*Question*
Q: The distance between two consecutive z discs or z lines is called what? Read this paragraph and choose the correct option from the provided answers: When a sarcomere shortens, some regions shorten whereas others stay the same length. A sarcomere is defined as the distance between two consecutive Z discs or Z lines; when a muscle contracts, the distance between the Z discs is reduced. The H zonethe central region of the A zonecontains only thick filaments and is shortened during contraction. The I band contains only thin filaments and also shortens. The A band does not shortenit remains the same lengthbut A bands of different sarcomeres move closer together during contraction, eventually disappearing. Thin filaments are pulled by the thick filaments toward the center of the sarcomere until the Z discs approach the thick filaments. The zone of overlap, in which thin filaments and thick filaments occupy the same area, increases as the thin filaments move inward. Choices: - contractile - ligule - radius - sarcomere A:
**Answer**
sarcomere

*Question*
Q: Obligate anaerobes live and grow in the absence of what? Read this paragraph and choose the correct option from the provided answers: Visit this site (http://openstaxcollege. org/l/fermentation2) to see anaerobic cellular respiration in action. Other fermentation methods occur in bacteria. Many prokaryotes are facultatively anaerobic. This means that they can switch between aerobic respiration and fermentation, depending on the availability of oxygen. Certain prokaryotes, like Clostridia bacteria, are obligate anaerobes. Obligate anaerobes live and grow in the absence of molecular oxygen. Oxygen is a poison to these microorganisms and kills them upon exposure. It should be noted that all forms of fermentation, except lactic acid fermentation, produce gas. The production of particular types of gas is used as an indicator of the fermentation of specific carbohydrates, which plays a role in the laboratory identification of the bacteria. The various methods of fermentation are used by different organisms to ensure an adequate supply of NAD+ for the sixth step in glycolysis. Without these pathways, that step would not occur, and no ATP would be harvested from the breakdown of glucose. Choices: - molecular carbon - molecular nitrogen - atomic oxygen - molecular oxygen A:
**Answer**
molecular oxygen

*Question*
Q: What hormone, which is associated with luteinizing hormone and male sexuality, helps bring about physical changes in puberty? Read this paragraph and choose the correct option from the provided answers: What causes puberty to begin? The hypothalamus in the brain "tells" the pituitary gland to secrete hormones that target the testes. The main pituitary hormone involved is luteinizing hormone (LH) . It stimulates the testes to secrete testosterone. Testosterone, in turn, promotes protein synthesis and growth. It brings about most of the physical changes of puberty, some of which are shown in Figure below . In addition to the changes shown below, during puberty male facial hair begins to grow, the shoulders broaden, and the male voice deepens. You can watch an animation of these and other changes that occur in boys during puberty at the Interactive Body link: http://www. bbc. co. uk/science/humanbody/body/interactives/lifecycle/teenagers/ . Choices: - steroids - epinephrine - estrogen - testosterone A:
**Answer**
testosterone

*Question*
Q: Which system consists of all the bones of the body? Read this paragraph and choose the correct option from the provided answers: The skeletal system consists of all the bones of the body. How important are your bones?. Choices: - circulatory system - nervous system - digestive system - skeletal system A:
**Answer**
skeletal system