The cell is an organism’s basic unit of structure and function. Many forms of life exist as single-celled organisms. Larger, more complex organisms, including plants and animals, are multicellular. In this chapter, we focus mainly on eukaryotic cells—cells with a nucleus.
作者： Sophia
See the world with a 1.5x lens, view the human nature with a 0.5x lens. Explore the nature with a microscope, while you stand high when you ever tried to explore humanity.
作者： Molly
When we really want to help a vulnerable group, what we need to do first is to understand and respect them, they are not the tool for you to showcase your great ability.
Nucleic acids are polymers made of monomers called nucleotides. Nucleic acids store, transmit, and help express hereditary information.
Proteins are all constructed from the same set of 20 amino acids, linked in unbranched polymers. The bond between amino acids is called a peptide bond, so a polymer of amino acids is called a polypeptide. A protein is a biologically functional molecule made up of one or more polypeptides, each folded and coiled into a specific threedimensional structure.
Carbohydrates include sugars and polymers of sugars. The simplest carbohydrates are the monosaccharides, or simple sugars; these are the monomers from which more complex carbohydrates are built. Disaccharides are double sugars, consisting of two monosaccharides joined by a covalent bond. Carbohydrate macromolecules are polymers called polysaccharides,composed of many sugar building blocks. Lipids are the one class of large biological molecules that does not include true polymers, and they are generally not big enough to be considered macromolecules.
Water (H2O) is made up of two hydrogen atoms covalently bound to an oxygen atom. While this bonding involves the sharing of electrons, they are not shared equally. The oxygen atom, having more protons (+ve), attract the electrons (-ve) more strongly (i.e. the oxygen has a higher electronegativity). Thus the oxygen atom becomes slightly negative and the hydrogen atoms become slightly positive
Matter is made up of elements. An element is a substance that cannot be broken down to other substances by chemical reactions. Of the 92 natural elements, about 20–25% are essential elements that an organism needs to live a healthy life and reproduce.
Repost from BBJ’s blog
Remember, always maintain your passion for your inner yearning and devote time to it.
我经常幻想着等到我们毕业了，对比每次生日板报更新的有趣的内容，脑海里重现当时班里流行的“热梗”，那将会是一件多么幸福的事情。
