BIOL2171 Lecture Notes - Lecture 2: Amadori Rearrangement, Trehalose, Aldehyde
Topics 2 and 3: Carbohydrates and Energy
Carbohydrates
• Form the bulk of our nutrition
• Found in almost every type of food, particularly in bread, pasta and rice, but also in its soluble
form in soft drinks and juices
• Glucose is the major fuel in blood plasma, but it is rarely found in this form is food
• Most commonly occurring sugar is disaccharide sucrose which is derived form a variety of
plants such as sugar beet and sugar cane
• Lactose is the main carbohydrate found in milk, while trehalose is found in mushrooms
• Glucose is found in 2 forms that are at equilibrium: the linear form an the ring form
o In solution less than 0.1% is found in the linear form
o Of the ring form, 36% is found in α-D-gluopyraose oforatio ad 6% i the β-D-
glucopyranose conformation. These forms are interconvertible via the linear form
o The linear form shows that glucose is an aldehyde, so is therefore fairly reactive
• This can cause problems particularly when glucose levels are too high in diabetics
• In a Millard reaction, glucose can react with free amino acid groups in proteins,
forming so called Amadori product
• This reaction starts in a similar way to the familiar Schiff-reaction between
aldehydes and amines
• We cannot digest all types of carbohydrates
o Cellulose is a polysaccharide that is indigestible by humans
• Based o repetitie uits of β1, gluose
• Ruminants can digest cellulose with help of bacteria
o Repetitions of α1, gluose are foud i starh, hih is digestile y huas
o Agarose (used in food industry as well as in bacteriology) cannot be digested by bacteria
or man
• Pectins are widely used in the food industry to solidify liquid products (custard, ice cream,
smoothies, etc.)
o These are modified polysaccharides based on galacturonic acid
o Polysaccharides bind a large amount of water explaining their use as solidifiers
Energy Metabolism
• Any chemical reaction produces or consumes a certain amount of heat
• For biological reactions, it is often more relevant to know how much useable energy a reaction
can yield
• Free energy is used to characterise biological reactions
o Takes into account heat energy and entropy (degree or order) of the system
o ΔG = ΔH - TΔS, ith the teperature eig ostat i iologial systes
o Negative free energy: reaction can provide usable energy and the reaction will proceed
towards the products
o Positive free energy: reaction will proceed toward substrates spontaneously, but
requires energy input to proceed toward products
o Concentration of substrates and products is the most important biological variable that
changes the free energy of a reaction
• Full oxidation of glucose yields a large amount of energy (2800kJ/mol)
• Instant oxidation (burning) will generate an equivalent amount of heat
• The body however wants to store and convert this energy into movement, ion gradient,
biosynthesis of valuable building blocks
• The energy generated in any metabolic reaction can be measured experimentally
• To illustrate the energy demand of your body you can use a simplified formula of metabolic
rate
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Document Summary
Lactose is the main carbohydrate found in milk, while trehalose is found in mushrooms: glucose is found in 2 forms that are at equilibrium: the linear form an the ring form. In solution less than 0. 1% is found in the linear form: of the ring form, 36% is found in -d-glu(cid:272)opyra(cid:374)ose (cid:272)o(cid:374)for(cid:373)atio(cid:374) a(cid:374)d 6(cid:1007)% i(cid:374) the -d- glucopyranose conformation. These forms are interconvertible via the linear form: the linear form shows that glucose is an aldehyde, so is therefore fairly reactive, this can cause problems particularly when glucose levels are too high in diabetics. Energy metabolism: any chemical reaction produces or consumes a certain amount of heat. For biological reactions, it is often more relevant to know how much useable energy a reaction can yield. Full oxidation of glucose yields a large amount of energy (2800kj/mol) Adp (1 atp for every 100000 adp: although, in a living cell, the reaction is kept far away form equilibrium (usually around.