Epithelium is the thin tissue forming the outer layer of a body's surface and lining the alimentary canal and other hollow structures.
The four levels of protein structure are distinguished from one another by the degree of complexity in the polypeptide chain. A single protein molecule may contain one or more of the protein structure types: primary, secondary, tertiary, and quaternary structure. 1. Primary Structure: describes the unique order in which amino acids are linked together to form a protein.
2. Secondary Structure: refers to the coiling or folding of a polypeptide chain that gives the protein its 3-D shape. There are two types of secondary structures observed in proteins. One type is the alpha (α) helix structure. This structure resembles a coiled spring and is secured by hydrogen bonding in the polypeptide chain. The second type of secondary structure in proteins is the beta (β) pleated sheet. This structure appears to be folded or pleated and is held together by hydrogen bonding between polypeptide units of the folded chain that lie adjacent to one another
3. Tertiary Structure: refers to the comprehensive 3-D structure of the polypeptide chain of a protein.
4. Quaternary Structure: is the structure of a protein macromolecule formed by interactions between multiple polypeptide chains. Each polypeptide chain is referred to as a subunit. Proteins with quaternary structure may consist of more than one of the same type of protein subunit.
Answer: The correct answer is B) city hall:control center.
As per the question, model of cell looks like a city where different buildings correspond to different organelles ( membrane bound subcellular compartments like nucleus, golgi complex, vacuole, endoplasmic reticulum).
Nucleus is a specialized membrane bound compartment that possesses the genetic material ( DNA) of the Eukaryotes ( like plants and animals).
Nucleus controls all the essential activities of the cell by regulating the expression of gene ( segment of DNA corresponding to a particular protein).
Therefore, in the model of cell, city hall;control center represents the nucleus of the cell.
Answer:
A theory. Theories explain a phenomnon while laws state a phenomenon but do not explain them. Ex: Theory of evolution by Darwin explains how evolution works, while the law of thermodynamics states what occurs, but offers no interpreation of its meaning.
Explanation:
For example,
1). movement of titonic plates
2). volcanic eruptions
3). global warming
