Unit 7: Metabolism Of Nutrients And Energy Balance Flashcards
Explain the role of Adenosine Triphosphate (ATP) in the body
-Energy associated is transferrred to chemical bonds of ATP
-Formed from Adenosine Diphosphate (ADP) and a free phosphate
ADP + P + energy = ATP (requires energy)
-The high energy phosphate bonds of ATP can be broken to release free energy
ATP –> ADP + P + energy for body cells
How efficient is the conversion of the chemical energy of food to the chemical energy of ATP?
~50%
What is the energy from ATP used for?
- Movement (muscles)
- Synthesizing compounds
- Transporting nutrients
ATP has 3 phosphate groups. The negative charges on the phosphate groups make ATP vulnerable to what?
Hydrolysis
When the bonds between the phosphate groups are hydrolyze they break , splitting into one or two phosphate groups and releasing energy
Often, the hydrolysis of ATP occurs simultaneously with reactions that will use that energy. This is known as?
Coupled Reactions
Body uses ATP to transfer the energy released during catabolic retractions to power anabolic reactions
Define Catabolism
Breaking down of body compounds
Release energy
Define Anabolism
Creation of body compounds
Require energy
Ex. Making of glycogen, triglycerides, protein
Explain Glycolysis
- Preliminary phase of glucose catabolism
- Occurs in Cytoplasm of cell
- Results in: splitting glucose (6-carbon) into 2 pyruvate (3-carbon)
- Anaerobic (does not require oxygen)–important source of energy when oxygen is limited
- Yields small amount of ATPl
Under Anaerobic conditions what happens to Pyruvate?
- Yields energy quickly but cannot be sustained
- Converted to lactic acid
- Lactic acid is converted back to pyruvate after rest or travels to the liver to be converted back to glucose.
- The glucose can then be used by muscle cells to replenish glycogen or produce energy aerobically again
Under aerobic conditions what happens to pyruvate?
- Energy expenditure is slower paced
- Pyruvate breaks down to Acetyl CoA
- Total energy yield is greater and can be sustained
Explain the functions of Acetyl CoA
- Synthesize Fats: efficient way to store energy, glucose, fatty acids, amino acids can be used to make Acetyl CoA and therefore fat
- Generate ATP: Acetyl CoA proceeds through TCA cycle, releasing energy in its C-C bonds and hydrogens with their electrons to the electron transport chain
Explain the Tricarboxylic Acid (TCA) cycle a.k.a. The Krebs cycle
- requires oxygen
- second stage of glucose catabolism
- occurs in mitochondria of the cell
- generates ~94% of energy from glucose
Explain the steps of the TCA cycle
- Oxaloacetate (compound made from pyruvate) starts the TCA cycle
- Oxaloacetate (4-carbon) combines with Acetyl CoA (2-carbon) to make 6-carbon compound
- This compound is changed to a 6-carbon compound that release CO2 becoming a 5-C, then 4-C compound
- The original 4-C Oxaloacetate is formed again and picks up a new Acetyl CoA
- The breakdown of Acetyl CoA releases hydrogens with their electrons which are carried by coenzymes made from B vitamins to the electron transport chain
What B vitamins are required by the TCA cycle?
- Thiamin
- Niacin
- Pantothenic Acid
All 3 are essential components of coenzymes TPP, NAD, and CoA - Riboflavin
- B12
What is produced from 1 cycle of the TCA cycle? (2 Acetyl CoA)
- 4 CO2
- 4 pairs of hydrogen ions: H+
- 2 FADH2
- 6 NADH + H+
- 2 GTP
What are the products of glycolysis?
- 4 ATP (Net 2 ATP because 2 ATP are used to begin reaction)
- 4 NADH + H+
Explain the Electron Transport Chain
-Final stage of glucose catabolism
-transfer of electrons from one coenzyme to another in an oxidation-reduction process
-Phosphorylation of ADP to ATP (Oxidative phosphorylation)
-Hydrogen is combined with oxygen to produce water
C6H12O6 + 6O2 –> 6CO2 + 6H2O + energy (ATP)
Define Deamination
Removal of an amino group from an amino acid or other compound
Explain Oxidative Phosphorylation
ADP and P are combined (requiring oxygen) to form ATP
ATP is Phosphorylated
What is the ATP production from the Electron Transport Chain?
28 ATP
What is the total ATP production from Glucose metabolism
Electron Transport Chain: 28 ATP Glycolysis: 2 ATP GTP: 2 ATP ----------------------------------- Total: 32 ATP
Why might the total ATP production be 30 ATP?
The NADH + H+ generated in the cytoplasm during glycolysis pass electrons to shuttle molecules which move them to the mitochondria. One shuttle, malate, contributes electrons to the Electron Transport Chain before the first site of ATP synthesis, yielding 5 ATP. Another, glycerol phosphate, adds its electrons to the chain beyond that first site, yielding 3 ATP. Thus, sometimes 5 or 3 ATP result from glycolysis
Explain Gluconeogenesis
Making glucose from noncarbohydrate sources.
The glycerol portion of a triglyceride (3-carbon) and most amino acids can be used. Fatty Acids (2-carbon) cannot be used. Liver is the major site of gluconeogenesis but the kidneys become involved under certain circumstances (Starvation)
Fatty acids are ensymatically combined catabolized by combining with CoA, where each chain is cleaved at the second carbon forming multiple units of Acetyl CoA. This is known as?
Beta-Oxidation or Fatty Acid Oxidation
Glycerol to Pyruvate
Glycerol is a 3-C compound and so can be easily converted to other 3-C compounds. It can therefore, go either “up” to form glucose or “down” to from pyruvate then Acetyl CoA
Fatty Acids to Acetyl CoA
2 carbon fragments from fatty acids combine with CoA to from Acetyl CoA. As each 2-C fragment breaks off hydrogens and their electrons are released and carried to the electron transport chain by coenzymes made from the B vitamins Riboflavin and Niacin
Beta-Oxidation of Palmitic Acid
C16 + CoA –> C14 + Acetyl CoA + 2 hydrogen pairs
C14 + CoA –> C12 + Acetyl CoA + 2 hydrogen pairs
C12 + CoA –> C10 + Acetyl CoA + 2 hydrogen pairs
Hydrogens are picked up by NAD and FAD which act as carriers in the ETC in the production of ATP. The Acetyl CoA enters the TCA cycle and generates more hydrogen pairs for ATP production
The extraction of energy from fats (beta-oxidation and TCA cycle) are dependent on what? This means that aerobic exercise is recommended for?
Dependent on oxygen
Recommended for burning of body fat and weight control
During anaerobic exercise what is halted?
Fat catabolism
About how much total energy from fat oxidation comes through beta-oxidation?
Through TCA cycle?
Beta -oxidation: 0.25
TCA cycle: 0.75
Triglycerides from food or stored as fat are excellent sources of energy as ATP, built are a minor source of glucose why?
Because most of a triglyceride molecule is made of fatty acids
The primary role of Amino Acids is protein synthesis; they are only catabolized when: (3)
1, Insufficient energy or glucose
- Excess of protein for body requirements
- Proteins are of such poor quality that protein synthesis is curtailed
Amino acids are deaminated before then enter the pathways of energy production/storage. Describe deamination, and its products
Enzymatic removal of the amino group from the amino acid; resulting in production of ammonia. Requires Vitamin B-6, riboflavin and niacin. Ammonia is combined with CO2 by the liver to form urea which is then excreted in the urine by the kidneys
Why is the production of urea important?
Urea is far less toxic than ammonia
An amino acid can enter the metabolic pathways through pyruvate, Acetyl CoA or certain intermediates of the TCA cycle, depending on what?
The carbon-skeleton of the amino acid
Only amino acids that can be converted to Pyruvate can produce glucose through what?
Gluconeogenesis
Approximately how many amino acids are potential sources of glucose?
~0.5 of the amino acids
Unlike fat, amino acids are…
A fairly good source of glucose in the absence of carbohydrates
The body is more efficient at storing excess dietary fat as body fat than…
Converting excess carbohydrate/protein to body fat
Body proteins from muscle and lean tissue start to be catabolized when glycogen stores are depleted and no carbohydrates are available. This happens:
After several hours of fasting or low carb dieting
A high intake of protein may be provided by a diet very low in carbohydrate, a high intake of protein cannot prevent what?
Loss of body protein
Define Ketone bodies
- normal metabolites of the body
- at low production the body can metabolize
Explain how Ketosis occurs
- during fasting or low-carb dieting
- lack of carbohydrate stimulates breakdown of fatty acids
- Acetyl-CoA accumulates because there is insufficient oxaloacetate
- Acetyl-CoA cannot form citric acid in TCA cycle
- Acetyl-CoA fragments condense to form ketone bodies
- Ketone bodies reach high concentration in blood
Who can Ketosis happen to?
- untreated diabetes
- starved for glucose
What are some characteristics of Ketosis?
- acetone breath (sweet smelling)
- suppresses appetite
- increases urine output
- causes nausea
What are some consequences of severe Ketosis?
- Acidosis (low pH of blood)
- Loss of water from body tissue (to excrete Ketones)
- Sodium and potassium become depleted
- Blood pressure drops
- Death can result from collapse of circulatory system
Define Direct Calorimetry
- actual measurement of energy as heat
- using a bomb calorimeter it calculates the energy in foods by measuring total amount of heat released after complete combustion
- can also be used to measure energy expenditure of a person (total amount of heat released)–this requires a specially designed chamber and is expensive
Define Indirect Calorimetry
- measurement of oxygen consumption and carbon dioxide production to determine the amount of energy used by the body
- requires of portable respiration device–less expensive
- allows for a measurement of a wider range of physical activities
Define Gross Energy Values
- Amount of energy determined by a bomb calorimeter when food is burned
- In the body energy from food is less than gross energy value because some is excreted in feces and urine (incomplete digestion/absorption)
Define Physiological Fuel Values and list them
-mathematical adjustment from gross energy values to better represent amount of energy available in the body Carbohydrates: 4 Lipids: 9 Protein: 4 Alcohol: 7
List the gross energy values
Carbohydrates: 4.10
Lipids: 9.45
Protein: 5.65
Alcohol: 7.10
Explain Satiety
- hormonal regulated but also influenced by nutrient composition of the diet
- Protein has greatest satiety because it takes longer to digest (glucose levels constant)
- High-fibre foods also provide satiety
- High-fat foods are not satiating but provide a concentrated source of glucose
Explain Energy Density
-fat and high-sugar/ refined white sugar are high energy-density foods. It is easy to consume a lot of high-energy dense foods before satiation causes eating to stop
Explain the function of water to satiety
- Water dilutes food energy
- High-water content foods (soups, salads, fruit) have a low energy density
- A small amount if food needs to be consumed to induce satiety
- A combination of high fibre and water content gives low energy density
Define Basal Metabolism
- Basal Metabolic Rate (BMR)
- minimum energy required to maintain vital life processes
- Measurement of BMR usually done in the morning under specific conditions
List the conditions of which BMR is measured
- Morning
- Subject is awake
- 12-15 hours after eating (absence of digestion/absorption)
- Lying quietly with complete physical and mental rest
- Room temperature (~25 degrees)
- Subject is wearing light clothing
What factors can increase BMR?
- height
- growth
- body composition (gender)
- fever
- stresses
- environmental temperature (both heat and cold)
- hormones (gender)
- smoking
- caffeine
What factors can decrease BMR?
- age
- fasting/starvation
- malnutrition
- sleep
Explain how BMR can be increased by exercise
- certain types of exercise can also build lean muscle mass
- leaner the body tissue the higher the BMR
- Exercise is emphasized in maintaining BMR for weight control
Define Thermic Effect of Food
The energy required to digest, absorb, transport, metabolize, and store nutrients from food
(Rise in body temperature after a food is consumed)
Depends on macronutrients (Protein foods create the greatest thermos effect)
~10% of total energy intake is estimated for the Thermic effect of food
Explain Thermogenesis
- additional energy expended when a person must adapt to chaining circumstances (dramatically)
- Known as adaptive thermogenesis
- It is so variable and specific to individuals it is not included when calculating energy requirements
How to measure BMR?
Men = 1 kcal/kg body weight/hour Women = 0.9 kcal/kg body weight/hour
How to measure energy expenditure from physical activity?
Physical activity =40-50% BMR sedentary work =55-65% BMR light work =65-70% BMR moderate work =120-140% BMR for heavy work
Define Resting Metabolic Rate (RMR)
-measure of energy output similar but slightly higher than BMR because its criteria for recent food intake and physical activity are not as strict
What are the Thermic effects of the macronutrients
Carbohydrates: 5-10%
Fat: 0-5%
Protein: 20-30%
Alcohol: 15-20%
Explain Body Mass Index (BMI)
- anthropometric measure based on relationship of body weight to height
- high correlation to body fat
- suitable only for people between 20-65 years old
- not valid for pregnant, breastfeeding, or muscular athletes
The lowest mortality rates are associated with a BMI of?
20-25
Risk of health problems increases with a BMI above or below?
18.5-25
As BMI increases so does the risk of?
Obesity-related diseases (diabetes, cardiovascular)
What is the draw pack of measuring BMI?
Tells nothing of body composition
Explain Percent Body Fat
- measured by hydrodensitometry or bioelectrical impedance (specialist purposes)
- measured by skin fold
Explain the Skin Fold Test
- used to measure percent body fat
- provides rough approximation
- measures thickness of fold of skin using a special caliper
- two most common sites: triceps and subscapular
- measure is compared to appropriate standard
Waist measurements
- indicator of health risks from high body fat
- measured at narrowest part of trunk (navel)
- provides indication of fat stored in the abdominal area (visceral fat)
Apple-shaped people have a higher risk of?
Chronic disease (type 2 diabetes, heart disease, hypertension, breast cancer)
Abdominal fat is easier to lose through diet and exercise than fat stored in hip area. TRUE OR FALSE?
TRUE
What waist circumference is associated with higher risk of disease?
Men: greater than 102 cm (40 inches)
Women: greater than 90 cm (35 inches)
Obstetrics in abdominal or upper region of the body is a strong predisposing condition to diabetes and cardiovascular disease. TRUE OR FALSE?
TRUE
What is the basic cause of obesity sometimes referred to as?
Obesogenic environment: ur environment has been designed to maximize weight gain
When might a person be considered underweight?
10% or more below ideal body weight
Approximately what percentage of girls/women between the ages of 14-24 have an eating disorder?
5%
What are some causes of being underweight?
- insufficient consumption of quality and quantity of food
- poor absorption/utilization of food consumed
- wasting diseases (TB, AIDS, hyperthyroidism, cancer which increase BMR)
- excessive physical activity
- psychological/emotional disorders
What are some risks of being underweight?
- nutrient deficiencies
- anemia
- higher risk of infection and disease
- retarded growth
- amenorrhea (cessation of menstruation)
- chronic fatigue
- heart irregularities
- hypotension
- psychological problems
- complications in pregnancy
