adsorb - to form a thin layer of molecules of a substance on the surface of a solid or liquid.

anemia - a condition where your red blood cells do not carry enough oxygen, usually because the number of red cells is too low

alleles - One of a set of alternate forms of a gene. An example is the different alleles of eye color. Each of the different forms of the gene code for eye color, only each codes for a different color i.e. blue, brown, green.

cellular respiration - the process organisms undergo that converts glucose to energy, usually using oxygen and glucose to produce ATP, carbon dioxide, and water.

centrifuge - a machine that rotates (spins) rapidly and uses centrifugal force to separate substances of different densities. You've used a centrifuge before. Have you ever watched a washing machine on spin cycle? A washing machine uses centrifugal force in the spin cycle to separate the water from your clothes.

chromatography - a way of finding out which substances a mixture contains by passing it through or over something that absorbs the different substances at different rates.

chromosomes - The self- replicating genetic structures of cells containing the DNA that bears in its sequence the cell's array of genes. In prokaryotes (bacteria), chromosomal DNA is circular, and the entire genome is carried on one chromosome. Eukaryotic (mammalian and other higher organisms) genomes consist of a number of chromosomes whose DNA is associated with different kinds of proteins.

cytoskeleton - parts of the cell that give it structure and hold things 
together - typically proteins

debris - parts or fragments of something that has been broken down.

denature - a protein is said to be denatured if it unfolds or uncoils so that its function is abolished even though the primary string of amino acids remains intact.

diffusion molecules have energy, so when they are dissolved in water
they move around a lot. The motion of any one atom or molecule has no particular
direction, but a whole population of molecules will eventually get distributed more or
less uniformly in the solution. Think about what happens if you put a drop of ink in a glass
of water.

ecosystem - a group of interdependent organisms and the environment they live in and depend on.

electric charges - atoms acquire an electric charge when they have too many
electrons (negative charge) or too few electrons (positive charge). Positive charges
attract negative charges, and like charges repel each other. Think of the static that
can develop on the screen of a TV set. This charge attracts oppositely charged dust, paper, 
or other material..

electron micrograph - A picture taken by a very high powered microscope that magnifies enough to see large molecules. In both light and electron microscopes, illumination is provided by a source (lamp, filament in the electron gun) which is focused by a condenser lens onto the specimen. A first magnified image is formed by the objective lens. This image is further magnified by the projector lens onto a ground glass screen (light) or fluorescent screen (electrons). For a comprehensive comparison of microscope principles, click here.

elution - to remove one substance from another by washing it out with a solvent. For example, rinsing an adsorbed material from the surface it is attached to.

endoplasmic reticulum - structures outside the nucleus of a cell that contain RNA. This is where protein synthesis actually takes place

extraction - separation of a material (substance) from a mixture by dissolving one or more of the substances in a solvent

facilitate - to make something easier to do

fluid mosaic - the model used to describe the structure of cell membranes. Fluid- refers to the motion of the molecules in the membrane. The molecules are able to move, like molecules in a liquid, instead of being stationary, like molecules in a solid. Mosaic-something consisting of a variety of elements. In this case, a cell membrane is made up of several different kinds of lipids and proteins.

food chains - the sequence of food and nutrient distribution among different species. For example, small plant cells in water are eaten by small fish, small fish are eaten by big fish, big fish are eaten by people

glycolysis - the first step in cellular respiration. The breakdown of 6-carbon glucose to two 3-carbon pyruvic acids.

Golgi apparatus - a long, twisted tube or backbone to which newly
formed proteins attach and complex sugar molecules are attached 
to the certain newly formed proteins

gradient - a measure of change in a physical quantity, such as concentration or temperature, over a specified range or distance.

heredity - the transmission of qualities from parent to offspring through the genes. Also see inherit.

homogenous - same, alike, or unvarying in consistency, or components

immiscible - describes two or more liquids that will not mix together to form a single homogenous (unvarying) substance.

inherit - to receive a trait from a parent (or ancestor.) You inherit bodily traits such as eye color from your parents. Also see heredity.

intoxication - to make drunk with alcohol, drugs or other substances. When using intoxication to describe an effect of a substance on the body (the pathology of a substance) intoxication also means poison or to poison someone.

ions - an atom that has lost or gained one or more electrons.  Thus,
a positively charged ion is one that has lost an electron and a negatively
charged ion is one that has gained an electron.

jaundice - a yellowing of the skin, usually showing up in the whites of the eyes, fingernails, and other lightly pigmented parts of the body surface. There are three main causes: 1) accumulation of a breakdown product (called bilirubin) of excessive destruction of red blood cells (bruises often have localized jaundice in the early stage of healing), 2) a failure of the liver to remove the normal amounts of bilirubin, or 3) failure of elimination of bilirubin via the bile that is normally made in the liver and dumped into the intestine as a waste product.

ketones - a class of body chemicals in which part of the molecule contains a carbon-oxygen bond (C= O).These form from the breakdown of fats and proteins in the liver. The can accumulate to toxic levels if the blood sugar falls too low (as in certain diabetes situations, starvation, or eating a high fat-low carbohydrate diet). They are toxic because they make the body fluids too acid for enzymes to work properly.  

kinetic energy - energy associated with motion. A rock rolling down a hill has kinetic energy. Also see potential energy.

Krebs' cycle - the second stage in cellular respiration where citric acid goes through a series of reactions that produce water, carbon dioxide and free electrons.

lipids - Lipids are also known as fats, but they include compounds of many different kinds. Chemically, these compounds are built on a backbone of glycerol, which was a three-carbon chain. Each carbon, in turn, bonds via an oxygen molecule to so-called fatty acids.   Fatty acids have an acid group (COOH) at one end that is attached to a chain of carbons. Lipids differ mainly in the nature of the fatty acid chains.

molecules - When two or more atoms bond together, they are called
molecules. Examples include water (H2O - two atoms of hydrogen and
one of water), carbon dioxide (C02 - one atom of carbon and two atoms 
of oxygen)

nitrites - chemicals that contain a nitrogen and oxygen atom (NO) that are made from nitrates by microbes in the gut or soil. Nitrates provide the nitrogen content in fertilizer. Obviously, farm animals can be poisoned by eating fertilizer and even plants that have been over-fertilized.  These are poisonous because they bind to hemoglobin and keep it from carrying oxygen in the blood. In large enough concentrations, nitrites and their reaction products can promote cancer. See for information on nitrites/nitrates in drinking water.

opacity - ability of material to stop light. For example, muddy water is
more opaque (cloudy) than clear tap water. Opacity is expressed as a comparison
between light striking the material and light transmitted.

organelles - Literally, the term means "little organs." Inside a cell, there are various little structures that perform specific functions, much like the multicellular organs of our body do.  In the cell, these include generating energy (the organelle is the mitochondrion), making proteins (the organelles are ribosomes and Golgi apparatus), and others.

osmosis - the movement of a solvent (like water) from an area of lesser to greater concentrations so that the solvent will be evenly distributed. So for example, if you put a cell in pure water (that has no dissolved chemicals in it), the water outside would move inside to increase the concentration
of water inside the cell.  Because most of the dissolved material in a cell cannot get out (to lower the concentration of water outside the cell), water will keep coming inside until it bursts the cell. This movement of water is a special case of the principle of diffusion, which applies to dissolved substances, which also tend to distribute evenly if there are no barriers

partition - to separate something into different parts or sections.

permeability - the speed at which a membrane will allow substances to pass through it.

phagocytosis - the process by which certain cells destroy toxins and other organic matter by wrapping their cell membrane around it, and incorporating it into the phagocytic cell, where enzymes break down the chemicals and destroy them.

phosphate bonds (high energy) - adenosine diphosphate has two phosphate groups bonded like this: O - P - O - P.  The ADP can capture external energy and store it in a third phosphate group.  The bond that holds the third phosphate group to the molecule has high energy and can readily release it. A similar principle applies to other compounds that store energy in phosphate bonds.

phospholipids - Phospholipids are typical lipids, except that a phosphate group (POO4) is bonded to one end of one of the fatty acid chains. See lipids.

porous - containing pores, or holes that permit the movement of fluids or gases. An example of a porous material is a sponge. Porosity is the extent to which a substance contains pores. Swiss cheese has high porosity compared to cheddar.

potential energy - energy that an object (or piece of matter) has because of its position, or an arrangement of its parts (for example chemical bonds.) A rock at the top of a hill has potential energy. Also see kinetic energy.

proteins - molecules made of long strings of repeating units, called amino acids.
Amino acids have carbon, hydrogen, oxygen, and nitrogen in them. When they
attach to each other in long strings, they coil. The coiled folds back on itself to
form an irregularly shaped clump.

solvent - a material (usually a liquid) in which other substances are dissolved

substrate - fluid or solid in which an item is placed, or environment in which something may function. For example, a fish's substrate is water. In this case, the substrate that the protein is placed into is a jello-like gel. In chemistry, the substrate is also whatever is acted upon, for example, and antibody's substrate is the part of the germ it attacks.

sucrose - a type of sugar. Sugars are carbohydrates.

sugar - compounds that contain only carbon, hydrogen, and oxygen, usually in a ring 
structure of 5 or six carbons. Common table sugar (sucrose) is the  best known example, but there are 
other kinds of sugar; it has two molecules of the body's most common sugar, glucose.



Peer Curriculum | Cell Biology Home Page | Communication Exercises
Copyright 2001-2003
Web Site Privacy Statement