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melisa1 [442]
3 years ago
5

The ara operon is controlled by a regulator protein that exerts ________.

Biology
1 answer:
goblinko [34]3 years ago
7 0

AraC protein certain to the ara operator works as a repressor that avoid transcription of the same ara operon and the araC gene AraC protein is an activator in the presence of arabinose and repressor in the absence of arabinose -With arabinose absent, the AraC protein stays as
a homodimer. One AraC protein put together to the ara initiator and the other protein now binds to a different regulatory site in DNA called the ara operator.

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Which statement is true about extracted lipid?
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Answer:

The right answer is (B) the extracted lipids cover twice the surface area of the intact red blood cells.

Explanation:

To explain this statement is necessary to take into consideration the structure of a lipid. On the first place lipids that form membranes are called phospholipids, this means they have one 'head' that is hydrophilic and a tail composed by the lipidic chain that is hydrophobic.

In a biologic context, the phospholipids form the cellular membrane. They do so by a bi-layer disposition, meaning that one the external side of the cell there is a layer of phospholipids with the hydrophilic head and in the internal side, there is a second layer of phospholipids with the hydrophilic head. The hydrophobic 'tails' are in the middle. This disposition is due to the fact that both the external and the internal environments are water based.

Therefore, since each cell has a bilayer membrane of phospholipids, when the cells are dissolved and all the lipids that used to form the membrane are put together, they will occupy twice the surface of the red blood cells.

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The production of biogas is an exothermic reaction​
Eddi Din [679]
That is the corrext answer
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3 years ago
One of gold's physical properties is its _____. A. color B. acidity C. basicity D. chemical reactivity
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Animal cells have which of the following characteristics? Select all that apply.
devlian [24]

Answer:

Animal Cell Structure

Animal cells are typical of the eukaryotic cell, enclosed by a plasma membrane and containing a membrane-bound nucleus and organelles. Unlike the eukaryotic cells of plants and fungi, animal cells do not have a cell wall. This feature was lost in the distant past by the single-celled organisms that gave rise to the kingdom Animalia. Most cells, both animal and plant, range in size between 1 and 100 micrometers and are thus visible only with the aid of a microscope.

Anatomy of the Animal Cell

The lack of a rigid cell wall allowed animals to develop a greater diversity of cell types, tissues, and organs. Specialized cells that formed nerves and muscles—tissues impossible for plants to evolve—gave these organisms mobility. The ability to move about by the use of specialized muscle tissues is a hallmark of the animal world, though a few animals, primarily sponges, do not possess differentiated tissues. Notably, protozoans locomote, but it is only via nonmuscular means, in effect, using cilia, flagella, and pseudopodia.

The animal kingdom is unique among eukaryotic organisms because most animal tissues are bound together in an extracellular matrix by a triple helix of protein known as collagen. Plant and fungal cells are bound together in tissues or aggregations by other molecules, such as pectin. The fact that no other organisms utilize collagen in this manner is one of the indications that all animals arose from a common unicellular ancestor. Bones, shells, spicules, and other hardened structures are formed when the collagen-containing extracellular matrix between animal cells becomes calcified.

Animals are a large and incredibly diverse group of organisms. Making up about three-quarters of the species on Earth, they run the gamut from corals and jellyfish to ants, whales, elephants, and, of course, humans. Being mobile has given animals, which are capable of sensing and responding to their environment, the flexibility to adopt many different modes of feeding, defense, and reproduction. Unlike plants, however, animals are unable to manufacture their own food, and therefore, are always directly or indirectly dependent on plant life.

Most animal cells are diploid, meaning that their chromosomes exist in homologous pairs. Different chromosomal ploidies are also, however, known to occasionally occur. The proliferation of animal cells occurs in a variety of ways. In instances of sexual reproduction, the cellular process of meiosis is first necessary so that haploid daughter cells, or gametes, can be produced. Two haploid cells then fuse to form a diploid zygote, which develops into a new organism as its cells divide and multiply.

The earliest fossil evidence of animals dates from the Vendian Period (650 to 544 million years ago), with coelenterate-type creatures that left traces of their soft bodies in shallow-water sediments. The first mass extinction ended that period, but during the Cambrian Period which followed, an explosion of new forms began the evolutionary radiation that produced most of the major groups, or phyla, known today. Vertebrates (animals with backbones) are not known to have occurred until the early Ordovician Period (505 to 438 million years ago).

Fluorescence Microscopy of Cells in Culture

Cells were discovered in 1665 by British scientist Robert Hooke who first observed them in his crude (by today's standards) seventeenth century optical microscope. In fact, Hooke coined the term "cell", in a biological context, when he described the microscopic structure of cork like a tiny, bare room or monk's cell. Illustrated in Figure 2 are a pair of fibroblast deer skin cells that have been labeled with fluorescent probes and photographed in the microscope to reveal their internal structure. The nuclei are stained with a red probe, while the Golgi apparatus and microfilament actin network are stained green and blue, respectively. The microscope has been a fundamental tool in the field of cell biology and is often used to observe living cells in culture. Use the links below to obtain more detailed information about the various components that are found in animal cells.

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