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Leto [7]
3 years ago
15

Earth's early atmosphere was primarily composed of

Biology
1 answer:
Paul [167]3 years ago
5 0

Answer:

The correct answer is ''carbon dioxide, water vapor and nitrogen.''

Explanation:

About 4.5 billion years ago, Earth was a very geologically active planet. So many volcanic fumes formed the primitive atmosphere, which was mostly made up of water vapor, carbon dioxide, sulfur, and nitrogen. At this point, oxygen was barely present and the oceans did not yet exist. The primitive atmosphere is the one before the Precambrian, it was reductive, that is, it lacked free oxygen, and only had ammonia, methane and hydrogen, the high temperature of the atmosphere in its early stages facilitated the reaction of these gases to form organic compounds from which life may have emerged. UV rays passed, because ozone did not exist.

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After which checkpoint is the cell first committed to continue the cell cycle through M?
Viktor [21]

The correct answer is: B) G1

Normal cells (unlike cancer cells), move through the cell cycle in a regulated way in order to make sure that cells don't divide under conditions that are unfavorable for them. Information about their own internal state (nutrients, signal molecules, DNA integrity) is signal to go or not to go through the cell division. Because of that there are few checkpoints in the cell cycle at which the cell examines the signals and makes a “decision”. The major checkpoints are:

• The G1- the first point at which it must choose, once it passes the G1 checkpoint the cell enters S phase

• The G2-the cell checks DNA integrity and checks if replication is done well.

• The spindle checkpoint-at the transition from metaphase to anaphase.

8 0
4 years ago
Complete the following sentences about heme by moving the terms to the correct targets Some terms will not be used.
Scrat [10]

Answer:

1. The prosthetic group of hemoglobin and myoglobin is heme.

2.The organic ring component of heme is porphyrin ring.

3. Under normal conditions, the central atom of heme is Iron (Fe2+).

4. In deoxyhaemoglobin the central iron atom is displaced 0.4 A out of the plane of the porphyrin ring system.

5.The central iron atom has six bonds: four to nitrogen atoms in the porphyrin, one to a histidine residue and one to oxygen.

Explanation:

1. The heme is the prosthetic group common to both the hemoglobin and myoglobin. It is made up of a central iron ring.

2. The porphyrin ring is the organic component of the heme that surrounds the iron ring. Its based on a tetrapyrole ring called porphin commonly found in other biomolecules such as cytochrome and chlorophyll in plants

3. Iron (Fe2+) is central to the heme structure. It has the ability to bind to an oxygen molecule at a time. This gives the protein- hemoglobin the ability to bind to 4 oxygen molecules at a time.

4. Deoxyhaemoglobin is simply a reduced form of hemoglobin which has lost oxygen molecule in red blood cells. It is purple blue in colour.

5. In the middle of the porphyrin ring, the iron binds to 4 nitrogen atoms. 2 free binding sites are available on either side of the plane heme structure with histidine surounding the heme molecule.

6 0
4 years ago
NEEDS TO BE DONE ASAP
inessss [21]

Answer:

Prokaryote

Explanation:

The kingdom Eukaryota has a nuclear envelop or a nuclear membrane while the kingdom prokaryote doesnt, this is common knowledge

7 0
3 years ago
Why are the leaves important to a plant?
Veronika [31]
Answer: C: Contain chloroplast that perform photosynthesis.

Explanation: Process of elimination deems C correct!
6 0
3 years ago
Read 2 more answers
On which bone does Mandibular Fossa occurs?
WINSTONCH [101]

Answer:

Mandibular Fossa occurs on temporal bone.

Explanation:

Mandibular fossa also known as glenoid fossa, the depression of temporal bones. Mandibular fossa articulates with the mandible and interacts with mandibular condyle. Glaserian fissure divides the mandibular fossa into two parts.

Articular tubercle bounds the mandibular fossa anteriorly. The mandibular fossa is bounded posteriorly by the temporal bone.  Mandibular fossa development may get arrested due to the separation of mandibular condyle.

8 0
3 years ago
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