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Hemoglobins: The oxygen-carrying proteins of Erythrocytes. They are found in all vertebrates and some invertebrates. The number of globin subunits in the hemoglobin quaternary structure differs between species. Structures range from monomeric to a variety of multimeric arrangements.

fMRI: Functional Magnetic Resonance Imaging

JoVE 5212

Functional magnetic resonance imaging (fMRI) is a non-invasive neuroimaging technique used to investigate human brain function and cognition in both healthy individuals and populations with abnormal brain states. Functional MRI utilizes a magnetic resonance signal to detect changes in blood flow that are coupled to neuronal activation when a specific task is performed.…


Accessory Organs

JoVE 10831

Accessory organs are those that participate in the digestion of food but do not come into direct contact with it like the mouth, stomach, or intestine do. Accessory organs secrete enzymes into the digestive tract to facilitate the breakdown of food.

Salivary glands secrete saliva—a complex liquid containing in part water, mucus, and amylase. Amylase is a digestive enzyme that begins breaking down starches and other carbohydrates even before they reach the stomach. The liver, gallbladder, and pancreas are the other accessory organs involved in digestion. All three secrete enzymes into the duodenum of the small intestine via a series of channels called the biliary tree. The liver and gallbladder work together to release bile into the duodenum. The liver produces bile, but it is stored in the gallbladder for secretion when needed. Bile is a mixture of water, bile salts, cholesterol, and bilirubin. Bile salts contain hydrophobic areas and hydrophilic areas which allows it to engage with both fats and water. Thus it breaks down large fat globules into smaller ones—a process called emulsification. Bilirubin is a waste product that accumulates when the liver breaks hemoglobin from red blood cells. The globin is recycled and the heme, which contains iron, is excreted in the bile. The presence of bilirubin is what gives feces its brown color

 Core: Biology

Synthesis of Luminol- Concept

JoVE 11216

Chemical reactions can be classified as endothermic or exothermic depending on whether the reactions absorb or release heat when they change to products. The difference in energy between reactants and products is known as the enthalpy of the reaction. This is found by calculating the difference in energies between the products and the reactants, or ΔH. If ΔH is positive, the reaction …

 Lab: Chemistry

Transcription Factors

JoVE 10983

Tissue-specific transcription factors contribute to diverse cellular functions in mammals. For example, the gene for beta globin, a major component of hemoglobin, is present in all cells of the body. However, it is only expressed in red blood cells because the transcription factors that can bind to the promoter sequences of the beta globin gene are only expressed in these cells. Tissue-specific transcription factors also ensure that mutations in these factors may impair only the function of certain tissues or body parts without affecting the entire organism. An additional layer of complexity is added by transcription factors in eukaryotes exerting combinatorial control. That means input provided by several transcription factors synchronously regulate the expression of a single gene. The combination of several transcriptional activators and repressors enables a gene to be differentially regulated and adapt to a variety of environmental changes without the need for additional genes.

 Core: Biology

Paracrine Signaling

JoVE 10716

Paracrine signaling allows cells to communicate with their immediate neighbors via secretion of signaling molecules. The signal only triggers a response in nearby target cells as the signal molecules degrade quickly or are inactivated by nearby cells if not taken up. Prominent examples of paracrine signaling include nitric oxide signaling in blood vessels, synaptic signaling of neurons, the blood clotting system, tissue repair/wound healing, and local allergic skin reactions. One of the essential paracrine signaling molecules is the gas nitric oxide (NO). Nitric oxide is produced by a family of enzymes known as nitric oxide synthases. Blood vessels contain several layers of cells. The innermost layer of cells is the endothelium. Endothelial cells have nitric oxide synthase, which produces nitric oxide that diffuses in all directions. The nitric oxide that reaches the blood does not contribute to signaling but immediately reacts with biochemicals, such as hemoglobin. Nitric oxide molecules that diffuse in the opposite direction, towards the next layer of the blood vessel, participate in some important signaling. The layer just exterior to the endothelium is made up of smooth muscle cells. The function of smooth muscle cells is to contract. When these cells contract, they clamp down on the blood vessel, narrowing its diameter and consequently rais

 Core: Biology

Protein Folding

JoVE 10679

Proteins are chains of amino acids linked together by peptide bonds. Upon synthesis, a protein folds into a three-dimensional conformation which is critical to its biological function. Interactions between its constituent amino acids guide protein folding, and hence the protein structure is primarily dependent on its amino acid sequence.

Proteins perform a wide range of biological functions such as catalyzing chemical reactions, providing immunological defense, storage, transport, cellular communication, movement, and structural support. A protein’s function mostly depends on its ability to recognize and bind other molecules, analogous to a lock and key. Hence the specific activity of each protein depends on its unique three-dimensional architecture. For a protein to be functional, it must fold accurately. Most proteins go through several intermediate forms before folding into the most stable, biologically active structure. Misfolding of proteins has detrimental effects on the overall functioning of the cell. In humans, several diseases are due to the accumulation of misfolded or unfolded proteins. These include cystic fibrosis, Alzheimer’s, Parkinson’s, ALS, and Creutzfeldt-Jakob disease. Proteins are made up of one or more chains of amino acids, called polypeptides. A polypeptide is synthesized as a linear chain which rapid

 Core: Biology

Macromolecules- Concept

JoVE 10590


Organisms contain a wide variety of organic molecules with numerous functions which depend on the chemical structures and properties of these molecules. All organic molecules contain a carbon backbone and hydrogen atoms. The carbon atom is central in the formation of a vast variety of organic molecules ranging in size, shape and complexity; inorganic molecules on the other…

 Lab Bio

Ion-Exchange Chromatography

JoVE 10269

Source: Laboratory of Dr. B. Jill Venton - University of Virginia

Ion-exchange chromatography is a type of chromatography that separates analytes based on charge. A column is used that is filled with a charged stationary phase on a solid support, called an ion-exchange resin. Strong cation-exchange chromatography preferentially separates…

 Analytical Chemistry

Synthesis of an Oxygen-Carrying Cobalt(II) Complex

JoVE 10430

Source: Deepika Das, Tamara M. Powers, Department of Chemistry, Texas A&M University

Bioinorganic chemistry is the field of study that investigates the role that metals play in biology. Approximately half of all proteins contain metals and it is estimated that up to one third of all proteins rely on metal-containing active sites to…

 Inorganic Chemistry

Measuring Vital Signs

JoVE 10107

Source: Meghan Fashjian, ACNP-BC, Beth Israel Deaconess Medical Center, Boston MA

The vital signs are objective measurements of a patient's clinical status. There are five commonly accepted vital signs: blood pressure, heart rate, temperature, respiratory rate, and oxygen saturation. In many practices, pain is…

 Physical Examinations I
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