AP BIO Unit 2 Review - Cell Structure and Function
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Eukaryotic vs Prokaryotic Cells
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P
Bacteria and Archaea
Lack nuclei and other membrane-enclosed organelles
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E
Internal membranes
Compartmentalized
- allows for concentration gradients
- cell components have own function in own space
- prevents molecules from roaming freely in the (selective)
Plant and animal cells have most of the same organelles: a nucleus, endoplasmic reticulum, Golgi apparatus, and mitochondria. Some organelles are found only in plant or in animal cells. Chloroplasts are present only in cells of photosynthetic eukaryotes
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Both
Ribosomes
Genetic Material
Cytoplasms: inside of a cell where reactions take place
Cytocol: the liquid in a cell
Plasma Membranes
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Cellular Components
\ Chloroplast
- Photosynthetic
- Membranes contain chlorophyll pigments and e- transport proteins
- Plants, algae
- Own DNA + evolves independently -> endosymbiotic theory
- Double outer membrane * Intermembrane space
- Stroma * Fluid * outside thylakoid * Within the inner membrane * Site of Calvin-Benson cycle * Carbon fixation reactions of photosynthesis * Contains ribosomes + DNA * Helps synthesize organic materials from CO2 and H2O
- Thylakoid * Flattened membranous sac * Light in -> chemical energy
- Granum * Stack of thylakoids * Function in light reaction of photosynthesis
- Plastid * Family including chloroplasts, chromoplasts, amyloplasts * In cells of photosynthetic eukaryotes
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Endoplasmic Reticulum
- Mechanical support, protein synthesis, intracellular transport
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Plasma membrane
- Bounds all cells
- hydrophilic heads and hydrophobic tails * charged p groups + hydrophobic fatty acid * Amino acids with charged side groups are hydrophilic. These hydrophilic amino acids associate with the hydrophilic phosphate region of the cell membrane
- Bilayer of phospholipids
- fluidity
* cholesterol
* When temperatures are low, the fluidity of the cell membrane may decrease to a point that makes it nonfunctional. Cholesterol prevents this by packing between the phospholipids in the membrane. This increases the spacing between phospholipids, which increases the fluidity of the membrane
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- The surface area must be large enough to adequately exchange materials * Metabolic requirements set upper limits * Surface area increases by n^2, volume increases by n^3 * Small cells have a greater surface area to volume ratio * Increase in volume -> * Surface area decreases * Demand for internal resources increases
- Surface area increases
\ \ Plant Cell Walls
- Cellulose fibers embedded in other polysaccharides and proteins
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Extracellular matrix
- Support, adhesion, movement, regulation
\ \ RIbosomes
- Comprise ribosomal RNA (rRNA) and protein
- Synthesize proteins according to mRNA sequence
- All forms of life
- Free ribosomes in the mitochondrial matrix
\ \ Endoplasmic Reticulum
- Rough * Membrane-bound ribosomes * Compartmentalizes * Phospholipid factory for the plasma membrane and organelles (endomembrane system)
- Smooth * Detoxification * Lipid synthesis * Liver cells
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Golgi apparatus
- Membrane-bound
- Flattened membranous sacs
- Modifies and packages proteins
- Cis side receives, trans face ships
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Mitochondria
- ATP synthesis
- Mitochondrial matrix * Pyruvate oxidation * Krebs cycle (citric acid cycle) * Enclosed by the inner membrane * Contains ribosomes, enzymes, and mitochondrial DNA * Own DNA + evolves independently -> endosymbiotic theory
- Double membrane * Provides compartments for different metabolic reactions * Outer smooth * inner highly convoluted and folded * increases surface area allows for more ATP to be synthesized * E- transportation and ATP synthesis occur here
- crista * Infolding of the inner membrane
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Lysosomes
- Recycle cell's organic materials
- Membrane enclosed sacs
- Hydrolytic enzymes * Intracellular digestion
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Vacuole
- Membrane-bound sac
- Food * Formed by phagocytosis (endocytosis)
- COntractile * Freshwater protists, pump out excess water
- Central * Mature plant cells, hold organic compounds and water * Fills with water -> pressure to cell wall -> maintain cell shape
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Cytoskeleton
\ Cytoskeleton
- Struct support
- Motility
- Signal transmission
- Motor proteins “walk” on
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Microtubules
- Shape cell
- Hollow
- Tubulin polymer
- Guide organelle movement
- Separate chromosomes in dividing cells
- Cilia * Hair * Flutters * Brings up mucus * The large number on the cell surface
- Flagella * One or few
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Microfilaments
- Thin rod
- 2 acetone intertwined * Actin interacts with myosin * Contract muscle cells * Amoeboid (crawling) movement * Cytoplasmic streaming (circular flow of cytoplasm within cells)
- Muscle contraction, amoeboid movement, cytoplasmic streaming, support microvilli
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Intermediate filaments
- Diameter between microtubules and microfilaments
- coiled
- Support cell shape, fix organelles in place
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Communication, Transport, and Diffusion
\ [[Cell junctions[[
- Plasmodesmata * Perforates cell walls * Connects cytoplasm of adj plant cells * Lets in water, small solutes, and larger molecules
- tight junctions * neighboring cells tightly pressed and bound by proteins * Continuous seal * The barrier prevents EC leaks
- Desmosomes * Cells -> sheets * Anchored by int. Fil. (keratin) * Attach muscle cells
- Gap/communicating junctions * Cytoplasmic channel in adj cells * Membrane proteins surround the pore
\ ^^Most efficient^^
- sphere - equal distance all sides
- smaller cells - higher surface area to volume ratio
\ [[Active vs passive transport[[
Active transport requires direct energy because it is against concentration gradients
\ ^^Osmosis^^
Water travels from low solute to high solute density
solute travels from high to low solute density
Hypotonic SOlution: The solution has a lower solute density which causes the cell to gain water
Hypertonic SOlution: The solution has a higher solute density which causes the cell to lose water
Isotonic SOlution: No net movement of water
\ [[Membrne Proteins[[
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Endosymbiont Theory
Membrane-bound organelles evolved from previously free-living prokaryotic cells via endosymbiosis.