Metabolic Roles of Organelles
Metabolic Roles of Organelles
- Organelles work in partnership with each other to support cellular function
- Many of the cell's organelles are optimized for efficient metabolism
- This means that the cell can capture, store, and utilize energy to the best effect
- This is a common feature of all organisms, although eukaryotes utilize organelles for this
The Organelles and Cell Structures That Support Metabolism Diagrams
Cell Structures With a Metabolic Role - Animal Cells
Cell Structures With a Metabolic Role - Plant Cells
Endoplasmic reticulum
- Plays an important role in protein synthesis
- Using ribosomes bound in the membrane of the ER
- Provides some mechanical support to the cell
- Whilst the cytoskeleton performs the bulk of this role, the ER also plays a supporting role
- Being made of membrane material (largely phospholipid bilayers), the ER can provide a measure of structural support to the cell
- Acting as an ultrastructural skeleton
Mitochondria
- Mitochondria play a central role in metabolism
- They are the site of many of the key stages of the aerobic respiration pathway
- The most metabolically active cells eg, muscle cells tend to have more mitochondria than less active ones eg, bone cells
Mitochondrial adaptations for metabolism
- The mitochondrial double membrane compartmentalizes the organelle for different metabolic reactions
- The folding of the inner membrane into cristae increases the surface area
- This allows for more ATP to be synthesized
- The Krebs cycle (citric acid cycle) reactions occur in the matrix (central space) of the mitochondria
- The reactions of electron transport and ATP synthesis take place on the inner mitochondrial membrane
Lysosomes
- Lysosomes contain hydrolytic enzymes, which perform the following metabolic reactions
- Intracellular digestion eg, of waste organic matter
- The recycling of a cell’s organic materials eg, excess proteins being hydrolyzed back to amino acids for reuse in the cell
- Programmed cell death (apoptosis)
Vacuoles
- Vacuoles have many roles
- Storage and release of
- Macromolecules
- Cellular waste products
- In plants, the vacuole aids in retention of water for turgor pressure
Chloroplasts
- The chloroplast plays a central role in harnessing light energy in photosynthesis
- And converting it into stored chemical energy in the form of food
- Within the chloroplast are thylakoids and the stroma
- The thylakoids are organized in stacks, called grana
- Membranes contain chlorophyll pigments and electron transport proteins that make up the photosystems
- The light dependent reactions of photosynthesis occur in the grana
- The stroma is the fluid within the inner chloroplast membrane and outside of the thylakoid
- The carbon fixation (Calvin-Benson cycle) reactions of photosynthesis occur in the stroma
Exam Tip
In all discussions about metabolism and cellular energy, avoid the common mistake of stating that 'energy is produced' eg, in the mitochondria. This goes against the laws of physics that states that 'energy cannot be created or destroyed'. It's such a common mistake that even your textbooks might state that energy is produced!
A better form of words would be to say that energy is released (from food).