Coevolution happens when the genetic development between two or more species affects the evolution of each other. An example would be hummingbirds and bird-pollinated (ornithophilous) flowers. The ornithophilous flowers give nourishment to the birds with their nectar that has high sugar content. The birds in return aids in the pollination of these flowers.
If mitosis occurred without cytokinesis, the cell would contain two nuclei and twice the DNA. If cytokinesis occurred without mitosis , one of the new cells would lack DNA and a nucleus altogether. The cell cycle is regulated by signals both inside and outside of the cell.
1. form on the surface 2. form below the Earth's crust 3. cool quickly 4. cool slowly 5. have large mineral crystals <span>6. have small mineral crystals
those are your choices right? if so then...
1, 3, 5 are your answers
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Answer:
The correct answer is: d.a nonpolar side chain.
Explanation:
- Protein can be defined as one of the factors which determine the structure as well as the function of a cell.
- Proteins are composed of polymeric chains of polypeptides, which are made up of amino acid monomers linked to each other by peptide bonds.
- Amino acids can be broadly categorised into non-polar and polar based on the nature of the side chain.
- The non-polar amino acids possess hydrocarbon side-chains which are hydrophobic in nature, so they tend to avoid interaction with water molecules and usually remain in the protein interior. They are uncharged and cannot form any hydrogen bonds with water molecules.
- The polar amino acids possess charged or polar side-chains which are hydrophilic in nature, so they tend to undergo interaction with water molecules and usually remain on the protein surface. They can form hydrogen bonds with molecules of water.
- Beta sheets can be defined a secondary structure of the protein in which the polypeptide sequence forms horizontal strands which are linked to each other by loops. Each strand interact with each other by the formation of hydrogen bonds between the C=O group of one peptide (amide) bond in one strand with the N-H group of another peptide (amide) bond in another strand.
- Apart from these bonds, the non-polar side chains of each amino acid in one strand forms hydrophobic or Van der Waals interactions with the non-polar side chains of each amino acid in the other strand. The polar or charged side chains of the amino acids on each strand form either hydrogen bonds with water molecules or with oppositely charged side chains.
- In the given question, glycine and alanine are non-polar amino acids but serine is a polar amino acid. The side-chains of the non-polar amino acids will tend to face towards the interior of the beta sheet thereby forming hydrophobic interactions with each other, while the serine will tend to face the exterior of the beta sheet so that it can form hydrogen bonds with water molecules.
- As the number of non-polar amino acids is far more than polar amino acids so the effect of non-polar amino acids will prevail in the beta-sheet.
The brain, heart and the skeleton are the integral parts of the nervous system, circulatory system and the skeletal system respectively. The nervous system is made of the brain and the spinal cord with neurons as the structural and functional units of it. The circulatory system is made up of the heart and its blood vessels. The skeletal system is made up of the bones and cartilages making the skeleton of the body.
The brain regulates the heart beat and the blood pressure. The heart nourishes the brain with oxygen and nutrients by pumping blood. The bone cells are nourished by the blood pumped by the heart. The bone marrow of the skeleton produces the new red blood cells which enter the blood circulatory system. Also the the ribs and the breast bone of the skeleton protects the heart, the cranium of the skeleton prtects the brain. The bones also provide calcium which is necessory for the functioning of the nervous system. The brain controls the skeletal movements of the body. The cerebellum of the brain controls the voluntary skeletal movements and the medulla controls the involuntary skeletal movements of the body. The blood brain barrier formed by the endothelial cells of the capillary walls located in the brain seperates the circulating blood from the brain and the extraclellular fluid in the central nervous system and acts as a selective semipermeable border.
