A&P 2 Chapter 23: Nutrition

Summarize important events of the absorptive and postabsorptive states, and explain how these events are regulated.

*The absorptive state* - this is the fed state (the four hours directly after eating) -Time during and shortly after eating -Nutrients are being absorbed by the GI tract into the blood -Anabolism exceeds catabolism and nutrients are stored (building up of nutrients vs. the breakdown of nutrients) -Glucose is major energy source -Dietary amino acids and fats are used to remake degraded body protein or fat -Excess nutrients are transformed to fat if not used for anabolism -Insulin is the hormone that directs most events of the absorptive state *Insulin control of events of post absorptive state* Insulin is produced in beta cells of pancreatic cells and is produced and released from pancreas in response to rising blood glucose and amino acid levels after a meal -Insulin enhances the entry of glucose into cells that insulin binds -Insulin is a hypoglycemic hormone -Diabetes mellitus is a disorder of inadequate insulin production or abnormal insulin receptors *The postabsorptive state* - is the fasting state (at night or after 12 hours from eating) -GI tract is empty and body reserves are broken down to supply energy -Net synthesis of fat, glycogen, and proteins ends and catabolism of these substances begins to occur -Goal of postabsorptive state - to maintain blood glucose levels -Glucose levels in the blood must be maintained because the brain uses glucose as its energy source *Sources of blood glucose in postabsorptive state* 1) glycogenolysis in the liver - glycogen stores in the liver are the first line of glucose reserves 2) glycogenolysis in skeletal muscle - before liver glycogen is exhausted, glycogenolysis begins in skeletal muscle with help through the liver 3) Lipolysis in adipose tissues and the liver - adipose and liver cells produce glycerol by lipolysis and liver converts the glycerol to glucose (via gluconeogenesis) and releases it to the blood *Control of events of postabsorptive state* -Under sympathetic nervous system and hormone control -Lower glucose levels stimulate alpha cells of pancreatic islets to release glucagon, which raises blood glucose levels (hyperglycemic)

Describe how body temperature is regulated, and indicate the common mechanisms regulating heat production/retention and heat loss from the body.

*Ways we produce heat:* 1. basal metabolism 2. muscular activity (shivering) 3. thyroxine and epinephrine (stimulating effects on metabolic rate) 4. temperature effect (warmer cells metabolize faster, producing more heat) 5. constriction of cutaneous blood vessels *Ways we lose heat:* 1. dilation of cutaneous blood vessels 2. enhanced sweating 3. fever (controlled hyperthermia)

Describe several metabolic functions of the liver.

1. many conversions of more complex carbohydrates to simple carbohydrates 2. storage of nutrients 3. conversion of excess nutrients to fats 4. metabolism/inactivation of drugs/alcohol in preparation for excretion 5. breakdown of bile pigments

Define basal metabolic rate and total metabolic rate. Name factors that influence each.

BMR - the energy the body needs to perform only its most essential activities at rest and having not eaten for 12 hours TMR - rate of kilocalorie consumption needed to fuel all ongoing activities, involuntary and voluntary -Food ingestion causes a rapid increase in TMR (called food-induced thermogenesis)

List minerals essential for health. What is a trace mineral?

Calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium Trace minerals- tiny amount of minerals

Distinguish between nutritionally complete and incomplete proteins

Complete proteins are those that you find in eggs, milk, fish and most meats and they meet all the body's amino acid requirements for tissue maintenance and growth. Incomplete proteins are nutritionally incomplete because they are low in one or more of the essential amino acids.

Distinguish between core and shell body temperature.

Core body temperature has the highest temperature. The core includes organs such as the organs inside the skull and thoracic and abdominal cavities. The shell temperature has the lowest body temperature (it includes the skin).

Explain what is meant by body energy balance.

Energy intake = energy output Energy input is energy released during food oxidation (breakdown) Energy output is energy lost as heat, energy used to do work, and energy stored as fat or glycogen (stored glucose) When energy intake and energy output are balanced, body weight remains stable.

Describe how amino acids are metabolized for energy.

In order for amino acids to be used for energy, they must be deaminated (their amine group NH2) must be removed What is left over of the amino acid is converted to pyruvic acid or an acid intermediate that will enter the Krebs cycle

Define nitrogen balance and indicate possible causes of positive and negative nitrogen balance

Nitrogen balance is a homeostatic state. The rate of protein synthesis equals the rate of protein breakdown and loss in healthy adults. If protein production (making) and protein breakdown (breaking) is equal, then we are in nitrogen balance -Positive nitrogen balance = amount of protein used for building tissues is greater than that being broken down and used for energy (like in growing children, pregnant women, or in tissue repair) -Negative nitrogen balance = protein breakdown for energy exceeds amount of protein incorporation into tissues (poor diets, or due to emotional or physical stress)

Define nutrient, essential nutrient, and calorie

Nutrient: A substance in food the body uses to promote normal growth, maintenance and repair. Essential nutrient: cannot be made by the body in sufficient quantities to meet the body's needs. They must be obtained by the diet. "Essential" does not equal required. Essential and nonessential nutrients are both vital for normal functioning. calorie: energy required to heat 1g of H2O at 1 degree celsius. 1,000 calories = 1 Calorie

Describe the need for protein synthesis in body cells.

Protein synthesis is consistently occurring and we make about 500-1000 lb of protein in our lifetime. We don't need to eat that much protein because we can convert and make some nonessential amino acids. (which happens in the liver) You must have every amino acid that you need to make a protein present, otherwise, the protein will not be produced.

Distinguish between fat- and water-soluble vitamins, and list the vitamins in each group.

Water-soluble vitamins are absorbed along with water through the GI tract -B-complex vitamins -Vitamin C -Any ingested water-soluble vitamins will be excreted usually within 1 hour -Excess amounts of these vitamins is rare Fat-soluble vitamins bind to ingested lipids and are absorbed with their digestion products (through lymph) -Vitamins A, D, E, and K -Usually stay in the body much longer than water-soluble vitamins -Too many fat-soluble vitamins can be toxic

Explain the concept of amino acid or carbohydrate-fat pools, and describe pathways by which substances in these pools can be interconverted.

We have nutrient pools - stores of nutrients - that we can rely on between meals. Many of the nutrients can be interconverted - converted from one form to another (mostly done in the liver). The liver, adipose tissue, and skeletal muscles are the primary effectors determining the amounts and directions of interconversions of nutrients. Chlyomicrons are lipoproteins -lipoproteins are lipids surrounded by proteins to make them water soluble

List the six major nutrient categories. Note important sources and main cellular uses.

carbohydrates, lipids, proteins, vitamins, minerals, and water. Sources: *Carbohydrates* - mostly plants. We use carbohydrates as energy sources and for fiber *Lipids (triglycerides)* - animal products such as meat and dairy foods. Uses: absorption of fat-soluble vitamins, energy fuel for liver and skeletal muscle, myelin sheath and cell membranes, cushioning of body organs, insulation, and cholesterol is used in bile salt and steroid hormone production *Protein* - animal products. Proteins are important structural materials of the body, while others function as enzymes and hormones. Proteins are not normally used for energy sources. *Vitamins* - found in all major food groups. You must have a balanced diet to get all vitamins. Most vitamins function as coenzymes which help enzymes do their function. *Minerals* - work with other nutrients to ensure a smoothly functioning body (iron is used in heme/hemoglobin, for example *Water* - drinking water and water is found in most dietary foods

Differentiate between LDLs and HDLs relative to their structures and major roles in the body.

low density lipoproteins carry cholesterol throughout the body to tissue cells for various functions high-density lipoproteins formed within cells to remove cholesterol from the cell bringing it to the liver for disposal