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RSB [31]
3 years ago
5

Biological membranes are said to be selectively permeable. What does this term mean, and how does this affect the way the molecu

les are able to move through cellular membranes?
Biology
1 answer:
valina [46]3 years ago
5 0

Answer:

This means that some cells are able to letter molecules pass through them and this makes it easier for the molecules to pass through.

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Strontium-90 has a half life of 29 years, how much strontium-90 is left from the Chicago pile reactor that was active around 87
agasfer [191]

Answer:

The answer is below

Explanation:

The half life of a substance is the time required by that substance to reduce to half of its initial value. The half life is calculated using the formula:

N(t)=N_o(\frac{1}{2} )^\frac{t}{t_\frac{1}{2} } \\\\where\ N(t)=quantity\ of\ substance \ remaining, N_o=initial\ quantity\\of\ substance, t=time\ and \ t_\frac{1}{2}=half\ life\ of\ substance

Given that t = 87 years, half life = 29 years, therefore the quantity of strontium-90 left is:

N(t)=N_o(\frac{1}{2} )^\frac{87}{29} \\\\N(t)=N_o(\frac{1}{2} )^\frac{t}{t_\frac{1}{2} } \\\\N(t)=N_o(\frac{1}{2} )^3\\\\N(t)=\frac{1}{8} N_o

That is one-eight of Strontium 90 would be left after 87 years

6 0
3 years ago
Explain why some parts of a plant can act as both a source and a sink.
Varvara68 [4.7K]

Answer:

Some organs are both a source and sink. Leaves are sinks when growing and sources when photosynthesizing. Rhizomes are sinks when growing but become sources in the spring when they provide energy for new growth.

5 0
3 years ago
What would happen to human blood cells if they were placed in a salt water solution?
OLEGan [10]

Answer:

The red blood cells will shrink in size when water diffuses out of them.

7 0
3 years ago
The lifetime of an intracellular signaling molecule must be short for the cell to be able to cause a change in the concentration
ivann1987 [24]

Answer:

Statement B is false.

Explanation:

PKA and PKG is both have binding domains to attach with nucleoside monophosphate and help in modulating these enzymes that explains that PKA is more related to the PKG than PKC at the level of amino acid.

At the level of  polypeptide chain level PKG has single polypeptide chain whereas in PKA modulatory domains are located on different poly peptide chain. Both are activated by the nucluoside triphosphate, more precisely PKA by cAMP and PKG is by cGMP respectively, whereas PKC is activated by DAG or Ca or both depending on the isofom.

Thus, the correct answer is - option B.

4 0
3 years ago
Select all that apply.
QveST [7]
The answers are A) ectoderm and B) endoderm.

Fertilization is a fusion of male and female gametes which leads to the formation of a zygote. The zygote undergoes mitosis and transforms into a single-layered blastula. Gastrulation is a transformation of the blastula into a two-layer or three-layer gastrula. Cnidarians are a diploblastic animal because their gastrula has only two layers - endoderm and ectoderm.
7 0
3 years ago
Read 2 more answers
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