Dehydration Synthesis

In the dehydration synthesis reaction above, two glucose molecules link to form the disaccharide maltose. In the process, it forms a water molecule.Source: OpenStax Biology 2e Dehydration Synthesis (OpenStax Biology 2e) Most macromolecules are made from single subunits, or building blocks, called  monomers. The monomers combine with each other using covalent bonds to form larger … Continue reading Dehydration Synthesis


Osmotic pressure changes red blood cells' shape in hypertonic, isotonic, and hypotonic solutions. (credit: Mariana Ruiz Villareal) Tonicity describes how an extracellular solution can change a cell's volume by affecting osmosis. A solution's tonicity often directly correlates with the solution's osmolarity.  Osmolarity describes the solution's total solute concentration. A solution with low osmolarity has a greater number … Continue reading Tonicity


In osmosis, water always moves from an area of higher water concentration to one of lower concentration. In the diagram, the solute cannot pass through the selectively permeable membrane, but the water can.Source: OpenStax Biology 2e Osmosis is the movement of water through a semipermeable membrane according to the water's concentration gradient across the membrane, which … Continue reading Osmosis

What are Channel Proteins?

Facilitated transport moves substances down their concentration gradients. They may cross the plasma membrane with the aid of channel proteins. (credit: modification of work by Mariana Ruiz Villareal) OpenStax Biology 2e The integral proteins involved in facilitated transport are transport proteins, and they function as either channels for the material or carriers. In both cases, they … Continue reading What are Channel Proteins?


Diffusion through a permeable membrane moves a substance from a high concentration area (extracellular fluid, in this case) down its concentration gradient (into the cytoplasm). (credit: modification of work by Mariana Ruiz Villareal) OpenStax Biology 2e Diffusion is a passive process of transport. A single substance moves from a high concentration to a low concentration area … Continue reading Diffusion

Selective Permeability

The plasma membrane's exterior surface is not identical to its interior surface.Source: OpenStax Biology 2e OpenStax Biology 2e Plasma membranes are asymmetric: the membrane's interior is not identical to its exterior. There is a considerable difference between the array of phospholipids and proteins between the two leaflets that form a membrane. On the membrane's interior, … Continue reading Selective Permeability


By Nyebilder - Tilsendt meg per e-post fra opphavsperson., CC BY 3.0, OpenStax Biology 2e The variations in peripheral proteins and carbohydrates that affect a cell’s recognition sites are of prime interest in immunology. In developing vaccines, researchers have been able to conquer many infectious diseases, such as smallpox, polio, diphtheria, and tetanus. Immunologists … Continue reading Immunologist

How Viruses Infect Specific Organs

HIV binds to the CD4 receptor, a glycoprotein on T cell surfaces. (credit: modification of work by NIH, NIAID)Source: OpenStax Biology 2e OpenStax Biology 2e Glycoprotein and glycolipid patterns on the cells' surfaces give many viruses an opportunity for infection. HIV and hepatitis viruses infect only specific organs or cells in the human body. HIV … Continue reading How Viruses Infect Specific Organs