AQA A Level Biology复习笔记4.1.3 Mitochondria & Chloroplast DNA
Mitochondria & Chloroplast DNA
Mitochondria
A single mitochondrion is shown – the inner membrane has protein complexes vital for the later stages of aerobic respiration embedded within it
- The site of aerobic respiration within eukaryotic cells, mitochondria are just visible with a light microscope
- Surrounded by double-membrane with the inner membrane folded to form cristae
- The matrix formed by the cristae contains enzymes needed for aerobic respiration, producing ATP
- Small circular pieces of DNA (mitochondrial DNA) and ribosomes are also found in the matrix (needed for replication)
Chloroplast
Chloroplasts are found in the green parts of a plant – the green colour a result of the photosynthetic pigment chlorophyll
- Larger than mitochondria, also surrounded by a double-membrane
- Membrane-bound compartments called thylakoids containing chlorophyll stack to form structures called grana
- Grana are joined together by lamellae (thin and flat thylakoid membranes)
- Chloroplasts are the site of photosynthesis:
- The light-dependent stage takes place in the thylakoids
- The light-independent stage (Calvin Cycle) takes place in the stroma
- Also contain small circular pieces of DNA and ribosomes used to synthesise proteins needed in chloroplast replication and photosynthesis
Exam Tip
The mitochondria and chloroplasts of eukaryotic cells contain DNA which is short, circular and not associated with protein, just like the DNA of prokaryotes!
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