ABSORPTION AND METABOLISM

1. ABSORPTION AND METABOLISM

2. The results of digestion... Through the digestive process, the macro- nutrients are broken down into their base components. Protein is broken down into amino acids by the protease enzymes (primarily pepsin) in the stomach.

3. Carbohydrates consist of starch and sugar molecules, which started breaking down already as they mixed with the amylase (ăm'ə-lāce‘) or ptyalin (tī'ə-lĭn) found in saliva. The body changes all of the starch and sugar molecules to a simple sugar called glucose. Part of this glucose will be used for energy immediately. Part will be stored as glycogen in your muscles and your liver to be saved for future use.

4. Bile salts, produced in the liver and stored in the gallbladder, emulsify the fat (lipids), breaking it and all fat-soluble vitamins such as D, E, K, and A into smaller and smaller molecules called fatty acids. The main metabolic organ, the liver, and the pancreas continue the digestion process. Pancreatic juice containing enzymes and the bile of the liver eventually break down the nutrients into small enough form to be absorbed into the small intestine.

5. Nutrients are now in molecular form... The amino acids that form proteins, the glucose that forms sugars and starches found in carbohydrates, and the fatty acids that form lipids are now reduced to even smaller molecules made of… carbon (C), oxygen (O), hydrogen (H), and sometimes nitrogen (N). Glucose Amino Acid Fatty Acid

6. The surface area of the intestine is well suited to its function of nutrient absorption. The mucosal folds called villi and microvilli give a total absorptive area for the small intestine a 600-fold increase over the projected surface area of a smooth-surfaced tube of equivalent length. Total surface area is roughly about the size of a tennis court. Absorption... In addition to nutrients, the water in our food and drink is also absorbed from the small intestine into the bloodstream to provide the body with the fluid it needs. Intestinal villi

7. Through the bloodstream and to the liver... The liver removes the glucose, converts it to glycogen, and stores it. It is released again as the body needs it. The amino acids are either released by the liver and sent to the muscle cells or are converted to urea for excretion. The bile from the liver takes care of the fatty acids, making them absorbable into the blood stream and sent to the cells for use or storage.   From the liver, the nutrients go back into the bloodstream for delivery all over the body to the cells. Once the nutrients enter the bloodstream by passing through the walls of the small intestine into the capillaries, the blood then carries most of the nutrients to the liver. 

8. Transport of molecules... The movement or ‘transport’ of nutrient molecules through intestinal wall, blood vessel wall, or cell membrane may be either PASSIVE or ACTIVE. Passive transport does not require energy, moving materials into an area of lower concentration. Active transport requires energy (ATP) to move materials into a higher concentration.

9. The four main kinds of passive transport are diffusion, facilitated diffusion, filtration, and osmosis. Some type of Passive transport is used in absorbing fats, the fat soluble vitamins A, D, E, and K, and water. Active transport (energy required) is used in absorption of glucose, amino acids, calcium, iron, folic acid, ascorbic acid, thiamin, and some B vitamins.

10. The nutrients are absorbed through the walls of the small intestine into the bloodstream. Parts of a cell... They travel through the bloodstream to the liver. They are eventually released from the liver back into the bloodstream, and delivered to the cells. Nutrients are then transported through the outer membrane into the interior of the body’s cells. where energy is generated control center of the cell the primary substance of the cell converts stored genetic information strands of genetic information

11. So now what happens inside the cell? Stomach Small Intestine Bloodstream Liver Bloodstream Cell The carbohydrate sugars and starches were reduced to simple glucose in the stomach and small intestine during digestion. In that small molecular form, they were passively or actively transported through the bloodstream to the liver (where they were stored as glycogen) and then back into the bloodstream and out to the cells. Now that they are finally in the cell… the process of metabolism can begin.

12. What is metabolism? Metabolism is the sum of all chemical reactions occurring within a cell or organism. Through metabolism, living cells use nutrients in many chemical reactions that provide energy for vital processes and activities. As the body uses nutrients to create energy, metabolism takes place.

13. Two types of metabolism... There are two types of metabolism: catabolism and anabolism. Catabolism is a type of metabolic process occurring in living cells by which complex molecules are broken down to PRODUCE ENERGY. Catabolic reactions are normally exothermic….. heat and energy yielding. Anabolism is a constructive metabolic process that USES ENERGY to combines simple substances such as amino acids in the creation of complex cell structures and compounds. Molecules break down; energy ( ) is produced Compounds are created; energy ( ) is used

14. Step 1 of the metabolic process... glycolysis Enzyme Enzymes are proteins, synthesized in cells. They act as catalysts, causing all the body's chemical processes to take place quickly and completely. Energy They break the glucose molecule in half, forming two 3-carbon molecules. These molecules are called pyruvic acid or pyruvate. This process is called glycolysis and occurs in the cytoplasm of the cell. A small amount of energy is released during this process, as the bonds within the molecule are broken. This is a CATABOLIC reaction. Black spheres are carbon atoms, white are hydrogen, and red are oxygen.

15. Step 2 of the metabolic process... acetyl group formation A co-enzyme made of Vitamin B and called ‘CoA’ bonds with 2 of the carbon atoms in pyruvate, forming an acetyl (ə-sēt'l)molecule group. CoA kicks out the 3rd carbon atom of pyruvate.This formation occurs within the mitochondria of the cell. Oxygen Exhaled as CO2 Oxygen Carbon CoA Vitamin B Carbon Carbon That 3rd carbon atom bonds with 2 free-floating oxygen atoms to form CO2, carbon dioxide, and is exhaled.

16. Step 3 of the metabolic process... Krebs Cycle Oxygen Oxygen Step 3 occurs within the mitochondria of the cell. Carbon Carbon Carbon Carbon Exhale CoA Vitamin B Oxygen Oxygen Now enzymes and co-enzymes begin to break up the acetyl group. The CoA goes back to work again in another place. The two carbon atoms are removed. They hook up with free-floating oxygen atoms and end up being exhaled as CO2… carbon dioxide. CoA Vitamin B

17. Step 4 of the metabolic process... Electron transport chain Energy Energy Energy Energy Energy Hydrogen removed on electron transport chain H H H H H At this point, the hydrogen atoms have extra electrons attached to them. The electron transport chain strips off the extra electrons and carries their energy away. The remaining hydrogen atoms bond with oxygen atoms to form molecules of H20… water. H Oxygen H2O This occurs within the mitochondria of the cell and is still a catabolic reaction.

18. Step 5 of the metabolic process... ATP transports the energy Energy The energy cannot get to the part of the cell it needs to without assistance. It has to be transported in a vehicle called Adenosine (ə-dĕn'ə-sēn') Triphosphate… ATP. Phosphate Phosphate Energy Phosphate Phosphate Phosphate Phosphate Phosphate Phosphate Energy Energy Reaching its destination, enzymes break off the extra phosphate… releasing large amounts of energy. ADP… adenosine diphosphate picks up the energy Then the ADP picks up another free floating phosphate (a salt), and becomes ATP. Phosphate Phosphate The ADP returns to pick up more energy and phosphates.

19. Step 6 of the metabolic process... Newly created energy is used up The newly created energy now combines with the amino acids of protein to form new cytoplasm for the cells. This “building up” of organs and body tissues is an ANABOLIC process. Energy + amino acids = new growth Anabolism maintains the cells, and is responsible for growth of a variety of compounds and tissues. It creates muscle, hair, skin, organs, flesh, bone, chemicals such as hormones and enzymes, nails, and muscle. Some hormones, referred to as anabolic steroids, help the body grow muscle.

20. Influences on metabolism... Your metabolic rate is “how fast the chemical processes of metabolism take place”. Metabolic rate is influenced by 5 factors. Extreme temperature changes, such as with fevers or the environment, may increase or slow rates. Body size affects metabolic rate. The greater the surface area is in relation to mass… the higher the metabolic rate needs to be just to stay warm.

21. Body composition affects metabolic rate. Lean tissue requires a higher rate than fatty tissue. Generally women have a lower metabolic rate than men, and younger people have a higher rate than older people who have started to lose lean tissue. Metabolic rates are affected by age. Rates are high for young people, as they are building new cell materials during growth. Adult metabolic rates drop to maintenance levels. Energy supplies can affect metabolism. When the energy supply (food) is scarce or severely limited, metabolic rates decrease.

22. How is energy measured? In chemistry, a calorie (small c) is not a ‘thing’…but a unit of heat measurement. One calorie is the amount of energy needed to raise the temperature of 1.0 gram of water 1.0° Celsius. Most people use the word calorie incorrectly. They are actually talking about kilocalories (kcal). A kcal equals 1,000 calories and is referred to as a Calorie (capital C). Suppose your favorite snack food or drink label reports that a serving contains 0 Calories. Does that always mean it is calorie-free? (remember… it takes 1,000 calories to equal 1 Calorie) A joule (jool) is another unit of heat energy. 1 joule (J) is equal to 0.239 calories.

23. What is basal metabolism? Basal metabolism is energy used by a body at rest to maintain involuntary, life-supporting processes such as breathing, regulating heartbeat, growing new cells, and maintaining body temperature. About 2/3rds of the energy your body produces is spent on basal metabolism. Basal metabolism is expressed as basal metabolic rate, or BMR. BMR is a measure of heat given off per time unit… usually as kcalories per hour. You can use your BMR to estimate your daily kcalorie needs.

24. Calculating basal metabolic rate... Calculating your basal metabolic rate (BMR) can help you determine your nutrition and energy needs for the day. Although a precise measurement of BMR takes special equipment and/or procedures, you can get an estimate. • Find your mass in kilograms. Divide your weight in pounds by 2.2. • Find your basal metabolic rate (BMR) or the kcalories you use per hour. If you are female, mulitply your mass by 0.9. If you are male, multiply by 1.0 • Determine kilocalories (Calories) used per day by multiplying your BMR by 24. A 130 pound female would use about 1,272 Calories per day “at rest”. A 180 pound male would use 1,416 Calories per day “at rest”.

25. Calculating total daily caloric needs... With 2/3rds of the body’s energy used on basal metabolism the remaining 1/3rd is used for voluntary activities. The number of kcalories a voluntary activity uses will depend on how physical the activity is, the amount of time you spend doing it, and your own level of fitness. To determine your daily kcalorie needs for both basal metabolism and voluntary activities, take your kcalories needed for basal metabolism… Multiplied by 1.20 for a sedentary lifestyle Multiplied by 1.30 for a lifestyle of light activity Multiplied by 1.40 for a lifestyle of moderate activity Multiplied by 1.50 for a lifestyle of vigorous activity

26. Metabolism and weight management... When the number of kcalories in the food you consume exceeds the number of kcalories you use up in basal metabolism and voluntary activities… the excess kcalories will be stored in the body as fat. For every 3,600 excess kcalories you consume, you will gain one pound of weight. To maintain or lose weight, you must either reduce the number of kcalories you are consuming OR you can use up more kcalories by increasing your level of physical activity.

27. ABSORPTION AND METABOLISM THE END