B. this shows the cross pollination needed for these flowers to reproduce
Virus is a microscopic particle that can infect the cells of a biological organism.
Viruses can only replicate themselves by infecting a host cell and therefore cannot reproduce on their own.
At the most basic level, viruses consist of genetic material contained within a protective protein coat called a capsid; the existence of both genetic material and protein distinguishes them from other virus-like particles such as prions and viroids.
They infect a wide variety of organisms: both eukaryotes (animals, fungi and plants) and prokaryotes (bacteria).
A virus that infects bacteria is known as a bacteriophage, often shortened to phage.
The study of viruses is known as virology, and those who study viruses are known as virologists.
It has been argued extensively whether viruses are living organisms.
Most virologists consider them non-living, as they do not meet all the criteria of the generally accepted definition of life.
They are similar to obligate intracellular parasites as they lack the means for self-reproduction outside a host cell, but unlike parasites, viruses are generally not considered to be true living organisms.
A primary reason is that viruses do not possess a cell membrane or metabolise on their own - characteristics of all living organisms.
Examples of common human diseases caused by viruses include the common cold, the flu, chickenpox and cold sores.
Serious diseases such as Ebola, AIDS, bird flu and SARS are all also caused by viruses.
virus is a microscopic particle that can infect the cells of a biological organism.
Viruses can only replicate themselves by infecting a host cell and therefore cannot reproduce on their own.
At the most basic level, viruses consist of genetic material contained within a protective protein coat called a capsid; the existence of both genetic material and protein distinguishes them from other virus-like particles such as prions and viroids.
They infect a wide variety of organisms: both eukaryotes (animals, fungi and plants) and prokaryotes (bacteria).
A virus that infects bacteria is known as a bacteriophage, often shortened to phage.
The study of viruses is known as virology, and those who study viruses are known as virologists.
It has been argued extensively whether viruses are living organisms.
Most virologists consider them non-living, as they do not meet all the criteria of the generally accepted definition of life.
They are similar to obligate intracellular parasites as they lack the means for self-reproduction outside a host cell, but unlike parasites, viruses are generally not considered to be true living organisms.
A primary reason is that viruses do not possess a cell membrane or metabolise on their own - characteristics of all living organisms.
Examples of common human diseases caused by viruses include the common cold, the flu, chickenpox and cold sores.
Serious diseases such as Ebola, AIDS, bird flu and SARS are all also caused by viruse
Prokaryotes
Answer is.
<span><span>anonymous </span> 3 years ago</span>Proteins are involved in almost all of the cell's functions. They can act as:
Transportation: they can transport hydrophobic molecules in blood for example
Regulation: protein hormones and enzymes
Receptor: can act as receptors on cell surface and in the subsequent signal transduction (G-protein for instance)
It is true that all proteins are made up of up to 20 amino acids, but there are several reasons for their diverse actions:
-One reason is the possible sequence and number of amino acids: Met-Ser-His is different from Met-His-Ser for example. Besides, you have different chain length, for a protein is made up of long chain of polypeptide (longer than 50-70 amino acids) and can have any of the 20 amino acids with repetition, so using simple probability, this can provide up to practically unlimited combination with proteins that have chains of thousands of amino acids.
-Another very crucial reason for the diversity of protein action is the conformation. A protein passes by at least 3 conformational stages before becoming mature. The straight amino acid chain is the primary structure of the protein that can never be active. Spatial modification of this primary structure results in a secondary structure, Helix or Beta-pleated sheets (or other coiling structure), that is also inactive. Further coiling and bending of the secondary structure produce a 3-dimentional conformation that is the active form of the protein. Moreover, many proteins can undergo further conformational rearrangement and combination with other protein sub-units producing a quaternary structure.
An increase in volume DECREASES the pressure in the chest (pressure and volume vary inversely when temperature is held constant -- Boyle's law). Gas can only flow from an area of higher pressure to an area of lower pressure. It can't go uphill -- ever. It can only go from high to low pressure. When the diaphragm and intercostals contract, the diaphragm flattens and the rib cage rises. That increases the volume of the chest. That increase in volume decreases the pressure inside the chest (temperature is held constant -- because the temperature of the chest cavity does not change appreciably. It remains at body temp.). Air then flows from the area of higher pressure (atmospheric) to lower pressure (intrathoracic). That continues until the pressures are equal.
When the diaphragm and intercostals relax, the chest cavity decreases in size, the pressure increases to above atmospheric, and gas flows again from the area of higher pressure (intrathoracic) to lower pressure (atmospheric) until they are again equal.
It has nothing to do with the concentration of oxygen. You can ventilate a lung with ANY gas. It has to do with the change in pressure and only the change in pressure -- which is a function of the volume of the chest cavity.
<span>They are composed of similar materials: DNA is a deoxyribonucleotide polymer while RNA is a ribonucleotide polymer. A nucleotide is composed of a nitrogenous base, a sugar, and a phosphate group. In ribonucleotides, the sugar is ribose, while in deoxynucleotides, the sugar is deoxyribose. Adenine, guanine, and cytosine are nitrogenous bases in both DNA and RNA, while thymine is found only in DNA and uracil is found only in RNA.</span>
