胆汁里不含消化酶,为什么能促进脂肪消化?

答:初中《生理卫生》教材第85页上说“肠液和胰液里含有多种能消化糖类、蛋白质、脂肪的消化酶,胆汁里不含消化酶,但是能促进脂肪的消化。”胆汁里不含消化酶,为什么能促进脂肪的消化呢?要回答这个问题,首先要掌握胆汁的成分和作用。胆汁中不含消化酶,但含有与消化有关的胆盐、胆固醇、脂肪酸和卵磷脂等。胆     

母亲是18-三体携带者,能生育正常宝宝吗?

<正>答:18三体综合征又称Edward综合征,本病临床症状复杂,主要特征是生长发育障碍,智力低下,小眼,眼距宽。耳低位、畸形,先天性心脏病,有特殊握拳姿势等。本病最常见的染色体畸变是单纯18三体,即     

用2n作母本,用4n作父本也能产生3n西瓜种子吗?

高中《生物》课本 P150上,谈到三倍体西瓜的培育过程。其中有这样一段话:“……用四倍体植株作母本,用二倍体植株作父本,进行交配,就能在四倍体植株上结出三倍体西瓜的种子。”对此,不少师生提出另一种设想:如果反过来,用二倍体(2n)植株作母本,用四倍体     

既是稻田，又是水库

侗族的稻鱼鸭生产结构都是以水为基础的，蓄水的田坎最高达到50公分，暴雨季节每亩地能蓄水335吨，但这个事实被人们忽视了。     

Iron Availability Compromises Not Only Oligodendrocytes But Also Astrocytes and Microglial Cells

When disrupted, iron homeostasis negatively impacts oligodendrocyte (OLG) differentiation and impairs myelination. To better understand myelin formation and OLG maturation, in vivo and in vitro studies were conducted to evaluate the effect of iron deficiency (ID) not only on OLG maturation but also on astrocytes (AST) and microglial cells (MG). In vivo experiments in an ID model were carried out to describe maturational events during OLG and AST development and the reactive profile of MG during myelination when iron availability is lower than normal. In turn, in vitro assays were conducted to explore proliferating and maturational states of each glial cell type derived from control or ID conditions. Studies targeted NG2, PDGFRα, CNPAse, CC1, and MBP expression in OLG, GFAP and S100 expression in AST, and CD11b, ED1, and cytokine expression in MG, as well as BrDU incorporation in the three cell types. Our results show that ID affected OLG development at early stages, not only reducing their maturation capacity but also increasing their proliferation and affecting their morphological complexity. AST ID proliferated more than control ones and were more immature, much like OLG. Cytokine expression in ID animals reflected an anti-inflammatory state which probably influenced OLG maturation. These results show that ID conditions alter all glial cells and may impact myelin formation, which could be regulated by a mechanism involving a cross talk between AST, MG, and oligodendrocyte progenitors (OPC).     

On What It is to Fly Can Tell Us Something About What It is to Live

The plurality of definitions of life is often perceived as an unsatisfying situation stemming from still incomplete knowledge about ‘what it is to live’ as well as from the existence of a variety of methods for reaching a definition. For many, such plurality is to be remedied and the search for a unique and fully satisfactory definition of life pursued. In this contribution on the contrary, it is argued that the existence of such a variety of definitions of life undermines the very feasibility of ever reaching a unique unambiguous definition. It is argued that focusing on the definitions of specific types of ‘living systems’—somehow in the same way that one can define specific types of ‘flying systems’—could be more fruitful from a heuristic point of view than looking for ‘the’ right definition of life, and probably more accurate in terms of carving Nature at its joints.     

Storm Resistant Boat Designing Based on the Geometry and Movement of Water Strider

A novel conceptual model of boat is developed based on the bionic properties of water strider. This four-legged model is called storm resistance boat. Concentrated balancing forces, asymmetry of arms and smooth motion against waves and the effect of arms length on the reduction of drag and effects of wave are the major characteristics of water strider which are considered for designing this model. The results indicate the characteristic improvement of the small boat and its resistance against strong waves as well as marine ill-conditions. This boat can be considered as a high speed rescue boat in marine traffic.     

What Is Resource Consumption and How Can It Be Measured?

When analyzing the metabolism of our economy, the usual choice for a measure of resource consumption is the throughput of matter and energy. This, however, cannot be sufficient, since consumption by definition is always relating to the destruction or transformation, and hence a change in quality, not only in quantity, of material or energy flows. Here, an approach is presented that takes the entropy production associated with any process as a measure for the resource consumption of that process. Entropy production is thereby used to approximate the intuitive notion of consumption, which can best be described by the term loss of potential utility. This article delivers theoretical evidence for the validity of this choice, and a second article in a future issue will present an application taken from the metallurgical sector. The related concept of exergy analysis is discussed and compared against the entropy approach.