Signature of the Cell

The cell is one of the most basic units of life. There are millions of different types of cells. There are cells that are organisms onto themselves, such as microscopic amoeba and bacteria cells. And there are cells that only function as part of a larger organism, such as the cells that make up your body. The cell is the smallest unit of life in our bodies. In the body, there are brain cells, skin cells, liver cells, stomach cells, and the list goes on. All of these cells have unique functions and features. And all have some recognisable similarities.

All cells have a 'skin', called the plasma membrane, protecting it from the outside environment. At the centre of the cell is the cell nucleus. The cell nucleus contains the cell's DNA, the genetic code that coordinates protein synthesis. In addition to the nucleus, there are many organelles inside of the cell - small structures that help carry out the day-to-day operations of the cell. One important cellular organelle is the ribosome. Ribosomes participate in protein synthesis. The transcription phase of protein synthesis takes places in the cell nucleus. After this step is complete, the mRNA leaves the nucleus and travels to the cell's ribosomes, where translation occurs. Another important cellular organelle is the mitochondrion. Mitochondria (many mitochondrion) are often referred to as the power plants of the cell because many of the reactions that produce energy take place in mitochondria. Also important in the life of a cell are the lysosomes. Lysosomes are organelles that contain enzymes that aid in the digestion of nutrient molecules and other materials.

Einstein's Theory of relativity - E=mc2

In 1905, Albert Einstein published the theory of special relativity, which explains how to interpret motion between different inertial frames of reference - that is, places that are moving at constant speeds relative to each other. Einstein's theory was based on two key principles:

• The principle of relativity: The laws of physics don't change, even for objects moving in inertial (constant speed) frames of reference.
• The principle of the speed of light: The speed of light is the same for all observers, regardless of their motion relative to the light source. (Physicists write this speed using the symbol c.)

Einstein's theory of special relativity created a fundamental link between space and time. The universe can be viewed as having three space dimensions - up/down, left/right, forward/backward - and one time dimension. This 4-dimensional space is referred to as the space-time continuum.

If you move fast enough through space, the observations that you make about space and time differ somewhat from the observations of other people, who are moving at different speeds. In other words Einstein postulated that, space and time are intimately linked together i.e the relationship is relative hence the Theory of Relativity

The video simulation above is a demonstration of this phenomenon. The phenomenon, you see on the video, is known as time dilation, where the time on a ship moving very quickly appears to pass slower than on Earth. This strange behaviour of space and time is only evident when you're travelling close to the speed of light, so no one had ever observed it before. Experiments carried out since Einstein's discovery have confirmed that it's true - time and space are perceived differently, in precisely the way Einstein described, for objects moving near the speed of light.

It is this relative relationship between space and time that led Einstein to apply the same principle of relativity to come with the famous equation E=mc2 relating mass (m) and energy (E)with the speed of light (c). His theory states that as an object approached the speed of light, the mass of the object increases. That is another story but note that many subsequent experiments by other scientists seem to bear out Einstein's theory.