Questions and Answers
What is the primary genetic material form found in prokaryotes?
Circular DNA
Which of these groups of organisms are discussed in Chapter Two?
Prokaryotes and eukaryotes are the only two major groups of cellular organisms.
True
Prokaryotes are characterized by the absence of a ______.
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Match the following characteristics with prokaryotes or eukaryotes:
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How have prokaryotes contributed to biotechnology?
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Study Notes
Variety of Life: Prokaryotes, Viruses, and Fungi
- Study focuses on prokaryotes (bacteria), viruses, and fungi within microbiology due to similar study techniques such as microscopy and sterile procedures.
Prokaryotes and Eukaryotes
- Prokaryotes emerged approximately 3,500 million years ago, primarily comprising bacteria.
- Eukaryotes evolved around 2,000 million years ago during the late Pre-Cambrian period, likely from prokaryotic ancestors.
- Eukaryotes include protoctists, fungi, green plants, and animals.
Characteristics of Prokaryotes
- Cells lack true nuclei; DNA is freely located in the cytoplasm.
- Average cell size is about 0.5 - 5 micrometers.
- Prokaryotic ribosomes are classified as 70S and are smaller than those in eukaryotes.
- Typically unicellular or filamentous in form.
- Possess a rigid cell wall primarily composed of murein (peptidoglycan).
Characteristics of Eukaryotes
- Cells are larger, with a diameter up to 40 micrometers.
- Genetic material organized as linear DNA within a nucleus, with associated proteins and RNA.
- Eukaryotic ribosomes are 80S and are larger. They may be attached to the endoplasmic reticulum.
- Can be unicellular, filamentous, or multicellular.
- Have diverse organelles, such as mitochondria, chloroplasts, Golgi apparatus, and lysosomes, all typically membrane-bound.
- Plant cell walls are strengthened by cellulose, while fungal cell walls contain chitin.
Flagella and Respiration
- Prokaryotic flagella are simple structures lacking microtubules and are external to the cell membrane.
- Eukaryotic flagella have a complex '9+2' arrangement of microtubules and are surrounded by the cell membrane.
- Respiration in prokaryotes occurs via mesosomes, while eukaryotes utilize mitochondria for aerobic respiration.
Photosynthesis
- Prokaryotes lack chloroplasts; photosynthesis occurs on cell membranes.
- Eukaryotic photosynthesis is conducted within chloroplasts, which contain thylakoid membranes usually organized in stacks.
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Description
Explore the diversity of life in Chapter 2, focusing on prokaryotes, viruses, and fungi. This chapter delves into their characteristics and classifications, providing a comprehensive overview for biology students. Understand how these distinct organisms are compared and studied within the biological sciences.
