Answer:
Water, carbon dioxide, and oxygen are among the few simple molecules that can cross the cell membrane by diffusion (or a type of diffusion known as osmosis ). Diffusion is one principle method of movement of substances within cells, as well as the method for essential small molecules to cross the cell membrane.
Explanation:
Answer:
Salinity in an estuary varies according to one's location in the estuary, the daily tides, and the volume of fresh water flowing into the estuary. In estuaries, salinity levels are generally highest near the mouth of a river where the ocean water enters, and lowest upstream where freshwater flows in.
Explanation:
The correct option is C.
The heart is part of the cardiovascular system. The heart pump the blood round the body several times in a day. The blood is made up of several types of cells which carry out specific function in the body, these include the white blood cells which serves as soldiers of the body. The lymph refers to the fluid that circulate throughout the lymphatic system. Both the blood and the lymph are carried round the body by the cardiovascular system during the process of circulation.<span />
Answer:
Transcription, mRNA (processing, transport, localization and stability), translation.
Explanation:
- Transcription is regulated in two levels, though chromatin regulation (methylation and acetylation) to loose or increase histone's affinity to DNA and through cis and trans elements such as promoters, enhancers, and silencers (cis) to active/deactivate and RNA polymerase and transcription factors and co-factors (trans).
- mRNA can be regulated using poly-A tails or 5'-caps to shorten or give them more time before they degrade, it could also be spliced to eliminate introns.
- In the translation stage, the regulation occurs during the initiation through a scanning procedure that ensures the 40s ribosomal subunit bind correctly to the untranslated portion of RNA
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The electron transport chain is the final stage of aerobic respiration leading to the forming of ATP in the inner membrane of the mitochondrion<span>.
</span>Mitochondrion<span>, is a membrane-bound organelle found in the cytoplasm of almost all eukaryotic cells.
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<span>An eukaryote is any organism whose cells contain a nucleus and any other organelles within the membranes.</span>
