Cell Membrane
The cell membrane has the ability to selectively regulate materials that go into and out of the cell. The membrane has both passive and active roles in transporting materials into and out of the cell. It is mostly composed of phospholipids but there are also a variety of proteins embedded in the membrane that form several functions. Some are for recognizing signals from other cells (receptors) and others are to aid in transport through the membrane.
Cytoplasm
The cytoplasm is a liquid or gel-like organelle. All of the other organelles "float" within this cytoplasm. Many of the important biochemical reactions necessary for metabolism take place in this organelle. The cytoplasm is also constantly moving by the process of cyclosis. This cyclosis in an important form of intracellular (within the cell) transport.
Nucleus
The nucleus is a large organelle that is easily visible using a compound microscope. The nucleus contains chromosomes (46 chromosomes in a normal human body cell). This number does vary between species and again shows us that main theme--"a unity and diversity exists within all living forms." The chromosomes contain the genetic information in the form of genes. These genes are coded by the molecular code DNA. Your DNA code determines your various traits such as hair color, eye color and even number of fingers. The nucleus is often described as a "control center" because it contains the genetic code necessary for most of the cell's activities.
At the end of the video below about the nucleus there are additional links to videos about other organelles.
At the end of the video above about the nucleus there are additional links to videos about other organelles.
Vacuoles
The vacuoles are storage compartments within cells. Various vacuoles are named for the substance they store. Two examples are food vacuoles and contractile vacuoles, which store excess water and can contract it back out of the cell. One difference between plant and animal cells is usually the presence of a large central vacuole inside a plant cell. This is important and acts like a liquid skeleton for plants--that is why many plants start to wilt or droop when they lack water.
Ribosomes
The ribosomes are small organelles that even cannot be seen with the highest magnification of our compound microscopes. Ribosomes perform the process of protein synthesis. Remember the life process synthesis is taking small, simple substances and creating larger, more complex ones. Some ribosomes are free floaters in the cell's liquid cytoplasm and usually synthesize proteins that will be used within the cell. Other ribosomes attach to membranes (many to Endoplasmic Reticulum---another organelle) and they usually form proteins that will be used outside the cell.
The mitochondria are organelles that look like little sausages and perform cellular respiration. The cross section view allows us to see the highly folded internal membrane that increases surface area so that the life process of respiration can occur inside. Remember respiration is the process that converts stored chemical bond energy (glucose) into small usable ATP packets. The gas oxygen is necessary for this process to happen aerobically. That is why all cells, plant or animal, need both raw materials glucose and oxygen. Here is a terrific animation of a mitochondria in action.
Chloroplasts
The chloroplasts are green organelles found within plants, algae and some bacteria. Chloroplasts contain the green pigment chlorophyll. This pigment can absorb some of the sun's energy to convert the inorganic (No C & H) compounds CO2 and H2O into the organic (Has C & H) substance stored chemical bond energy (C6H12O6) or glucose. This process is called photosynthesis meaning light (photo) is necessary to combine the simple substances into a more complex one (synthesis). Since animal cell's lack chloroplast this is another difference that separates the two.
