Show Advanced Search


Containing Text
- - -
Filter by author or institution
Filter by publication date
October, 2006
Filter by journal section

Filter by science education

Base Composition: The relative amounts of the Purines and Pyrimidines in a nucleic acid.

Determining the Mass Percent Composition in an Aqueous Solution

JoVE 10172

Source: Laboratory of Dr. Neal Abrams — SUNY College of Environmental Science and Forestry

Determining the composition of a solution is an important analytical and forensic technique. When solutions are made with water, they are referred to as being aqueous, or containing water. The primary component of a solution is referred to as…

 General Chemistry

What are Nucleic Acids?

JoVE 10684

Nucleic acids are long chains of nucleotides linked together by phosphodiester bonds. There are two types of nucleic acids: deoxyribonucleic acid, or DNA, and ribonucleic acid, or RNA. Nucleotides in both DNA and RNA are made up of a sugar, a nitrogen base, and a phosphate molecule.

A cell’s hereditary material is comprised of nucleic acids, which enable living organisms to pass on genetic information from one generation to next. There are two types of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA and RNA differ very slightly in their chemical composition, yet play entirely different biological roles. Chemically, nucleic acids are polynucleotides—chains of nucleotides. A nucleotide is composed of three components: a pentose sugar, a nitrogen base, and a phosphate group. The sugar and the base together form a nucleoside. Hence, a nucleotide is sometimes referred to as a nucleoside monophosphate. Each of the three components of a nucleotide plays a key role in the overall assembly of nucleic acids. As the name suggests, a pentose sugar has five carbon atoms, which are labeled 1o, 2o, 3o, 4o, and 5o. The pentose sugar in RNA is ribose, meaning the 2o carbon carries a hydroxyl group. The sugar in DNA is deoxyribose, meaning the 2o

 Core: Biology

Extraction - Student Protocol

JoVE 11199

Cellulose Recovery

Extraction and filtration can separate compounds based on their solubility properties. In this lab, you'll separate a mixture of cellulose, caffeine, and benzoic acid based on their solubilities in dichloromethane, or DCM, and water.

Caffeine and benzoic acid are both soluble in DCM, but cellulose is not. Thus,…

 Lab: Chemistry

Buffers - Student Protocol

JoVE 11154

Preparing 50 mM NaH2PO4 Buffer, pH 7

In the first part of this experiment, you will prepare a sodium phosphate solution buffered at pH 7.0. Monosodium phosphate is a weak acid with the conjugate base, disodium phosphate. Unadjusted monosodium phosphate solutions usually have a pH of about 4 - 6.

Buffers are most…

 Lab: Chemistry

What are Proteins?

JoVE 10677

Proteins are chains of amino acids that are connected by peptide bonds and folded into a 3-dimensional structure. The side chains of individual amino acid residues determine the interactions among amino acid residues, and ultimately the folding of the protein. Depending on the length and structural complexity, chains of amino acid residues are classified as oligopeptides, polypeptides, or proteins. An amino acid is a molecule that contains a carboxyl (–COOH) and an amino group (–NH2) attached to the same carbon atom, the ⍺-carbon. The identity of the amino acid is determined by its side chain or side residue, often called the R-group. The simplest amino acid is glycine, where the residue is a single hydrogen atom. Other amino acids carry more complex side chains. The side chain determines the chemical properties of the amino acid. For example, it may attract or repel water (hydrophilic or hydrophobic), carry a negative charge (acidic), or form hydrogen bonds (polar). Of all known amino acids, only 21 are used to create proteins in eukaryotes (the genetic code encodes only 20 of these). Amino acids are abbreviated using a three letter (e.g., Gly, Val, Pro) or one letter code (e.g., G, V, P). The linear chain of amino acid residues forms the backbone of the protein. The free amino group at one end is called the N-terminus, while t

 Core: Biology

Simple Distillation - Student Protocol

JoVE 11202

Simple Distillation

In this lab, you will use simple distillation to separate a mixture of cyclohexane and toluene.

Before you start the lab, put on the appropriate personal protective equipment, including a lab coat, safety goggles, and gloves. This experiment must be conducted in a hood.


 Lab: Chemistry

The Soil Ecosystem

JoVE 11102

Plants obtain inorganic minerals and water from the soil, which acts as a natural medium for land plants. The composition and quality of soil depend not only on the chemical constituents but also on the presence of living organisms. In general, soils contain three major components:

  1. Inorganic mineral matter, which constitutes about 40 to 45 percent of the soil volume.
  2. Organic matter, also known as humus, which makes up about 5 percent of the soil volume. Water and air, covering about 50 percent of the soil volume. Healthy soil has an adequate quantity of air, water, minerals, and organic matter to promote plant growth. Based on its physical structure, the soil is composed of four distinct layers: O-horizon or topsoil A-background B-horizon or subsoil C-horizon or base soil O-horizon comprises freshly decomposing organic matter - a result of the decomposition of plants, animals, or microorganisms. It is also known as topsoil. This humus layer is significant in improving soil fertility, moisture, and air retention. Though the humus is a smaller percentage of the overall soil volume, it is nevertheless essential. A-background is a mixture of organic and inorganic components and is the beginning of true mineral soil formed by the weathering of rock. <

     Core: Biology

Antibody Structure

JoVE 10898

Antibodies, also known as immunoglobulins (Ig), are essential players of the adaptive immune system. These antigen-binding proteins are produced by B cells and make up 20 percent of the total blood plasma by weight. In mammals, antibodies fall into five different classes, which each elicits a different biological response upon antigen binding.

Antibodies consist of four polypeptide chains: two identical heavy chains of approximately 440 amino acids each, and two identical light chains composed of roughly 220 amino acids each. These chains are arranged in a Y-shaped structure that is held together by a combination of covalent disulfide bonds and noncovalent bonds. Furthermore, most antibodies carry sugar residues. The process of adding sugar side chains to a protein is called glycosylation. Both the light chain and heavy chain contribute to the antigen binding site at each of the tips of the Y structure. These 110-130 amino acids are highly variable to allow recognition of an almost unlimited number of antigens. This region is also called the variable region and is part of the antigen binding fragment. Each arm of the Y-shaped unit carries an identical antigen binding site. Antibodies can crosslink antigens: when one arm binds to one antigen and the other arm binds to a second, structurally identical antigen. Crosslinking is facilitated by the f

 Core: Biology
More Results...