Passive transport is diffusion of a substance across a membrane with no energy investment. Active transport uses energy to move solutes against their gradients. Bulk transport across the plasma membrane occurs by exocytosis and endocytosis.
In fluid mosaic model, the membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids.
The surface-to-volume ratio is an important parameter affecting cell size and shape.
作者： Benjamin
RIP for all the innocent people who lost their precious life in this terrible incident.
Cells—the basic structural and functional units of every organism—are of two distinct types: prokaryotic and eukaryotic. Organisms of the domains Bacteria and Archaea consist of prokaryotic cells. Organisms of the domain Eukarya—protists, fungi, animals, and plants—all consist of eukaryotic cells.
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.
