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Results for: 'SI'
Mycobacterium tuberculosis: Drug Resistance and Natural Selection
By: HWC, Views: 5451
The evolution of drug resistance in microorganisms, such as M. tuberculosis, that cause human diseases is of particular concern to biologists. When Mycobacterium tuberculosis infects the lungs of humans, it causes the disease tuberculosis, also called TB. Once infected, the lungs act as a new...
Brief Summary on Photosynthesis - Animation
By: HWC, Views: 5660
Can increase its weight by 150 pounds as it grows. Where does the new tissue come from? From the soil? From water? Or possibly from the air? The amazing truth is that new material. comes from an invisible gas in the air. In the process of photosynthesis, plants capture carbon dioxide ga...
Gastrulation: cross section of the frog
By: HWC, Views: 5742
Gastrulation Most animals enter a phase early in development called gastrulation. In this phase, a tiny ball or disc of cells rearranges to form three embryonic layers of tissue, called germ layers. The germ layers of the embryo—now called a gastrula—are called the endoderm, mesoderm, and eco...
What are the Parts of a Plant Cell?
By: HWC, Views: 5706
Every chloroplast in a plant cell is packed with stacks of flattened sacs called thylakoids. The thylakoid membranes contain chlorophyll, as well as most of the other components required for the light reactions of photosynthesis. The chlorophyll-containing structures within the membranes are c...
By: HWC, Views: 5475
The slight positive charge of a hydrogen atom in a water molecule can attract an atom with a slight negative charge, such as the nitrogen in a molecule of ammonia. This forms a hydrogen bond between the two atoms. Hydrogen bonds join the two strands of a DNA molecule. Although hydrogen bo...
Anatomy and Chemical Makeup of a Single Hair (Animation)
By: HWC, Views: 4938
The hair's outer cuticle surrounds hair cells filled with tough keratin macrofibrils. Each macrofibril consists of smaller microfibrils. A microfibril is made up of three keratin polypeptide chains. The chains are linked together by disulfide bonds. A hair consists of keratin chains held...
Functional zones in a mitochondrion
By: HWC, Views: 4646
A mitochondrion has a double membrane system. The outer membrane faces the cytoplasm. The inner membrane divides the organelles interior into two compartments. The enzymes that carry out the second stage reactions are in the semifluid matrix inside the inner compartment. Embedded in the ...
By: HWC, Views: 4648
Prophase is the first step in the mitotic process. During prophase, the chromosomes condense. The centrosomes begin to form a spindle and move into position on opposite sides of the cell. Sister chromatids are held together by a protein called cohesin at the centromere. Prometaphase is the sec...
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