Metabolism And Nutrition

Human Anatomy and Physiology II

Biology 1414

Unit 8

Metabolism and Nutrition

Objective 1

Define metabolism and differentiate between catabolism and anabolism. Be able to apply the latter two terms to various metabolic reactions.

Unit 8 - Objective 1

Definition of Metabolism

Metabolism is defined as the sum total of all chemical reactions that occur in the body.


Catabolism

Catabolism is that part of metabolism that involves the break down of large, complex molecules into smaller, more simplified products. This occurs during digestion, removal of hydrogen (dehydrogenation), carboxyl groups (decarboxylation) and amino groups (deamination), oxidation, etc.


Anabolism

Anabolism is that part of metabolism that involves the synthesis of larger, more complex molecules from small, simple reactants. Examples of anabolism would include the synthesis of glycogen from glucose, protein from amino acids, fat from glycerol and fatty acids and construction of new antibodies and new enzymes.


Objective 2

Indicate the location of , diagram and describe the major metabolic pathways involved in the catabolism of glucose to carbon dioxide and water. Indicate where hydrogens are given off, where ATP is made where oxygen is utilized, where water is produced and identify key assigned intermediates.


Glucose Catabolsm

Glucose Catabolism is one of the primary metabolic events that occurs during cell metabolism. The portion of cell metabolism that breaks down glucose is generally called cellular respiration. Cellular respiration has three major events; glycolysis, the Krebs cycle and the electron transport system (ETS).


Location of the Major Metabolic Pathways

Metabolic Pathway Location

Glycolysis Cytoplasm

Krebs Cycle Mitochondria

(matrix)

Electron Transport Mitrochondria

System (cristae)


Events of GlycolysisIn phase one, Glycolysis takes in glucose as a “fuel” and transforms it into a “super active” intermediate compound called Fructose-1,6- Diphosphate (F-1,6-DP). This is accomplished by using two ATP molecules to phosphorylate the sugar at carbons 1 and 6. In phase two, the F-1,6-DP sugar then splits (lysis) into two, half sized sugar fragments which become Glyceraldehyde Phosphate and Dihydroxyacetone Phosphate.


Events of GlycolysisIn phase three, the two half sized intermediates are oxidized down to two pyruvic acid molecules. During this process, inorganic phosphate is added from the substrate of the cytoplasm to each intermediate, hydrogen along with its electrons are removed from each intermediate, NAD picks up the hydrogens for transport and all of the phosphate is removed (4 total) from the intermediates. This phosphate is added to ADP to form four ATP molecules.


Events of GlycolysisThe removal of hydrogen is called dehydrogenation and is an oxidation process.

When NAD picks up hydrogen, a reduction process occurs. The addition of phosphate is called phosphorylation and results in the net production of two ATP molecules ( two used up in phase one minus four produced in phase three). The overall transformation of glucose into two pyruvic acids is also an oxidation process.


Events of GlycolysisExamine the following slide in order to visualize the event of Glycolysis.


Summary of Glycolysis

Events of The Krebs CycleThe Krebs cycle is named after Hans Krebs and is a metabolic event that follows glycolysis. This process occurs in the fluid matrix of the mitochondrion, uses the pyruvic acid from glycolysis and is aerobic. To begin the Krebs cycle, pyruvic acid is converted to acetyl COA.


Conversion of Pyruvic Acid to Acetyl COA

The conversion of pyruvic acid to acetyl COA is a three step process:

1. First, each of the two pyruvic acids are

decarboxylated . At this point, two carbon

dioxides are produced and diffuse to the

blood. This event yields two acetyl groups.

2. Next, hydrogen is removed from each

acetyl group and added to NAD.The removal of hydrogen

is called dehydrogenation which is an oxidation process.

The addition of hydrogen to NAD is a reduction process.

3. Finally, COA is added to each acetyl group. Unit 8 - Objective 2

Events of The Krebs Cycle

AcetylCOA which results from the conversion of pyruvic acid then reacts with oxaloacetate using an enzyme called citrate synthase. This results in the first major product of the Krebs cycle called citric acid. Because of this, the Krebs cycle is sometimes called the citric acid cycle. The citric acid is then systematically decarboxylated and dehyrogenated in order to use up the acetyl groups that were attached to the oxaloacetate. This allows oxaloacetate and COA to be used in the next cycle.


Events of The Krebs CycleThe conversion of citric acid back to oxaloacetate involves three dehydrodenations that form three reduced NAD (NADH2) molecules, one dehydrogenation that forms one reduced FAD

(FADH2), two decarboxylations that form two carbon dioxides and one substrate phosphoporylation that forms an ATP molecule. When two acetylCOA’s are utilized, two cycles occur and the above output is doubled.


Output of The Krebs Cycle

1. Six CO2 molecules

2. Eight reduced NAD molecules (NADH2)

3. Two reduced FAD molecules (FADH2)

4. Two ATP molecules


Events of The Krebs CycleExamine the following slide in order to visualize the events of the Krebs Cycle.


Summary of the Krebs Cycle

Events of the Electron Transport System (ETS)

The electron transport system can also be called the electron transport chain. This metabolic process uses the reduced NAD and FAD that is produced by glycolysis and the Krebs cycle. The ETS takes place in the cristae of the mitochondrion and uses oxygen directly (aerobic). This system contains respiratory enzyme complexes that include iron compounds called cytochromes. The cytochromes accept hydrogen from NAD and FAD.


Events of the Electron Transport System

After receiving hydrogen, the cytochromes split hydrogen into an electron and a hydrogen ion. Electrons from hydrogen are passed through the chain to oxygen. Hydrogen ions are passed into the space between the inner and outer membane of the mitochondrion where they accumulate and create an elevated hydrogen potential. The high potential causes the hydrogen ions to pass through an ATP synthase protein portal.


Events of the Electron Transport System

The hydrogen from NAD will yield 3 ATP’s and the hydrogen from FAD will yield 2 ATP’s. The ETS will process 10 reduced NAD’s from glycolysis and the Krebs cycle to yield 30 ATP’s.The ETS will also process 4 reduced FAD’s from the Krebs cycle to yield 4 ATP’s.

The hydrogen ions that pass back into the mitochondrial matrix then combine with the oxygen that has gained electrons to form water.


Summary of the Electron Transport System

When hydrogen loses electrons in the ETS, this is called oxidation. When Oxygen accepts those electrons, it is called reduction. When ATP synthase adds phosphate to ADP when it passes hydrogen ions to reduced oxygen, this process is called oxidative phosphorylation. The addition of hydrogen ions to oxygen creates enough water to yield a net of 6 waters for the process of cellular respiration. Make note of this when you observe the slide for Objective 3.


Summary of the Electron Transport System

Examine the following slides in order to visualize the events of the electron transport system.


Processing Reduced NAD in the ETS

Processing Reduced FAD in the ETS

Oxidative Phosphorylation

Summary of Total ATP ProductionExamine the following slide in order to view the summary of total ATP production in Glycolysis, the Krebs cycle and the Electron Transport System.


ATP Formation During Cellular Respiration

Objective 3

Write the general balanced equation that shows the catabolism of glucose to carbon dioxide and water. Include in the equation the formation of ATP from ADP and phosphate and oxygen utilization.


General Equation for Cellular Respiration

C6H12O6 + O6 + 36 ADP + 36 PO4

6CO2 + 6H2O + 36 ATP + Heat


Objective 4

Diagram and describe how lipids and proteins are catabolized into carbon dioxide and water.

Unit 8 - Objective4

Catabolism of Lipids

Lipids such as triglycerides are broken down to fatty acids and glycerol. Fatty acids are broken down to acetylCOA through a process of beta oxidation. AcetylCOA is then taken into the Krebs cycle and converted into carbon dioxide, reduced NAD and FAD and ATP. Glycerol is converted into Glyceraldehyde phosphate or dihydroxyacetone phosphate in Glycolysis and converted into reduced NAD , ATP and pyruvic acid.


LIPID METABOLISM

Catabolism of Proteins

Proteins are broken down to amino acids. Amino acids are deaminated and converted into metabolic fragments. For example, glycine is converted into an acetyl group that can become acetyl COA. AcetylCOA is then broken down in the Krebs cycle as discussed in the slide before last. The amine group from glycine is then used as part of urea formation.

Unit 8 - Objective4

Amino Acid Metabolism

Summary of Lipid and Protein Catabolism

View the following slide for a summary of lipid and protein catabolism


Catabolism of Lipids and Proteins

Objective 5

Describe what is meant by the following: beta oxidation, deamination, glycerol catabolism, ketone body formation, fatty acid catabolism, amino acid catabolism.


Beta Oxidation

Beta oxidation is a catabolic process that breaks down fatty acids two carbon units at a time. The two carbon units become acetyl groups that are converted into acetyl COA. An acetyl COA is then used in the Krebs Cycle to make one ATP , 3 NADH2 and 1 FADH2. If a fatty acid has 18 carbon units, then 9 acetyl COA units would be made. Think how much extra ATP and reduced NAD And FAD can be made because of this!


Deamination

Deamination is a catabolic process that removes an amino group from an amino acid in preparation for its use in the Krebs Cycle or a similar metabolic pathway.


Glycerol Catabolism

When fat is digested it is broken down to glycerol and fatty acids. Glycerol is then converted to glyceraldehyde phosphate (GALP) and used at a mid point in glycolysis (see Glycolysis in Objective 2). The GALP is then broken down to form ATP, reduced NAD and pyruvic acid.


Fatty Acid Catabolism

When fat is digested it is broken down to glycerol and fatty acids. The fatty acids are then broken down by the process of beta oxidation to produce acetyl COA as discussed in a previous slide.


Ketone Body FormationIf a person is not getting enough glucose through the diet (rare!) because of fasting, starvation, etc. or if glucose is not being transferred from the blood to body cells (as in diabetes mellitus), then oxaloacetate from the Krebs Cycle is converted to new glucose. Without oxaloacetate, Acetyl COA cannot be used and accumulates. The liver then converts excess acetyl COA into ketones (acetone, acetoacetate, etc.). These ketones are acidic and as they accumulate, they cause ketoacidosis.


Amino Acid CatabolismIf more amino acids accumulate than can be used in the synthesis of new proteins, then they can be catabolized or broken down by a process called deamination. Deamination removes amino groups from the amino acid to yield a fragment that can be used in the Krebs Cycle.


Objective 6

Discuss the role of LDL, HDL and saturated fats in cholesterol metabolism.


Role of LDL in Cholesterol Metabolism

LDL stands for low density proteins made in the liver. These metabolic units contain small portions of phospholipids an triglycerides and large quantities of cholesterol. The LDL is designed to transport its stored material from the liver to cells and tissues. Cholesterol from LDL’s can be transported to blood vessels and stored as part of plaque deposits


Role of HDL in Cholesterol Metabolism

HDL stands for high density lipoprotein which is made in tissues during increased activity. This metabolic unit transports phospholipid, triglyceride and cholesterol from tissues, including blood vessels, back to the liver.

The cholesterol that is transported back to the liver is converted into Bile which is excreted and stored in the gall bladder. This is a good way to eliminate cholesterol from the body.


Role of Saturated Fats in Cholesterol Metabolism

Saturated fats are triglycerides that contain fatty acids that have a full compliment of hydrogen. This type of fat stimulates the liver to make cholesterol for storage in body tissues and to inhibit the release of cholesterol from the body.

In terms of good nutrition it is recommended that unsaturated fats be substituted for saturated fats a high percentage of the time in the diet.


Summary of Lipoproteins

Observe the following slide for the lipid composition of lipoproteins.


Comparison of LDL, HDL, Triglycerides and Cholesterol

Objective 7

Define the following as they relate to metabolism: oxidation, reduction, decarboxylation, dehydrogenation, oxidative phosphorylation, celllar respiration, glycolysis, pyruvic acid, coenzyme A, Krebs cycle, electron transport system (ETS), glycogenesis, glycogenolysis, gluconeogenesis Unit 8 - Objective 6

Cellular Respiration

Cellular respiration is a group of catabolic reactions in the cell that breaks down food fuels such as glucose. These reactions can be grouped into metabolic processes called glycolysis, the Krebs cycle and the electron transport system. The main purpose of cellular respiration is to provide a constant supply of ATP for various cell activities.


Glycolysis

Glycolysis (= splitting sugar) is an anaerobic process that occurs in the cell cytoplasm. This process breaks down glucose into two pyruvic acids. During this conversion, ATP and reduced NAD is formed.


Pyruvic Acid

Pyruvic acid is the end product of glucose breakdown that occurs in the process of Glycolysis.


Coenzyme A

Coenzyme A, which is made using the vitamin pantothenic acid, is an important cofactor that is used to transport acetyl groups into the Krebs Cycle.


Krebs Cycle

The krebs cycle is a part of cellular respiration that occurs in the matrix of the mitochondrion. This process regenerates oxaloacetate during each cycle which is used to pick up acetyl groups to form citric acid. As acetyl groups are broken down during this cycle, ATP and reduced NAD and FAD are synthesized. Since the mitochondrion uses oxygen this process is considered aerobic.


Electron Transport System

The electron transport system (ETS) occurs in the cristae of the mitochondrion and is aerobic. This part of cellular respiration uses the reduced NAD and FAD from glycolysis and the Krebs Cycle and oxygen to generate large quantities of ATP and water.


Oxidative Phosphorylation

Oxidative phosphorylation is a process that occurs in the electron transport system (ETS) and involves the addition of phosphate to ADP to make ATP. ATP production occurs in the ETS when electrons are removed from the hydrogen being transported by reduced NAD and FAD. The electrons from the hydrogen are ultimately passed on to Oxygen. Oxygen is the final electron acceptor in the body!


Glycogenesis

Glycogenesis is an anabolic process that occurs mainly in the liver and muscle when there is excess glucose. This process combines hundreds of glucose molecules to form glycogen. Glycogen

is then stored in the cell as a “starch-like” compound .


Glycogenlolysis

Glycogenolysis is a catabolic process that occurs mainly in the liver an muscle. This process is essentially a reversal of glycogenesis (see previous slide). During glycogenolysis, stored glycogen is broken down to release glucose for use in the body.


Comparison of Glycogenesis and Glycogenolysis

Gluconeogenesis

Gluconeogenesis is a process that produces new glucose from non-carbohydrate sources. The metabolic pathways can convert materials such as oxaloacetate (from the Krebs cycle), lactic acid, amino acid fragments and fat derivatives into glucose. Even though gluconeogenesis is anabolic, other factors in the body are “sacrificed” to make the new glucose. This can ultimately cause deterioration.


Objective 8

Define the term nutrient and list six major classes of nutrients.


Definition of Nutrient

A nutrient is defined as a substance in food that is used by the body to promote growth, repair and maintenance.


Major Classes of Nutrients

1. Carbohydrates

2. Lipids

3. Proteins

4. Minerals

5. Vitamins

6. WaterUnit 8 - Objective 8

Objective 9

Define the term mineral and give the proper symbol and function of the following: calcium, phosphorous, iron, iodine, sodium, potassium, magnesium, zinc.


Definition of Mineral

A mineral is an inorganic substance made from a metal and a nonmineral. For exmple, The metal sodium forms a sodium ion in water that can react with a chloride ion that forms from chlorine gas that can dissolve in water. This results in sodium chloride which is an inorganic salt and one of the more abundant minerals in the earth.


CalciumCalcium ( Ca+2) is a cation that has multiple uses in the body. Included in the list of uses are:

1. Assists blood clotting

2. Assists hardening of teeth and bones

3. Assists nerve cell function

4. Helps to initiate muscle contraction


PhosphorousPhosphorous is used mainly in the form of phosphate ( PO4

-3). This anion can be used to:

1. Combine with ADP to form ATP

2. Combine with calcium to form

a crystalline bone salt called

calcium phosphate.

3. Form buffers for acid-base control


IronIron ( Fe+2) is a cation that has several uses in the body. Included in the list are:

1. Used as a cofactor in enzyme

activity

2. Used to make cytochromes found in

the ETS

3. Used to form hemoglobin


IodineIodine ( I-1) is an anion that is used mainly to form thyroid hormones.


SodiumSodium (Na+1) is a cation that is used to:

1. Create a positive condition outside

the cell.

2. Assist depolarization of nerve and

muscle cells

3. Osmotically control water in the

extracellular fluid (ECF)


PotassiumPotassium (K+1) is a cation that is used to:

1. Assist repolarization in nerve and

muscle cells

2. Assist osmotic control of water in the

intracellular fluid (ICF)

3. Contribute to synthesis reactions


MagnesiumMagnesium (Mg+2) is a cation that is used

to:

1. Assist enzymes that are involved in

in the formation of ATP

2. Maintain sensitivity in nerve cells


ZincZinc (Zn+2) is a cation that is used to:

1. Assist enzymes such as carbonic

anhydrase

2. Contribute to structure of certain

proteins e.g. tumor suppressor protein

3. Required for normal growth, wound

healing, taste, smell, sperm

production, prostate activity, etc.


Objective 10Define what is meant by the term vitamin and give or recognize the function (s) of the following vitamins. Indicate whether each vitamin is water or fat soluble and discuss how this characteristic influences vitamin retention: Vitamins A, D, E, K, C, Niacin, Riboflavin, Thiamine and Pantothenic Acid.


Definition of VitaminA vitamin is a specialized organic compound that is used to assist enzymes in various metabolic reactions. For example the enzyme succinate dehydrogenase removes hydrogen from succinic acid in the Krebs cycle and then transfers this hydrogen to FAD which is made from riboflavin. The hydrogen transfer to FAD is called reduction. Reduced FAD then transports hydrogen to the ETS.


Vitamin A

Vitamin A is a fat soluble vitamin that can take the form of retinol or retinal. This vitamin can be stored in fats and oils, and, if there is excessive storage, toxicity can result. The functions for Vitamin A include:

1. Serves as an antixoidant

2. Assists the formation of light sensitive pigments

in rod and cone cells of the retina.

3. Assists growth of teeth, bones and reproductive

cells.


Vitamin D

Vitamin D is a fat soluble vitamin that is made in the skin due to exposure to sunlight, This vitamin can be stored in fats and oils, and, if there is excessive storage, toxicity can result. The functions for Vitamin D include:

1. Stimulates calcium absorption in the body

2. Assists bone formation, blood clotting and nerve

function.


Vitamin E

Vitamin E is a fat soluble vitamin that is found in vegetables. This vitamin can be stored in fats and oils, toxicity seldom results. The functions for Vitamin E include:

1. Antioxidant

2. Helps protect cell membranes


Vitamin K

Vitamin K is a fat soluble vitamin that is found in vegetables, liver and can be made by bacteria in the large intestine. This vitamin is not stored in large amounts in the body. The functions for Vitamin K include:

1. Formation of blood clotting proteins

2. Used as an part of the electron transport system

and assists ATP formation


Vitamin C

Vitamin C is a water soluble vitamin that is found in fruits and vegetables. This vitamin cannot be stored in the body and must be consumed on a constant basis. The functions for Vitamin C include:

1. Antioxidant

2. Assists connective tissue formation

3. Assists formation of serotonin, bile and active

folacin

4. Assists iron absorption


Niacin

Niacin is a water soluble vitamin that is found in green, leafy vegetables meats and nuts. This vitamin cannot be stored in the body and must be consumed on a constant basis. The functions for Niacin include:

1. Assists formation of NAD for use in cellular

respiration

2. Inhibits cholesterol formation

3. Dilates peripheral blood vessels and causes

flushing


Riboflavin

Riboflavin is a water soluble vitamin that is found in legumes, eggs, milk, yeast, meats and nuts. This vitamin cannot be stored in the body and must be consumed on a constant basis. The functions for Riboflavin include:

1. Assists formation of FAD for use in cellular

respiration


ThiamineThiamine is a water soluble vitamin that is found in legumes, eggs,, yeast, meats and green leafy vegetables. This vitamin cannot be stored in the body and must be consumed on a constant basis. The functions for thiamine include:

1. Assists transformation of pyruvic acid to

acetyl COA

2. Assists formation of pentose sugars such as

ribose and deoxyribose. Remember these!

3. Assists the formation of acetylcholine

4. Assists the oxidation of alcohol


Pantothenic AcidPantothenic Acid is a water soluble vitamin that is found in legumes, eggs,, yeast, meats and grains. This vitamin cannot be stored in the body and must be consumed on a constant basis. The functions for pantothenic acid include:

1. Used in the formation of coenzyme A

2. Involved in the synthesis of steriods and the heme

unit of hemoglobin


Objective 11Give the source and functions of the following hormones and indicate the cause and symptoms of the hormonal disorders listed below: insulin, thyroid stimulating hormone (TSH), thyroxine, growth hormone (GH), diabetes mellitus, hypoglycemia, hyperglycemia, cretinism, giantism, acromegaly, dwarfism


InsulinInsulin is a hormone produced by the beta cells of the pancreas. This hormone helps transfer glucose from the blood into the body cells and tissues. This hormone also helps tissues convert glucose into fat an glycogen.


HypoglycemiaIf an excess of insulin is produced, it can cause too much glucose to move out of the blood and into the cells and tissues of the body. This can result in a low blood sugar condition called hypoglycemia


HyperglycemiaIf too little insulin is produced, blood glucose accumulates and does not go into cells and tissues. This results in a high blood glucose condition called hyperglycemia.


Diabetes MellitusIf the beta cells of the pancreas become diseased and stop producing insulin at an early age, this results in a pathological condition called diabetes mellitis. This disease is sometimes called Type I ,or juvenile, diabetes because it results in chronic hyperglycemia that must be controlled for the life of the individual. Type II diabetes mellitus is due to age and poor response to insulin.


Thyroid Stimulating HormoneThyroid stimulating hormone (TSH) is produced and released from the anterior pituitary. As the name suggests, this hormone stimulates the thyroid to release thyroxine; either in the form T4 or T3.


ThyroxineThyroxine is a hormone produced by the follicles of the thyroid gland and is used to increase cell metabolism. This function helps to maintain proper growth, repair and body temperature. Excess thyroxine leads to hyperthyroidism and very high metabolism. Below normal thyroxine production leads to hypothyroidism and very low metabolism.


CretinismCretinism is a disease of very young children and occurs when below normal amounts of thyroxine are produced. This results in very low metabolism, growth and development. “Cretins” become severely stunted and retarded.


Growth HormoneGrowth Hormone (GH) is produced and released from the anterior pituitary. This hormone increases fat utilization, protein production and body organ development. The long bones of the body are especially stimulated to grow in length.


GiantismGiantism is a disease caused by excess secretion of growth hormone (GH). This disease occurs in young, fast growing children and results in excessive height for the person’s age and genetic background.


AcromegalyAcromegaly is a disease also caused by excess secretion of growth hormone (GH). This disease occurs in adults and results in overdeveloped body parts such as hands, feet, forehead, jaw and internal organs.


DwarfismDwarfism is a disease caused by below normal secretion of growth hormone (GH). This disease occurs in young children and results slow growth and very short height.


Objective 12Recognize and/or list five products produced by lipid and protein anabolism


Lipid AnabolismLipid anabolism is a constructive metabolic process that produces new lipids from such materials as glycerol, fatty acids, phosphates, etc. Products of lipid anabolism include:

1. Fats (triglycerides)

2. Oils

3. Waxes

4. Phospholipids 5. Steriods Unit 8 - Objective 12

Protein AnabolismProtein anabolism is a constructive metabolic process that produces new proteins from amino acids. Products of protein anabolism include:

1. New enzymes

2. New antibodies

3. New muscle proteins; actin, myosin, etc.

4. New Collagen for the skin

5. New keratin for the hair and fingernailsUnit 8 - Objective 12

Metabolism And Nutrition

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