5. Metabolism of Food Components Flashcards
What’s 1 calorie?
Energy needed to increase the temperature of 1 gram of water by 1oC (from 16.5 to 17.5oC)
calorie conversion value?
1 kilocalorie (kcal) = 1,000 calories
1 megacalorie (Mcal) = 1,000,000 calories
1 kcal/g = 1 Mcal/kg
1 calories = 4.184 joules
Energy sources are divided into 2:
- Exogenous (obtained outside the body)
fat (9kcal/g)
protein (4 kcal/g)
carbohydrate (4 kcal/g) - Endogenous (available within the body)
adipose tissue (fat storage), glycogen (muscle and liver)
digestion and absorption processes mechanism
- break down complex molecules into simple ones, so they can be absorbed by the body
a) carb -> monosaccharides/simple sugar
b) fat (triglyseride) -> fatty acid
c) protein -> amino acid - nutrients are transported to muscles via blood vessels -> product ATP through a series of metabolism
equation of catabolic reaction
Foods + O2 -> CO2 + H2O + ATP
energy allocation in the body tree
gross energy -> energy feces + digestible energy
digestible energy -> energy in urine + metabolizable energy
metabolizable energy -> heat incresment + net energy
amongst carb, fat, and protein, which one has the highest loss during digest? which one has the highest physio fuel values? which one has the highest gross and available energy?
protein, fat, fat, fat
carbohydrate:
- main form
- transportation
- storage
- production
- glucose (easiest to absorbed)
- transported to muscle tissue (and other tissues) via blood vessels
- stored in the liver and muscles as glycogen
- ATP is produced more quickly using carbs than fat or protein
fat:
- storage
- usage
- production
- stored in adipose and muscle tissue
- use fatty acids for energy
- produce ATP more slowly than carbohydrates
protein
- transportation
- usage
- production
- broken down into amino acids, absorbed, and transported via blood vessels
- provide building blocks for metabolic function and tissue formation
- provide 5-15% of the energy for ATP production
cellular oxidation of carbohydrates
carbohydrates through digestion and absorption, food is broken down into: glucose (sugar) -> glycolysis -> stored as glycogen or fat and synthesized into other component -> oxidized to energy -> acetyl coA -> krebs cycle -> ATP is produced as energy, CO2 and H2O are released
cellular oxidation of fat
through digestion and absorption, food is broken down into:
fatty acid and glycerol (metabolic pathway) beta oxidation -> stored as triglycerides in fat cells and into cellular membrane -> oxidized to energy -> acetyl coA -> krebs cycle -> ATP is produced as energy, CO2 and H2O are released
cellular oxidation of protein
through digestion and absorption, food is broken down into:
amino acid -> transamination -> stored as glycogen or fat and new protein -> oxidized to energy oxidized to energy -> acetyl coA -> krebs cycle -> ATP is produced as energy, CO2 and H2O are released
in hunger state, what happens to fatty acid and glycerol?
- FA is used to form ketone bodies for energy
- glycerol is used to form glucose for brain/blood cells
when is body weight stable?
when amount of energy consumed is equal to the amount of energy expended.
one pound of body weight is equal to ….
3500 kcal
food intake is influenced by
- appetite, initiates eating through the sight, smell, thought, or taste of food →Psychological hunger
- hunger the feeling that motivates us to eat and controlled by hypothalamus → Real hunger (empty stomach)
- satiety the feeling of satisfaction and fullness, that causes us to stop eating → Reminds us to stop eating until the body needs food
food component satiating and hunger characteristic
- Protein: The most satiating
- Complex carbohydrate: Satiating
- High-fat foods: Stimulate and entice people to eat mor
metabolism is affected by:
age, gender, body composition, diet, exercise, stress, disease, drugs
energy expenditure is affected by several factors:
metabolism, daily activity, exercise, thermal effect of foo
ratio of energy expended
10% thermal effect of food
30-35% physical activity
50-65% basal metabolism
what is basal metabolism?
- Energy required by a subject in a state of total rest (physical & mental), at normal body temperature and a “post-absorptive” condition (12 hours after eating) → calculated for 24 hours
- Energy to pump heart, breathe, and regulate body temperature
how to measure basal metabolism?
- experiment by calculating the amount of heat produced during exhalation = basal metabolic rate: +- 1270 kcal
- body weight (normal): man: 1 kcal/kg BW/hour. woman: 0.9 kcal/kg BW/hour
- metabolic body size (MBS): (Bw in kg)^3/4. basal metabolism: 70 x MBS
- harris-benedict equation (for male>10 tahun and all female): 66.5 + [12.5 x BW (kg)] + [5 x BH (cm)] - [6.75 x age (years)]
- FAO/WHO/UNU: 11.6 x BW + 379
factors affecting BMR
- age: as you grow older, BMR will decrease. it decreases by 2% yearly. ( lean body mass decrease, adipose mass increases)
- height: taller body surface area, higher BMR
- growth: increases BMR
- body composition: lean body mass increase BMR
- fever: increases BMR. temp +1 degree -> BMR increases 14%
- stress: increases BMR
- ambient temperature: either hot or cold, could increase BMR
- genetic: slower vs faster metabolism
