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3 years ago

Which type of cell is responsible for causing apoptosis in cancer cells and virus-infected cells?

1 answer:

6 0

The answer is natural killer cells.

Natural killer cells are a type of lymphocytes and they are important for the innate immune system. They recognise stressed cells much faster than other immune cells. Their response is rapid and usually only a few days after a viral infection. They also respond to <span>cancer cell </span>formation. While other immune cells can detect only those harmful cells that have specific markers on the surface of the cell membrane, natural killer cells can even detect those cells that miss markers for apoptosis.

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Which of these processes has a cooling effect on Earth?

Bingel [31]

I believe the answer is B: Earth's oceans absorb some of the carbon dioxide from the atmosphere.

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3 years ago

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Which compound was abundant in Precambrian Earth’s oceans, before complex life evolved on Earth?

Ganezh [65]

The Precambrian time refers to the time 4.5 billion to 542 millions year ago. This period is characterized by having reduced atmosphere and included reduced compounds. Scientists believed that atmosphere at that time was devoid of free oxygen and CO2 was present in excess. Before the complex life evolved on the Earth, the Precambrian Earth's ocean contained dissolved carbon dioxide.

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3 years ago

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imagine a cell-surface receptor protein is being newly synthesized. How can it get into the membrane that it will ultimately be

motikmotik

Answer:

the steps for a new receptor synthesis:

Explanation:

Do not forget the steps vary from an eukarityc cell to prokarityc one.

IN AN EUKARYOTIC CELL:

1- Transcription: in the nucleus, mRNA is synthesized from the DNA sequence that codifies the protein. Exons are spliced if needed by spliceosomes.

2- From nucleus into cytoplasm: mRNA goes through nuclear membrane into the cytoplasm were ribosomes, substrates for protein synthesis and other organelles are.

3- Ribosomes recognize a signal in mRNA and start reading the genetic code, three consecutive nucleotides at a time and adjust the correspondent tRNAs (tRNAs carry the aminoacids)

4- Peptide bonds are formed between consecutives aminoacids, and a polypeptide is build up according to the mRNA sequence.

5- (The mRNA has a signal that is recognized by the rough endoplasmic reticulum) The peptide goes into this reticulum (RER) and then into Golgi apparatus. (more chemical modifications are made if needed). By this moment the protein has an inserted portion in a lipid membrane.

6- The protein is transported in a vessel that finally fusions with cytoplasmic membrane and the receptor is in destiny. Hydrophobic aminoacid sequences are inserted in membrane.

IN A PROKARYTIC CELL:

1- Transcription (no splicing is needed, there are not exons)

2- There are not nucleus and cytoplasm divided (no transport)

3- Ribosomes recognize a signal in mRNA and start reading the genetic code, three consecutive nucleotides at a time and adjust the correspondent tRNAs (tRNAs carry the aminoacids)

4- Peptide bonds are formed between consecutives aminoacids, and a polypeptide is build up according to the mRNA sequence.

5- The mRNA has a signal that is guides the growing protein to cellular membrane. Hydrophobic aminoacid sequences are inserted in membrane.

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3 years ago

What are strategies used by organisms to survive in an ecosystem ?

LenKa [72]

Answer:

Some animals have camouflage which helps them not get eaten.

Explanation:

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3 years ago

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How did Mendel's<br> experiments provide evidence for the principle of<br> independent assortment?

Mrac [35]

Answer and Explanation

Mendel selected a group of dwarf plants and sel pollinated them by dusting mature pollen grains onto them. He then collected the resulting seeds and planted them and noticed these seeds germinated and grew into dwarf plants only.

He also selected tall plants and self-pollinated them. the resulting seeds he observed that they grew into a micture of tall and dwarf plants. He took the seeds of tall plants only and repeated the experiments for many generations until he obtained only tall plants.

He then crossed cross-pollinated purebreeds tall garden pea with pure breed variety. He planted the seeds and observed the offsprings were all tall plants. He crossed two of these tall offsprinf from the F1 and planted the resulting seeds. the second filial generation consisted of a mixture of tall and dwarf plants.

He counted these plants and noted that the ratio of tall to dwarf was about 3:1. From this, he postulated that there are now laws governing inheritance.The law of independent assortment and law of segregation.

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3 years ago