Summary
In this unit you learned about the parts and pieces of individual cells.
- Some cellular components such as ribosomes and flagella/cilia are present in both prokaryotic and eukaryotic organisms
- Membrane-bound organelles are a hallmark of eukaryotic cells.
- Some organelles are specific to a type of eukaryotic cell, such as chloroplasts which are found only in photosynthetic organisms
- Each organelle has a distinct and important function.
- Some cellular components found a ‘system’ such as the endomembrane system or the cytoskeleton.
| Table 1. Components of Prokaryotic and Eukaryotic Cells | ||||
|---|---|---|---|---|
| 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 cell | Yes | Yes | Yes |
| Cytoplasm | Provides turgor pressure to plant cells as fluid inside the central vacuole; site of many metabolic reactions; medium in which organelles are found | Yes | Yes | Yes |
| Nucleolus | Darkened area within the nucleus where ribosomal subunits are synthesized. | No | Yes | Yes |
| Nucleus | Cell organelle that houses DNA and directs synthesis of ribosomes and proteins | No | Yes | Yes |
| Ribosomes | Protein synthesis | Yes | Yes | Yes |
| Mitochondria | ATP production/cellular respiration | No | Yes | Yes |
| Peroxisomes | Oxidizes and thus 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 | No | Yes, primarily cellulose |
| Chloroplasts | Photosynthesis | No | No | Yes |
| 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 cell, and enables unicellular organisms to move independently | Yes | Yes | Yes |
| Flagella | Cellular locomotion | Some | Some | No, except for some plant sperm cells. |
| Cilia | Cellular locomotion, movement of particles along extracellular surface of plasma membrane, and filtration | Some | Some | No |
Synthesis
Let’s match our earlier disease list with the right organelle. Think about how the function of these organelles directly relates to the disease symptoms.
- Cystic Fibrosis: plasma membrane
- Pompe disease: lysosomes
- Leigh’s Disease: mitochondria
- Emery-Dreifuss muscular dystrophy: nuclear envelope
We’ll come back to cystic fibrosis in the next section, where we will focus in greater detail on the cell membrane.