點解lipid高energy過carbohydrate?

點解lipid高energy過carbohydrate?
Actually, the carbon chain of a lipid is very long up to C18. This means that when energy is released, the number of mole of CO2 and H2O formed will be greater. During the oxidation, energy is released. Hence the more of moles of CO2 and H20 formed, the high energy value it has.

Use peanut oil as an example.
peanut oil with this fatty acidCH3(CH2)18COOH and a glycerol group

When peanut oil is used to release energy, it splits into glycerol and fatty acid. The glycerol will feed into the glycolytic pathway via triose phosphate,TP, to release energy. Of course, it will also undergo kreb cycle.
But for the fatty acid ,a two carbons will be removed form it first so as to form an acetyl group after decarboxylation and dehydrogenation. This acetyl group will be added to a co-enzyme forming acetyl coenzyme A. When acetyl coenzyme A is formed, it is then fed to the kreb circle to release energy.


When this reaction completes, another 2C atom will be removed again form the shortened fatty acid carbon chain (now it only has 14C[18-2(前次)-2((今次)=14C]). This process forms an acetyl group and the acetyl coenzyme A which is feed to the kreb cycle to release energy. This reaction repeats itself until the whole carbon chain of a fatty acid is used up. This process is called beta-oxidation occurring in the matrix of the mitochondrion.

Since there are 18 carbons in a fatty acid and also a glycerol group, the energy contain for the lipid must be higher than carbohydrate. Carbohydrate only has 6C.

Type of lipid which has how many carbon in the chain.
see http://class.fst.ohio-state.edu/fst601/Lectures/LIPID.htm


I hope you will find my answer helpful.

2007-03-19 15:48:43 補充：
glycerol份子的結構是H2C(OH)HC(OH)CH2(OH)而每一個C(OH)會attached to 3個fatty acidCH3(CH2)18COOH 的份子當水份子被移走時而這個份子便是lipids.也即是會有 3個fatty acidCH3(CH2)18COOH 的份子及一個glycerol份子會被氧化,

2007-03-19 15:48:57 補充：
由於3個fatty acidCH3(CH2)18COOH 的份子共有19乘3個碳份子,也表明在aerobic respiration時,會有more number of mole of CO2 and H2O formed,所以lipid高energy過carbohydrate

you have known that the ratio of h:o of lipids is higher than carbohydrates .
the ratio of h:o lipids is MORE than 2:1
the ratio of h:o of carbohydrates is EQUAL to 2:1
CARBOHYDRATES:
they are the cheapest and the most readily available food.
they are the main source of energy to our body.
Thus, one gram of carbohydrates releases 17kJ of energy to our body.
LIPIDS:
many mammals accumulate large amount of fat under the skin and around internal organs.
the layer of fat under the skin also acts as a heat- insulating layer that reduces heat loss from body surface.
thus, one gram of lipids release 38kJ of energy to our body.

From the above, the higher ratio of them releases a greater energy





i hope this things can slove your question

2007-03-16 22:18:22 補充：
this things i have just finished my test, so i can answer you and i have summarize to youi hope it can help you

其實lipid唔只個h:o ratio大, 佢既structure比carbohydrate更複雜.
正因為佢複雜既structure, 中間既bonding可以儲存更多既energy.
當lipid被break down時, 大量既energy就可以release出黎.
而比起lipid黎講, carbohydrate就結構上比較簡單,
較容易被直接分解來realease energy,
要{容易又直接}咁被break down既話,
結構一定唔可以係complex,
(becaz complex structure須要更多energy去break down個bond)
因此內含既energy都唔會多,
因為通常high value energy只會store係1d較穩定又唔容易被拆散既bonding入面,
就好似lipid咁