《生物化学》课播讲前致学员的公开信

同学们好! 中国电视师范学院生物专业生物化学课将于今年9月1日播讲。为了有利于大家学好这门课,在开播前讲几点意见,供大家参考。本课使用的教材是钟洪枢、关基石主编的《生物化学》一书。计划讲授60学时。鉴于大家已经学过有机化学,所以第一章“糖类化学”、第二章“脂类化学”就不在课上介绍了。讲授中,对教科书的内容将会做某些增删,希望同学们在课后认真阅读教材。《生物化学》是一门实验性科学,生物化学实验是生物化学课的重要内容。由于条件所限,同学们不一定都有机会学习生化实验,故在课堂讲授中所安排的演示实验,希望大家能在听讲的同时,注意观察实验现象和学习了解有关实验技术,以便加深对课程内     

涡虫双头双尾的再生实验

实验步骤 1.将活涡虫移入到培养皿中,并加少量清洁的培养液。 2.用锋利的手术刀(也可用刮脸双面刀片代替)在解剖镜下(若无解剖镜也可用肉眼)对涡虫进行切割。将切下的残片移入到其他培养皿中(一个培养皿中只放一个残片)。 3.在培养皿中加入足量的培养液,加盖防止水分蒸发干。 4.将培养皿放于15℃左右的阴暗处保存,每隔2     

“叶”的一章教学应注意的问题

植物在生活过程中所需的有机养料,都是通过光合作用制造的,这是绿叶的主要生理功能。此外,叶还具有进行呼吸作用和蒸腾作用的生理功能。研究绿叶的生理功能是本章教学的中心问题,完成好本章的教学任务,我们认为应注意以下几个问题:     

九月份生物各学科实验准备

植物学(实验一和实验二) 材料用具:显微镜(低倍镜)、小块紫色洋葱鳞茎(若无紫色洋葱时,还需准备碘液染色)、内盛清水的小烧杯、吸管、镊子、刀片、牙签(代替解剖针)、载玻片、盖玻片、小片吸水纸、绘图纸,番茄、红色柿子椒各一个(演示用)。示范镜的准备:1.示成熟的番茄果肉细胞:用牙签挑取果肉细胞制成装片观察。2.示辣椒表皮细胞:将柿子椒用小刀切成小块,清除掉果肉制成无色表皮细胞,观察胞间连丝,如用卡宝染液(改良苯酚品红染色液)染色效果更好。卡宝染色液配制方法如下: ①取3克碱性品红,溶于100m170％酒精中,配成母液     

我们怎样开展对青少年的青春期教育

对中学生进行青春期教育是学校进行系列化教育的重要一环,是学校、家庭和社会的共同任务,也是关系到国家民族的未来,使青少年健康成长的重要问题。因此,有必要正确引导中学生了解生理和心理上的变化,克服消极因素,以便使他们集中精力,学好知识本领,     

大麦花粉发育的电镜观察(封二照片说明)

本文用透射电镜观察了大麦(品种苏啤一号)花药中花粉母细胞发育成花粉粒的过程。图1 花粉母细胞时期花药横切面局部,×2350。花药可分为两个部分:花药壁层和花粉母细胞。花药壁层由四层细胞组成,自外向内为表皮     

Recycle use of immobilized glucoamylase by tangential flow filtration unit

Various properties of glucoamylase immobilized onto corn stover supporting material and separation of immobilized enzyme by tangential flow filtration unit were studied. Optimum pH and temperature of immobilized enzyme were 3.5 and 60 degrees C, respectively. Enzyme stability was studied in a packed-bed column. The starch conversion rate was attained at 81% for 15 days; after that, the hydrolysis rate gradually decreased. Size of supporting material proved to be an important factor, with higher activity and good loading yield resulting from smaller supporting material. Glucoamylase immobilized onto supporting material less than 44 mum was used for hydrolysis of 10% soluble starch at pH 3.5 and 40 degrees C for 3 h. Then immobilized glucoamylase was separated from the product by means of a tangential flow filtration unit using a 0.2-mum pore size Nylon 66 membrane filter. This operation was continued until 180 ml filtrate was obtained from a 260-mL starting volume. Then, the next batch was started by adding 180 mL starch substrate into the reactor. The batchwise experiments were repeated 20 times. The average filtration rate of each batch was determined and found to sharply decline during the first four batches. Thereafter, it gradually decreased from batch to batch. The cause of decreasing filtration rate appeared to be due to retrogradation of starch. The percentage of starch hydrolysis within 20 batches was in the range 89-96%. The filtration rate becomes higher if the hydrolyzation time is extended to 14 h. Resistance to filtration was also investigated. Almost all of the total resistance is related to insoluble materials, with the significant part of this from the resistance due to insoluble materials deposited on a surface of membrane and boundary layer resistance. Using a microscopic method, no microorganisms were found in the filtrate.     

Energetic and rate effects on methanogenesis of ethanol and propionate in perturbed CSTRs

Energetic and reaction-rate interactions between hydrogenic (hydrogen-producing) and hydrogenotrophic (hydrogen-consuming) bacteria were investigated in five perturbation experiments performed on steady-state, mixed-culture methanogenic CSTRs receiving ethanol, propionate, or both hydrogenic substrates. When a large quantity of propionate was suddenly added to a propionatefed CSTR, P(H(2) ) increased to 10(-4) atm and propionate oxidation remained energetically favorable. When ethanol was added to a CSTR receiving ethanol, P(H(2) ) rose to 6.3 x 10(-3) atm within 5 h. In both perturbations, P(H(2) ) remained at levels such that oxidation of the hydrogenic substrate remained energetically favorable throughout the transient. Sudden increase in ethanol concentration in the ethanol- and propionate-fed CSTR resulted in an increase in P(H(2) ) such that propionate oxidation became energetically unfavorable and was blocked. Propionate utilization resumed when the added ethanol was depleted and P(H(2) ) returned to its previous steady-state levels. Ethanol perturbation of ethanol- and propionate-fed CSTRs led to the formation of reduced products, including n-propanol and four-through seven-carbon n-carboxylic acids, when P(H(2) ) was elevated; these products disappeared after P(H(2) ) returned to previous, steady-state levels. The transformations were consistent with reaction energetics. Reduced product formation may have been a sink for reducing equivalents, as an alternative to oxidation for propionate utilization, as indicated by an electron equivalents balance over the time course of experiments.     

An adaptive state estimator for detecting contaminants in bioreactors

An algorithm is presented for detecting the appearance of contaminants during batch or fed-batch fermentations, using only presently available on-line measurements. Its adaptive nature enables it to rely on almost no prior knowledge of the real process. The necessary on-line measurements are total biomass and its production rate; it is also shown how a physical variable such as oxygen uptake can be used alone instead. The algorithm's properties are studied theoretically and through simulations. These were confirmed by on-line experimental results, obtained with a Yeast culture, both pure and contaminated by a Bacteria. The algorithm does not detect contaminants when none are there, and it also provides a convergent estimate of a pure culture's specific growth rate. Contaminated cultures are recognized by the algorithm, and this detection can be made more or less conservative. After detection, the various estimates may diverge, due to general observability difficulties, though this divergence can itself be monitored. Moreover, the algorithm is easy to tune and its qualitative behavior is quite insensitive to its adjustable parameters. A practical criterion and scheme for implementation are proposed. The generality of the approach, which far exceeds the experimental system used, is finally discussed.