The "water-loving" hydrophilic heads of phospholipids orient themselves outwards towards the watery cytoplasm inside the cell and interstitial fluid outside the cell. Meanwhile, the "water-fearing" hydrophobic tails of phospholipids orient themselves inwards toward one another.

Interstitial fluid is the substance surrounding living tissue cells, its solute concentration is critical to the maintenance of homeostasis for the cells. Cells may have to spend valuable energy to keep unwanted materials from passing through their semi-permeable membranes in some conditions.

Diffusion, facilitated diffusion, and osmosis are all examples of passive transport because no energy is required to move molecules across the cell membrane. The driving force is the concentration gradient of the substance.

Active transport always requires energy since molecules are being pumped against their concentration gradients by being transported from areas of low concentration to areas of high concentration. Osmosis and diffusion are examples of passive transport and do not require energy.

In a hypertonic solution, the cell has a greater concentration of water molecules inside it than the solution does. Because of this, the water will move out of the cell in an effort to balance the concentration of water molecules both inside and outside of the cell.

One of the primary differences between plant cells and animal cells is that plant cells must be able to undergo photosynthesis. Photosynthesis takes place in the chloroplasts, which contain the pigment chlorophyll. Chloroplasts are not found in animal cells, but are found in plant cells.

Both animal and plant cells contain Golgi bodies, smooth endoplasmic reticulum, and mitochondria.

Mitochondria are the only organelle defined correctly. The main processes of cell respiration, namely the electron transport chain, occur in the mitochondria to produce energy in the form of ATP. Because of this, mitochondria are known as the "powerhouses" of the cell.

Ribosomes are responsible for transcribing RNA and creating new proteins. The Golgi body packages proteins into vesicles that can be transported out of the cell. Lysosomes contain enzymes that can digest old or damaged proteins. The smooth endoplasmic reticulum is responsible for synthesizing lipids and for degrading toxins, such as alcohol.

Ribosomes are composed of a unique type of RNA, rRNA, and are located within the cytoplasm of the cell and on the surface of the rough endoplasmic reticulum. Here, proteins are assembled from amino acids piece by piece using instructions copied from DNA.

The mitochondria are organelles that are often referred to as the "power plant" of the cell. Mitochondria are responsible for extracting energy from food molecules and binding it in the high energy bonds of the ATP molecule.  

The Golgi apparatus can be thought of as the "shipping center" of the cell. Here, proteins and other materials are packaged in vesicles which are transported to other sites in the cell or outside the cell membrane for "export".