Understanding Metabolism

1. Understanding Metabolism • Almost every living creature including humans depend on the sun’s energy to survive. • Plants rely on the sun to provide the light energy that powers photosynthesis is the process of plants producing carbohydrate from water and carbon dioxide. “Lecture 6: Understanding Metabolism PowerPoint" by Dr. Michael Kobre, Achieving the Dream OER Degree Initiative, Tompkins Cortland Community College is licensed under CC BY 4.0

2. Metabolism • Within plants the sun’s energy is captured in the energy of chemical bonds that hold the atoms of sugars and starches together. • As humans, we use the sun’s energy indirectly. We do not photosynthesize for our energy needs. Instead, we depend on plants, or on animals that eat plants as our food sources to supply us our needed energy and structural material to grow, repair and function.

3. Metabolism • How do we obtain energy from food? • In the human body, we the process of metabolism to release energy from the chemical bonds in the nutrients we consume that the body uses for fuel. • As we break bonds during metabolism, those broken bonds release energy in a very controlled version of the same process by which wood (a carbohydrate) burns in a fire.

4. Metabolism • Both wood and food have potential to provide energy when their bonds are pulled apart. • When wood burns in the presence of oxygen, it’s bonds break apart and wood generates heat and light (energy), steam (water), and some carbon dioxide and ash (waste).Similarly, during the body’s metabolism, energy, water, and carbon dioxide are released but in a slower, more controlled fashion.

5. Metabolism • Energy extracted from the metabolism of fuel nutrients like carbohydrates and lipids enables our body to grow, repair, replace and generally function. • Fuel: Are compounds that cells can use for energy. The major fuels are glucose, fatty acids, and amino acids. Other alternative fuels include ketones, lactic acid, glycerol, and alcohol.

6. Metabolism Terms: • Metabolism: Is basically the sum total of all the chemical reactions that break things down and build things up in living cells. • Energy metabolism: includes all the those reactions shown above plus also takes into account energy spent obtaining and processing nutrients from food we consume. Procuring and processing uses energy too.

7. Metabolism Terms: • Two types of chemical reactions in the body: • Building reactions-Anabolism: where the cells can use the basic units of energy yielding nutrients to build body compounds. E.g. building muscle and bone • Anabolism: reactions in which small molecules are put together to build larger ones. Anabolic reactions require energy.

8. Metabolism Terms: • Breakdown reactions-Catabolism: in the body, the breakdown of body compounds is known as catabolism. Catabolic reactions usually release energy. • Catabolism: reactions in which large molecules are broken down into smaller ones. Catabolic reactions usually make energy available for the body to use as it’s energy source.

9. Metabolism "Metabolism.jpg" by Vtvu is licensed under CC BY-SA 3.0

10. Metabolism Terms: • Transfer of energy in reactions: When a chemical bond is broken, energy can be released as heat, captured in another chemical bond, or most times both happen. • Coupled reactions: Are pairs of chemical reactions where energy released from the breakdown of one compound is used to create a bond in the formation of another compound.

11. Metabolism • Energy released during catabolism is often captured by intermediate molecules (called high-energy compounds) that can easily transfer that energy to other compounds. • ATP (adenosine triphosphate): a common high-energy compound composed of a purine (adenine), and sugar (ribose), and three phosphate groups. Think of it as a rechargeable battery for cells.

12. Adenosine Triphosphate – A Rechargeable Battery for Living Cells "Structure of Adenosine Triphosphate (ATP)-01.jpg" by OpenStax College is licensed under CC BY-SA 3.0

13. Reactions In The Body • ATP, as its name indicates, contains three phosphate groups. The energy in the bonds between each phosphate group is higher than the energy in most other chemical bonds. When energy is needed, hydrolysis (breakdown) reaction readily break these high-energy bonds, splitting off one or two phosphate groups and aloowing the release of their energy.

14. Reactions In The Body • Cells in the body convert the energy stored in food to the energy currency of ATP molecules with about a 50% efficiency, losing the rest of the energy from the bond as heat. Once converted, ATP energy is used for work in cells, again about 50% is lost as heat. Thus, the overall efficiency of the human body in converting food energy to work is 25%, 75% is released as heat which gives us our core body temperature at rest.

15. Site of Reactions • Metabolic activity is happening all the time within our trillions of cells. The type and extent of metabolic activity vary depending on the type of cell. E.g. the liver cells are the most metabolically active and the adipose cells of the body use a fraction of the energy the liver’s cells require.

16. Site of Reactions Typical Animal cell Mitochondrion where ATP is made inside of cells "Eukaryotic Cell (animal).jpg" by Mediran is licensed under CC BY-SA 3.0 "Animal mitochondrion diagram en (edit).svg" by Mariana Ruiz Villarreal is in the Public Domain, CC0

17. Helpers In Reactions • Metabolic chemical reactions almost always require enzymes to facilitate their action. • In many reactions, the enzymes need additional molecules to assist them. Enzymes assistants are called coenzymes. Coenzymes are small organic molecules that associate closely with most enzymes, but are not proteins themselves.

18. Helpers In Reactions • The many of relationships between coenzymes and enzymes differ in detail. Without its coenzyme, most enzymes cannot function. • Some of the B vitamins we consume serve as coenzymes helpers to the enzymes that release energy from glucose, glycerol, fatty acids, and amino acids in metabolism.

19. Helpers In Reactions "Nutrition Metabolic Summary.jpg" by Boumphreyfr is licensed under CC BY-SA 3.0

20. Deamination Waste Products produced during Metabolism • When amino acids are metabolized for energy or used to make fat, they must have their Nitrogen Atoms removed. Two byproducts are produced. One is, of course, the carbon structure without its amino group, often a keto acid. The other product is ammonia, a toxic compound chemically identical to the ammonia in bottled cleaning solutions. If the body produces larger quantities then it can handle, the bloods acid/base balance becomes upset and can poison the body.

21. Ammonia to Urea in the Liver • During metabolism, our liver continuously produces small amounts of ammonia in deamination reactions. Some of this ammonia provides the nitrogen needed for making some of nonessential amino acids. The liver quickly combines any remaining ammonia with carbon dioxide to make urea, a much less toxic compound.

22. Urea Excreted via Kidneys • Our liver’s cells release urea into the bloodstream, where it circulates until it enters the kidneys. The kidneys remove urea from the blood for excretion in the urine. Normally, our liver captures all the ammonia, makes urea from it, and releases it into the bloodstream. The kidneys receive and clear urea. If our liver is sick, the blood ammonia levels become be high, if the kidneys are failing, blood levels of urea will become high.

23. Breaking Down Nutrients for Energy • Carbohydrates, lipids and protein all provide our cells with energy. Each of the above nutrients contain differing energy amounts based on the number of carbon-hydrogen bonds they contain. The more carbon-hydrogen bonds, and the larger the molecule, the more energy contained and can be used to make ATP energy in our cells.

24. Calories In Nutrients We Consume • The kCalories-per-Gram Secret Revealed • Fat provides 9 kcal/gram (double the energy). • Carbohydrate provides 4 kcal/gram. • Protein provides 4 kcal/gram. • Fat provides more energy because the bonds in fat molecules are easily oxidized and have many more carbon-hydrogen bonds resulting in more ATP.

25. The Body’s Energy Budget • Every day, a healthy diet delivers 1000’s of Kcals from foods, and our body uses most of them to perform functions. As a result, body weight changes very little, if at all. Many of us manage energy balance without even thinking about it at all. Some people however, eat too much food and gain weight, and some people do not eat enough and lose weight.

26. The Economics of Feasting • When we consume too much, metabolism in cells favor body fat formation. Our adipose cells enlarge and multiply in number regardless of whether the excess energy is derived from protein, fat or carbohydrate. The pathway from dietary fat to body fat, however, is the most direct, and the most efficient. Consuming too much fat will make you gain weight fast.

27. The Economics of Feasting When we store excess energy from dietary fat in our adipose cells, only 5% of the ingested energy consumed is used to convert and store dietary lipid as body fat. When compared to carbohydrate, 25% of the ingested energy is required to convert and store carbohydrates as body fat.

28. The Economics of Feasting • Converting and storing carbohydrate and protein as body is indirect and inefficient for us. Before we convert protein to fat for storage, protein must first and foremost must fulfill many roles our cells. Carbohydrates, first fill the body’s needed glycogen stores I the liver and muscle cells before being converted to triglyceride and being stored.

29. Energy Balance • Fasting—Inadequate Energy Intake Glucose is needed for normal brain function. In the absence of Glucose, protein in the body must be broken down to make glucose. The Shift to ketosis starts when glucose runs out. Ketones molecules are produced when glucose is not available in the diet. Ketosis causes a suppression of the appetite, a slowing of metabolism, and eventually makes us very sick if we don’t consume enough carbohydrates.

30. Energy Balance • Fasting Inadequate Energy Intake: • Symptoms of Starvation • Muscle wasting • Decreased heart rate, respiratory rate, metabolic rate, and body temperature • Impaired vision • Organ failure • Decreased immunity • Depression, anxiety, and sometimes food-related dreams

31. In Summary • If energy intake exceeds the body’s energy needs, the result will be weight gain-regardless of whether the excess intake is protein, carbohydrate, or fat. If we consume balanced, moderate meals our body will have a much better chance of maintaining normal functions. Eating everything in moderation is a much better choice for good health.