavor Enhancers** Monosodium Glutamate (MSG), often called \"micin,\" is a common flavor enhancer that makes food taste more savory. While MSG can improve taste, excessive consumption can cause health issues like headaches and dizziness. The safe limit for MSG consumption is 120 mg per kg of body weight. Natural flavor enhancers like salt, garlic, onions, and pepper are healthier alternatives. **d. Preservatives** Preservatives are added to food to extend its shelf life and prevent spoilage. Natural methods of preservation include salting and sugaring. Artificial preservatives include benzoic acid, sodium benzoate, and potassium benzoate. Overconsumption of these preservatives can lead to health problems like cancer. **e. Aroma Additives** Aroma additives are used to make food smell more appealing, often mimicking natural fruit aromas. These additives are used to create the illusion of natural flavors in foods and drinks. For example: vanilla extract, lemon extract, and menthol. **f. Thickeners and Emulsifiers** Thickeners and emulsifiers are added to stabilize and improve the texture of food. Examples of thickeners include agar-agar, tapioca, and gelatin. Emulsifiers, such as lecithin found in mayonnaise and butter, help maintain the distribution of fat in water, preventing separation. 4. **Healthy Diet and Nutrition Facts** **1. Healthy Diet** A healthy diet means eating a balanced variety of nutritious foods and reducing the intake of unhealthy foods. This doesn\'t mean eating less, but rather choosing nutritious foods in the right portions. Foods to avoid or limit include fried foods, sodas, and packaged foods. One recommended healthy diet method is the \"My Plate\" method. This method helps you eat regularly while meeting daily nutritional needs. When using the \"My Plate\" method, divide your plate as follows: half the plate should be 2/3 vegetables and 1/3 fruits, and the other half should be 2/3 carbohydrates and 1/3 protein. Additionally, remember to drink 8 glasses of water a day, wash your hands before eating, and exercise for at least 30 minutes daily. **2. Nutrition Facts** Nutrition facts are labels on food or drink packaging that provide information about the nutritional content of the product. Typically, the nutrition facts are based on a single serving size. Nutrition facts help people make informed choices when buying food or drinks. The label includes serving size, total energy (calories), and the percentage of daily value (% DV). - Serving Size: Indicates the amount of food consumed in one serving. - Total Energy: Shows the number of calories (kcal) obtained from one serving. - Percentage of Daily Value (% DV): Indicates the amount of nutrients obtained from one serving as a percentage of the daily recommended intake. If you consume more than one serving of a product, the total intake of calories and nutrients will be higher. **[Digestive System]** The food you eat needs to be digested so your body can get the nutrients it needs to function. Did you know that the digestive system, from the mouth to the rectum, is about nine meters long? The organs in the digestive system are divided into three main functions: digestion, absorption, and elimination. **A. Digestion** Digestion is the process where the food you eat is broken down into small nutrients. - **Mechanical digestion** involves physically breaking food into smaller pieces, which happens in the mouth and stomach. - **Chemical digestion** uses enzymes to break down food, occurring in the mouth, stomach, and small intestine. For example, in the stomach, the enzyme pepsin breaks down proteins into amino acids, and hydrochloric acid (HCL) helps pepsin work and kills harmful bacteria. **B. Absorption and Elimination** - **Absorption** happens after digestion. Nutrients from digested food are absorbed in the small intestine and carried by the blood to the rest of the body. - **Elimination** occurs in the large intestine, where undigested food is processed and then expelled from the body. **Functions of Digestive Organs** **1. Mouth** - **Mechanical digestion:** Teeth cut, tear, and grind food into small pieces. The tongue helps push food around. - **Chemical digestion:** Saliva from glands in the mouth contains the enzyme [amylase,] which breaks down starch (a complex carbohydrate) into glucose (a simple sugar). **2. Esophagus** - **Esophagus:** A muscular tube that connects the mouth to the stomach. When you swallow, a flap called the [epiglottis] covers your windpipe to prevent food from entering your lungs. [Peristalsis], a series of muscle contractions, pushes food down the esophagus to the stomach. **3. Stomach** - **Mechanical digestion**: Smooth muscles in the stomach wall churn food. - **Chemical digestion**: Gastric juices containing [pepsin and hydrochloric acid] break down proteins become amino acid and kill bacteria. The food becomes a thick liquid called [chyme] after about two hours. **4. Small Intestine** - **Length:** About six meters long but only 2-3 cm in diameter. - **Chemical digestion:** The liver and pancreas release chemicals to help digestion. The liver produces bile, stored in the gallbladder and released to break down fats. The pancreas produces enzymes to digest carbohydrates, proteins, and fats. - **Absorption:** The inside of the small intestine has tiny finger-like projections called villi that increase the surface area for nutrient absorption. **5. Large Intestine** - **Length:** About 1.5 meters. - **Function:** Absorbs water and processes undigested food into solid waste. Contains good bacteria that produce Vitamin K. The end of the large intestine is [the rectum], where waste is stored before being expelled through [the anus.] 3D digestive animation: https://www.youtube.com/watch?v=B0CRWq3nc80 **Digestive Disorders** **1. Diarrhea** - **Cause:** Infection by bacteria or protozoa like Entamoeba coli. - **Symptoms:** Irritated large intestine walls, increased peristalsis, and poor water absorption leading to dehydration and stomach cramps. - **Prevention:** Maintain food hygiene, wash hands before eating, drink clean water, and keep personal and environmental hygiene. **2. Constipation** - **Cause:** Slow movement of feces through the colon, resulting in hard, dry stools. - **Prevention**: Eat high-fiber foods and drink plenty of water. **3. Gastritis (Stomach Ulcers)** - **Cause:** Inflammation of the stomach lining due to bacteria (Helicobacter pylori), excessive stomach acid, stress, irregular eating, or spicy/acidic foods. - **Prevention:** Eat regularly, wash hands before eating, and avoid foods that trigger excessive stomach acid. **4. Appendicitis** - **Cause:** Infection of the appendix by bacteria. - **Symptoms:** Rapid bacterial growth leads to inflammation, swelling, and pus formation in the appendix.