21. Primary cells are most economical for infrequent use.22. It has been successfully tested on a broad range of cell lines, hard-to-transfect and primary cells . 23. Zinc carbon dry cells are single-use primary cells . 24. In primary cells the positive and negative electrodes are known as the cathode and anode, respectively. 25. Pectin is an important cell wall polysaccharide that allows primary cell wall extension and plant growth. 26. The primary cell wall of land plants is composed of the polysaccharides cellulose, hemicellulose and pectin. 27. Primary cells cannot divide indefinitely and thus cannot be cultured for long periods of time in vitro.28. Primary cells , for example stem cells, especially fall into this category, although many other medical research purposes.29. The major polysaccharides making up the primary cell wall of land plants are cellulose, hemicellulose, and pectin. 30. These " primary cells " can then be further expanded and transferred into fresh dishes through micropropagation.
