肝臟 ` 排毒

排毒
毒是泛指一些油溶性的化學物質, 這些物質隨著脂肪吸收進入血液, 之後便立即達肝臟; 小部份再經循環系統去到每一個器官. 肝臟中的細胞色素P-450氧化酶 CYP (Cytochrome P-450 Oxidase)會把那些油溶性的有害物質加以氧化, 使其水溶性增加, 方便肝臟把毒隨瞻汁遣返小腸, 再隨大便排出體外. 除此之外, 肝臟另一排毒方法是進行生物轉化, 把有毒而又不溶於水的成份轉為水溶性的穀胱甘肰(Glutathione)衍生物.

瀝青和廢氣氛都含Pyrene, 例如Benzo(a)Pyrene BP. BP可致癌. 肝臟用P-450將BP轉變成非水溶性(醌)Quinone; 之後用醌還原酶Quinone Reductase, NQO1將它轉為水溶性再排出體外. 食物中番茄, 葡萄, 咖哩和蒜都能刺激NQO1的生成.

冥想靜坐時用硫化氫(Hydrogen Sulphide)可以用來鍛鍊心肌(Preconditioning), 令它在心肌梗塞時不會受重傷. 同樣道理, 浸在有硫磺味的溫泉中,也可以強心健健體. 吃蒜頭時將它拍扁,可從破裂後的Alliin分子中找到一種細胞內的溶解體Alliinase生物催化劑. 這催化劑能把Alliin轉為一個不穩定的分子Allicin, Allicin再分解, 成為一些可以被細胞吸收,及可以在細胞內衍生硫化氫的化學成分.

服藥時不要用西柚汁送, 因為西柚汁會抑制CYP, 很容易導致藥物過量, 從而中毒. 另一副作用,西柚汁/皮中的西柚苷(Naringin)是黃酮的一種, 它可以抑制一個幫助腸腔吸收帶正電物質的蛋白質,Organic Anion Transporting Protein(OATP).

陳皮的檸苦素(Limonoids, 其中Limonin和Nomilin最有保健作用)能提高肝的生物轉化功能.
<本草綱目>: [陳皮同補藥則補, 同升藥則升, 同降藥則降].

酒如何傷肝
酒精可以被胃壁直接吸收, 過量的酒精可令胃血管內壁(Endothelium)受傷, 從而不能如常分泌一氧化氮(Nitric Oxide)來舒張血管. 整個胃便會因此而缺氧潰瘍. 內皮細胞不若氣管, 沒有軟骨把它們撐開, 必須不斷分泌一氧化氮, 紓緩血管壁上的平滑肌, 才能保持舒張. 長期飲烈酒, 可令血管失去彈性, 從而引致血壓上升, 心臟負荷增加, 心肌慢慢增厚, 形成心臟肥大(Hypertrophy), 之後大有可能造成心衰竭.

至於一次性飲酒過量, 酒精若多到連胃和小腸都不能將其吸收, 酒入大腸灼傷了大腸上皮細胞, 細菌便可走進血管, 直達肝臟, 再釋放出現外毒素和內毒素使肝臟受傷, 發炎, 硬化. 硬化不會致癌, 但因為肝臟或胰臟內有各種酵素酶, 有能力快速消化掉一切纖維; 不過同時那些酵素會挑起一個局部性的免疫風暴, 隨之而來是免疫系統的重撃, 誘發癌變. 例如, 肝臟能分泌一個令細胞増生的蛋白質IGF-1, Insulin-like Growth Factor-1, IGF-會導致肝癌.

有關肝臟功能的五種指標

1. 白蛋白(Albumin) - 白蛋白完全來自肝臟, 若血液中的白蛋白含量下降, 可能表示有慢性肝病,如肝硬化.
2. ALT(Alanine Transaminase) - ALT, AST和ALP稱[肝酵素]. 因為只有肝細胞才有ALT, 若在血液中驗到ALT, 應該是肝受了傷害. 有兩種情況會導致ALT上升: 肝炎病毒感染和薬物/食物中毒.
3. AST(Aspartate Transaminase) - AST是肝, 紅血球, 肌肉的一個酵素, 若發現AST上升但ALT正常, 便是有了肝以外的其它損傷.
4. ALP(Alkaline Phosphatase) - ALP主要是膽管細胞的酵素, 若膽管栓塞(膽石), ALP指標會上升.
5. Bilirubin - 主要來自紅血球的血紅素(Hemoglobin). 在正常情況下, 肝細胞會把Bilirubin轉為水溶性的物質, 藉膽汁經小腸,大腸排出體外. 血液若出現過量的話Bilirubin, 顯示肝的排毒功能可能出現問題.

護肝食品
綠茶素 - 干擾素乙肝病毒
乳薊 - 減低肝硬化
半胱胺酸(Cysteine) - 提高肝細胞抵抗血中有害的氧化物

Essential Fatty Acid

Nomenclature
Fatty acids are straight chain hydrocarbons possessing a carboxyl (COOH) group at one end. Biological fatty acids can be of different lengths, the last position is labelled as a "ω". Since the physiological properties of unsaturated fatty acids largely depend on the position of the first unsaturation relative to the end position and not the carboxylate, the position is signified by (ω minus n). Double bonds are cis and separated by a single methylene (CH2) group unless otherwise noted. So in free fatty acid form, the chemical structure of stearidonic acid is ω-3 18:4 : 18-carbon chain with 4 double bonds, and with the first double bond in the third position from the CH3 end.

Essential fatty acids (EFAs) 

EFAs refers to fatty acids required for biological processes, and not those that only act as fuel. Humans and other animals must ingest because the body requires them for good health but cannot synthesize them. There are two known EFAs for humans: alpha-linolenic acid (an omega-3 fatty acid) and linoleic acid (an omega-6 fatty acid). Other fatty acids that are only "conditionally essential" include gamma-linolenic acid (an omega-6 fatty acid), lauric acid (a saturated fatty acid), and palmitoleic acid (a monounsaturated fatty acid).

The biological effects of the ω-3 and ω-6 fatty acids are mediated by their mutual interactions. In the body, essential fatty acids serve multiple functions:

• They are modified to make:
• the classic eicosanoids (affecting inflammation and many other cellular functions)
• the endocannabinoids (affecting mood, behavior and inflammation)
• the lipoxins from ω-6 EFAs and resolvins from ω-3 (in the presence of aspirin, downregulating inflammation.)
• the isofurans, neurofurans, isoprostanes, hepoxilins, epoxyeicosatrienoic acids (EETs) and Neuroprotectin D. 

• They form lipid rafts (affecting cellular signaling).
• They act on DNA (activating or inhibiting transcription factors such as NF-κB, which is linked to pro-inflammatory cytokine production).

1. Almost all the polyunsaturated fats in the human diet are EFAs. Essential fatty acids play an important role in the life and death of cardiac cells. 
2. Low plasma concentrations of DHA predict low concentrations of cerebrospinal fluid 5-hydroxyindoleacetic acid (5-HIAA). It is found that low concentrations of 5-HIAA in the brain is associated with depression and suicide.
3. There are high concentrations of DHA in synaptic membranes of the brain. This is critical for synaptic transmission and membrane fluidity. The omega-6 fatty acid to omega-3 fatty acid ratio is important to avoid imbalance of membrane fluidity. Membrane fluidity affects function of enzymes such as adenylate cyclase and ion channels such as calcium, potassium, and sodium, which in turn affects receptor numbers and functioning, as well as serotonin neurotransmitter levels. Modern Western diets typically have ratios of omega-6 to omega-3 in excess of 10 to 1, some as high as 30 to 1, partly due to corn oil which has an omega-6 to omega-3 ratio of 49:1. The optimal ratio is thought to be 4 to 1 or lower. 

Mammals lack the ability to introduce double bonds in fatty acids beyond carbon 9 and 10, hence ω-6 linoleic acid (18:2,9,12) LA, and the ω-3 linolenic acid (18:3,9,12,15) ALA, are essential for humans in the diet. These two fatty acids cannot be synthesised by humans, as humans lack the desaturase enzymes required for their production. EFAs start with the short chain polyunsaturated fatty acids (SC-PUFA):
 * ω-3 fatty acids: α-Linolenic acid or ALA (18:3)
 * ω-6 fatty acids: Linoleic acid or LA (18:2)
(ω-9 fatty acids (Oleic acid) are not essential in humans, because humans generally possess all the enzymes required for their synthesis)

These two fatty acids form the starting point for the creation of longer and more desaturated fatty acids, which are also referred to as long-chain polyunsaturated fatty acids (LC-PUFA):
ω-3 fatty acids:
 * eicosapentaenoic acid or EPA (20:5)
 * docosahexaenoic acid or DHA (22:6)
ω-6 fatty acids:
 * gamma-linolenic acid or GLA (18:3)
 * dihomo-gamma-linolenic acid or DGLA (20:3)
 * arachidonic acid or AA (20:4)
(Traditionally speaking, the LC-PUFAs are not essential. Because the LC-PUFA are sometimes required, they may be considered "conditionally essential", or not essential to healthy adults.)

Food Sources
Some of the food sources of ω-3 and ω-6 fatty acids are fish and shellfish, flaxseed (linseed), hemp oil, soya oil, canola (rapeseed) oil, chia seeds, pumpkin seeds, sunflower seeds, leafy vegetables, and walnuts. Plant sources of ω-3 contain neither EPA nor DHA. The human body can convert α-linolenic acid (ALA) to EPA and subsequently DHA. This however requires more metabolic work.

Canola Oil
Canola oil is low in saturated fat and contains both omega-6 and omega-3 fatty acids in a ratio of 2:1. If consumed it also reduces Low-density lipoprotein and overall cholesterol levels, and as a significant source of the essential omega-3 fatty acid is associated with reduced all-cause and cardiovascular mortality. It is recognized by many health professional organizations including the American Dietetic Association and American Heart Association. Canola oil has been given a qualified health claim from the United States Food and Drug Administration due to its high levels of cholesterol-lowering fats.

Simple Facts of Egg

The yolk of one large egg (50 g total, 17 g yolk) contains approximately: 2.7 g protein, 0.61 g carbohydrates, and 4.51 g total fat. It also contains about 60 calories and 210 mg cholesterol.

The egg white of one large egg (33 g) contains: 3.6 g of protein, 0.24 g of carbohydrate and 55 milligrams of sodium. It also contains about 17 calories and no cholesterol.
(USDA National Nutrient Database)

Egg Yolk
All of the fat-soluble vitamins (A, D, E, and K) are found in the egg yolk. Egg yolk is one of the few foods naturally containing vitamin D.

The yellow color is due to lutein and zeaxanthin, which are yellow or orange carotenoids known as xanthophylls. Lutein was found to be concentrated in the macula, a small area of the retina responsible for central vision. The hypothesis for the natural concentration is that lutein helps keep the eyes safe from oxidative stress and the high-energy photons of blue light.

The composition (by weight) of the most prevalent fatty acids in egg yolk is typically as follows:
Unsaturated: Oleic acid (47%), Linoleic acid (16%), Palmitoleic acid (5%), Linolenic acid (2%)
Saturated: Palmitic acid (23%), Stearic acid (4%), Myristic acid (1%)

Choline (grouped within the B-complex vitamins) must be consumed through the diet in order for the body to remain healthy. It is used in the synthesis of the constructional components in the body's cell membranes. Dietary recommendations have discouraged people from eating certain high choline foods, such as egg and fatty meats.

Egg White
The egg white is about two-thirds of the total egg's weight out of its shell, with nearly 92% of that weight coming from water. The remaining weight of the egg white comes from protein, trace minerals, fatty material, vitamins, and glucose.

It contains approximately 40 different proteins: 54% Ovalbumin (nourishment; blocks digestive enzymes), 12% Ovotransferrin (binds iron), 11% Ovomucoid (blocks digestive enzymes), 4% Ovoglobulin G2, 4% Ovoglobulin G3, ...

Egg white is a fining agent that can be used in the clarification and stabilization of wine.

The physical stress of beating egg white can create a foam. There are two types of physical stress caused by beating them with a whisk (denaturation):
1. Whisk drags the liquid through itself, creating a force that unfolds the protein molecules.
2. Mixing of air into the whites causes the proteins to come out of their natural state.
These denatured proteins gather together where the air and water meet and create multiple bonds with the other unraveled proteins, and thus become a foam, holding the incorporated air in place. This process is called coagulation (proteins consist of amino acids; some are hydrophilic (attracted to water) and some are hydrophobic (repelled by water)).

Egg vs Peanut (per 100 g)

	Egg, hard-boiled	Peanut
Vitamin A equiv.	140 μg (18%)
Thiamine (vit. B1)	0.066 mg (6%)	0.6 mg (52%)
Niacin (vit. B3)		12.9 mg (86%)
Riboflavin (vit. B2)	0.5 mg (42%)
Pantothenic acid (B5)	1.4 mg (28%)	1.8 mg (36%)
Vitamin B6		0.3 mg (23%)
Folate (vit. B9)	44 μg (11%)	246 μg (62%)
Vitamin B12	1.11 μg (46%)
Choline (B-complex)	225 mg (46%)
Vitamin D	87 IU (15%)
Vitamin E	1.03 mg (7%)
Calcium	50 mg (5%)	62 mg (6%)
Iron	1.2 mg (9%)	2 mg (15%)
Magnesium	10 mg (3%)	184 mg (52%)
Phosphorus	172 mg (25%)	336 mg (48%)
Potassium	126 mg (3%)	332 mg (7%)
Zinc	1.0 mg (11%)	3.3 mg (35%)
Cholesterol	424 mg
Cholesterol (raw yolk)	1240 mg

Protein	Egg, hard-boiled	Peanut
Alanine	0.7	0.997
Arginine	0.755	3.001
Aspartic acid	1.264	3.06
Cystine	0.292	0.322
Glutamic acid	1.644	5.243
Glycine	0.423	1.512
Histidine	0.298	0.634
Isoleucine	0.686	0.882
Leucine	1.075	1.627
Lysine	0.904	0.901
Methionine	0.392	0.308
Phenylalanine	0.668	1.3
Proline	0.501	1.107
Serine	0.936	1.236
Threonine	0.604	0.859
Tryptophan	0.153	0.2445
Tyrosine	0.513	1.02
Valine	0.767	1.052
	12.575	25.3055

花生雞腳湯的生物化學

一場蛋白質的盛宴

Peanut, or groundnut (Arachis hypogaea) are known by many other local names such as earthnut, ground nut, monkey nut, and pig nut. Despite its name and appearance, the peanut is not a nut, but rather a legume. Hypogaea means "under the earth"; after pollination, the flower stalk elongates causing it to bend until the ovary touches the ground. Continued stalk growth then pushes the ovary underground where the mature fruit develops into a legume pod, the peanut.

Most of the edible tissue on the feet consists of skin and tendons, with no muscle. Collagen is a group of naturally occurring proteins found in animals, in the form of elongated fibrils, is mostly found in fibrous tissues such as tendon, ligament and skin, and is also abundant in cornea, cartilage, bone, blood vessels, the gut, and intervertebral disc.

Peanut nutritional value per 100 g (3.5 oz).

Carbohydrates	21 g
Fat	48 g
saturated	7 g
monounsaturated	24 g
polyunsaturated	16 g
Protein	25.3055 g
Water	4.26 g
Thiamine (vit. B1)	0.6 mg (52%)
Niacin (vit. B3)	12.9 mg (86%)
Pantothenic acid (B5)	1.8 mg (36%)
Vitamin B6	0.3 mg (23%)
Folate (vit. B9)	246 μg (62%)
Vitamin C	0.0 mg (0%)
Calcium	62 mg (6%)
Iron	2 mg (15%)
Magnesium	184 mg (52%)
Phosphorus	336 mg (48%)
Potassium	332 mg (7%)
Zinc	3.3 mg (35%)

* Percentages are relative to US recommendations for adults

Protein	25.3055
Glutamic acid	5.243	20.72%
Aspartic acid	3.06	12.09%
Arginine	3.001	11.86%
Leucine	1.627	6.43%
Glycine	1.512	5.97%
Phenylalanine	1.3	5.14%
Serine	1.236	4.88%
Proline	1.107	4.37%
Valine	1.052	4.16%
Tyrosine	1.02	4.03%
Alanine	0.997	3.94%
Lysine	0.901	3.56%
Isoleucine	0.882	3.49%
Threonine	0.859	3.39%
Histidine	0.634	2.51%
Cystine	0.322	1.27%
Methionine	0.308	1.22%
Tryptophan	0.2445	0.97%

Collagen is a composed of a triple helix, which generally consists of two identical chains (α1) and an additional chain that differs slightly in its chemical composition (α2). The most common motifs in the amino acid sequence of collagen are Glycine-Proline-X and Glycine-X-Hydroxyproline, where X is any amino acid other than glycine, proline or hydroxyproline. Abundance in Skin (Residues/1000):

X	Amino Acid	Mammal	Fish
Gly	Glycine	329	339
Pro	Proline	126	108
Ala	Alanine	109	114
Hyp	Hydroxyproline	95	67
Glu	Glutamic acid	74	76
Arg	Arginine	49	52
Asp	Aspartic acid	47	47
Ser	Serine	36	46
Lys	Lysine	29	26
Leu	Leucine	24	23
Val	Valine	22	21
Thr	Threonine	19	26
Phe	Phenylalanine	13	14
Ile	Isoleucine	11	11
Hyl	Hydroxylysine	6	8
Met	Methionine	6	13
His	Histidine	5	7
Tyr	Tyrosine	3	3

Proteinogenic ("protein building") amino acids are amino acids that are precursors to proteins, and are produced by cellular machinery coded for in the genetic code of any organism. There are 22 standard amino acids, but only 21 are found in eukaryotes. Proteinogenic amino acids can be condensed into a polypeptide (the subunit of a protein) through a process called translation (the second stage of protein biosynthesis, part of the overall process of gene expression).

In contrast, non-proteinogenic amino acids are either not incorporated in proteins (like GABA, L-DOPA, or triiodothyronine), or are not produced directly and in isolation by standard cellular machinery (like hydroxyproline and selenomethionine). Non-proteinogenic amino acids are incorporated in nonribosomal peptides, which are not produced by the ribosome during translation.

Humans can synthesize 11 of these 20 from each other or from other molecules of intermediary metabolism. The other 9 must be consumed in the diet and so are thus called essential amino acids. The essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Peanut has all 9 essential amino acids. Collagen in animal skin has 8 with tryptophan is missing. Peanut has cystine but collagen does not.

9 Essential Amino Acids

Histidine	Used by many proteins as a regulatory mechanism. However only a few histidines are needed for this, so it is comparatively scarce.
Isoleucine	Their molecules are rigid and have large aliphatic hydrophobic side chains. Their mutual hydrophobic interactions are important for the correct folding of proteins, as these chains tend to be located inside of the protein molecule.
Leucine	Behaves similarly to isoleucine
Lysine	Behaves similar to arginine. Contains a long flexible side-chain with a positively-charged end. DNA-binding proteins have their active regions rich with arginine and lysine. The strong charge makes these two amino acids prone to be located on the outer hydrophilic surfaces of the proteins; when they are found inside, they are usually paired with a corresponding negatively-charged amino acid, e.g., aspartate or glutamate.
Methionine	Always the first amino acid to be incorporated into a protein. It's methyl group, if activated, is used in many reactions where a new carbon atom is being added to another molecule.
Phenylalanine	The biggest amino acids, contain large rigid aromatic group on the side-chain. Like isoleucine, leucine and valine, these are hydrophobic and tend to orient towards the interior of the folded protein molecule.
Threonine	Has a short group ended with a hydroxyl group. Both threonine and serine are very hydrophilic, the outer regions of soluble proteins tend to be rich with them.
Tryptophan	Behaves similarly to phenylalanine and tyrosine. Precursor of serotonin. Naturally fluorescent.
Valine	Behaves similarly to isoleucine

Amino acids that find in peanuts:

Glutamic acid	Behaves similarly to aspartic acid. Has longer, slightly more flexible side chain.
Arginine	Functionally similar to lysine.
Aspartic acid	Usually is located on the outer surface of the protein, making it water-soluble. Binds to positively-charged molecules and ions, often used in enzymes to fix the metal ion.
Cystine	A dimeric amino acid formed by the oxidation of two cysteine residues that covalently link to make a disulfide bond. Through formation of disulfide bonds within and between protein molecules, cystine is a significant determinant of the tertiary structure of most proteins. Cysteine is an α-amino acid. The thiol side chain in cysteine often participates in enzymatic reactions, serving as a nucleophile.

Amino acids that find in collagen:

Glycine	It is not optically active. It is the smallest amino acid, rotates easily, adds flexibility to the protein chain. As too much flexibility is usually not desired, as a structural component it is less common than alanine.
Proline	Can disrupt protein folding structures like α helix or β sheet, forcing the desired kink in the protein chain. Common in collagen, where it often undergoes a post-translational modification to hydroxyproline.
Alanine	Behaves fairly neutrally, and can be located in both hydrophilic regions on the protein outside and the hydrophobic areas inside.
Hydroxyproline	A common non-proteinogenic amino acid. It is produced by hydroxylation of the amino acid proline by the enzyme prolyl hydroxylase following protein synthesis. Although it is not directly incorporated into proteins, hydroxyproline comprises roughly 4% of all amino acids found in animal tissue, more than seven amino acids which are directly incorporated. Hydroxyproline and proline play key roles for collagen stability. They permit the sharp twisting of the collagen helix.
Hydroxylysine	It arises from a post-translational hydroxy modification of lysine. It is most widely known as a component of collagen.