Lecture Notes Chapter 41

Lecture Notes Chapter 41 - Lecture Notes Chapter 41 Why do...

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Lecture Notes Chapter 41 Why do we have to eat? Chemical energy and the building blocks for growth has to be taken up in the form of complex organic substances As opposed to plants and prokaryotes, which can synthesize these components from inorganic precursors Chemical energy is required for all the cellular work in the body Organic raw materials used for biosynthesis (carbon skeletons) Essential nutrients that the body cannot synthesize e.g. vitamins, minerals Animal are heterotrophs that require food for: Chemical energy for all the cellular work in the body Organic raw materials used for biosynthesis (carbon skeletons) Essential nutrients that they cannot synthesize In general, animals fall into one of three dietary categories Herbivores eat mainly autotrophs (plants and algae) Carnivores eat other animals Omnivores regularly consume animals as well as plants or algal matter Animal feeding mechanisms Suspension feeders Substrate feeders Fluid feeders Bulk feeders Homeostatic mechanisms manage an animal’s energy budget Largest use of energy is for production of ATP (derived from oxidation of organic fuel molecules in cellular respiration Excess energy can be used for biosynthesis Glucose is a major fuel molecule in cells, and its levels are regulated by hormones Glucose levels are high during phases high-energy requirement Rapid conversion to ATP o Sustained high glucose levels are pathological Normally, glucose is stored in an osmotically inactive form Glycogen in muscles and liver o Rapid enzymatic conversion into glucose o However: further conversion to fat! Glucose is a highly desirable but rare nutrient in a “natural” diet Fruit eating birds, bats Nectar-feeding humming birds 1
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Imbalances in the homeostatic mechanisms to regulate nutritional intake can lead to problems The regulation of nutritional intake and nutrient levels in the blood are examples of negative feedback regulatory loops glucose levels satiety hunger Micro-nutrients, vitamins, and minerals Vitamins are organic substances that cannot be synthesized by the body Vitamins often participate in enzymatic reactions as co-factors (prosthetic groups, co-enzymes) o Water-soluble o Fat soluble Vitamins are required in very small quantities normally supplied by a balanced diet Some vitamins are toxic in high doses o hyper-vitaminosis Vitamin deficiencies are rare in western societies
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Lecture Notes Chapter 41 - Lecture Notes Chapter 41 Why do...

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