Answer:
When water is boiled water molecules changed into vapors when these vapors condensed water changed into liquid.
So it is reversible reaction.
Explanation:
Water molecules are connected through the hydrogen bonding. When water is boiled the kinetic energy of water molecules increased and point is reached when kinetic energy is so high and water molecules overcome the external pressure and escape from the surface. Thus water molecules convert into vapors.
In case of cooling process extra energy is released. Vapors becomes cooled and kinetic energy decreased vapors are changed into liquid state.
When water is boiled water molecules changed into vapors when these vapors condensed water changed into liquid.
So it is reversible reaction.
Answer:
A. A prokaryote lacks a well-defined nucleus.
C. A prokaryote lacks cell organelles.
Explanation:
A prokaryote has DNA or RNA just floating in the cytoplasm. There is no nucleus to hold them inside. A prokaryote also lacks a mitochondria and other organelles, so it is different from a eukaryote.
In eukaryotes, there are two distinct types of cell division: a vegetative division, whereby each daughter cell is genetically identical to the parent cell (mitosis), and a reproductive cell division, whereby the number of chromosomes in the daughter cells is reduced by half to produce haploid gametes (meiosis).
1. The correct answer is: The viral envelope proteins interact with CD4 and a co-receptor on the cell membrane.
Binding and entering the host cell are the first steps of the HIV virus infection. So, these steps play a major role in determining the ability of HIV to degrade the human immune system. Binding of HIV to CD4+ T lymphocytes (express chemokine receptors CCR5 and CXCR4 called co-receptors) triggers the fusion of the viral and host cell membranes, initiating infection (viral core gets into the cytoplasm).
Attachment of the virion can be:
• Nonspecific-envelop protein of the virus (Env) binds to cell-surface heparan sulfate proteoglycans
• Specific-Env binds to integrin.
2. The correct answer is: Activation of the host cell by cytokines, growth factors, or antigens.
After the viral capsid enters the cell, single-stranded RNA genome is released from the attached viral proteins and copied it into a complementary DNA (cDNA) molecule thanks to an enzyme called reverse transcriptase. Next step is the integration of the viral DNA into the host cell's genome. This process is done by another viral enzyme called integrase. The integrated DNA is transcribed into RNA and then translated into proteins that will help the package of new viruse particles.
3. The answer is: false
Reverse transcriptase is an enzyme that catalyzes the formation of DNA from an RNA template. Since the genome of the virus (HIV) is single stranded RNA, reverse transcriptase copies it into a complementary DNA (cDNA) molecule. Thanks to this enzyme, formed cDNA can be integrated into host’s genome. Because of this proprety, antiretroviral drugs used to treat HIV infection work as reverse-transcriptase inhibitors.
Answer:
In biology, tissue is a cellular organizational level between cells and complete organs. A tissue is an ensemble of similar cells and their extracellular matrix from the same origin that together carry out a specific function. Organs are then formed by the functional grouping together of multiple tissues.
