Topic 9 On the Menu Grade 9 Science and Technology PDF

Topic 9 On the Menu Grade 9 Science and Technology Nutrients A nutrient is a food substance the body needs. The body needs nutrients to provide energy, build and repair tissues, regulate metabolism and transport substances. In order to get all the nutrients required, one must...

Topic 9 On the Menu Grade 9 Science and Technology Nutrients A nutrient is a food substance the body needs. The body needs nutrients to provide energy, build and repair tissues, regulate metabolism and transport substances. In order to get all the nutrients required, one must eat a balanced diet. Nutrients- Carbohydrates Carbohydrate, a macronutrient, includes sugar, starch and fiber. Sugar and starch provide short-term energy. (1st source of energy used by the body) ○ Sugar (simple carbohydrate) provides a brief energy boost - found in fruits, vegetables, honey, juice, candy, etc. Nutrients- Carbohydrates ○ Starch (complex carbohydrate) provides energy over an extended period of time - found in pasta, bread, cereals, rice, legumes (beans), tubers (potatoes, beets, turnips…), etc. Nutrients- Carbohydrates Fiber cannot be digested; however, it helps prevent constipation. ○ Found in fruits, vegetables, whole grain cereals, beans etc. Nutrients- Fats Fat, a macronutrient, provides long-term energy or stored energy - used when carbohydrates have been used up. Found in oils, butter, margarine, salad dressings, cream, nuts, cheese, meat, fries, chips, pastries, etc. Saturated fats and trans fats should be avoided as much as possible. Nutrients- Proteins Protein, a macronutrient, is used to 1) build and repair tissues and 2) provide energy in case of emergency - used when carbohydrates and fats are not available. Found in meat, poultry, fish, eggs, legumes, tofu, nuts, etc.… Nutrients- Vitamins Vitamin, a micronutrient, helps regulate metabolism. Metabolism refers to the chemical reactions in our cells converting the food we eat into energy our body needs. Found in fruits, vegetables, meats, meat substitutes, milk, nuts, etc. Nutrients- Minerals Mineral, a micronutrient, helps regulate metabolism. Found in fruits, vegetables, legumes, milk, meat, fish, etc. Nutrients- Water Water 1) helps regulate metabolism and 2) transports substances. The human body requires 2-3L of water everyday. Found in almost everything we eat but is found in higher quantities in beverages, fruits and vegetables. Nutrients- Energy Value Carbohydrates, fats and proteins all have the ability to provide the cells with energy. Energy is commonly measured in calories or kilojoules (kJ). 1 calorie= 4.18 kJ Each nutrient provides a standard amount of energy per gram. Nutrient Energy Carbohydrate 17 kJ/g Protein 17 kJ/g Fat 37 kJ/ g Nutrients- Energy Value Converting between kJ and calories is simple - use the following conversion factor. Examples…. A) How many kJ is 250 calories? B) How many calories is 3050 kJ? Nutrients- Cellular Respiration The chemical reaction that allows the release of stored energy from a nutrient molecule is called cellular respiration. Energy Needs The average daily nutritional energy requirements for a 13-15 year old adolescent is 10500 kJ/day (~ 2500 calories/day). Energy is needed for… ○ Basal metabolism (maintenance of vital functions like heartbeat, breathing and cellular activities) ○ Physical Activities (running, playing soccer, walking, skating, etc.) ○ Digestion and absorption of food. Energy Needs In order to meet our daily energy needs, we need to maintain a balance between carbohydrates, fats and proteins. Total Energy Carbohydrates Fats Proteins 100% of kJ 55% of kJ 30% of kJ 15% of kJ ingested ingested ingested ingested 10 500 kJ 5 775 kJ 3 150 kJ 1 575 kJ - 340 g 85 g 93 g Energy Needs Our weight will vary according to the balance between energy in (from food) and energy out. To maintain a constant weight, the number of kJ you use must be equal to the number you consume. To gain weight, the number of kJ you use must be less than the number you consume. To lose weight, the number of kJ you use must be greater than the number you consume. Indicators Indicators are substances that react chemically in the presence of a specific substance - used to detect the presence of a specific substance. A good indicator must produce a reaction that can easily be detected. Indicators Reactions that an indicator might produce: Color change Gas release (effervescence, bubbling in a liquid) Sudden appearance of a solid (precipitate) Variation in energy (heat or explosion) Indicators Test Testing Presence Original Positive Result Negative Result of... Appearance Biuret Protein Blue Pink or Purple in Colour other than presence of pink or purple protein Indicators The following are examples of everyday indicators… Pregnancy test (presence of hormone human chorionic gonadotropin) Breathalyzer Smoke detector pH pool test Forms of Energy Energy is necessary to produce work or motion. It cannot be created or destroyed, it can only be transferred or transformed. Chemical energy is contained in the chemical bonds that hold the atoms of the molecule together - released during reactions that break these bonds. ○ Fuels such as wood and gasoline release a large quantity of chemical energy when they burn. There is also chemical energy stored in the food we eat. The energy is released during cellular respiration. Forms of Energy Mechanical energy (ME) is the form of energy related to the movement of a body or its position in space (ME = KE + PE). Kinetic energy (KE) is the energy of movement and potential energy (PE) is the energy due to position. e.g. A book sitting on a table has more potential energy than one sitting on the floor below. Forms of Energy Thermal energy is the energy stored in a body caused by the internal movement of its particles. ○ Refrigerators lower the thermal energy inside the appliance so the air cools. ○ Wood fires release thermal energy and increase the temperature. Forms of Energy Radiant Energy is the energy contained in light and other “electromagnetic waves”. ○ Sunlight ○ Microwaves ○ Radio waves. ○ Infrared waves. Forms of energy Energy Transformation is the process of converting one form of energy into another. e.g. Chemical energy in a pizza you eat can be transformed into mechanical energy required for throwing a ball.