【简答题】Cells differ widely in form and function but they all have certain characteristics. Firstly, they are bounded by a limiting membrane, the plasma membrane. Secondly, they have the ability to break down...
【多选题】Nucleotides have a variety of important functions in all cells, including:
A.
They are the precursors of DNA and RN
B.
They are essential carriers of chemical energy—a role primarily of ATP and to some extent GTP.
C.
They are components of the cofactors NAD, FAD, Sadenosylmethionine, and coenzyme A, as well as of activated biosynthetic intermediates such as UDP-glucose and CDP-diacylglycerol.
D.
Some, such as cAMP and cGMP, are also cellular second messengers.
【简答题】Some desert animals can ___1___ the very strong summer heat and dryness because they have very unusual characteristics. The camel, for example, can hear an increase in the temperature of its body and ...
【单选题】The first is the wear-and-tear hypothesis that suggests the body eventually succumbs to the environmental insults of life. The second is the notion that we have an internal clock which is genetically ...
A.
There are two broad theories concerning what triggers a human's inevitable decline to death
B.
Some scientists believe that humans contain an “internal time clock” which forces them eventually to die.
C.
We all must die some day.
D.
My biology professor gave an interesting lecture Thursday.
【简答题】细胞膜是半渗透膜 It’s _____, meaning that 能使某些物质进入或阻隔在胞外 it lets some thing _____ in and out but blocks others. 膜上有许多受体 The cell membrane is _____ with tiny projections. 它们都有功能 如介导细胞间的粘附 They all have _____, ...