BIOL2171 Lecture Notes - Lecture 2: Amadori Rearrangement, Trehalose, Aldehyde

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15 Jun 2018
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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-gluopyraose oforatio ad 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 repetitie uits of β1, gluose
Ruminants can digest cellulose with help of bacteria
o Repetitions of α1, gluose are foud i starh, hih is digestile y huas
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 teperature eig ostat i iologial systes
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.

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