understand the key points of Glycolysis and identify alternate forms of energy production employed
Glycolysis - “Breaking down glucose.” Takes place in the cytosol of the cell, breaking glucose into 2 units of pyruvate (3-carbon compound) .
Glycolysis has 2 roles: Break down carbohydrates to generate energy To provide building blocks for synthesizing other needed compounds.
8 Steps in Glycolysis
Activate the glucose molecule by attaching a phosphate group to it. The attached phosphate group is supplied by ATP, which means that energy is required for this step and that ADP is formed.
The molecule is rearranged and a 2nd phosphate group is added using ATP, forming Fructose 1,6-bisphosphate. Again, ATP provides the phosphate, making this a energy-requiring step.
Fructose 1,6-bisphosphate is split in half to form two 3-carbon molecules, each of which has 1 phosphate-glyceraldehyde 3-phosphate and dihydroxyacetone phosphate. Dihydroxyacetone phosphate is eventually converted into glyceraldehyde 3-phosphate. Thus, step 4 onward occurs twice for each molecule of glucose that enters Glycolysis.
A dehydrogenase enzyme oxidizes each of the two 3-carbon molecules. NAD is reduced, forming 2 NADH + 2 H+. A phosphate molecule is added to each 3-carbon molecule.
An enzyme transfers 1 phosphate from each of the 3-carbon molecules to an ADP, forming 2 ATP, This is the first synthesis of the high-energy compound ATP in the pathway.
Water is removed from each of the 3-carbon molecules, which produces two 3-carbon-phosphate molecules.
An enzyme transfers 1 phosphate from each of the 3-carbon molecules to an ADP, thereby producing a total of 2 ATP.
The last step in Glycolysis is the formation of pyruvate. Generally, pyruvate enters the mitochondria for further metabolism. A total of 2 pyruvates are formed from each glucose that enters Glycolysis.
Alternate forms of energy employed:(how it is done with fats, protein, not just carbs?)
Gluconeogenesis – the pathway to produce glucose from certain amino acids, present only in liver (primarily) cells and certain kidney cells
Begins in the mitochondria, then moves to cytosol
Amino acids to form pyruvate
when carbohydrates are in short supply
a very-low carbohydrate diet induces ketosis
Key Steps in Ketosis:
Insufficient insulin production: Blood insulin drops, usually as a result of type 1 diabetes or low carbohydrates.
Large amounts of Fatty Acids release by adipose cells: a fall in blood insulin promotes lipolysis, which causes fatty acids stored in adipose cells to be released rapidly into the bloodstream.
Fatty acids flood into the liver and are broken down into acetyl-CoA: most of the fatty acids in the boold are taken up by the liver.
High amounts of ATP slow the citric acid cycle: As the liver oxidizes the fatty acis to acetyl-Coa, the capacity of the citric acid cycle to process the acetyl-CoA molecules decreases. This is mostly because the metabolism of fatty acids to acetyl-CoA yields many ATP. When the cells have plenty of TP, there is no need touse the citric acid cycle to produce more.
High amounts of acetyl-CoA unite in pairs to form ketone bodies: these metabolic changes encourage live cells to combine 2 acetyl-CoA molecules to form a 4-carbon compound. This compound is further metabolized and eventually secreted into the bloodstream as ketone bodies (acetoacetic acid and the related compounds, beta-hydroxybutyric acid and acetone
identify the conditions that lead to ketogenesis and its importance in survival during fasting
When a person is in a state for semi-starvation/fasting, the amount of glucose in the body falls, so insulin production falls.
This fall in blood insulin then causes fatty acids to flood into the bloodstream and eventually form ketone bodies in the liver.
The heart, muscles and some parts of the kidneys then use ketone bodies for fuel. After a few days of ketosis, the brain also begins to metabolize ketone bodies for energy.
The adaptive response is important to semi-starvation/fasting. As more body cells begin to use ketone bodies for fuel, the need for glucose as a body fuel diminishes. This then reduces the need for the liver and kidneys to produce glucose from amino acids (and from the glycerol released from lipolysis), sparing much body protein from being used as a fuel source. This maintenance of body protein mass is a key to survival in semi-starvation or fasting- death occurs when about half of the body protein is deplete, usually after about 50-70 days of total fasting.
Ketone bodies are products of incomplete fatty acid oxidation. This occurs mainly with hormonal imbalances-chiefly, in adequate insulin production to balance glucagon action in the body. These imbalances lead to a significant production of ketone bodies and a condition called ketosis.
What is the fate of energy from macronutrients during the fed state?
Feasting increases insulin production by the pancreas, which encourages the burning of glucose for energy, as well as synthesis of glycogen and to a lesser extent, protein & fat.
Fat - excess goes immediately into storage in adipose cells, little energy in this process.
Protein excess doesn’t promote muscle development. Excess protein can reside in amino acid pools in the body, but the amount is not significant. Amino acids left over in the body after a large meal can be used to synthesize fatty acids, but this is typically of minor importance in humans The process of storing amino acids as fat requires ATP & B vitamins biotin, niacin & panthothenic acid. The energy cost of converting dietary protein to body fat is higher than its conversion of dietary fat to body fat.
Carbohydrates consumes in excess of need is used first to maximize glycogen stores. Once glycogen stores are filled, carbohydrates consumption stimulates the use of carbs. As fuel and the storage of excess amounts as body fat. This lessens the need for fat catabolism, however the pathway for storing carbs. as body fat is not very active in hums In addition, it requires the B-Vitamins biotin, miacin & pantothenic acid, & its energetically expensive to convert carbs to body fat.
The pathway for synthesis of fat from excess carbohydrates/protein intake, is called lipogenesis, are found primarily in the cytosol of live cells. Synthesis involves a series of steps that link the acetyl-Coa formed from either glucose or amino acids into a 16-carbon saturated fatty acid, palmitic acid. Insulin increased the activity of a key enzyme (fatty acid synthase) used in the pathway. Ultimately, the fatty acids & glycerol (produced during Glycolysis from glyceraldehyde 3-phosphate) are used to synthesize triglycerides, which are subsequently delivered by very low density lipoprotein via the bloodsteam to adipose tissues for storage.
What is the fate of energy from macronutrients during the Fasted state?
The body undergoes a series of adaptations that prolong survival
Slowing of the metabolic rate & reduction in energy requirement. This helps show the breakdown of lean tissue to supply amino acids for gluconeogenesis.
Another adaptation – allows the nervous system to use less glucose (hence, less body protein) & more ketone bodies.
After several weeks of fasting, half or more of the nervous system’s energy needs are met by ketone bodies, nonetheless, some glucose must still be supplies via the catabolism of lean body mass. When lean body mass declines by 50% (usually within 7-10 weeks of total fasting) death occurs.
Describe energy balance and uses of energy by the body
Energy balance is the relationship between energy intake and energy expenditure.
When the calories consumes from food & beverages (energy intake) match the amount of energy expended, energy equilibrium occurs.
If energy intake exceeds energy expended, the result is a positive energy balance.
Negative energy balance results when energy intake is less than energy expenditures.
Identify the components of a sound weight loss plan
Control of energy intake
Regular physical activity
Control of problem behaviors
Describe the most common (3) eating disorders.
Anorexia Nervosa– extreme weight loss, a distorted body image and an irrational, almost morbid fear of obesity and weight gain.
Bulimia Nervosa – characterized by episodes of binge eating followed by attempts to purge the excess energy consumed by vomiting or misusing laxatives, diuretics or enemas.
Eating Disorder Not Otherwise Specified (EDNOS) – broad category of eating disorders in which individuals have partial syndromes that do not meet the strict criteria for anorexia nervosa or bulimia nervosa.
Identify health risks associated with eating disorders
Anorexia Nervosa – hair loss, fainting/fatigue, low body temperature, low metabolic rate/cold intolerance, loss of heart tissue/decreased heart rate, muscle tears/stress fractures, loss of menstrual periods, minimal subcutaneous fat, low bone mass, languno (skin disorder)
Blood potassium imbalance, dental decay, iron deficiency anemia, low WBC count/decline in immune function, constipation
4 behaviors of weight loss maintenance:
Eat a low fat, high carbohydrate diet
Eat breakfast – the body burns more fat throughout the day and there is less tendency to overeat due to hunger
Self-monitor by regularly weighting oneself & keeping a food journal.
Have a physical activity palnt – exercise helps maintain weight.
Thermic effect of food
The energy the body uses to digest, absorb, transport, store & metabolize the nutrients consumed in he diet.
What is Leptin?
Hormone made by adipose tissue that influences long-term regulation of fat mass.
Also influences reproductive functions, as well as other body processes, such as insulin release
What is Ghrelin?
Hormone made by the stomach, that increases food intake.
Body mass index (BMI)
The preferred weight for height standard because it is more closely related to body fat content.
Convenient to use because it easier to measure height & weight, than body fat.
Values apply to both men & women.
They don’t apply to children, teens, older adults, pregnant & lactating women.
BMI alone shouldn’t be used to diagnose overweight or obesity.
Basal Metabolic Rate (BMR)
Rate of energy use (e.g. kcal/min) by the body when at rest, fasting & awake in a warm, quiet environment.
Resting Metabolic Rate (RMR)
Aka resting metabolism.
Amount of energy the body uses when the person has not eaten in 4 hours and is resting (e.g., 15-30 min) and awake in a warm, quiet environment.
Its approximately 6% higher than basal metabolism because of the less strict criteria for the test.
Eating disorder characterized by a psychological loss or denial of appetite followed by self starvation; related in part to a distorted body image and to various social pressures commonly associated with puberty.
Eating disorder characterized by eating large quantities of food at one time (binge eating) and purging it from the body by vomiting or by misusing laxatives, diuretics, or enemas. Alternate means to counteract the excess energy intake are fasting and excessive exercise.
Claim miraculous weight loss or improved health – often by unhealthy or unrealistic eating plans and touting miracle foods, specific rituals or certain foods that people wouldn’t normally eat in lar amounts.
Metabolic pathway that converts glucose into 2 molecules of pyruvic acid, with the net gain of 2 ATP & 2 NADH + 2H+
Condition of having a high concentration of ketone bodies and related breakdown products in the bloodstream and tissues.
Adenosine Triphosphate (ATP)
Main energy currency for cells, ATP energy is used to promote ion pumping, enzyme activity and muscular contractions.
Class of fat-related substances that contain phosphorus, fatty acids and a nitrogen-containing base. Phospholipids are an essential part of every cell.
Compound that speeds the rate of a chemical process but is not altered by the process. Almost all enzymes are proteins (some are make of nucleic acids).
Main sites of energy production in a cell. They also contain the pathway for oxidizing fat for fuel, among other metabolic pathways.
Carbohydrate made of multiple units of glucose with a highly branched structure; sometimes knows as animal starch; the storage from of glucose in humans; is synthesized (and stored) in the liver and muscles.
Explain the process of glycolysis and why it is important.
Glycolysis: Metabolic pathway that converts glucose into 2 molecules of pyruvic acid, with the net gain of 2 ATP & 2 NADH + 2H+
Glycolysis has 2 roles:
Break down carbohydrates to generate energy
To provide building blocks for synthesizing other needed compounds.
During the fasting stage (in this senario), what were the likely sources of energy for the body’s cells?
In the first few hours the body fuels itself with stored liver glycogen and fatty acids from adipose tissue.
As the fast progresses, body fat continues to be broken down & liver glycogen becomes exhausted.
Although most cells can use fatty acids for energy, the nervous system & red blood cells use only glucose for energy.
To provide the needed glucose, the body begins breaking down lean body tissue and converts glucogenic amino acids, via gluconeogenesis to glucose.
What metabolic adaptations occurred to provide glucose for the nervous system during the fasting state?
The body slows down it’s metabolic rate & a reduction in energy requirement.
This helps slows the breakdown of lean tissue to supply amino acids for gluconeogenesis.
After a couple of weeks the nervous system to uses less glucose and more ketone bodies.
When Kevin began eating 400-600 kcal/day (after fasting for 4 days), how did the metabolic process in his body most likely change from the fasting state?
Feasting increases insulin production by the pancreas, which in turn encourages burning of glucose for energy, as well as the synthesis of glycogen and to a less extent, protein and fat.
Because he is still consuming less calories than he needs in a day to even meet his BMR requirements, he would continue breaking down some lean body mass and converting fat stores to ketones through ketosis for his body to use.}
Calculate your energy needs using the Estimated Energy Requirement equation. How does your caloric intake compare to this?
Using the EER formula of:
EER=354- (6.91 x AGE) + PA X ([9.36 x WT] + [726 x HT])
Input: Age, PA (Physical Activity Level), Wt (weight in kg = lb ÷ 2.2) and HT (Height in meters = inches ÷39.4)
354- (6.91 x 40) + 1.27 x ([9.36 x 75] + [726 x 1.57]) = 2261I am eating about 400 calories (1800 kcal/day) less than my energy output.
What evidence supports the role of genetics in determining body weight?
Studies of identical twins provide some insight into the contribution of nature (genetics) to body weight.
When identical twins are raised apart, they tend to show similar weight-gain patterns, both in overall weight and in body fat distribution.
Nurture – eating habits and nutrition, which vary between twins who are raised apart – seems to have less to do with weight-gain patterns than nature does.
What evidence supports the role of the environment in determining body weight?
Some researchers argue that body weight similarities among family members stem more from learned behaviors than from genetic similarities.
Even couples and friends (who generally have no genetic link) may behave similarly toward food and eventually assume similar decrees of leanness or fatness.
The effects of environment are supported by the fact that our gene pool has not changed much in the last 50 years, but the ranks of obese people recently have grown in what the CDC describe as epidemic proportions.
Why is it likely that both genetics and the environment determine body weight?
Hereditary factors interact with environmental factors to determine actually body weight and composition.
Even with a genetic potential for leanness, it is possible for a person who overeats to gain excess fat.
Conversely, an individual genetically predisposed to obesity can avoid excess fat storage with a healthy diet and sufficient amounts of regular physical activity.
By now, it's clear that a diet plan's success or failure is only limited by the public's gullibility. Numerous diet plans, books, and formulas have come and gone. List five or more red flags of a fad diet.
Promise a quick fix.
Dire warnings of danger from a single product or regimen.
Sound too good to be true.
Simplistic conclusions drawn from a complex study.
Recommendation based on a single study.
What BMI classifies underweight?
BMI < 18.5 is underweight.
What health problems are associated with being underweight?
Loss of menstrual function
low bone mass
complications with pregnancy and surgery
and slow recovery after illness.
What interventions could be recommended to aid in weight gain?
Should seek medical intervention to identify the cause of this condition and get appropriate treatment.
List the typical characteristics of a person with anorexia nervosa.
Rigid dieting, causing dramatic weight loss, generally to less than 85% of what would be expected for one’s age.
False body perception, even when extremely underweight; relentless pursuit of control.
Ritruals involving food, excessive exercise, and other aspects of life.
Maintenance of rigid control in lifestyle; security found in control and order.
Feeling of panic after a small weight gain; intense fear of gaining weight.
List the detrimental physical and psychological side effects of bulimia nervosa.
Repeated exposure of teeth to the acid in vomit causes demineralization, making the teeth painful and sensitive to heat, cold and acids. Eventually, the teeth may decay severely, erode away from fillings, and finally fall out.
Salivary glands may swell as a result of infection and irritation from persistent vomiting.
Stomach ulcers and tears in the esophagus develop, in some cases
Constipation may result from frequent laxative use.
Insulin is __________.
An anabolic hormone.
When muscles tissue is exercising under anaerobic conditions, the production of ___________ is important because it assured a continuous supply of NAD.
The common pathway for the oxidation of glucose and fatty acid is ________.
B. the citric acid cycle
The oxidation of fatty acids occurs in the ________.
Module 4: Energy Metabolism Energy Balance Weight Control & Eating Disorders