Putting It Together: Cellular Structure

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.

We’ll come back to cystic fibrosis in the next section, where we will focus in greater detail on the cell membrane.