Biology Test 6

Squamous epithelium is single layer of thin flattened cells with irregular boundaries and are present lining walls of blood 
vessels, air sacs of lungs etc.

Male cockroaches have a pair of short thread like un-joint anal styles found in the 9^th sternum of abdomen. This structure is unique to male cockroach only and is not found in females. Females only have a pair of anal cerci which is found in males as well.

The membranes of archaebacteria are built with a monolayer of branched chain lipids. They lack peptidoglycan in their cell wall. Their cell wall contains non-cellulosic polysaccharides and proteins.

A typical prokaryotic cell contains the plasma membrane, cytoplasm, ribosomes and genetic material etc. It does not have well-defined nucleus, membrane-bound organelles, and centrioles etc.

Both ribosomal subunit at the time of initiation of protein synthesis due to increase in magnesium concentration to form an individual ribosome known as monosome. Further increase in magnesium ion may cause the formation of the dimer.

Phosphoglycerides are glycerol based phospholipids. They are composed of a glycerol backbone, fatty acids and phosphorylated alcohol.

Chemically heparin is mucoitin-polysulphuric acid. Mucoitin is a polysaccharide, composed of glucosamine, glucuronic acid esterified sulphuric acid. It is a potent natural anticoagulant produced in the Mast Cells that causes antithrombin bind to thrombin and produce inhibition of blood coagulation.

Alcohol is produced by fermentation of a carbohydrate. For producing ethanol, yeast is added to a sugar solution and kept in absence of air for many days. Anaerobic conditions cause the enzymes in yeast (zymase) to convert glucose (sugar solution) to ethanol and carbon dioxide. 

the G1 checkpoint is the restriction checkpoint or the major check point. As the cell progresses through G1 depending upon the internal and external conditions, it will either delay G1 enter the G0 stage or proceed pas the restriction point. The decision to commit new round=d of cell division will occur when the cells will activate the cyclin-CDK-dependent transcription which will promote the entry into S phase.

In zygotene the homologous pair of chromosomes pair together by a process called as synapsis. The paired chromosomes are called bivalents. As a result of synapsis two homologous pairs are brought together through a characteristic ladder like structure called the synaptonemal complex. The bivalents have 4 chromatids and are called tetrad.