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Summary - Nutritional Physiology (WUR)
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Summary of HAP 30306 Nutritional Physiology
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Week 1 – Digestive system1
,Week 1 – Digestive system
2
, Week 1 – Digestive system
Lecture 1: Introduction to Mass flow of nutrients
Nutritional input Physiological output
- Total daily intake (kJ) - Physiological status
- Meal size, pattern - Health status
- Nutrient composition - Environment
→ Metabolism connects them
Translocation
= movement of macronutrients (carbohydrates, protein & fats)
through the body
Transformation
= regulation of carbs at the neural, endocrine & hormonal level
→ Movements are regulated by the neural and endocrine systems
What happens after consumption?
Hardly any influence on the fate of the food after swallowing.
Nutrients can either go to: 1) Digestion & absorption
2) Storage
3) Utilisation
Enzymes
= protein compounds that help speed up chemical reactions in the
human body such as in digestion (lower activation energy of reaction)
→ Otherwise, you would need an enormous amount of energy to
breakdown
- Enzymes need specific conditions to optimally work (temperature & Ph)
- Enzymes have a working range but will be less efficient
* Some enzymes need a co-factor for them to become active
Enzyme activity is influenced by:
- pH of incubation or environment
- Temperature / concentration of enzyme and substrate
- Inhibitors and activators
Pro-enzyme ‘zymogen’
= inactive precursor of an enzyme
→ Enzymes are stored as inactive
*Also for protection of the digestive system
Cofactor
= non-protein molecule that is needed to activate some enzymes
→ Will attach near the substrate binding site, to facilitate the
binding of the substrate to the enzyme
1) Co-enzyme 2) Prosthetic group 3) Metal ions
Ex: ATP, Vitamins Ex: Heme Ex: zinc & iron
3
, Week 1 – Digestive system
Why does the digestive system not digest itself?
• Activity is restricted to the presence of food
• Enzymes are stored in inactive form (zymogen)
• Highly regulated
• Non-digestible mucus layer coats the wall
Intermediary metabolism
= the sum of all intercellular chemical processes by which
nutrients are converted into cellular compounds
1) Anabolic reactions
= Synthesis of macromolecules
Ex: Protein synthesis
2) Catabolic reactions
= breakdown of macromolecules
→ Release of energy (energy, ATP, heat)
3) Interconversion of absorbed monomers
= process in which each substance is converted into the other
4) Unavoidable waste products
Post prandial phase = ‘the period following a meal’ Post absorptive phase = ‘The fasting period’
→ Digestion, absorption and storage → Utilization
- Metabolism of nutrients and the supply of tissues with essential fuels - After the meal has been digested, absorbed and stored
- Duration of phase: Glucose meal (~2-3 hrs), Fatty meal (~ 8 hrs) * INPUT < NEEDS
* INPUT > NEEDS
Homeostasis
DIT ‘Diet Induced Thermogenesis’
= ability of an organism to counteract factors that disturb vital
= the thermogenic effect of a meal
functions ‘body regulates itself’
→ Post-prandial metabolism increases from 2 to 20%
- Glucose regulation blood, body temperature ‘thermoregulation’,
- Effects depend on ingested nutrient:
Ph in blood (acid-base balance), Oxygen supply
Proteins > Carbohydrates > Fats
4
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