Question

answer each question

Answer 1

10, Mitochondria and chloroplasts likely evolved from engulfed prokaryotes that once lived as independent organisms. At some point, a eukaryotic cell engulfed an aerobic prokaryote, which then formed an endosymbiotic relationship with the host eukaryote, gradually developing into a mitochondrion. Eukaryotic cells containing mitochondria then engulfed photosynthetic prokaryotes, which evolved to become specialized chloroplast organelles. all A,B,C are correct.

11. All living things are composed of cells. Cells are the basic units of life and all tissues and organs are composed of cells. They are so small that they must be viewed with a microscope. There are different types of cells. Cells can either be eukaryotic or prokaryotic. Eukaryotic cells have a nucleus and membrane bound organelles. Plant and animal cells are eukaryotes. Plant cells are generally a square shape while animal cells are usually circular. Plant cells and animal cells have evolved different organelles to perform specific functions. Plant cells have chloroplasts, a cell wall and a central vacuole. Animal cells lack these three organelles. Plant cells have chloroplasts because they make their own food. Plant cells have a cell wall so that they do not burst when the central vacuole fills up with water. Prokaryotes do not have a nucleus, and lack membrane bound organelles. They are the oldest cells on earth. Bacteria are prokaryotes. Prokaryotes often move using special structures such as flagella or cilia.

Cells have many structures inside of them called organelles. These organelles are like the organs in a human and they help the cell stay alive. Each organelle has it’s own specific function to help the cell survive. The nucleus of a eukaryotic cell directs the cell’s activities and stores DNA. Eukaryotes also have a golgi apparatus that packages and distributes proteins. Mitochondria are the power house of the cell and provide the cell with energy. Both plant and animal cells have mitochondria. Lysosomes are like the stomach of the cell. They contain enzymes that digest the cell’s used parts. All of the cell’s organelles must work together to keep the cell healthy.

The cell membrane is the protective barrier that surrounds the cell and prevents unwanted material from getting into it. The cell membrane has many functions, but one main function that it has is to transport materials (salts, electrolytes, glucose and other necessary molecules) into the cell to support necessary life functions. Not only does the membrane let molecules into the cell, but it also lets wastes such as carbon dioxide out of the cell. The cell membrane is made up of a phosholipid bilayer. Each phopholipid contains a hydrophilic, or water loving head and ahydrophobic, or water fearing tail. These properties that the phospholipids have and the specific orientation they are arranged in provide the cell with an selectively permeable barrier.

12. An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a higher resolving power than light microscopes and can reveal the structure of smaller objects. A scanning transmission electron microscope has achieved better than 50 pm resolution in annular dark-field imaging modea and magnifications of up to about 10,000,000× whereas most light microscopes are limited by diffraction to about 200 nm resolution and useful magnifications below 2000×.

Electron microscopes have electron optical lens systems that are analogous to the glass lenses of an optical light microscope.

Electron microscopes are used to investigate the ultrastructure of a wide range of biological and inorganic specimens including microorganisms, cells, large molecules, biopsy samples, metals, and crystals. Industrially, electron microscopes are often used for quality control and failure analysis. Modern electron microscopes produce electron micrographs using specialized digital cameras and frame grabbers to capture the images.

13. In biochemistry, allosteric regulation (or allosteric control) is the regulation of an enzyme by binding an effector molecule at a site other than the enzyme's active site.

The site to which the effector binds is termed the allosteric site or regulatory site. Allosteric sites allow effectors to bind to the protein, often resulting in a conformational changeinvolving protein dynamics. Effectors that enhance the protein's activity are referred to as allosteric activators, whereas those that decrease the protein's activity are called allosteric inhibitors.

Allosteric regulations are a natural example of control loops, such as feedback from downstream products or feedforward from upstream substrates. Long-range allostery is especially important in cell signaling. Allosteric regulation is also particularly important in the cell's ability to adjust enzymeactivity.

14. An exoskeleton, in contrast to an endoskeleton, is an external anatomical feature that supports and protects an animal's body.All arthropods (such as insects, spiders and crustaceans) and many other invertebrate animals (such as shelled mollusks) have exoskeletons.Lobsters, for example, have tough outer shell systems which provide rigidity and shape to their bodies.