Answer:
Producers are always at the beginning of a food chain. Producers begin every food chain because they can make their own food.
They are the only cells with chloroplast
The barrier is cultural differences.
John, growing up in America learned that eye contact is a way of respect and to show you are paying attention.
Where Cho, growing up in Asia, many Asian counties don't have this "custom" to call it that.
I remember the secondary structure by visualizing it. Understand that primary structure is just the order of the amino acids. The tertiary structure is the 3dimensional configuration of the whole protein molecule with multiple interactions guiding its fold (disulfide bonds, ionic interactions, hydrogen bonds, van der walls). Secondary structure is a step towards the conformation of the protein where it is made up of either alpha-helices or beta-pleated sheets. The alpha helices look like a spiraling staircase while the beta-pleated sheets look like a repetition of long loops. These two structures hold itself by hydrogen bonds.
Cellulose is found in the cell walls of plant cells. It is permable so any substance disolveabls in water can pass through so it dose not act as a barrier. It gives the cell its strength and support. As water moves in to the cell by osmosis it stops the cell from bursting.
