Questions and Answers
What is the primary function of mitochondria in eukaryotic cells?
What is the structure that forms the inner folds of the mitochondrial membrane?
How are mitochondria inherited in animals?
Which of the following characteristics is NOT true about mitochondria?
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What are the pores in the outer mitochondrial membrane made of?
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What is the primary role of chloroplasts in plants?
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Which type of plastid develops in the absence of light?
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Which of these statements about chromoplasts is incorrect?
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How are proplastids related to other plastids?
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What distinguishes the structure of chloroplasts?
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Study Notes
Mitochondria
- Mitochondria, known as the powerhouse of the cell, are double membrane-bound organelles involved in aerobic respiration.
- They vary in shape, mostly resembling bean-shaped structures, and measure approximately 0.5 to 1.0 µm in diameter and about 10 µm in length.
- The outer membrane is smooth and contains porins that allow the transport of molecules; the inner membrane is folded into structures called cristae, housing essential proteins and electron carriers.
- Mitochondria metabolize carbohydrates, fatty acids, and amino acids into carbon dioxide and water while producing ATP as stored energy for cellular functions.
- Mitochondria possess their own DNA, RNA, and ribosomes, allowing them to synthesize enzymes independently and reproduce via division.
- Maternal inheritance is observed in mitochondria; they are passed down through eggs and absent from sperm.
Plastids
- Plastids are double membrane-bound organelles primarily found in plant and algal cells, serving as chemical synthesizers and storage compartments.
- All plastids develop from proplastids, which are colorless and immature structures found in meristematic tissues.
- Chloroplasts, the most common plastids, contain chlorophyll for photosynthesis and give plants their green color.
- Chromoplasts provide coloration in flowers and fruits, assisting in pollination and seed dispersal, originating from chloroplasts losing their green pigments.
- Leucoplasts are colorless plastids that develop in low light and serve as storage for carbohydrates, lipids, and proteins, with types including amyloplasts (starch), elaioplasts (lipids), and proteioplasts (proteins).
Chloroplast Structure and Function
- Chloroplasts are present in green plant parts and some bacteria, made up of two membranes with an intermembrane space.
- The outer membrane is permeable due to protein porins, while the inner membrane encloses the stroma, which contains DNA, RNA, ribosomes, and enzymes.
- The thylakoid membranes, stacked in grana, contain chlorophyll and participate in converting light energy to chemical energy during photosynthesis.
Cytoskeleton
- The cytoskeleton is a network of fibers providing structural support and shape to cells, differentiated into microtubules, intermediate filaments, and microfilaments.
- Microtubules are hollow tubes formed from tubulin, involved in chromosome movement during cell division and cilia movement.
- Intermediate filaments are solid strands providing mechanical support and stability without undergoing assembly or disassembly.
Vacuole
- Vacuoles are liquid-filled vesicles found predominantly in plant cells, with young cells containing multiple small vacuoles that merge into a central vacuole at maturity.
- Surrounded by the tonoplast membrane, central vacuoles store cell sap and maintain turgor pressure, contributing to the rigidity and shape of plant cells.
Nucleus Structure
- The nucleus, discovered by Robert Brown, is the cell's control center, typically spherical but can be lobed in some cells.
- Composed of an outer membrane, nucleoplasm, nucleoli, and chromatin, it manages cellular activities and houses genetic information.
- Nuclear pores facilitate transport between the nucleus and cytoplasm, allowing the passage of substances.
Chromatin and Chromosome Structure
- Chromatin consists of DNA and histone proteins, condensing into chromosomes during cell division, which contain hereditary information organized into genes.
- Chromosomes vary in number across species (e.g., humans have 46), with structures classified as metacentric, sub-metacentric, acrocentric, or telocentric based on centromere position.
Prokaryotic vs Eukaryotic Cells
- Prokaryotic cells have a primitive nucleus not enclosed by a membrane, while eukaryotic cells possess a true nucleus with a nuclear membrane.
- Eukaryotic cells contain complex organelles (e.g., mitochondria, ER, Golgi apparatus), absent in prokaryotic cells, which consist of simpler structures.
- DNA in prokaryotes is a single circular molecule, whereas eukaryotes have multiple linear DNA molecules, complexed with histone proteins.
Cell Chemistry and Techniques
- Cell chemistry encompasses the molecular composition of cells; techniques such as centrifugation, chromatography, and spectrophotometry are used to study cells.
- The endoplasmic reticulum (ER), golgi complex, lysosomes, and peroxisomes are critical for cellular processes such as protein synthesis, packaging, and oxidation reactions.
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Description
Test your knowledge about mitochondria, the powerhouse of the cell. Discover their structure, function, and significance in aerobic respiration through this engaging quiz. Ideal for students of biology seeking to deepen their understanding of cell biology.
