Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 37m
3. Water1h 26m
4. Biomolecules2h 23m
5. Cell Components2h 26m
6. The Membrane2h 31m
7. Energy and Metabolism2h 0m
8. Respiration2h 40m
9. Photosynthesis2h 49m
10. Cell Signaling59m
11. Cell Division2h 47m
12. Meiosis2h 0m
13. Mendelian Genetics4h 44m
14. DNA Synthesis2h 27m
15. Gene Expression3h 6m
16. Regulation of Expression3h 31m
17. Viruses37m
- Viruses
  37m
18. Biotechnology2h 58m
19. Genomics17m
- Genomes
  17m
20. Development1h 5m
21. Evolution3h 1m
22. Evolution of Populations3h 53m
23. Speciation1h 37m
24. History of Life on Earth2h 6m
25. Phylogeny2h 31m
26. Prokaryotes4h 59m
27. Protists1h 12m
28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
  17m
30. Overview of Animals34m
- Overview of Animals
  34m
31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
34. Vascular Plant Transport1h 2m
- Water Potential
  1h 2m
35. Soil37m
- Soil and Nutrients
  20m
- Nitrogen Fixation
  16m
36. Plant Reproduction47m
- Flowers
  33m
- Seeds
  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
39. Digestive System1h 10m
- Digestion
  1h 3m
- Blood Sugar Homeostasis
  7m
40. Circulatory System1h 49m
41. Immune System1h 12m
42. Osmoregulation and Excretion50m
- Osmoregulation and Excretion
  50m
43. Endocrine System1h 4m
- Endocrine System
  1h 4m
44. Animal Reproduction1h 2m
- Animal Reproduction
  1h 2m
45. Nervous System1h 55m
- Neurons and Action Potentials
  1h 8m
- Central and Peripheral Nervous System
  46m
46. Sensory Systems46m
- Sensory System
  46m
47. Muscle Systems23m
- Musculoskeletal System
  23m
48. Ecology3h 11m
49. Animal Behavior28m
- Animal Behavior
  28m
50. Population Ecology3h 41m
51. Community Ecology2h 46m
52. Ecosystems2h 36m
53. Conservation Biology24m
- Conservation Biology
  24m

5. Cell Components

Mitochondria & Chloroplasts

General Biology

5. Cell Components

Mitochondria & Chloroplasts

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3:12 minutes

Problem 1

Textbook Question

What are three attributes of mitochondria and chloroplasts that suggest they were once free-living bacteria?

Verified step by step guidance

Mitochondria and chloroplasts have their own DNA, which is circular and similar to bacterial DNA. This suggests that they could replicate their DNA and function independently like bacteria.

Both mitochondria and chloroplasts have double membranes, which supports the endosymbiotic theory. The theory proposes that these organelles were originally free-living bacteria that were engulfed by early eukaryotic cells.

Mitochondria and chloroplasts have their own ribosomes, which are more similar in size and structure to bacterial ribosomes than to those found in the cytoplasm of eukaryotic cells. This indicates they could synthesize their own proteins independently, like bacteria.

These organelles reproduce by a process similar to binary fission, which is characteristic of bacteria. This mode of reproduction is different from the division processes typically seen in eukaryotic cells, such as mitosis and meiosis.

Both mitochondria and chloroplasts are involved in energy metabolism, with mitochondria being crucial for cellular respiration and chloroplasts essential for photosynthesis. These processes are similar to those carried out by free-living bacteria, further suggesting a bacterial origin.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Endosymbiotic Theory

The endosymbiotic theory posits that mitochondria and chloroplasts originated from free-living bacteria that were engulfed by ancestral eukaryotic cells. This theory explains how these organelles retained their own DNA and double membranes, suggesting a symbiotic relationship that evolved over time.

DNA Structure and Replication

Mitochondria and chloroplasts contain their own circular DNA, similar to bacterial DNA, which is distinct from the linear DNA found in the nucleus of eukaryotic cells. This DNA replicates independently of the cell's nuclear DNA, further supporting the idea that these organelles were once independent organisms.

Ribosomes and Protein Synthesis

Both mitochondria and chloroplasts possess their own ribosomes, which are more similar to prokaryotic ribosomes than to those found in eukaryotic cells. This allows them to synthesize some of their own proteins, indicating a level of autonomy consistent with their bacterial ancestry.