Can someone please answer these 4 questions. I’m begging you

Biology

1 answer:

Natasha_Volkova [10]3 years ago

3 0

Hormones are any member of a class of signaling molecules in multicellular organisms, the job of hormones in a body is to be messengers and controlling and corddinating things in the body peptide hormones is the molecular structure of hormones . Amino acids is what they are composed of. The ovaries and the testes are organs that produce hormones

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Every cell is surrounded by a thin membrane. What is the main function of this cell membrane?. A. to limit the size of the cell

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Answer: Option B

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This membrane is selectively permeable which means it allows only specific molecules to pass through them.

The main function of cell membrane is to protect the cell from the outer environment and by the invasion of harmful bacteria and viruses.

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The data obtained from the meselson–stahl experiment after one generation of replication eliminated the dispersive model of dna

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<h2>Given statement is false</h2>

Explanation:

According to dispersive model of DNA replication,DNA molecules are hybrids of parental and daughter DNA;In this model each individual strand is a combination of original and new DNA

Meselson and Stahl did an experiment on DNA replication using E.coli bacteria

E.coli was grown in a medium containing heavy isotope of nitrogen,bacteria took up the nitrogen and used to synthesize new biological molecules,including DNA
It was grown for many generations,the nitrogenous bases of the bacteria's DNA were all labelled with heavy nitrogen
Bacteria were then switched to light nitrogen isotope and allowed to grow for several generations
They then measured the density of the DNA using density gradient centrifugation
This method separates molecules such as DNA into bands by spinning them at high speeds in the presence of another molecule, such as cesium chloride
Each DNA produced two DNA molecules each with one new strand and one old strand called semi conservative replication(half of the parental DNA conserved in daughter DNA)
Each DNA strand act as a template for synthesis of new strand
Hence,dispersive model of DNA was eliminated and semi-conservative model of DNA replication was proved by the above experiment