The cell membrane is semipermeable because allows only certain molecules to pass through.
Explanation:
Semipermeability is a common property of cell membranes, due to their predominantly lipid composition, which gives them a hydrophobic character.
The cytoplasmic membrane is constituted by a double layer of lipids, in addition to structural proteins and glucides, which prevent the entry of polar or charged molecules. This characteristic allows lipids and small molecules without charge to pass freely through it.
Regarding the other options:
<em> A. Cell membranes are associated with lysosomes, structures that contain enzymes. However, this characteristic is not related to semipermeability.</em>
<em> C. They allow the passage of small molecules - devoid of charge - through them.</em>
<em> D. Not all non-polar molecules pass through, as some need a transporter.</em>
DNA replication is an enzyme mediated, 3-step process during which the DNA molecule produces a copy of itself. The 3 steps involved are as follows;
initiation
elongation
termination
<em>Initiation </em>involves the unwinding of the double helix structure of the DNA using DNA helicase enzyme
<em>Elongation</em> involves binding of RNA primer to the DNA strands and addition of bases to the primer<em> </em>to elongate the new chains. Bases are added to the leading strand continuously while the lagging strand is replicated in short segments (okazaki segments).
<em>Termination</em> involves the unbinding of RNA primer and substitution of its bases by DNA bases. The Okazaki fragments are then joined together using the DNA ligase enzyme.
<em>The short, numerous segments of DNA observed in the mixture is the Okazaki fragments of the lagging strand. This is due to the absence of the enzyme involved in the joining of these fragments.</em>
<em>Sugar transport in phloem is referred to as pressure flow and it involves the movement of sugar through the phloem vascular tissue from the regions where sugar is synthesized (by photosynthesis) to other parts of the plant's body that require sugar.</em>
The parts of plants where sugar is synthesized (usually the leaf) is known as sugar source while the parts where they are transported is referred to as the source. Sources are usually areas of of high osmotic concentration and high water pressure while sinks are usually areas of low osmotic concentration and low water pressure.
<em>Hence, sugar transport in the phloem can be said to be influenced by the rate of sugar production at the source (rate of photosynthesis), turgor pressure as well as sugar concentration in sinks and sources.</em>
The only option that has no known effect on sugar transport in the phloem is transcription.
