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What are the key differences between Eukaryotic and Prokaryotic cells?
- Simultaneous transcription/translation
- Divide by binary fission
- Have circular chromosomes
- 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)
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
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)
What is the key structure of the Nucleus?
- Double membrane bound organelle
- Outer membrane continuous with rER
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
What is the key function of the Nucleolus?
Site of ribosomal RNA synthesis and ribosomal subunit assembly
What is the key structure of the Mitochondria?
- Double membrane bound organelle
- Consist of: outer and inner membrane, and a matrix
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
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
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
What is the key structure of the Smooth endoplasmic reticululm (sER)?
Short anastomosing tubules not associated with ribosomes (“lava lamp” in EM)
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
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
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
Describe Early Endosomes.
- Membrane-enclosed structure near plasma membrane
- Lumen subdivided into cisternae (pH 6.2-6.5)Receives material, sorts, and sends
Describe Recycling Endosomes.
- Helps with recycling proteins
- Important for processes (insulin signaling)
Describe Late Endosomes.
Complex structure with onion-like internal membrane, pH 5.5, evolve/contribute to lysosomes
What is the key function of the Lysosomes?
Contains acid hydrolases – membrane resistant to hydrolytic digestion
What is the key structure of the Lysosomes?
Single membrane-bound organelle, digests macromolecules
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
What is the key structure of the Perixosome?
Single membrane bound protein
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
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
What is the key function of the Ribosomes?
Responsible for translating proteins
What is the size of eukaryotic and prokaryotic ribosomes?
- Prokaryotes = 30S + 50S = 70S
- Eukaryotes = 40S + 60S = 80S
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
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)
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
- · Microfilament based (actin)
- · Increases SA of plasma membrane (important for absorption)
What is the key function of Vesicles?
Used to transport proteinsthroughout cell
What are the key functions of Glycogen granules?
- Usually found in the cytoplasm
- Storage of glucose
- Highly branched polymers of glucose (25-30nm)
What does the Endomembrane contain?
Nuclear envelope, rER andsER, Golgi, Endosomes, lysosomes, vesicles
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
What does the extracellular matrix consist of?
Consists of proteoglycans, glycoproteins, glycosaminoglycans, collagen
What is the key function of the extracellular matrix?
- Provides mechanical/structural support for tissues
- Influences extracellular communication and cell migration
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