1. Unit I: Metabolism Food Utilization
Chapter 22

2. Body Weight Nutrition provides raw materials.
Metabolism provides chemical change of the nutrients.
Body Weight
Energy balance
homeostatic set point
Environmental and hereditary factors
Nutrition is the starting point for all human form and function (cell division, growth, development). Provides the raw material.
Metabolism provides the chemical change of those nutrients for the body’s use.
Digestive system provides a place for metabolism to take place.
Weight is determined by the body’s energy balance. Weight is stable with equal energy intake and output
fluctuates on short term
remains quite stable over many years’ time around a … : (experimentally demonstrated) make an animal obese  let it feed at will  will return to original weight
Set point varies
2. Body weight determined by combination of …
30-50% of variation between individuals due to heredity
rest due to eating and exercise habits

3. Gut-Brain Peptides Appetite regulators short term CCK – stop eating
Peptide YY - satiety
Ghrelin - hunger
long term
Leptin – levels proportional to fat stores
insulin – index of body fat
Weight gain is a struggle against appetite controlled by peptide hormones.
Act as chemical signals from the gastrointestinal tract to the hypothalamus.
Short term – peptides work over minutes to hours
makes you feel hungry and start to eat  satiated and end the meal
CCK – stimulates release of bile & pancreatic enzymes but also signal stop eating (G cells – small intestine)
Peptide YY – signal satiety, prevents stomach from emptying too quickly (G cells – small intestine)
Ghrelin – sensation of hunger, primes body for taking best advantage of nutrients (parietal cells – stomach)
2. Long term – regulates caloric intake and energy expenditure over weeks to years.
informs brain on how much adipose tissue the body has, activates mechanisms for adding or reducing fat.
Leptin – secreted by adipocytes; levels proportional to fat stores (obesity linked to unresponsiveness to leptin) receptor defect  overeating
Insulin – secreted by pancreas; similar to leptin but weaker effect – index of body fat because it promotes fat synthesis

4. Hypothalamus 2 neural networks:
Receptors for gut-brain peptides that regulate release of:
Neuropeptide Y
Melanocortin
Important for appetite regulation. (Arcuate nucleus in hypothalamus)
(act on other receptors of body as well.)
Hunger – can be inhibited by Leptin (long term regulator peptide)
Satiety

5. Appetite Regulation NPY: stimulated by Ghrelin (short term)
inhibited by insulin, PYY, leptin, CCK
Melanocrotin: stimulated by Leptin
inhibited by NPY
Insulin and leptin – long term regulators

6. Other Factors in Appetite Regulation
Briefly satisfied by:
chewing
swallowing
stomach filling
Gastric Peristalsis
Neurotransmitters
norepinephrine – carbohydrates
galanin – fats
endorphins – protein
Can be briefly satisfied by …
Hunger is stimulated partly by gastric peristalsis. Hunger contractions start soon after stomach is emptied and increase in intensity over hours.
Not just ‘how much’ but ‘what kind’ … stimulate desire for different foods
Lasting sensation with absorption of nutrients into blood

7. Calories
One calorie - amount of heat required to raise temperature of 1 g of water 1 °C
Fats contain about 9 kcal/g
Carbohydrates and proteins, about 4 kcal/g
sugar and alcohol are “empty” calories
Fuel
The MyPyramid.gov Steps to a Healthier You
Activity
GRAINS
VEGETABLES
FRUITS O I L S
MILK
MEAT & BEANS
Make half your grains whole
Vary your veggies
Focus on fruits
Get your calcium-rich foods
Go lean with proteins
… 1,000 calories = kilocalorie or Calorie
in physiology: Calorie is a measure of the capacity to do biological work – release of energy
2. Nearly all dietary calories come from carbohydrates, proteins, and fats.
kcal/g when completely oxidized
3. A. … suppress appetite but don’t deliver other nutrients the body requires  malnutrition
4. A chemical described as Fuel – oxidized solely to extract energy (ATP) from it

8. Nutrients Ingested chemical used for growth, repair or maintenance
Macronutrients
Micronutrients
Recommended daily allowances (RDA)
safe estimate of daily intake for standard needs
Essential nutrients can not be synthesized
minerals, vitamins, 8 amino acids and 1-3 fatty acids
A nutrient (raw material) is an … of the body
6 classes of nutrients in 2 groups:
Include water, carbohydrates, lipids, and proteins
must be consumed in large quantities
3. Minerals and vitamins
only small quantities are required
4. Meet nutritional needs of a healthy person
5. Many nutrients can be synthesized by the body even though not available in the diet; essential nutrients can’t be synthesized
essential to be included in diet!

9. Glycogen Metabolism Glycolysis Glycogenesis -- stimulated by insulin
average adult contains 440 g
Glycogenolysis --
only liver cells can release glucose back into blood
Gluconeogenesis –
Require 125 – 175 grams/day
The next couple of slides is how each of those nutrients are used by the body.
ATP is quickly used after it is formed -- it is not a storage molecule – energy transfer molecule
extra glucose will not be oxidized, it will be stored as other compounds (glycogen & fat).
2. synthesis of glycogen from glucose
… contained in liver & skeletal muscles, blood
3. glycogen  glucose: hydrolysis of glycogen; only involves 1 step
releases glucose between meals – stimulated by glucagon and epinephrine
a. the only cells that remove a phosphate group to make free glucose; muscle cells contribute indirectly by releasing pyruvic and lactic acids.
3. synthesis of glucose from noncarbohydrates, such as fats and amino acids
occurs mainly in liver; kidneys kick in after weeks of fasting (especially during long fasting)
When blood glucose levels are low:
Carbohydrates chiefly function as fuels and are components of larger molecules (nucleic acids, nucleotides, glycoproteins, glycolipids) ATP
4. … because quickly oxidized – require the most of
1 nondiet soft drink has 8tsp of sugar/12oz serving
should be starch  provides other nutrients as well; glucose  empty calories

10. Lipids Triglycerides are stored in adipocytes Lipogenesis --
Prostaglandins
Acetyl-CoA
Glycolipids
Phospholipids
Cholesterol
Steroids
Triglycerides
Fatty acids
Glycerol
Glucose
Pyruvate
Citric
acid
cycle
MITOCHONDRIA
ATP
ADP
Coenzyme A
CYTOSOL
CO2
Triglycerides are stored in adipocytes
Lipogenesis --
Lipolysis –
Require 80 – 100 grams/day
1. Most body’s stored energy (1 molecule stays for 2-3 weeks)
2. synthesizing fat from other sources:
lipogenesis begins with acetyl-CoA. Can use any organic substrate: amino acids and sugars because they can all be converted to acetyl.
takes place in any cell
3. breaking down fat for fuel converted to pyruvate
triglycerides (C3) can be broken down into Acetyl Co-A but only produces half as much ATP as glucose (C6).
Primary function as fuel; in the plasma membrane functions for structure, absorption of fat soluble vitamins, Vitamin D synthesis, and in blood clotting (protect & insulate)
Daily requirement of grams.
6-C glucose = 36 ATP
6 carbons from a fatty acid = 51 ATP
Triglyceride for insoluble droplets difficult for enzymes to access. Stored lipids can’t provide large amounts of ATP quickly.

11. Proteins Amino acid pool - May be used to synthesize new proteins
As fuel
Require 44 – 60 grams/day
dietary amino acids plus 100 g of tissue protein broken down each day into free amino acids
a. cells draw upon to make new proteins
b. can be used as an emergency fuel as well - Converted to glucose, fat, Or directly used as fuel.
2. Needed for muscle contractions, cell motility, component of cell membranes and organelles, transport, blood clotting, antibodies, enzymes, etc.
Proteins in body are structural proteins, enzymes, transport proteins.
Daily requirement between grams/day
(weight(lbs) * 0.37 = RDA of proteins in grams)

12. Other Nutrient Classes
Water
require 2.5 liters/day
Minerals
require 0.05 – 3,300 mg/day
Vitamins
require – 60 mg/day
Water is a solvent, coolant, reactant, or product of biochemical reactions
needed for dilution and elimination of metabolic wastes; and to maintain blood volume and pressure
2. Function in structure of bones and teeth; component of certain structural proteins, ATP, phospholipids; cofactors for enzymes (inorganic elements); electrolytes; buffers; production of stomach acid; maintenance of body fluid concentrations
3. Function as coenzymes (organic compounds)
Neither minerals or vitamins are fuels; essential to our ability to use other nutrients
excessive amounts are toxic & potentially lethal

13. Vitamins Fat-Soluble vitamins A, D3, E, and K hypervitaminosis
Water-Soluble
vitamins B & C
coenzymes
avitaminosis
Absorbed primarily from digestive tract along with micelles. Body contains a significant reserve of these with lipids deposits.
Vitamin A - maintains epithelia, visual pigments, growth & bone remodeling
D – bone growth, Ca absorption
E – prevents breakdown of vitamin A and fatty acids
K – essential for clotting
Dietary intake exceeds body’s ability to store, utilize, or excrete a vitamin. Most commonly involves fat-soluble vitamins.
A. Vitamin B – Meat, eggs, dairy; while C – citrus fruits
b. Major function: coenzymes
c. Vitamin Deficiency disease. Because they are readily exchanged between fluid compartments and excreted in urine. Only vitamins B12 and C are stored in significant quantities. Start showing signs in days/weeks.

14. Disorders Eating Disorders anorexia – lack of appetite
Bulimia – “eating binge”
Obesity – 20% over ideal weight
Protein Deficiency disease
Kwashiorkor
deficient in essential amino acids
Psychological problems – concern about food or weight
Self induced starvation
… followed by induced vomiting. More common than anorexia
…at this point, health risks appear. Results from (a.) failure to regulate food intake or (b.) underlying bodily malfunction. (rare)
Protein synthesis decreases throughout the body. Plasma osmolarity falls as fluid shifts to ECF from blood – edema.

15. Absorptive State 4 hours during and after a meal Regulated by insulin
KEY
= Catabolic
pathway
= Anabolic
= Stimulation
Glucose
levels elevated
Insulin
Triglycerides
Glycogen
Proteins
Lipid levels
elevated
Fatty acids
Glycerol
Amino acids
Pyruvate
Androgens
Estrogens
Growth hormone
LIPIDS
CARBOHYDRATES
PROTEINS
ATP
CO2
H2O
Acetyl-CoA
Citric
acid
cycle
Coenzymes
ETS
MITOCHONDRIA O2 G l y c o s i
Absorptive State
4 hours during and after a meal
Regulated by insulin
Metabolism changes from hour to hour depending on how long it has been since your last meal.
Fed state; absorb nutrients
time of nutrient absorption and may be used for immediate energy needs:
characterized by ↓ gluconeogenesis; stored by glycogenesis; and ↑ protein synthesis
regulated mainly by insulin: glucose uptake and glycogenesis; amino acid uptake and protein synthesis; triglyceride synthesis.
2. Carbs: glucose is readily available so the body doesn’t have to use stored fuels - blood glucose passes thru liver to be available to all cells for ATP synthesis
excess is converted by liver to glycogen or fat (released into circulation)
3. taken up by fat cells from chylomicrons in the blood; lypogenesis occurs
primary energy substrate for liver, fat and muscle cells
4. most pass through the liver and go onto other cells
in liver cells, may be used for protein synthesis, used for fuel for ATP synthesis or used for fatty acid synthesis

16. Postabsorptive State Homeostasis of blood glucose critical to brain
Absorbed by
other tissues.
Fatty acids
released by
adipocytes
Lipid levels decreased
Glucose levels decreased
For use primarily
by neural tissues.
Glucose released
by the liver
KEY
= Catabolic pathway
= Anabolic pathway
= Stimulation
Triglycerides
Glycogen
Proteins
LIPIDS
CARBOHYDRATES
PROTEINS
Glycerol O2
ATP
CO2
H2O
MITOCHONDRIA
Coenzymes
ETS
Citric
acid
cycle
Ketone bodies
Acetyl-CoA
Pyruvate
Amino acids
the liver
Amino acid
levels decreased
Glucagon
Epinephrine
Glucocorticoid
Glucagon,
Epinephrine,
Growth hormone G l u c o n e g s I
Glucose
Postabsorptive State
Homeostasis of blood glucose critical to brain
(fasting state)
Late morning, late afternoon, and overnight.
A. when stomach and small intestine are empty- stored fuels are used
Carbs: glucose is drawn from glycogen reserves for up to 4 hours (epinephrine - glycogenolysis) in skeletal and cardiac muscle and then synthesized from other compounds (glucocorticoid enhanced by growth hormone - gluconeogenesis) in liver
adipocytes and liver cells convert glycerol to glucose (glucocorticoids enhanced by growth hormone, epinephrine – lipolysis in adipocytes)
other cells (hepatocytes, adipocytes, and muscle cells) use for energy-- leaving glucose for brain (glucose-sparing effect)
when fatty acids are incompletely broken down  ketones (change pH balance when not enough carbs)
4. used as fuel when glycogen and fat reserves depleted
when amino acids are broken down  urea (highly toxic)  quickly converted to ammonia (less toxic)
Glycogenolysis occurs more here than after a meal!
Energy comes from 1st – glucose, 2nd – glycogen, 3rd – glycerol, 4th (emergency) – amino acids
Various hormones trigger glycogenolysis, gluconeogenesis, lipolysis

17. Estimated Calories expended
Metabolic Rate
Amount of energy used in the body in a given period of time (kcal/hr or kcal/day)
measured directly in calorimeter
measured indirectly by a spirometer
1 L O2 = 4.82 Cal/L
Basal metabolic rate (BMR)
adult male BMR is 2,000 kcal/day
Total metabolic rate (TMR)
Estimated Calories expended
by a 70-kg individual
Resting
Slow
walking
Speed
Climbing
stairs
Jogging
Competitive
swimming
Calories per hour
1000
800
600
400
200
A. water bath – closed chamber with water filled walls that absorb the heat given off by the body. Temperature change of the water
B. oxygen consumption
2. Metabolic rate depends on a lot of things (physical activity, mental state, hormones …). Baseline/standard of comparison to minimize effects of variables. not the minimum to sustain life
relaxed, awake, fasting (12-24hrs after meal), room comfortable temperature
must consume a minimum of 2,000 kcal to fuel essential metabolic tasks: active transport, muscle tone, brain activity, cardiac and respiratory rhythms, renal function
3. Sum of BMR and energy expenditure for voluntary activities (muscle contractions)
increases with pregnancy, anxiety, fever, eating, thyroid hormones, and depression – lowers TMR – prolonged starvation
Sendentary lifestyle = 2500 kcal/day
Job of hard physical labor = 5000 kcal/day
Reduce food intake  body reduces MR to conserve body mass  making it more difficult to loose weight

18. Exam 1 Chapters 21 & 22 Spelling counts! Multiple Choice 3x5 notecard
Fill in the blank
Matching
Short answer
True/False
Spelling counts!
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