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re genes turned on or off permanently in each cell?
Gene expression varies between cells. A muscle cell will express different genes than a white blood cell even though both cells have identical genomes. Gene expression varies over time as well. Signals from other parts of the body can temporarily turn on or off specific genes in response to environmental conditions. By m
Thyroxin is a hormone produced by the thyroid gland. Thyroxin is important in controlling both development and maturation. It also controls metabolism in adult organisms. Excess thyroxin results in overly rapid development or metabolism while a deficiency of thyroxin results in delayed development or a sluggish metabolism. Thy
[Animation] - Membrane-Bound Receptors that Activate G Proteins
How is cell signaling similar to metabolic pathways such as cellular respiration?
Many cellular processes use similar mechanisms to achieve different results. Metabolic pathways are series of enzyme-catalyzed reactions. Enzymes interact to remove and add phosphate groups to molecules or to move protons across a membrane. Similarly in cell signaling, receptor protei
[Animation] - Membrane-Bound Receptors, G Proteins, and Ca2+ Channels
How can one type of signal produce different responses in different cells?
Cell signaling pathways have many elements in common. G proteins and calcium channels are used in a number of different cell types to produce different responses. How is this possible? Different types of cells have different receptor proteins on their membranes. A liver cell will have differ
Is ATP always used to provide energy for cellular work? Adenosine triphosphate (ATP) is an important molecule for a wide variety of cellular functions. Students usually first learn about it in the context of cellular respiration. ATP is vital for all life as a source of energy for transport, synthesis of macromolecules, muscle contractions, and a wide of variety of other tasks. Howe
Animation - Mechanism of Action of Lipid-Soluble Messengers
How is the concentration of molecules that can freely pass through cellular membranes controlled inside cells? Many hormones are small, nonpolar molecules that can freely pass through a plasm membrane. Hormones are used in cell signaling and are used to turn specific genes on or off in specific cells. However, if hormones can freely diffuse in and out of cells it would seem to be di
How does the structure of a signal molecule determine its function?
Signal molecules can interact with either intracellular or extracellular receptors. For a signal molecule to bind with an intracellular receptor it must be able to pass through the cellular membrane. Generally signal molecules that enter the cell are nonpolar and fat soluble. These signal molecule
How do hormones interact with the nervous system? The nervous system provides rapid, short term communication between different body regions. Hormones act more slowly but generally have a longer effect. The two systems frequently interact with one another. The central nervous system can directly release hormones or it can signal tissues throughout the body to release hormones. Hormo
How do hormones work? Hormones influence the growth and develop of organisms. For example hormones determine whether individuals become male or female. Many hormones are steroids. Steroids are a class of lipids. All steroids share a carbon skeleton composed of
Animation - Effect of Sound Waves on Cochlear Structures
What determines the range of sound frequencies a person can hear?
Sound travels through the air and through water as waves of changing pressure. The volume of a sound is determined by the amplitude of the sound waves, taller waves are louder sounds than shorter waves. The frequency of sound is determined by the wavelength of the sound waves. Short waves are high-pi
[Animation] - Action Potential Propagation in Myelinated Neurons
What is the function of myelinated neurons?
The myelin sheath around most vertebrate axons provides a layer of insulation that prevents the loss of the electrical signal from an action potential. Myelin is lipid rich substance that does not conduct electricity well. Because of the insulation provided by the myelin, action potentials can travel much more rapidly do
How are genes on the same chromosome inherited? An important fundamental of genetics is the idea of independent assortment. This states that genes are inherited independently of one another. Imagine an individual has two different alleles (versions of a gene) for eye color (blue and brown) and two different alleles for hair color (blonde and black). If a gamete produced by that indi
[Animation] - How Intracellular Receptors Regulate Gene Transcription
What is the difference between inhibitor and activator proteins?
Gene transcription is controlled by multiple factors. Some proteins bind to DNA sequences and start the process of gene transcription. RNA synthesis can only occur when these activators are bound to specific DNA sequences. Inhibitors are other molecules that prevent transcription from occurring. Inhi
[Animation] - Signal Transduction by Extracellular Receptors
How can molecules that cannot penetrate the cellular membrane cause changes within a cell? Many signaling molecules are proteins or other molecules that cannot diffuse across the lipid bilayer of a biological membranes. Signaling molecules called first messengers, are able to affect events inside of cells by reacting with receptor proteins embedded in the lipid bilayer. The animatio
Hard Questions About Genetic Engineering Burkhard Mausberg
There is no doubt that genetic engineering has emerged as an important environmental issue. As the technology becomes increasingly common in the production of goods and services, serious questions arise concerning the potential for significant ecological damage. The challenge is
Brain, bodily awareness, and the emergence of a conscious self: these entities and their relations are explored by Germanphilosopher and cognitive scientist Metzinger. Extensively working with neuroscientists he has come to the conclusion that, in fact, the
War Robots – Can They End Up Evolving Into “Terminators” ?
It is estimated that the work of one in fifty US soldiers is now being done by a robot. As the use of technology in war grows, this report goes in search of the truth about the military's newest recruits.
The iRobot Development Laboratory in Boston, Massachusetts, may look like a scene from a science fiction film but this "hall of cool stuf
Bioprinting uses a 3D printing process to create synthetic human tissue. One day it could therefore be used to print replacement human organs. This video by Christopher Barnatt explores future medical and cosmetic bioprinting applications.
A DIVER carrying a computer that tries to recognise dolphin sounds and generate responses in real time will soon attempt to communicate with wild dolphins off the coast of Florida. If the bid is successful, it will be a big step towards two-way communication betwe
INSECT REPELLENT Thousands Of Times More Powerful Discovered !!!
Imagine an insect repellant that not only is thousands of times more effective than DEET – the active ingredient in most commercial mosquito repellants – but also works against all types of insects, including flies, moths and ants.
That possibility has been created by the discovery of a new class of insect repellant made in the laboratory of
Substances Produced By Our Body ( Endocannabinoids ), Similar To Those Found In
There is no longer any doubt that dietary restriction (DR) extends lifespan. Many studies have shown that limiting nutrient intake extends lifespan in yeast, worms, flies and as well as postponing age-related diseases in mice. However, scientists are still puzzling over the exact mechanism of DR, convinced its secrets are the key to new therapies for diseases
Richard Feynman Despised Baloney Disguised As "Intellectual Sophistication"
What's it like to be pals with a genius? Onstage at TEDxCaltech, physicist Leonard Susskind spins a few stories about his friendship with the legendary Richard Feynman, discussing his unconventional approach to problems both serious and ... less so.
The Mechanism By Which SLEEP DEPRIVATION Causes MEMORY IMPAIRMENT Was Identified
From high-school students to surgeons, anyone who has pulled an all-nighter knows there is a price to be paid the next day: trouble focusing, a fuzzy memory and other cognitive impairments. Now, researchers at Penn have found the part of the brain and the neurochemical basis for sleep deprivation’s effects on memory.
Why is diffusion involving water a special case? Water is necessary for life on earth. Not only is water directly involved in many key biochemical reactions, virtually all the molecular processes of life occur in an aqueous environment. Why is water so important? It is a small, weakly polar molecule. These properties mean that water molecules can pass through cellular membranes but
Why does the concentration of a solute cause the movement of water through osmosis?
Water is unusual in that it can cross a non-polar membrane but also react and form solutions with ions and polar molecules that cannot cross the same membrane. When water molecules react with a solute they are no longer free to cross the membrane. The more solute, the fewer molecules left
What is the purpose of pumping sodium and potassium across a membrane?
The sodium potassium pump is a well understood example of active transport. Sodium and potassium ions are pumped in opposite directions across the membrane building up a chemical and electrical gradient for each. These gradients can be used to drive other transport processes. In nerve cells the pump is
What is the use of a concentration gradient across a membrane?
When a molecule or an ion is moved across a membrane from an area of low concentration to an area of high concentration then a gradient is generated. This gradient can be chemical or it can also create a difference in electrical charge across the membrane if ions are involved. The concentration is a sou
Animation - Active Transport by Group Translocation
Why is phosphorylation such an efficient method of performing cellular work?
Many cellular processes involve the transfer of phosphate groups from one molecule to another. This process is known as phosphorylation. The bonds between phosphate groups and other molecules are often referred to as high energy bonds. A relatively large amount of free energy is released w
Animation - Photosynthetic Electron Transport and ATP Synthesis
Is the production of ATP in photosynthesis similar to the production of ATP in cellular respiration?
Photosynthesis is often described as the reverse of cellular respiration. Respiration breaks down complex molecules to release energy that is used to make ATP. Photosynthesis takes energy from photons and uses it to build complex molecules. However both systems use an elec
As explained in this animation, the random movement of molecules in a gas or a liquid will cause the molecules to become evenly distributed in the environment. If we look at the environments in which cells exist, for example inside a body or in a pond, we do not see an even distribution of molecules associated with life. C
How is the concentration of a substance within a cell related to the concentration of the same substance outside the cell?
Many molecules can pass freely across cellular membranes. Small molecules and nonpolar molecules are the ones that can move most easily across the lipid bilayer and enter the cell. Diffusion is the process that causes these molecules to move in or out
One way in which cells can control diffusion is through the control of movement of particular types of molecules. Some molecules can pass freely through a cellular membrane. Large polar molecules and ions cannot diffuse through the lipid bilayer. Carrier proteins can move molecules across the membrane. Cells will have carrier proteins for
How can more molecules be transported into areas with high concentrations of the molecule?
Cells often need to create concentration gradients across membranes. The concentration of a molecule is much higher on one side of the membrane than the other when a concentration gradient exists. In order to create or maintain a concentration gradient, individual molecules m
