Energy%20Value%20of%20Foods

1
Energy Value of Foods
2
Main Sources of Energy for Cells

• Carbohydrates and lipids (fats)
• Proteins (in cases of illness or injury)
• Cellular respiration is the process which
  releases chemical energy from foods
• Glucose Oxygen gas ?energy carbon dioxide
  water

3
Energy Value

• The amount of energy a food can provide to an
  organism
• Expressed in kilojoules (kJ)
• The calorie (Cal) is often used on packaging
• 1 Cal 4.184 kJ
• Energetic Value of Foods

Carbohydrates Lipids (fats) Proteins
17kJ/g 37kJ/g 17kJ/g
4
Energy Demands

• Basal metabolism
• Physical activities
• Digestion and absorption of what people eat
• (10 of daily energy or 1050 kJ)
• Teenagers 13-15 years old need on average 10
  500 kJ of energy per day

5
Basal Metabolism

• Amount of energy required to maintain vital
  functions- heart beat, respiration, stable body
  temperature, cellular activities
• In general, more elevated in males than females
  (7000 kJ vs. 5500 kJ)

6
Nutritional Requirements

• To meet energy needs, a certain proportion of
  carbohydrates, lipids, and proteins is needed
  (vary with age, sex, size, physical activity)

Energy values in Carbohydrates Lipids Proteins
of Kilojoules (kJ) 55 of kJ ingested 30 of kJ ingested 15 of kJ ingested
Grams (g) 340g 85 g 93 g
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Input and Output of EnergyEffects on Mass

• InputOutput ?mass maintained
• Inputltoutput ?loss of mass
• Inputgtoutput ?gain of mass
• The quality of what we eat is important as well

8
Transformation of Food

• Mechanical and Chemical

9
Mechanical transformation

• large pieces of food that are ingested have to be
  broken into smaller particles that can be acted
  upon by various enzymes

10
Chemical Transformation

• uses water and digestive enzymes to break down
  molecules
• smaller molecules can be absorbed and utilized by
  the cells

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Organs of digestive system Mechanical transformation Glands Secretion from glands Foods transformed Results of transformation
1.Mouth Chewing Salivary Saliva carbohydrates Carbohydrates partially broken down
2.Pharynx Swallowing - - - -
3.Esophagus peristalsis - - - -
4.Stomach Churning Peristalsis Gastric Gastric juices proteins Proteins partially digested
5.small intestine Emulsion of lipids by bile(secreted by the liver) churning Peristalsis pancreas Intestinal Pancreatic juices Intestinal juices Carbohydrates partially digested Proteins partially digested Lipids(fats) Glucose Amino acids Fatty acids Glycerol
6.large intestine churning Peristalsis - - - -
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Absorption of Nutrients
Site of Absorption Nutrients Absorbed
Small intestine Glucose Amino acids Fatty acids Glycerol Water Vitamins minerals
Large intestine Water Vitamins minerals