Carbohydrate

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Lecture 12 Carbohydrate a macronutrient
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Carbohydrate

• CHO a hydrocarbon
• main energy source for humans
• CHO provides up to 85 of energy in 3rd world
  countries
• CHO as low as 20 of energy in 1st world
  (Western) countries

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Recommended CHO intake

• 50-55 of Etotal for general population
• 55-70 of Etot for athletes

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what is a CARBOHYDRATE?

• Simple sugar
• Complex starch dietary fibre
• BUT this classification no longer used

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1. What is sugar?

• different combinations of GLUCOSE molecules
• eg. glucose, sucrose, fructose, lactose

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Glucose (C6H12O6)

• basic CHO unit
• 6 carbon ring structure
• a mono-saccharide
• abundant in animal plant tissues

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Glucose molecule (C6H12O6)

• CH2OH
• C O
• H H H
• C C
• OH OH H OH
• C C
• H OH

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Fructose (C6H12O6)

• fruit sugar
• a mono-saccharide
• the sweetest natural sugar

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Fructose molecule

• CH2OH O O
• C C
• H H OH CH2OH
• C C
• OH H

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Sucrose (C12H22O11)

• table sugar
• a di-saccharide
• the most abundant sugar in plants
• glucose fructose

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Sucrose molecule

• CH2OH
• C O
• H H H
• C C
• OH OH H
• C C
• H OH
• CH2OH O O
• C C
• H H OH CH2OH
• C C
• OH H

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Maltose (C12H22O11)

• small amounts found in many foods
• a di-saccharide
• formed by breakdown of starch in malting process
• glucose glucose

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Maltose molecule

• CH2OH CH2OH
• H C O H H C O OH
• C H C C H C
• OH H O OH H
• OH C C C C H
• H OH H OH
• Glucose Glucose

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Lactose (C12H22O11)

• milk sugar
• a di-saccharide
• less sweet than other sugars
• provides energy to suckling animals without being
  too sweet
• galactose glucose

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Sugar content of HONEY

• Substrate Composition
• Fructose 38.2
• Glucose 31.3
• Sucrose 1.3
• Maltose 7.3
• water 1.2

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2. What is Starch?

• STORAGE form of CHO in plants.
• Animal equivalent is GLYCOGEN

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Three types of starch

• Amylopectin
• long chains of Glucose molecules with many
  branches
• branches make Amylopectin more soluble
• larger, looser molecules

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Three types of starch

• Amylose
• long unbranched chain of Glucose molecules
  string of pearls
• much harder to digest because chains form dense
  clumps
• Amylopectin Amylose are insoluble in water
  until heated

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Three types of starch

• Resistant Starch
• chemical form of starch
• crystalline structure
• resistant to digestive enzymes
• behaves like dietary fibre in the intestine
• fermented in large bowel (colon)

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Resistant Starch

• Occurs either
• physiologically (bananas)
• cooking chilling (potato salad)
• Resistant Starch useful website

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Carbohydrate

• digestion of sugar and starch
• 2 sets of enzymes
• Amylase
• Disaccharidases
• Maltase, Sucrase, Lactase

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Recommended reading

• Whitney Rolfes
• Understanding Nutrition
• Chapter 4
• The Carbohydrates
• 2. Food Nutrition in Australia
• Chapter 16 Carbohydrates