The Fluid-Mosaic Model of the Cell Plasma Membrane
The fluid-mosaic model describes the plasma membrane of animal cells. The plasma membrane that surrounds these cells has two layers (a bilayer) of phospholipids [more…]
Examining Carbohydrates: Energy-Packed Compounds
Carbohydrates, as the name implies, consist of carbon, hydrogen, and oxygen (hydrate = water, hydrogen and oxygen). Carbohydrates are energy-packed compounds. They are broken down by organisms quickly, [more…]
The Basic Structure of Proteins
Without proteins, living things would not exist. Proteins are involved in every aspect of every living thing. Many proteins provide structure to cells; others bind to and carry important molecules throughout [more…]
What Is the Role of Nucleic Acids in Living Things?
Nucleic acids are large molecules that carry tons of small details: all the genetic information. Nucleic acids are found in every living thing — plants, animals, bacteria, viruses, fungi — that uses and [more…]
The Right Nutrition for the Human Body
The human body needs the proper nutrition — from the right proportion of foods in the various food groups — in order to run efficiently. If humans didn’t have such an evolved sense of taste, maybe they [more…]
Understanding How Animals Breathe
Breathing is the physical action of taking air in to the system and releasing gaseous waste. Respiration is the entire process of taking air in to the system, exchanging needed gases for unnecessary gases [more…]
How Does the Human Digestive System Work?
The human digestive system breaks down the food you consume, using as much of the nutrients as possible to fuel the body. After the energy is extracted from food through digestion and metabolism, the remainder [more…]
The Basic Structures of a Living Plant
Plants have a root system, a stem or trunk, branches, leaves, and reproductive structures (sometimes flowers, sometimes cones or spores, and so on). Most plants are [more…]
How Blood Flows through the Human Heart
Human hearts, as well as the hearts and circulatory systems of some other mammals, are complex. They need to have a higher blood pressure to get the blood circulated throughout their entire bodies. [more…]
The Path of Blood through the Human Body
When a heart contracts and forces blood into the blood vessels, there is a certain path that the blood follows through the body. The blood moves through pulmonary circulation and then continues on through [more…]
How a Human Kidney Works
In humans, the kidneys are the organs that produce urine. There are two kidneys, one on each side of your back, just below the ribs. Like most organs in the body, the function of the kidneys is closely [more…]
What's the Basic Structure of Nerves?
The nervous system sends messages from nerve endings to the brain and from the brain to cells, tissues, and organs. Cells of the nervous system sometimes secrete chemical messengers instead of neurotransmitters [more…]
The Changing States of Solids, Liquids, and Gases
When a substance goes from one state of matter — solid, liquid, or gas — to another state of matter, the process is a change of state. Some rather interesting things occur during this process. [more…]
How Would You Define Chemistry as a Science?
Chemistry is a branch of science that studies the composition and properties of matter and the changes it undergoes. Chemistry is far more than a collection of facts and a body of knowledge. It’s all about [more…]
What Chemists Do and Where They Work
Most chemists operate in two worlds of work. One is the macroscopic world that you see, feel, and touch. Chemists also operate in the microscopic world that you can’t directly see, feel, or touch. [more…]
How to Distinguish Pure Substances and Mixtures
Chemists can classify matter as solid, liquid, or gas. But there are other ways to classify matter, as well — such as pure substances and mixtures. Classification is one of the basic processes in science [more…]
How Scientists Measure Matter
Scientists are often called on to make measurements of matter, which may include such things as mass (weight), volume, and temperature. A worldwide measurement system has been adopted to ensure that scientists [more…]
The Properties of Chemical Substances
When chemists study chemical substances, they examine two types of properties: chemical properties and physical properties. Some physical properties are [more…]
What Are the Different Types of Energy?
Energy can take several forms — such as heat energy, light energy, electrical energy, and mechanical energy. But two general types of energy are especially important to chemists: kinetic energy and potential [more…]
How Is Energy Measured?
You can measure kinetic energy (energy of motion) with a thermometer. Measuring potential (stored) energy can be a difficult task. The potential energy of a ball stuck up in a tree is related to the mass [more…]
The Nucleus: The Center of an Atom
The nucleus, that dense central core of the atom, contains both protons and neutrons. Electrons are outside the nucleus in energy levels. Protons have a positive charge, neutrons have no charge, and electrons [more…]
Atomic Structure: The Bohr Model
There are two models of atomic structure in use today: the Bohr model and the quantum mechanical model. Of these two models, the Bohr model is simpler and relatively easy to understand. [more…]
Atomic Structure: The Quantum Mechanical Model
Two models of atomic structure are in use today: the Bohr model and the quantum mechanical model. The quantum mechanical model is based on mathematics. Although it is more difficult to understand than [more…]
The Laws of Quantum Physics: The Schrödinger Equation
The Schrödinger equation is one of the most basic formulas of quantum physics. With the Schrödinger equation, you can solve for the wave functions of particles, and that allows you to say everything you [more…]
Trapping Particles in Square Well Potentials: Wave Functions
One of the most fundamental problems of quantum physics deals with particles trapped on a submicroscopic level in a square well. The square well is always a favorite problem in quantum mechanics classes [more…]
