A2.2 Cell structure Flashcards
(18 cards)
What are the 3 main principles of cell theory?
All living organisms are made of cells, cells are the basic unit of life, and all cells come from pre-existing cells.
What exceptions exist to cell theory?
Striated muscle (multinucleated), aseptate fungal hyphae (no clear cells), and giant algae (unicellular but large).
What is the purpose of using measurement instruments in microscopy?
To make quantitative observations.
What is the purpose of modern microscopy techniques and their advantages?
Electron microscopy (high resolution); freeze-fracture & cryo-EM (3D views); fluorescent stains & immunofluorescence (targeted imaging of structures).
What microscopy skills should IB students know?
Making temporary mounts, staining, measuring with eyepiece graticule, focusing, calculating actual size and magnification, adding scale bars, and taking micrographs.
What structures are common to all cells?
DNA as genetic material, cytoplasm (mostly water), and a plasma membrane made of lipids.
What structures are found in prokaryotic cells (eg: Gram-positive bacteria?)
Cell wall, plasma membrane, cytoplasm, naked circular DNA, and 70S ribosomes.
What are key features of eukaryotic cells?
Plasma membrane, compartmentalized cytoplasm, 80S ribosomes, nucleus with histone-bound DNA, mitochondria, ER, Golgi, vesicles/vacuoles, lysosomes, and cytoskeleton.
What processes of life do unicellular organisms perform?
Homeostasis, metabolism, nutrition, movement, excretion, growth, response to stimuli, and reproduction.
How do animal, fungal, and plant cells differ?
Plant: cell wall (cellulose), large vacuole, chloroplasts. Fungi: chitin cell wall. Animal: no cell wall, smaller vacuoles, centrioles.
Give examples of atypical eukaryotic cells and their unique nuclei structures.
Aseptate fungal hyphae & skeletal muscle (multinucleated), red blood cells (no nucleus), sieve tube elements (no nucleus when mature).
What cell types and structures must be identified in micrographs?
Prokaryote, plant, and animal cells; structures include nucleus, mitochondrion, chloroplast, ER, Golgi, ribosomes, chromosomes, microvilli, membranes, etc.
What organelles must be drawn and annotated from electron micrographs (with functions)?
Nucleus (stores DNA), mitochondria (ATP production), chloroplast (photosynthesis), ER (protein/lipid synthesis), Golgi (modifies proteins), ribosomes (make proteins), etc.
What additional evidence supports the theory of endosymbiosis?
Genetic evidence shows mitochondria and chloroplasts share DNA sequences with specific prokaryotes (e.g., proteobacteria for mitochondria). Physiological evidence shows that mitochondria and chloroplasts resemble prokaryotes in shape and size. The engulfment of prokaryotes by ancestral eukaryotes can also be observed in some protists.
What does the sequential evolution of mitochondria and chloroplasts suggest about endosymbiosis?
Mitochondria likely evolved first in an ancient eukaryote via endosymbiosis, followed by chloroplasts in plants. Evidence supports this process as sequential, showing that some eukaryotes were mitochondrion-containing before acquiring chloroplasts.
How has multicellularity evolved in different lineages?
Multicellularity evolved multiple times in different lineages like fungi, algae, plants, and animals. It typically started with colony formation (groups of cells working together), followed by specialization of cells for specific functions. The evolution of cell-cell communication and division of labor were crucial steps in this transition.
What are the evolutionary advantages of multicellularity for organisms?
Larger body size, specialized cell functions (e.g., differentiation of tissues), and improved coordination of metabolic activities. Multicellularity also offers protection from predation and enhanced energy efficiency.
What evidence supports the theory of endosymbiosis?
Presence of 70S ribosomes in mitochondria and chloroplasts, their circular DNA, and the fact that both organelles replicate independently support the theory that they were once free-living prokaryotes.
