If the proteins from the rough ER require further modification, they are transported to the Golgi apparatus (or Golgi complex). Like the ER, the Golgi apparatus is composed of folded membranes. It searches the protein’s amino acid sequences for specialized “codes” and modifies them accordingly. These processed proteins are then stored in the Golgi or packed in vesicles to be shipped elsewhere in the cell.

In plants and some algae, organelles known as chloroplasts serve as the site of photosynthesis. Chloroplasts contain a pigment known as chlorophyll, which captures the sun’s energy to transform water and carbon dioxide into glucose for food. Chloroplasts allow autotrophic organisms to meet their energy needs without consuming other organisms
The “powerhouses” of the cell, mitochondria are oval-shaped organelles found in most eukaryotic cells. As the site of cellular respiration, mitochondria serve to transform molecules such as glucose into an energy molecule known as ATP (adenosine triphosphate). ATP fuels cellular processes by breaking its high-energy chemical bonds. Mitochondria are most plentiful in cells that require significant amounts of energy to function, such as liver and muscle cells.

ProteinsThe building blocks that make up proteins are called amino acids. Proteins consist of 20 different amino acids, mixed and matched to create a vast array of larger molecules that support every process in your body. Digestion of protein results in a pool of single amino acids that your cells incorporate into new proteins as the need arises in your body. These molecules make up muscles and organs, transmit signals between cells, constitute immune molecules, help create the new proteins your tissues require and can serve as a fuel source in a pinch.

LipidsUnlike the other macromolecules, lipids are not soluble in water, and they don’t form long sequences made up of similar or repeating smaller units. The fats you consume are molecules called triglycerides, consisting of three fatty acids attached to a glycerol. The chemical nature of the fatty acids contained within the lipid determines its physical characteristics. For instance, a fatty acid that is saturated with as many hydrogen atoms as it can hold is solid at room temperature, while unsaturated fatty acids are liquid. These macromolecules store energy within fat tissue, and they cushion your internal organs against trauma. They also form the structure of cell membranes and contribute to the synthesis of hormones.

Nucleic AcidsYour cells contain two types of nucleic acids, ribonucleic acid and deoxyribonucleic acid, or RNA and DNA, respectively. They differ from the other macronutrients in that they are not a source of calories in your diet, and their role is strictly to direct the synthesis of new protein molecules. Made up of units called nucleotides, the nucleic acid DNA contains the genetic blueprint that influences your personal characteristics, while the nucleic acid RNA pulls together amino acids to form new proteins as your cells need them.