- Describe the basic composition of cytoplasm
- Describe the structure and function of the nucleus and nuclear membrane
- Describe the structure, function, and components of the endomembrane system
- Describe the structure and function of ribosomes
- Describe the structure and function of mitochondria
- Describe the structure and functions of vesicles
- Describe the structure and function of peroxisomes
- Demonstrate familiarity with various components of the cytoskeleton
- Describe the structure and functions of flagella and cilia
- Explain the structure and function of cell membranes
- Identify key organelles present only in plant cells, including chloroplasts and vacuoles
- Identify key organelles present only in animal cells, including centrosomes and lysosomes
Table 1 provides the components of prokaryotic and eukaryotic cells and their respective functions.
|Table 1. Components of Prokaryotic and Eukaryotic Cells and Their Functions|
|Cell Component||Function||Present in Prokaryotes?||Present in Animal Cells?||Present in Plant Cells?|
|Plasma membrane||Separates cell from external environment; controls passage of organic molecules, ions, water, oxygen, and wastes into and out of the cell||Yes||Yes||Yes|
|Cytoplasm||Provides structure to cell; site of many metabolic reactions; medium in which organelles are found||Yes||Yes||Yes|
|Nucleoid||Location of DNA||Yes||No||No|
|Nucleus||Cell organelle that houses DNA and directs synthesis of ribosomes and proteins||No||Yes||Yes|
|Mitochondria||ATP production/cellular respiration||No||Yes||Yes|
|Peroxisomes||Oxidizes and breaks down fatty acids and amino acids, and detoxifies poisons||No||Yes||Yes|
|Vesicles and vacuoles||Storage and transport; digestive function in plant cells||No||Yes||Yes|
|Centrosome||Unspecified role in cell division in animal cells; source of microtubules in animal cells||No||Yes||No|
|Lysosomes||Digestion of macromolecules; recycling of worn-out organelles||No||Yes||No|
|Cell wall||Protection, structural support and maintenance of cell shape||Yes, primarily peptidoglycan in bacteria but not Archaea||No||Yes, primarily cellulose|
|Endoplasmic reticulum||Modifies proteins and synthesizes lipids||No||Yes||Yes|
|Golgi apparatus||Modifies, sorts, tags, packages, and distributes lipids and proteins||No||Yes||Yes|
|Cytoskeleton||Maintains cell’s shape, secures organelles in specific positions, allows cytoplasm and vesicles to move within the cell, and enables unicellular organisms to move independently||Yes||Yes||Yes|
|Flagella||Cellular locomotion||Some||Some||No, except for some plant sperm.|
|Cilia||Cellular locomotion, movement of particles along extracellular surface of plasma membrane, and filtration||No||Some||No|
Like a prokaryotic cell, a eukaryotic cell has a plasma membrane, cytoplasm, and ribosomes, but a eukaryotic cell is typically larger than a prokaryotic cell, has a true nucleus (meaning its DNA is surrounded by a membrane), and has other membrane-bound organelles that allow for compartmentalization of functions. The plasma membrane is a phospholipid bilayer embedded with proteins. The nucleolus within the nucleus is the site for ribosome assembly. Ribosomes are found in the cytoplasm or are attached to the cytoplasmic side of the plasma membrane or endoplasmic reticulum. They perform protein synthesis. Mitochondria perform cellular respiration and produce ATP. Peroxisomes break down fatty acids, amino acids, and some toxins. Vesicles and vacuoles are storage and transport compartments. In plant cells, vacuoles also help break down macromolecules.
Animal cells also have a centrosome and lysosomes. The centrosome has two bodies, the centrioles, with an unknown role in cell division. Lysosomes are the digestive organelles of animal cells.
Plant cells have a cell wall, chloroplasts, and a central vacuole. The plant cell wall, whose primary component is cellulose, protects the cell, provides structural support, and gives shape to the cell. Photosynthesis takes place in chloroplasts. The central vacuole expands, enlarging the cell without the need to produce more cytoplasm.
The endomembrane system includes the nuclear envelope, the endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, as well as the plasma membrane. These cellular components work together to modify, package, tag, and transport membrane lipids and proteins.
The cytoskeleton has three different types of protein elements. Microfilaments provide rigidity and shape to the cell, and facilitate cellular movements. Intermediate filaments bear tension and anchor the nucleus and other organelles in place. Microtubules help the cell resist compression, serve as tracks for motor proteins that move vesicles through the cell, and pull replicated chromosomes to opposite ends of a dividing cell. They are also the structural elements of centrioles, flagella, and cilia.
Animal cells communicate through their extracellular matrices and are connected to each other by tight junctions, desmosomes, and gap junctions. Plant cells are connected and communicate with each other by plasmodesmata.
In the context of cell biology, what do we mean by form follows function? What are at least two examples of this concept?