Answer:
transmission electron microscope
Explanation:
Barriers are the circumstances or any other things that hinder the growth and the development of the social and mental state. Intrinsic barriers and learning are types. The problem is the extrinsic barrier.
<h3>What are the barriers and their types?</h3>
An intrinsic barrier is the physical, mental, motivation, and attention-based difficulties. The extrinsic barrier is the outer factor that impedes the learning of the individual and can be due to poverty, economical state, death etc.
Learning difficulty is the problem with educational learning and the methods. This can be due to the low mental quotient, unable to understand and comprehend the study topics.
Therefore, it is an extrinsic barrier.
Learn more about the extrinsic barrier here:
brainly.com/question/25823012
The formula used can be found in Quora.com (population*average height)/Earth's circumference), gives the result of the number of the human chain.
If the average height of an American is 1.77m and the US population is 326, 292, 068 (June 2, 2017) and if everyone is already an adult.
US population 326, 292, 068
Average height according to study
is estimated as the same as arm span <span>1.77
</span>Earth circumference in meters: <span>40,075,000
</span>
<span>
(</span>326, 292, 068 people * 1.77m) / 40,075,000m = 14.411 times
There are 2 types of transport mechanisms that involve the movement of materials across the cellular membrane:
1. Passive Transport Mechanisms which is the movement of materials that does not require energy. Instead the movement relies on the permeability of the cell. Under this are three kinds of passive transport mechanisms:
a. Simple Diffusion:
- the movement of materials from a region of higher concentration to lower concentration. No external energy is necessary for the movement. The materials supply the energy themselves.
b. Facilitated Diffusion:
- This differs from simple diffusion because the movement is facilitated by proteins that make up the structure of the membrane. The proteins include channel proteins that allow ions and smaller molecules to cross the membrane. The other protein are the carrier proteins, which bind to materials like sugar molecules and move it across the membrane.
c. Osmosis:
- This is the diffusion of water across the membrane. Osmosis moves water from regions where there are more water molecules of water per volume to regions where there are less water molecules per volume.
2. Active transport on the other hand is a movement mechanism that requires energy. It uses the energy to send materials against the direction it is coming from through simple diffusion. This mechanism is used in a way to keep unwanted ions or other materials out of the cell.
The answer is the second choice
