Nucleic acid. A comparison of the two principal nucleic acids: RNA (left) and DNA (right), showing the helices and nucleobases each employs.
Nucleic acids are polymolecules, or large biomolecules, essential for all known forms of life. Nucleic acids, which include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), are made from monomers known as nucleotides. Each nucleotide has three components: a 5-carbon sugar, a phosphate group, and a nitrogenous base. If the sugar is deoxyribose, the polymer is DNA. Supramolecular assembly. An example of a supramolecular assembly reported by Atwood and coworkers in Science 2005, 309, 2037.
An example of a supramolecular assembly reported by Jean-Marie Lehn and coworkers in Angew. Chem., Int. Ed. Engl. 1996, 35, 1838-1840. A supramolecular assembly or "supermolecule" is a well defined complex of molecules held together by noncovalent bonds. Biofilm. IUPAC definition Aggregate of microorganisms in which cells that are frequently embedded within a self-produced matrix of extracellular polymeric substance (EPS) adhere to each other and/or to a surface.
Note 1: A biofilm is a fixed system that can be adapted internally to environmental conditions by its inhabitants. Protein. Once formed, proteins only exist for a certain period of time and are then degraded and recycled by the cell's machinery through the process of protein turnover.
A protein's lifespan is measured in terms of its half-life and covers a wide range. They can exist for minutes or years with an average lifespan of 1–2 days in mammalian cells. Abnormal and or misfolded proteins are degraded more rapidly either due to being targeted for destruction or due to being unstable. Biochemistry. Phospholipid. The left image shows a phospholipid, and the right image shows the chemical makeup.
Phospholipids are a class of lipids that are a major component of all cell membranes as they can form lipid bilayers. Most phospholipids contain a diglyceride, a phosphate group, and a simple organic molecule such as choline; one exception to this rule is sphingomyelin, which is derived from sphingosine instead of glycerol. The first phospholipid identified as such in biological tissues was lecithin, or phosphatidylcholine, in the egg yolk, by Theodore Nicolas Gobley, a French chemist and pharmacist, in 1847. Molecular motor. Examples Some examples of biologically important molecular motors: Theoretical Considerations Because the motor events are stochastic, molecular motors are often modeled with the Fokker-Planck equation or with Monte Carlo methods.
These theoretical models are especially useful when treating the molecular motor as a Brownian motor. Experimental Observation In experimental biophysics, the activity of molecular motors is observed with many different experimental approaches, among them: Many more techniques are also used. Non-biological Recently, chemists and those involved in nanotechnology have begun to explore the possibility of creating molecular motors de novo. Enzyme kinetics. Enzyme kinetics is the study of the chemical reactions that are catalysed by enzymes.
In enzyme kinetics, the reaction rate is measured and the effects of varying the conditions of the reaction are investigated. Studying an enzyme's kinetics in this way can reveal the catalytic mechanism of this enzyme, its role in metabolism, how its activity is controlled, and how a drug or an agonist might inhibit the enzyme. When enzymes bind multiple substrates, such as dihydrofolate reductase (shown right), enzyme kinetics can also show the sequence in which these substrates bind and the sequence in which products are released. An example of enzymes that bind a single substrate and release multiple products are proteases, which cleave one protein substrate into two polypeptide products.
Others join two substrates together, such as DNA polymerase linking a nucleotide to DNA. Knowledge of the enzyme's structure is helpful in interpreting kinetic data. Membrane transport protein. A membrane transport protein (or simply transporter) is a membrane protein involved in the movement of ions, small molecules, or macromolecules, such as another protein, across a biological membrane.
Transport proteins are integral transmembrane proteins; that is they exist permanently within and span the membrane across which they transport substances. The proteins may assist in the movement of substances by facilitated diffusion or active transport. These mechanisms of action are known as carrier-mediated transport. Types (Grouped by Transporter Classification database categories) 1: Channels/pores Facilitated diffusion. Ion channel. Not to be confused with: Ion Television or Ion implantation.
Study of ion channels (channelomics) often includes biophysics, electrophysiology and pharmacology, utilizing techniques including voltage clamp, patch clamp, immunohistochemistry, X-ray fluorescence, and RT-PCR. Basic features There are two distinctive features of ion channels that differentiate them from other types of ion transporter proteins:
Cell surface receptor. Biological thermodynamics. Biological thermodynamics is the quantitative study of the energy transductions that occur in and between living organisms, structures, and cells and of the nature and function of the chemical processes underlying these transductions.
Biological thermodynamics may address the question of whether the benefit associated with any particular phenotypic trait is worth the energy investment it requires. History German-British medical doctor and biochemist Hans Krebs' 1957 book Energy Transformations in Living Matter (written with Hans Kornberg) was the first major publication on the thermodynamics of biochemical reactions. In addition, the appendix contained the first-ever published thermodynamic tables, written by Kenneth Burton, to contain equilibrium constants and Gibbs free energy of formations for chemical species, able to calculate biochemical reactions that had not yet occurred. Cell membrane. Function A detailed diagram of the cell membrane Illustration depicting cellular diffusion The cell membrane is selectively permeable and able to regulate what enters and exits the cell, thus facilitating the transport of materials needed for survival.
The movement of substances across the membrane can be either "passive", occurring without the input of cellular energy, or "active", requiring the cell to expend energy in transporting it. The membrane also maintains the cell potential. 1. 2. 3. Biological membrane. This article is about various membranes in living things. For the membranes surrounding cells, see cell membrane. Cross-section view of the structures that can be formed by phospholipids in aqueous A biological membrane or biomembrane is an enclosing or separating membrane that acts as a selectively permeable barrier within living things.