Answer: cytosol
Explanation:
Ribosomes are special because they are found in both prokaryotes and eukaryotes. While a structure such as a nucleus is only found in eukaryotes, every cell needs ribosomes to manufacture proteins. Since there are no membrane-bound organelles in prokaryotes, the ribosomes float free in the cytosol.
I believe A. Barnacles living on a whale's skin is an example of a particular symbiotic relationship.
I believe the correct order is:
D - A nerve signal arrives at an axon terminal;
B - Voltage gated calcium channels open and calcium enters the cell;
C - ACh is released and diffuses across the axon terminal;
E - Ligand gated sodium channels open and sodium enters the cell.
A - A postsynaptic potential is produced;
Explanation:
The dendrites of the presynaptic neurons receive a signal. The signal stimulates the nucleus of the presynaptic neuron to produce an electrical signal that is managed by the axon hillock. the axon hillock again manages and transmits the nerve impulse into the axon towards the axon terminal. The signal is transmitted via saltatory conduction on myelinated axons for faster communication. When the nerve impulse reaches the axon terminal, it causes opening of voltage gated calcium ion channels. This will cause an influx of calcium ions into the presynaptic axon terminal. The influx of calcium ions then stimulates the synaptic vessicles in the presynaptic membrane that contain the neurotransmitter acetylcholine (ACh) to move towards the presynaptic membrane. They then fuse with the membrane and open up releasing all their acetylcholine into the synaptic cleft (space between presynaptic membrane and post synaptic membrane). The ACh will bind to ligand ion channels on post synaptic membrane causing opening of sodium channels and there is an influx of sodium inside the post synaptic membrane producing a membrane potential. The voltage gated calcium ion channels in the presynaptic membrane will then close and no more ACh is released. The cells then return to rest. The acetylcholine in the postsynaptic neuron is either broken down by the enzyme acetylcholinesterase into metabolites that are used by the cell or they are removed as waste into the surrounding glial cells called astrocytes that nourish neurons. They (ACh) also can be stored for future use by the post synaptic neuron.
Level: High School
Subject: Biology
Topic: The nervous system
Answer:
Chromatin
Explanation:
The DNA, which is the genetic material in virtually all living cells is found in a long chain of polynucleotides. This long nature of the DNA will prevent it from fitting into the nucleus of eukaryotic cells. Hence, the cell devises a way to make this work by forming a structure called CHROMATIN.
Chromatin is formed when the long DNA molecule wraps around a set of proteins called HISTONE. Histones bind to the DNA molecule, which could are the core of the proteins to form a NUCLEOSOME structure. Each nucleosome is the basic unit of Chromatins. This nucleosome undergoes further coiling to form the CHROMATIN, which eventually forms the chromosomes the genetic material is transferred as in the nucleus.
Answer:
The polar bears which live in the tundra are not as omnivorous as the polar bears of the temperate forest because there are lesser plants and trees to be seen in the tundra region. The polar bears of the tundra are white in colour so that they can camouflage with the snow which is an adaptation for them to hide from their predators. The polar bears also have thick layers of fat which help to keep them warm as the temperature is very cold in these regions.
The choice of diet is important for organisms because an organism will be able to survive in an environment only if it has enough food sources to survive in a particular area. Hence, an organism should have the adaptation to feed on the sources of food available in an area in order to survive in the area.
