Question

31) Which of the following provide the best description of totipotent stem cetlis?

a. They are converted from differentiated cells through the stimulation of some transcription factors.

b. They are present in adult brain to produce new nerve cells to facilitate learning and memory.

c. They can produce both blood and immune cells.

d. They are embryonic stem cells capable of generating every type of cells in the body.

32) Which of the following experimental results did does NOT contribute to our understanding of the fluid mosaic model of the plasma membrance?

a. fluorescence recovery after photobleaching

b. fluorescent antibodies marking two different fused cells.

c. nocodazole treatment of dividing cells.

d. live-cell imagining of a fluorescent-tagged integral membrane protein using a super-resolution microscope

e. freeze-fracture and electron microscopy

Answer 1

31. Totipotent cells are the embryonic stem cells capable of generating all types of cells in the body.

The potential of a cell to grow and develop into a multicellular or multiorganed higher organism is called cellular totipotency. This potential lies mainly in cellular differentiation, with the genes lying within the same cell and many of them that remain inactive in differentiated organs are able to express only under culturable conditions. Cell differentiation is the basic event of development in higher organisms and called cytodifferentiation. Development of shoot buds from single epidermal cells of hypocotyl is an example of plant totipotency.

32. The fluid mosaic model of plasma membrane proposed by Singer and Nicholson was not based on the study of Nocodazole treatment of dividing cells.

Fluid and mosaic model proposes that the cell membrane is made up of mosaic of proteins like a collage which  is moving forming a fluid matrix which is embedded in or attached to a double layer of phospholipids. This model is supported by experiments of fluorescence recovery after photo bleaching , fluorescent antibodies experiment with 2 fused cells , live cell imagining and freeze fracture and electron microscopy experiments