In flowering plants, double fertilization gives rise to a(n) ________ and a(n) ________.
A. Embryo; zygote
B. Pollen grain; endosperm
C. Ovary; embryo
D. Embryo; endosperm
E. Gametophyte; sporophyte
Ans: D. Embryo; endosperm
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Which statement best describes the mechanism(s) of posttranslational regulation of gene expression?
A. Covalent modification of newly synthesized proteins generally has no marked effect on protein function. B. Protein synthesis is often repressed by feedback or noncompetitive inhibition. C. Allosteric regulation following transcription of mRNA occurs in many biosynthetic pathways. D. Once a protein is synthesized, there is little to no posttranslational modification.
) Some Archaea are chemoorganotrophs and use organic compounds as electron donors for energy metabolism
Indicate whether the statement is true or false.
What is the function of the structural elements of a virus?
a. To provide a source of energy for the virus b. To package and protect the viral genome c. To use all of the cell proteins
Anaphylaxis is the term for reactions caused when certain antigens combine with
A) IgE antibodies. B) macrophages. C) IgG antibodies. D) complement. E) histamine.