Cell Structure and Function Study Guide


Cells are the fundamental unit of life that make up every living organism on earth. There are two major categories of cells: prokaryotic and eukaryotic. Prokaryotic and eukaryotic cells are are differentiated by the presence or absence of a nucleus. Nuclei are present in eukaryotes, while prokaryotes house their genetic material in a non-membrane-bound region called the nucleoid instead. This guide focuses on eukaryotic cells, and gives an overview of their components and the functions they serve within a cell.

Lesson Objectives:

  • Briefly understand the structures and functions of the basic components of a cell.

  • Briefly understand the functions of cells in an organism.

Universal Eukaryotic Structures

The three components found in every eukaryotic cell are the nucleus, cytoplasm, and plasma membrane.

  • The cell membrane encloses the contents of the cell and is composed of a phospholipid bilayer that glycoproteins, glycolipids, receptor proteins, and cholesterol molecules. It is semi-permeable, meaning it determines what molecules and substances can enter and exit the cell.

  • The cytoplasm consists of a fluid called cytosol, a thick liquid in which all organelles are located except for the nucleus. The function of the cytoplasm is to be a medium for the various chemical reactions occurring within and to help the cell in its growth and reproduction.

  • The nucleus is the largest organelle in a cell that contains an organism’s genetic material in the form of DNA. It is separated from the cytoplasm by a nuclear envelope, a double-layered phospholipid membrane that functions much like the outer cell membrane.



Other Eukaryotic Structures

Other organelles found within certain cells include (but are not limited to) the mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus, vacuoles, vesicles, and chloroplasts, each of which we’ll briefly touch on below.

  • Mitochondria produce the majority of a cell’s energy in the form of ATP.

  • The Endoplasmic Reticulum (ER) is divided into two regions, the Rough ER and the Smooth ER. The final stage of protein production occurs in the rough ER, while the smooth ER is responsible for the production of lipids and calcium storage.

  • Ribosomes are the site of protein synthesis and are found either freely floating within the cytosol or attached to the rough ER. They are responsible for sythesizing the polypeptide chains that form the basic structure of all proteins.

  • Once proteins and lipids are completed by the endoplasmic reticulum, they are transported to the Golgi apparatus to be modified and packaged into vesicles which will transport them to the appropriate location within the cell.

  • Vesicles are small membrane-bound organelles filled with various fluids. There are three types: lysosomes, peroxisomes, and transport vesicles. Lysosomes contain the digestive enzymes needed for cell immunity, Peroxisomes contain the enzymes that degrade fatty acids and some chemical toxins, and Transport vesicles carry molecules to and from other organelles in the cell.

  • Vacuoles are responsible for storing and releasing macromolecules and waste products of the cells.

  • Finally, Chloroplasts are organelles found exclusively in plant cells that serve as the site of photosynthesis. They contain a thylakoid system composed of several stacks of flattened, disc-like structures called thylakoids in which the light-dependent reactions of photosynthesis take place. A fluid called the stroma surrounds the thylakoids, and is the location in which the Calvin-Benson cycle reactions of photosynthesis take place.

cell structure


Cell Functions

The six major functions of a cell are to provide structure and support, facilitate growth, allow active and passive transport, produce energy, create metabolic reactions, and aid in reproduction. Let’s briefly go over each of these below.

  • Structure: The structure of every organism is formed by cells.

  • Growth: Cells facilitate the growth of an organism through mitosis, the process by which a single parent cell divides into two daughter cells.

  • Active and Passive Transport: Cells import nutrients for the metabolic processes necessary for life and export waste they produce. Small molecules such as oxygen, carbon dioxide, and ethanol are able to enter and exit a cell passively through the process of diffusion. Larger molecules like proteins and polysaccharides must be actively transported into and out of the cell via proteins embedded in the plasma membrane or vesicles that excrete or absorb larger molecules.

  • Energy Production: In order to survive, an organism needs a source of energy to carry out its metabolic processes. Plants obtain this energy through the process of photosynthesis, while animals acquire energy through the process of cellular respiration.

  • Metabolic Reactions: Cells carry out the metabolic chemical reactions necessary for an organism to live and function.

  • Reproduction: Cells facilitate reproduction through either asexual or sexual division. Asexual division involves the process of mitosis and produces two daughter cells that are genetically identical to their parent cell. Sexual reproduction involves both mitosis and meiosis and produces two daughter cells that are genetically different from their parent cells.

✅ Conclusion

  • Cells are the functional units of all forms of living organisms.

  • All eukaryotic cells contain a nucleus, plasma membrane, and cytoplasm.

  • Other common organelles include the mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus, vacuoles, vesicles, and chloroplasts.

  • The functions of a cell within an organism are structure, growth, transport, energy production, metabolic reactions, and reproduction.


1. What are the seven functions of a cell?

Cells contribute to the an organism’s structure, growth, transport of molecules, energy production, metabolic reactions, and reproduction.

2. How is the cell structure related to its function?

The presence of certain cell organelles gives a cell-specific function overall. Animal cells do not have a cell wall and are thus flexible, while plant cells have a rigid cell wall which gives rigidity to the plant on the whole.

3. What three structures are found in all eukaryotic cells?

The nucleus, cytoplasm, and plasma membrane.

4. What other common organelles contribute to a cell’s function?

The mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus, vacuoles, vesicles, and chloroplasts.

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  1. Cell https://www.britannica.com/science/cell-biology Accessed on 21 Dec, 2021

  2. Cell structure https://training.seer.cancer.gov/anatomy/cells_tissues_membranes/cells/structure.html Accessed on 21 Dec, 2021

  3. Cell structure https://www.ck12.org/biology/cell-structure/ Accessed on 21 Dec, 2021


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