Passive diffusion is a form of passive transport and a type of diffusion by which particles from a high concentration gradient passes through a biological membrane to a low concentration gradient. Diffusion, or simple diffusion on the other hand, is the passage of molecules without the need of a membrane.
Answer: Predicting the size, location, and timing of natural hazards is ... of understanding that can be used to predict natural hazards
Explanation:
Answer:
<u>3) Uncontrolled cell division occurred as a result of gene mutations</u>
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Explanation:
Spontaneous modifications within the genome may occur during the process of cell division. When copies of the DNA inside the cell are made, these mutations cause errors; and can include small single nucleotide polymorphisms, and large scale additions or deletions across multiple genes.
Some, like somatic mutations, exist only inside vegetative (body) cells, that cannot be passed onto offspring. This is caused by several factors like
- UV radiation,
- chemical mutagens,
- infective agents
UV radiation damages strands of DNA, by causing dimers to form; here, consecutive nucleotide bases covalently bond instead of those on the complementary strand. This conformational change causes errors in DNA proofreading and repair mechanisms where bases are not well-incorporated into the strand- tumors (clumps of uncontrolled cell growth) may form, resulting in melanoma, a type of skin cancer.
Triggering of the muscle action potential occurs after Ach binds to chemically gated channels in the motor end plate membrane. Acetylcholine (Ach) is a neurotransmitter produced by nerve cells.
An action potential is an electrical signal that travels along the cell membrane as a wave.
This action potential (muscle action potential) drives the contraction of muscle fibers.
When the action potential reaches the neuromuscular junction (i.e., the motor end-plate), acetylcholine (Ach) is released into the synaptic cleft.
Subsequently, Ach can bind and open specific channels localized on the surface of the muscle cells, thereby depolarizing them and triggering muscle contraction.
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