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What are the key differences between Eukaryotic and Prokaryotic cells?
- Prokaryotes:
- Simultaneous transcription/translation
- Divide by binary fission
- Have circular chromosomes
- Eukaryotes:
- Separation of transcription/translation
- Internal membranes to segregate function
- Exhibit endocytosis and exocytosis
- Significant processing of RNA
- Divide by mitosis/meiosis
- Have linear chromosomes (except mitochondria)
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What is the key structure of Plasma membrane?
- Lipid bilayer with proteins embedded
- Has glycocalyx (sugar coat) around membrane
- Hydrophobic region surrounded by 2 hydrophilic regions
Carbohydrates, glycolipids, glycoproteins face outside of cell
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What is the key function of Plasma membrane?
- Defines boundaries, retains contents, serves as permeability barrier
- Sites of specific function, transmit electrical/chemical signals
- Regulate transport of solutes
- Mediate cell-cell communication (gap junctions)
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What is the key structure of the Nucleus?
- Double membrane bound organelle
- Outer membrane continuous with rER
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What is the key function of the Nuclues?
- Site of DNA storage and transcription
- Euchromatin = lighter, not tightly packed, actively being expressed
- Heterochromatin = darker, tightly wound
- Nuclear pores regulate transport
- Nuclear lamina holds in membrane in place, anchors chromatin with intermediate filaments
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What is the key function of the Nucleolus?
Site of ribosomal RNA synthesis and ribosomal subunit assembly
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What is the key structure of the Mitochondria?
- Double membrane bound organelle
- Consist of: outer and inner membrane, and a matrix
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What is the key Function of the Mitochondria?
- Outer membrane: BCL2 = involved in apoptosis
- Provide energy by producing ATP = powerhouse of cell
- Site of regulation of apoptosis – “executioner of cell”
- Inner membrane: Cristae – highly folded to increase SA, Site of ETC and ATP synthesis
- Matrix: Semi-fluid, DNA here, Krebs cycle
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What is the key structure of the Rough endoplasmic reticulum (rER)?
- Studded with ribosomes (appears dotted on EM)
- Lumen of rER goes into lumen of sER
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What is the key function of the Rough endoplasmic reticulum (rER)?
- Site of protein synthesis and modification of new proteins
- 3 types of proteins made here:
- Secreted proteins
- Integral membrane proteins
- Proteins involved in endomembrane system
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What is the key structure of the Smooth endoplasmic reticululm (sER)?
Short anastomosing tubules not associated with ribosomes (“lava lamp” in EM)
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What is the key function of the Smooth endoplasmic reticululm (sER)?
- Site of lipid and steroid synthesis
- Glycogen metabolism
- Calcium storage – sarcoplasmic reticulum in skeletal/cardiac muscle
- Principle organelle in detox of noxious substances
- · Cytochrome P450
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What is the key structure of the golgi complex?
- Stack of flattened membrane sheets (cisternae), adjacent to one side of nucleus
- Cisternae closest to rER is forming face (cis-Golgi network)
- Farthest from rER is maturing face (trans-Golgi network)
- In between called medial Golgi
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What is the key function of the golgi complex?
- Functions to modify proteins and glycolipids
- · Glycosylation (O-linked)
- Sorting and packaging of molecules for secretion/transport
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Describe Early Endosomes.
- Membrane-enclosed structure near plasma membrane
- Lumen subdivided into cisternae (pH 6.2-6.5)Receives material, sorts, and sends
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Describe Recycling Endosomes.
- Helps with recycling proteins
- Important for processes (insulin signaling)
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Describe Late Endosomes.
Complex structure with onion-like internal membrane, pH 5.5, evolve/contribute to lysosomes
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What is the key function of the Lysosomes?
Contains acid hydrolases – membrane resistant to hydrolytic digestion
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What is the key structure of the Lysosomes?
Single membrane-bound organelle, digests macromolecules
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What are some diseases that evolve from the Lysosomes and why?
- I-cell – no M6P tag, enzymes don’t go to lysosome
- Gaucher’s – spleen, hepatomegaly, anemia, mental retardation
- Tay-Sachs – inability to break down GM2 – rapid motor, mental deterioration, skeletal, respiratory and cardiac dysfunction, high incidence in Ashkenazi Jews
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What is the key structure of the Perixosome?
Single membrane bound protein
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What is the key function of the Perixosome?
- Cats go Per – catalase degrades hydrogen peroxide
- Breaks down long chain (>16) FAs
- Detox alcohol into acetaldehyde
- 2 important enzymes, urate oxidase and catalase
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What are some disease that evolve from the Perixosomes and why?
- Refsum – least severe
- Zellweger’s – missing key proteins essential for targeting peroxisomal enzymes to organelle, remains in cytosol, develop neurological, visual and liver disorders
- X-linked adrenoleukodystrophy – mostly males, leads to adrenal failure, neurological impairment and death, defect in transport of very long-chain FA into peroxisome
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What is the key function of the Ribosomes?
Responsible for translating proteins
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What is the size of eukaryotic and prokaryotic ribosomes?
- Prokaryotes = 30S + 50S = 70S
- Eukaryotes = 40S + 60S = 80S
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What are some Cytoskeletal elements?
- Microtubules (composed of a- and b- tubulin)
- · 25nm = largest
- Microfilaments (composed of actin)
- · 7nm = smallest
- Intermediate filaments(composition varies)
- · 8-12nm = medium sized
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What are the key functions of Centrosomes and Centrioles?
- Centrosomes organize microtubule spindles
- Centrosome also called Microtubule Organizing Center (MTOC)
- Contains centrioles and other ring-shaped structures initiating MT formation
- Control number, polarity, direction, orientation of MT
- Important for aligning spindles during cell division
- Usually grow on + end, anchored on – end
- NOT centromere (where chromatids meet)
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What are the key funcitons of Cilia, Flagella and Microvilli?
- Cilia and Flagella
- · MT based, important for movement of EC fluid or cell locomotion
- · Organized in 9+2 formation (9 MT doublets outside, 2 singlets inside)
- · Uses Dynein as motor protein
- Microvilli
- · Microfilament based (actin)
- · Increases SA of plasma membrane (important for absorption)
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What is the key function of Vesicles?
Used to transport proteinsthroughout cell
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What are the key functions of Glycogen granules?
- Usually found in the cytoplasm
- Storage of glucose
- Highly branched polymers of glucose (25-30nm)
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What does the Endomembrane contain?
Nuclear envelope, rER andsER, Golgi, Endosomes, lysosomes, vesicles
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Go through the process of secretion.
- Ribosomes synthesize proteins on rER, pass to Golgi for procession (cisàtrans), placed in secretory vesicle for movement
- Vesicles make way to plasma membrane for fusion/release
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What does the extracellular matrix consist of?
Consists of proteoglycans, glycoproteins, glycosaminoglycans, collagen
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What is the key function of the extracellular matrix?
- Provides mechanical/structural support for tissues
- Influences extracellular communication and cell migration
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Name the cellular junctions and their function.
- Gap junctions - Cell-cell connections that transfer material
- Hemidesmosomes - Anchors cell to basement membrane
- Desmosomes - Provides localized button-like junctions between cells
- Tight junctions - Permeability barrier, regulates cell polarity
- Adhesive junctions - Connects cells into sheets
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