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Energy For Life Chapter 7 Nature's Energy Conversions Life on Earth could not exist without plants Without oxygen, which comes from plants, oxygen-breathing animals would not exist BUT, without oxygen-breathing animals, plants would not exist either!! Plant’s and energy conversion Plants are like a solar cell, they convert energy from the sun into chemical potential energy The cells of the green plants have special parts that capture the energy from the sun and convert it into energy the plant can use. The plant then uses that energy to produce oxygen and food molecules (chemical potential energy) which are used by animals, this process is called PHOTOSYNTHESIS The cells of the plant Green plants have cells called chloroplasts, inside each of the chloroplasts there is chlorophyll pigment, this is where photosynthesis takes place. The photosynthesis rxn is: CO2 + water + light energy glucose (sugar) + oxygen Glucose Glucose is a simple sugar Glucose is a carbohydrate that is rich in chemical potential energy that when eaten by animals is converted to a usable energy Glucose is the main source of energy for all cells. Cells can also get energy from proteins, fats, and other food molecules. Out human bodies use carbohydrate as a source of ENERGY Cell Respiration Cellular respiration is a process used by all plant and animal cells to obtain energy from food When we eat, we break down food into a usable from of energy which drive most reactions in our body Cell Respiration is the opposite of photosynthesis! The cell respiration rxn is: Glucose + oxygen CO2 + water + energy Cell respiration in the human cell is like a car, both need oxygen and fuel to operate and they both release carbon dioxide and water Cell respiration in animals takes place in specialized cells called mitochondria In order to operate, an organism must eat food (glucose) to get energy. 2 Energy Conversions: In plants: Input energy converter output energy Solar energy chloroplasts chemical potential (glucose) In Animals: Input energy converter output energy Chemical potential mitochondria muscular activity (kinetic energy) Energy Conversions: Plants to Animals Usually only 10% of the energy Energy is being converted from one from to another all of the time Most of the time, energy is being lost as waste, either as heat (thermal energy), sound, or poop. Thus, when you do physical activity, a ton-of-energy is lost to cool the body down or as heat. As you move up a food pyramid, there are less and less organisms due to less energy being available to them. at one level is passed on to the next level 0.1J 1J 10J 100J 1000J The need for energy Energy in organisms is usually used for movement, growth, reproduction and to keep the body temperature constant. The major use of energy in animals is for HOMEOSTASIS, which is balance. The body is like a thermostat, when it is too cold, the body turns up the heat, if the body is too warm, the body turns down the heat. The body likes to be at equilibrium at all times! The human body does a couple things to adjust it’s temperature, they are: Blood vessels move close to the skin surface to increase the rate of heat transfer Perspiration: to cool the body off you sweat. Some animals pant Shivering: warms the body up by causing the muscles to burn more energy Blood vessels can constrict to prevent blood to the limbs and thus heat loss. Sources of Energy for Animals Food is the fuel that gives us energy to keep warm, be active, and stay alive. Recall: The main source of energy is carbohydrates, which comes from plants due to photosynthesis 3 sources of energy: 1) Carbohydrates: -Glucose is the main simple carb, it is broken down in the body to produce energy, or it is stored as glycogen. Glycogen is stored in the liver and muscles to be used later. -Experts say that 55-65% of our diet should be carbs -Carbo Loading is when athletes take in extra carbs so that they can store them -Food rich in carbs: pasta, breads, potatoes 2) Fats: Fat is need for insulation, to store energy, and to make energy Once carbos run low, the body then use fats as a backup energy source. However, fats can produce about 2X the amount of energy as carbs! 2 types of fats exist: 1) Saturates: these come from animal fat and oils and cause heart disease 2) Unsaturated fats: come from vegetable oils and these reduce heart disease -We should try to eat only unsaturated fats and fats 3) Proteins: Proteins contain about the same amount of energy as carbs, but its harder for the body to break down proteins, thus it proteins take longer to produce energy Proteins is a poor source of energy, but are needed in many other body processes, such as: build body tissue and muscles, growth and repair of the body Proteins are ‘building blocks’ of our body: by eating meats we take in a lot of proteins Human Energy For Change Our need for energy changes as we grow older As a fetus and infant, most of the energy is needed for growth and development. When the baby is in the womb, an umbilical cord is used to pass minerals, nutrients, and other chemicals from the mother to the baby. As people age, their metabolic needs change, when kids go through puberty their metabolism increase so that enough energy is available to increase in mass and height. What affects metabolism There are many factors that affect metabolism(=rate at which the human body uses energy) they are: 1) Age: younger people have higher metabolism 2) Time of day: metabolism is higher in the morning, and peaks around 10am. 3) Exercise: Activity increases metabolism 4) Level of fitness: athletes have high metabolism One way to avoid gaining weight is to stay active, not just reduce food intake!!