Please Answer : Exam For Tomorrow - 2 + 1 Questions Only

1) Desmosomes: Desmosomes (also called anchoring junctions) function like rivets, fastening cells together into strong sheets. Intermediate filaments made of sturdy keratin proteins anchor desmosomes in the cytoplasm. Desmosomes attach muscle cells to each other in a muscle. Some "muscle tears" involve the rupture of desmosomes.

Gap Junctions: Gap junctions (also called communicating junetions) provide cytoplasmic channels from one cell to an adjacent cell and in this way are similar in their function to the plasmodesmata in plants. Gap junctions consist of membrane proteins that surround a pore through which ions, sugars, amino acids, and other small molecules may pass. Gap junctions are necessary for communication between cells in many types of tissues, including heart muscle, and in animal embryos.

Tight Junctions: At tight junctions, the plasma membranes of neighboring cells are very tightly pressed against each other, bound together by specific proteins. Forming continuous seals around the cells, tight junctions prevent leakage of extracellular fluid across a layer of epithelial cells. For example, tight junctions between skin cells make us watertight by preventing leakage between cells in our sweat glands.

Plasmadesmata: In plants, their function is not to hold cells together but to allow transport between the cells, like a passageway through the cell walls. check out the diagram on wikipedia. The dark line you refer to, is probably the cell walls between the cells.

2) (a) When a cell is broken by mechanical homogenization (step1), the various membranous organelles become fragmented and form different spherical membranous vesicles. Vesicles derived from different organenlles can be separated by various techniques of centrifugation. In the procedure depicted here, the cell homogenate is first subjected to low-speed centrifugation to pellet the larger, denser particles, leaving the smaller vesicles (microsomes) in the supernatant (step2). The microsomes can be removed from the supernatant by centrifugation at higher speeds for longer periods of time (step3). A crude microsomal fraction of this type can be fractioned into different vesicle types in subsequent steps.
(b) Electron micrograph of a smooth microsomal fraction in which the membranous vesicles lack ribosomes.
(c) Electron micrograph of a rough microsomal fraction containing ribosome-studded membranes.

(See attachment)

3) NADH->O2 produces 3ATP/2e;      FADH 2 ->O 2 produces 2ATP/2e...

thanks to duddy for helping

You're welcome. Good luck on your exams.