Lecture Exam 1 Covers Ch 24 and 25 digestion and metabolism Multiple choice and short answer 100 pts Bring scantron and #2 pencil 2 Review sheets on my website Body Temperature Homeostasis We maintain a core temperature of 37 o C Body temperature is the balance of the heat produced by body tissues, particularly liver and muscles, and the heat the body loses. If core temperature drops Skin blood vessels constrict Release of thyroid hormones, epinephrine and norepinephrine increases cellular metabolism Shivering If core body temperature too high Dilation of skin blood vessels Decrease metabolic rate Stimulate sweat glands Fever: a homeostatic imbalance Fever higher than normal body temperature It is part of your body's defense against infection. Most bacteria and viruses that cause infections do well at the body's normal temperature. A slight fever can make it harder for them to survive. Fever also activates your body's immune system. How body temperature works Body temperature is set by the hypothalamus When you're ill, body temperature may be set a few degrees higher body directs blood away from skin to decrease heat loss. you feel chilly and may shiver to generate heat until the blood around your hypothalamus reaches the new set point. When your temperature begins to return to normal, you may sweat profusely to get rid of the excess heat. Homeostasis of blood glucose concentration Especially important for the nervous system and red blood cells Nervous system Uses glucose for ATP production because fatty acids can t pass the blood-brain barrier Red blood cells Derive all of their ATP from glycolysis of glucose RBCs lack mitochondria and thus lack the Krebs cycle and electron transport chain Metabolic adaptations Your metabolism depends on how recently you have eaten Absorptive state Blood is nutrient-rich Most body cells use glucose for ATP production Excess fuel molecules are stored Post-absorptive state Blood glucose levels start to fall Energy needs must be met by stored fuels Maintaining blood glucose critical Glucose produced by breakdown of liver glycogen, fats, proteins 1
During the absorptive state During the absorptive state 50% Dietary lipids 40% stored as Triglycerides 10% stored as Glycogen Most dietary lipids are stored in adipose tissue The liver packages triglycerides into VLDLs transported to adipose tissue for storage During the absorptive state Metabolism during the post-absorptive state Absorbed amino acids Protein synthesis Liver Muscle and other tissues About 4 hours after the last meal Absorption in small intestine nearly complete Blood glucose levels start to fall Main metabolic challenge: maintain normal blood glucose levels Glucose production Breakdown of liver glycogen, lipolysis, gluconeogenesis using lactic acid and/or amino acids Glucose conservation Oxidizing fatty acids and other fuel molecules ATP The post-absorptive state: producing glucose The post-absorptive state: conserving glucose Breakdown of liver glycogen Lipolysis Breakdown of triglycerides Gluconeogenesis Lactic acid Amino acids Oxidation of fatty acids most cells Oxidation of lactic acid heart muscle Oxidation of amino acids hepatocytes Oxidation of ketone bodies hepatocytes Breakdown of muscle glycogen skeletal muscle 2
Chapter 25: Metabolism and Nutrition Good nutrition is key to good health Nutrition Overview Why we eat What are nutrients? Why isn t alcohol a nutrient? What are the main functions of nutrients in your body? What are the 6 types of nutrients and their functions? What is a calorie? What is an essential nutrient? What are micronutrients? Water Energy (calories) Building blocks Essential nutrients Primarily vitamins and minerals What is a Nutrient? Any substance that the body uses to: provide energy (calories) regulate body processes Contribute to cell and body structure Alcohol provides energy but it doesn t nourish the body. It is a toxin when consumed in large amounts. What are the 6 types of nutrients? Carbohydrates Fats Protein Vitamins Minerals Water 3
The most important nutrient? We can t survive long without it Water is critical for body functions The body is about 70% water Found both inside and outside the cells Functions Helps regulate body temperature Transports nutrients Excretion of waste products Nutrients supply energy What is a calorie? Carbohydrates Protein These nutrients supply energy (calories) to power muscle contraction, maintain body temp and other cell functions The way we measure the energy that food provides Scientific definition: the amount of heat to raise 1 ml of water 1 Celsius Fats Energy (Calories) from Nutrients How do we get energy from food? Nutrient Carbohydrate Protein Fat Energy 4 cal/g 4 cal/g 9 cal/g Fat is the most energy-rich nutrient Alcohol contributes 7 cal/g, but is not a nutrient. What is the fate of a hamburger? Contains carbohydrates, fats and proteins Broken down during digestion in the stomach and intestine into their subunits Carbohydrates to glucose Fats to fatty acids Proteins to amino acids 4
Cellular respiration burns carbs, fat and protein Nutrients help regulate body processes Carbs Glucose Lipids Fatty acids Protein Amino acids Krebs Cycle Vitamins and minerals (the micronutrients) and water Blood pressure Metabolism Iodine is a component of thyroid hormone Body temperature Food as Building Material Nutrients contribute to cell and body structure Proteins, minerals and water provide structure to bone, muscle and other tissues Bone Muscle How does the body use carbohydrates? Catabolized to provide Energy Primary energy source for the body Provide Fiber A complex carbohydrate that humans can t digest Health benefits Decreases blood cholesterol levels Makes you more regular Reduces the risk of colon cancer Why do we need Fats? Saturated and unsaturated fats Dietary fats provide Energy for the body fat-soluble vitamins essential fatty acids (omega-3 and omega-6) Adipose tissue stores energy for later use Saturated fats are the storage molecules usually found in animals Solid at room temp Unsaturated fats are usually found in plants Liquid at room temp 5
What are trans fats and why are they bad? Omega-3 fatty acids A trans fat Hydrogenated fats Start with unsaturated fatty acids cis bond between carbons in the carbon chain This is oleic acid, found in olive oil Convert to trans fatty acids Trans bond between carbons Created industrially by hydrogenating plant oils First sold as Crisco in 1911 Solid at room temp, longer shelf-life Found in stick margarine, many fast foods, baked goods Trans fats are bad because Increase risk of heart disease Raise levels of LDL cholesterol Essential (can t be made by the body, must be obtained from food) Found in fish, plant and nut oils canola oil, soy beans, olive oil, walnut oil Salmon, halibut, sardines Cholesterol LDL and HDL cholesterol Cholesterol has many important functions in the body Found in cell membranes Used to make Bile acids used to digest fats Sex hormones (testosterone, estrogen) Vitamin D (important for healthy bones) Only found in animal tissues (not in plants) HDL or Healthy cholesterol Removes excess cholesterol from cells and delivers it to liver for elimination Protects against heart disease LDL or Lousy cholesterol Transports cholesterol to the cells, sticks to artery walls Contributes to plaque build-up High levels of LDL cholesterol raise the risk of heart disease Protein an all important nutrient Why do we need Protein? Helps build and maintain body tissues Main job is to build muscle, bone, skin and hair Regulates body functions Some hormones are proteins Protects you from illness Antibodies are protein Also used for energy Sources: meat, eggs, beans, nuts 6
Essential Amino Acids Must be obtained from the diet the body can t synthesize them. Different foods contain different essential amino acids. The Micronutrients Essential (can t be made by body) Required in small amounts ( micro ) for normal growth and reproduction, and health Vitamins Fat-soluble: A, D, E and K Water-soluble: C, B-vitamins Minerals Calcium, iron, iodine, zinc and others Fat soluble vitamins Water-soluble Vitamins Vitamin A, D, E, K Key features Found in fats in food Stored in body fat Toxic if consumed in excess Vitamin A and D deficiencies are common in developing countries Vitamin C, B-vitamins Need to be consumed regularly Not stored in the body to any extent Excess excreted in urine Toxicity rare Have very diverse functions B vitamins are involved in energy metabolism Key functions of minerals Micronutrients important for healthy BONES Calcium and phosphorous part of the structure of bones and teeth Vitamin D (a hormone) Helps regulate blood calcium levels Increases calcium absorption from intestine Needed for normal calcification of bone Vitamin K Role in synthesis of bone proteins 7
Micronutrients needed for healthy BLOOD Iron Found in hemoglobin, the oxygen-carrying protein in red blood cells (RBCs) Zinc Important for immune system Folate Formation of new cells, including RBCs Vitamin B-12 Formation of blood cells Vitamin K Needed for blood coagulation What is good nutrition? Getting the right nutrients Foods that provide energy Essential nutrients that the body can t make Getting the correct amount of food energy (cal) Basic advice for good nutrition Eat a variety of foods Fruits, vegetables and whole grains Eat less don t overeat Avoid too much junk food Exercise more Desert Island Scenario Assume you are alone on a desert island for a year. You can have water and one other food. Pick the food you think would be best for your health. Explain why. Corn Alfalfa sprouts Hot dogs Spinach Bananas Milk chocolate What is malnutrition? Malnutrition Not enough food Poor health that can be improved by eating more/ eating better food Hunger and food insecurity threaten low-income people around the world Why is it a global concern? Underlies high infant mortality rates Contributes to more than half of all child deaths Related to poor growth and mental development in children Leads to lower productivity in adults 8
Three types of Malnutrition Causes of Malnutrition Undernutrition 0.8-1.1 billion Overnutrition 1.1 billion Nutrient deficiency 2-3.5 billion Immediate causes Not eating enough food Disease Underlying causes in the household Poor access to food Poor water and sanitation Inadequate health services Inadequate maternal, prenatal and child care Worldwide incidence Undernutrition Not enough calories (inadequate energy) to support optimal growth in children to maintain a healthy, active body in adults Aka protein-energy malnutrition (PEM) Common: 1 in 5 people in the developing world are chronically undernourished FAO (Food & Agricultural Organization of UN) Which is bigger problem protein or calorie deficiency? When people get enough calories, they almost always meet their protein needs No evidence of protein deficiency without an accompanying calorie deficiency If get only 75-80% of their calorie needs, they still meet protein needs Where do undernourished people live? Sub-Saharan Africa and South Asia Health problems associated with undernutrition Wasting extreme thinness, or very low weight-for-height Transitory (short term) lack of food Often caused by famine Natural disasters (droughts, floods, EQs) Human conflicts Represents about 10% of the world s hungry 9
Health problems associated with undernutrition Stunting short height for age Due to chronic (long term) undernutrition Infections/disease more common Low productivity (poor work capacity) What is the main nutrition problem in the US? Obesity Obesity Results from regular intake of excess energy Major risk factor for chronic diseases Cardiovascular disease Certain types of cancer Type 2 diabetes Excess nutrients are stored as body fat Obesity rates in the US 68% of American adults are overweight 34% are considered obese In Santa Clara County obesity levels are 18% During the past 20 years there has been a dramatic increase in obesity in the United States In 1980s, 15% of US population was obese Childhood Obesity A serious health concern for children and adolescents Of children 2 to 19 years old 32% are overweight 17% are obese Obese children and adolescents are at risk for health problems Increased risk of cardiovascular disease (high blood pressure, high cholesterol, and Type 2 diabetes) 10
The most common nutrient deficiency? Iron deficiency Functions of iron in the body Iron is present in all tissues Functions Carrier of oxygen in hemoglobin Electron transport in cytochromes Integral part of enzyme reactions Iron is an integral part of hemoglobin, the oxygen-carrying protein in red blood cells Iron deficiency anemia Iron Deficiency Anemia Common Most common in menstruating women and young children In pregnant women: increases the risk of miscarriage, maternal mortality & low-birth weight infants In children: effects growth, development and mental performance Symptoms: low energy, loss of productivity Preventing iron deficiency Interventions Fortify grain products: In U.S. grains supply 1/3 of iron for most people Iron Supplements for women Dietary Diversification Foods rich in Vitamin C increase iron absorption from plants (beans, lentils, green leafy veggies) Cooking in iron skillet Breast feeding Best dietary sources: meat, fish, poultry, seafood 11