FS exam 3 Flashcards
what are the sources of toxic components in food? p46
Naturally occurring chemicals
Compounds produced by processing
Food additives
Microbial toxins
what is the GRAS list? what are some examples?
Generally Recognized As Safe. 不用测试也知道是安全的。salt, pepper, baking powder, vitamin E
what is the difference between Food additives and Dietary Supplements?
FA: 需要 pre-market approval, 如果有没有授权的添加剂会被seized。DS: 不需要 pre-market approval, 包含很多substances not legal to use in foods, harm must be demonstrated before seizing products
what is GRAS review?
（再检查一次是不是安全的）添加剂被 toxicologists review之后，如果被测为安全的，那就会被认定成GRAS. Not formally tested like other additives.
how is Acute Toxicity (LD50) done? what if LD50 is low?
median lethal dose (LD50): 要吃多少compound才会在2周内杀死一半的实验品。发现很低=很毒= rejected without further testing
What are some species used to test for toxicity testing? why choose them? how about the second species used?
purebred lab rats: inexpensive, small, short lifespan, virtually identical genetically. 最好第二个实验品是primate, 但是它们endangered, expensive and difficult to work with.
所以过去第二个都用 dog：reasonable size, not expensive, reasonable to work with.
what are some difficulties faced when choosing species for toxicity testing? what is done to deal with the difficulty?
实验品的 ages, sizes，gene 都不一样. 所以选purebred, often beagles. animals 比起人类可能对某些chemical 比较sensitive or not sensitive. 我们可以把他们当 model for toxicity, 可是还是要有加进safety factors.
how is Short Term Toxicity done? what should be measured? p46
Normally in two species, measure the weight gain food consumption organ weights complete blood profile histopathological examination of organs
What is the purpose of the short term toxicity?
喂食狗狗high level of the substance, 然后看看身体哪些地方有损坏，以后就知道研究这个东西时要注重哪一方面
what does biochemical test determine? p46
find fate of compound in animal。在做chronic的时候，常常顺便做biochemical
Absorption
Distribution
Storage
Tissues accumulation
Metabolism
Enzyme profiles
确保某些物质不会在身体里造成伤害what is done to prevent toxicity in the body?
比较不用担心那些不会被absorb或被absorb后会被rapidly excreted的物质。liver 会试着 detoxify foreign chemicals. 它因为没有specific enzyme for everything it might encounter，所以它一般use a series of enzymes and try to add oxygen to the compound.大部分情况下毒素会降低，也有可能变得更毒
what happens to the enzymes when tissues are damaged? how is it used in biochemical study?
和那个tissue相关的enzyme会在血里出现。所以analysis of enzyme levels 可以说明 chemical在哪里有cause effect. Ex: 血里有肝的enzyme=liver damage
What does Mutagenicity tests try to determine? how is it done?
一个物质是否increases mutation rate. Treated and untreated animals mated and fetuses examined.
what are some difficulties of Mutagenicity tests? how is it overcome?
在动物身上做：要过好几个generations才能发现mutation. 所以用 bacteria and human white blood cells 就可以短期内观察好几个 generations
what is Teratogen? what does it cause? how is it caused?
compound that causes a miss-read in the DNA而造成birth defect, ex: thalidomide； 可能是发生在egg fertilize时，一开始的cell division
what are some sources for Teratogen?
如果浓度够高，alcohol and vitamin A are teratogenic。ex: acne drug, accutane
how are Teratogenicity studies done?
要在conception(受精）前喂食compound ，然后examine fetuses.
how is Reproductive Studies done? what is observed?
Three generations of animals; observe
Fertility
Length of gestation
Live births
Still births
Body weights
Survival at 4 days
Gross abnormalities
不能加入会影响fertility的化学物，因为要看看哪些东西会增加或减少fertility。而且还要看length and outcome of gestation 是不是正常how is Chronic Feeding Studies done? how long is it done
和 reproductive studies一起，为了找 no effect dose. 2 years
what is the No Effect Level? how is it related to Acceptable Daily Intake (ADI)? what is ADI?
level where NO harmful effect can be noted in the most sensitive species tested。no effect level/100= ADI。一个人一天内可以吃的最多的量
why do we choose 100 when calculating ADI? what are some exceptions to that rule?
因为人类的实验不ethical, 所以在动物上做实验，然后假设人类被动物敏感100倍。但事实上是不太可能的。这个只是安全起见。但是有exceptions:
1. 如果有东西是 essential，可以加到 RDI的程度。有很多nutrient的 upper level > 1/100th the NOEL. 2. 如果一个东西cause cancer, the ADI is 0，除非有special legislative action要不然不能加
what is Delaney Clause?
法律：如果发现是carcinogens，不能加进食物里
how is cancer testing done?
for a lifetime, at very high concentrations - highest concentration that does not shorten the life span of the animal。在1000个实验品里用10的量如果没有结果，还是有几率这个物质会产生cancer，所以要加大量。这样做可能会高估，但还是安全起见比较好
how is Ames test done?
一个很快的screening test。所有carcinogen会造成 mutations但不是所有mutagens是carcinogen。如果会造成mutation的才要做更多的测验。Ames test 用来测试 the ability of a compound to cause mutations in bacteria
what are the things we look at considering the testing safety of ingredients? p47
Conversion to toxic compounds
Excretion in less toxic forms
Evidence of non-absorption
Half-life and storage in tissue
Synergism and antagonism
Stress effect on different, sex, age and ethnic groups or disease states.
what are some problems faced when determining the safety of a compound? p47
Impossible to determine absolute safety
Can’t use human subjects
Extrapolation from animals to humans
Extrapolation from large to small doses
Cost
Safety of additive may be greater than food
Final decision comes down to judgment
what are some Acceptable Applications of food addictive?
Improve nutritional value
Enhance quality
Reduce waste
Improve storage quality
Enhance acceptability
Facilitate preparation
Make food more available
what are some Unacceptable Acceptable Applications of food addictive?
To disguise inferior products
To deceive the consumer
To provide otherwise desirable results that lower the nutritional value
To replace good manufacturing practices
To use in amounts greater than are necessary
what are the Most Common used additives based on weight of usage? what are their functions?
Sucrose; High fructose corn syrup; Dextrose (Glucose); Salt; affect taste/ 如果够多，preserve by lowering water activity
what additives cost the most and add the most value to products?
Flavors
what are some Preservatives? how are they labeled on packages?
antioxidants, sequesterants (molecules that bind iron and other minerals to protect flavor) and antimicrobial agents；它们必须要标签。label上面大部分的ingredient都不是preservatives（是nutrient/flavor) ,可是如果它是，就必须要写出来。
how did FDA try to regulate Dietary supplements? why did it fail?
如果说它们被当做herbal product然后像食物一样吃，那就是regulate as a food。如果是加在食物里或分开放，那就是 food additives or drugs。FDA 想要保证它们有所说的功效，可是因为公司反对，而且东西很赚钱，国会最终没让FDA这么做
what is FDA’s power on regulating Dietary supplements?
制造商在marketing之前，不用证明安全性。如果要下架,FDA必须证明not safe
what is the difference between health claim and structure function claim?
health claim: must be proved
structure function claim: requires no proof.
what are some myths and realities of herbs? p48
Natural is not equal to safe
Used for thousands of years is not equal to effective and safe
Herb as a plant is not the same as a capsule or tablet
All brands of herbs are not the same
what are some suggestions of The National Institute of Health? p48
Claims: Government 要控制 information; Congress 要要求 science-based supplement claims
Education：利用 media & editors to counter extravagant claims, 用有关 relevant professional societies 来增加 consumer awareness of how research works; develop consumer education modules
Understanding use：Prepare & implement detailed consumer studies, including extent of use & justification for children
what is the definition of Recombinant DNA? Genetic Engineering? p49
Recombinant DNA: Transfer of genetic material from one source into a living cell for replication and expression.重组DNA=原有基因+另一个DNA
Genetic Engineering - manipulation of the gene pool using biochemical techniques.通过生化方式改基因
how is biotechnology done? what is the goal? what is it used on? p49
把genetic info 从生物A身上取下来，然后用vector 放到另一个上，由此把new genetic material made into protein。这是为了在生物上加上trait，或者让它产生大量的valuable protein，又或停止一个protein的产生。用在medical
Why Study Biotechnology?
为了改变很多带有genetic成分的disorder, defects, diseases。还可以synthesize complex protein medicines
how was biotechnology done in the old days?
selective breeding for desirable traits in plants or animals, find mutants that can survive，最后大量繁殖
what are some common vectors?
plasmids and viruses
how does restriction enzymes work? how is it diff from other enzymes? p49
Restriction Enzymes - bacterial enzymes that cut DNA into pieces at very specific sites.可以把DNA切开的enzyme。大部分enzyme会把DNA切太小片，只有restriction enzyme可以切够大，才可以manipulate
how to select the right restriction enzyme to cut? how should the restriction enzyme cut the gene?
如果知道gene的base sequence还有material on either side，就可以选出来。如果enzyme剪在gene的中间，会把它inactivate。所以如果要选gene of interest, enzyme就必须剪在near ends of gene
what is PCR (Polymerase chain reaction)? when is it used? what are the characteristics?
做很多DNA copy的其中一种方法。用在small or old samples。ex: minute samples。fast and specific.例如信纸上的口水
what is RFLP (Restriction fragment length polymorphism)? how is it done? p50
a technique that looks for patterns in DNA。当 2 alleles differ in 1 base pair, restriction enzymes 会把DNA切成很多块。
how is RFLP (Restriction fragment length polymorphism) used? p50
比较两个DNA的pattern可以看出来是不是从同一个人来的。也可以用来看是不是有些pattern只有在患有某disease的人身上才有，而其他人没有。按道理说，如果可以放进去那个不好的gene 的 functional form，病就可以治
what is the diff between sense and anti sense strand? p50
sense: 正确的protein code, 被复制的。anti: 不正确的；和 sense相反，帮助复制
how is Flavr Savr Tomato preserved? what are the advantages and disadvantages?
sense and antisense RNAs are complementary 所以会绑在一起。在一起时就不能做 protein。在番茄里加入 antisense之后，会把它变soft 的 enzyme就没用了。 好处：nothing is added. 坏处：只能拿走某些特性，不能 add new。
how can the technology of Flavr Savr be used on medical stuff?
移除characteristics of cancer cells that cause them to divide uncontrollably
how can biotechnology be used on heart attack?
artery 里的 blood clot 是心脏病其中一个原因。可是当身体试着dissolve时，病人已经heart muscle严重damage或已经死了。Tissue Plasminogen Activator (TPA)：和人类生产的protein一样，可是一次性high concentration注射几秒内分解clot
how was diabetics cured in the past? how about now?
以前用从pig pancreas拿出来的insulin，因为和人的很像，而且效果一样好。现在，把人类insulin放进bacteria里，product和人类的一样
how were children with hemophilia 血友病 used to be treated? what was the danger during the AIDS epidemic？
从别人血里得到clotting factor，可是要很大量的血才能得到足够的。所以受血人有高风险收到virus。EX: AIDS epidemic时期,有血友病的男生最高infection rate。
how are hemophilia treated now? why not just change the genes all together?
clotting factor 由 genetically engineered bacteria 生产，因为是生长在blood stream里的agent 所以没有infection几率。repair genes 比生产 protein medicine (TPA or EPO) 慢
what are some FDA policy conditions for food that use genetic engineering? p50
要 characterized有哪些genetic change。
Stable enough to minimize rearrangements (基因不可以move around)。
Toxicants and anti-nutritional factors要和正常的一样或更少。Nutrient levels要大于或等于，不可以少了bioavailability.
what are some requirements for adding new substances in genetically engineered food? p50
平常食物里没有的东西需要 Pre-market approval, 要被当成food additive测试和label。如果new protein是从常见的allergenic source来的，那么它也会被当成allergenic所以要label。（可能还要其他action）
如果一个食物本身没有注明是genetic engineering，可是在那之后产生了的蛋白质是本来食物里也有的，需要标签吗？为什么？
no; nothing has been added to food that was not there before
