FILL IN 9) In passive cell transport, substances move from
concentrations to
concentrations.
10) in order for substances to diffuse, a
gradient must exist.
11) A concentration gradient is a
of concentrations between two regions.
12)
proteins or channel proteins are used to aid substances across the cell membrane in passive transport.
13) During passive transport, substances travel
the concentration gradient.
14) Facilitated diffusion uses
to help aid some substances across the cell membrane.
15) Cell membranes are
because they allow some substances to pass through more easily than others.
hp

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation:

after making a punnet square using bv bv bv bv you will find that the ratio will be 9: 7 or a 128.6% probability.

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in the year 2850, humans successfully colonized mars. the martian modules that were constructed could hold only a small population of people. it is now a century later, and the population on mars has grown to 600 people. of the current mars population, 45 people express the recessive phenotype for phenylketon- uria (pku) syndrome (pp genotype).

explanation: