Ribosomes may be attached to the endoplasmic reticulum or may float around in the cytoplasm freely. Ribosomes synthesize proteins using mRNA during transcription.

Vacuoles store waste to be excreted by the cell, as well as water to maintain cell volume and shape.

Golgi apparatus packages proteins, lipids, and other materials for transport and secretion outside of the cell.  

Lysosomes are structures in the cell that digest waste products.

Chloroplasts are found in plant cells and are the location of photosynthesis.

The basic structure of a carbohydrate contains carbon, hydrogen, and oxygen.

Lipids are made of carbon, hydrogen, oxygen, and occasionally phosphorous.

Proteins are made of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.

The only elements that will always be found in all three (lipids, proteins, and carbohydrates) are carbon, hydrogen, and oxygen.  

Cell are the basic functional unit of biology, representing the smallest form of biological organization. Tissues are made of groups of specialized cells that operate together. Organs are made of multiple tissue types and perform biological functions. Organ systems are comprised of multiple organs that work together to accomplish a biological process. Together, several organ systems form a full living organism, making organisms the highest level of biological organization.

For example, a goblet cell secretes mucus. Goblet cells are part of epithelial tissue, found in the stomach. The stomach is an organ made of smooth muscle, epithelium, and connective tissue. Together, the stomach, intestines, esophagus, and other organs form the digestive system. The full organism is composed of the digestive system, respiratory system, circulatory system, etc.

An ecosystem will have abiotic and biotic factors that interact with each other for survival and reproduction. An abiotic factor is non-living and is generally a part of the surroundings where an organism is found. Examples include soil, water, and oxygen. Biotic factors are referred to as living or were alive at one point, but are now dead. Examples of these are bacteria, mammals, and plants.

Transpiration is the process by which plants return water back into the atmosphere as vapor. This pathway is an important step in the water cycle. The stomata are pores found in the leaves, and participate in gas exchange with the air via transpiration. The opening of the pore is enveloped by a pair of cells called the guard cells, which control access to the pore. Roots are a part of the plant that are generally found underground and anchor the plant to the soil. They also absorb water and nutrients for the plant. The stem provides structural support for the plant, and the seeds are a means by which a plant can reproduce.

The oxygen cycle is the movement of oxygen through three main components: the atmosphere; the biosphere, which contains all the ecosystems; and the lithosphere, which is the earth’s crust. The largest amount of oxygen is found in the earth’s crust, and the smallest is in the biosphere. The oxygen in the crust is found as silicate, oxide minerals, and mantle. The existence of the oxygen cycle is heavily dependent on photosynthesis. Plants conduct photosynthesis by consuming carbon dioxide from the atmosphere and releasing oxygen into the air. However, this only contributes a very small amount to the oxygen cycle. Respiration and decay due to bacteria are two ways in which the oxygen in the atmosphere is recycled or consumed.

The growth of a population is very dependent on the amount of resources available in the environment. A limiting factor is a resource or condition that can decrease the rate of population growth. When a group of organisms is faced with a limiting factor, they will show a logarithmic growth rate. This represents an S-shaped curve, with the plateau at the top representing carrying capacity. The carrying capacity is governed by the limiting factors and is the maximum number of organisms that can be sustained with the available resources. In the absence of a limiting factor, the growth rate of a population will be exponential (J-shaped). Some common limiting factors are food, nutrients, oxygen, and sunlight. In most cases, an excess of water means that a population can flourish and continue to grow; therefore it is not perceived as a limiting factor.

Water is a very important molecule in order for life to take place. It is the solvent in which chemical reactions take place, as well as a reactant for certain reactions. Water's polarity also causes polar molecules to dissolve and nonpolar compounds to aggregate. As a result, nonpolar molecules are not dissolved in water.

Water is often called the universal solvent and is one of the most important compounds on Earth. The molecular structure of water promotes intermolecular hydrogen bonding, a very strong force between molecules. The result is known as cohesion, the phenomenon of water molecules "sticking" to one another. Cohesion leads to other water properties, such as high surface tension and capillary action, which are essential to supporting life. Hydrogen bonding is only possible in water molecules because of the polarity of the bond between oxygen and hydrogen; oxygen carries a partial negative charge, and hydrogen carries a partial positive charge. Water also have a very high specific heat, which means that it requires a lot of energy to raise the temperature of water. This promotes homeostasis and temperature stability in biological organisms.

In the liquid state, cohesion promotes stability, but in the gaseous state water molecules must separate from one another to move around. Essentially, cohesion must be overcome in order for water to boil. This leads to a high heat of vaporization, rather than a low heat of vaporization.

Molecules that are hydrophobic or "water fearing" will have a hard time dissolving in an aqueous solution. Lipids, which are nonpolar molecules, would not be able to dissolve in water.