<span>Only one sperm normally fuses
with an egg because if more than one sperm fuses, through a process
called polyspermy, development of the zygote usually stops.
</span>
<span>Fertilization of one egg by
two sperm is possible, but the resulting zygote is almost never viable
because such a zygote would have three sets of chromosomes instead of
the normal two. This condition, called triploidy, is usually
incompatible with life. Those rare triploid infants that do survive to
term have severe and multiple birth defects and rarely live more than a
few days. </span>
<u>Answer</u>:- Active transport
<u>Explanation</u>:-
There are two types of membrane transports
1. Passive transport - this type of transport occurs without the input of any energy and the molecules move along the concentration gradients that is from <em>high concetration to low concentration.</em>
2. Active transport- this type of transport takes place to move the molecules against the concentration gradient that is from <em>low concentration to high concentration.</em>
<em>The active transport is of two types:</em>
1. <em>Primary active transport-</em> in this type of transport <em>ATP</em> is used as an energy source to move the substances against the concentration gradient.
2.<em>Secondary active transport</em> - in this type of transport the gradient formed by the active transport is utilized and it involves the movement of 2 substances at a time aross the membrane. That is the movement of one molecule is coupled to another.
- The membrane proteins that are associated with active transport are called as <em>carrier proteins</em>. These proteins have a binding site for the molecules that they transport. Once they bind to the specific molecules, a conformation change is induced and this leads to the transport of the molecule across the membrane.
So, the <em>active transport is basically responsible for utilizing the energy from ATP and carrier proteins to move the substances across the membrane against their concentration gradient i.e. from low concentration to high concentration.</em>
When a nerve impulse reaches the end of an axon, the axon terminal released ACh into the synaptic cleft. 2. ACh diffuses across the cleft and attaches to the ACh receptors on the sarcolemma of the muscle fiber. 3. ACh binding triggers electrical events that ultimately generate an action potential.
I believe it’s A I think, I think I’m right
<span>Primary immunodeficiencyvdiseases are a group of more than 250 rare, chronic disorders that affect how the body’s immune system works. Primary immunodeficiency diseases are caused by genetic defects. I hope this helped</span>
