Anatomy of the Cell Flashcards
Cell
Basic structural unit of all living organisms
Composition of a Cell
Water = 80%
Protein = 15%
Lipid = 2.5%
Carbohydrate = 1.5%
Inorganic = 1.0%
Plasma Membrane - Function (3), Composition, Properties (2)
Controls entry and exit of cell
Protects the cell
Separates cytoplasm from external environment
Bimolecular layer of amphiphatic phospholipid molecules with hydrophilic heads and hydrophobic tails
Fluid - change shape, membrane proteins can diffuse laterally in membrane
Selectively-permeable - molecules like water/oxygen/hydrophobic molecules can pass, but molecules like ions and large molecules can’t
Trilaminar
Cytoplasm - Composition, Properties,
Solution of proteins, electrolytes and carbohydrates
Fluid and gel-like properties
Cytoskeleton
Determines shape and fluidity of cell
Includes –> MIcrofilaments, Intermediate filaments
Microtubules
Organelles
Membrane-bound subcellular structures within the cytoplasm
Small intracellular organs with specific function and structural organisation
Inclusions (3)
Other structures in cytoplasm which may or may not be bound by a membrane
Dispensable and may be present only as transients
Components synthesised by the cell itself or taken up from the extracellular environment
Integral Proteins
Within the plasma membrane
Movement of signals across (signal transduction)
I.e. Receptors, Channels, Transporters, Enzymes, Cell Attachment
Nucleus
Contains the genetic code (DNA)
Nucleolus - 1-3um, rRNA transcribed
Nuclear membrane - pores present
Inner membrane
Outer membrane - studded with ribosomes, continuous with RER
mRNA and tRNA transcribed in nucleus
Euchromatin - open, uncondensed, active
Heterochromatin - closed, condensed, inactive
Mitochondria
Energy production
Cellular respiration - electron transport chain
ATP production - via OXPHOS
Synthesis of some lipids/proteins
Oblong, cylindrical organelles
0.5-2um length
Outer Membrane
Inner membrane - folded into cristae (increase SA)
Mitochondrial DNA
Ribosomes
Formed in nucleolus
Protein synthesis
Small 40S subunit - binds RNA
Large 60S subunit - catalyses peptide bond formation
Endoplasmic Reticulum
Network of Interconnecting membrane-bound compartments in cell
Rough ER
Studded with ribosomes
Protein synthesis - destined for membrane insertion or secretion
Glycoprotein formation
High RER = Metabolically active cell
Low RER = Metabolically inactive cell
Smooth ER
Cholesterol and Lipid synthesis/detoxification
Continues protein processing from RER
Most cells have little SER
Golgi Apparatus
Modification & Packaging of macromolecules - adds sugars, cleavage, vesicle sorting
Flattened membrane bound cisternae
Sub-compartments
Transport vesicles arrive from ER
Cis- and trans-Golgi
Lysosome
Contains hydrolytic enzymes for intracellular digestion
Microfilaments - Diameter, Globular, Filamentous, Assembly
7nm diameter
Actin
Globular actin polymerises to form FIlamentous actin
Assemble into filaments then disassemble (dynamic)
Intermediate FIlaments
> 10nm diameter
6 Main Proteins
BInd intracellular elements together and to membrane
More than 50 types - neurofilaments, desmin, cytokeratins, vimentin, lamin, etc
Microtubules
25nm diameter
Alpha and Beta-tubulin proteins
Hollow tubule
Assembled and Disassembled
Originate from centrosome and include MAPs (stabilising proteins)
Important in Cilia, Flagella and Mitotic Spindle
Dynein and Kinesin attach and move along - associate with organelles and vesicles
Intracellular Junctions
Specialised membrane structures which link individual cells together into a functional unit
Prominent in epithelia
Occluding Junctions/ Tight Junctions
Prevent diffusion
Focal region of close apposition between adjacent cells
Contain occludin and claudin
Anchoring Junctions/ Zonula Adherens
Link submembrane actin bundles of adjacent cells
Transmembrane cadherin bind to each other in the extracellular space and to the actin of the cytoskeleton (link molecules)
Desmosomes/ Macula adherens
Link submembrane intermediate filaments of adjacent cells
Common in skin - mechanical stability
Desmocollin and Desmoglein
Communicating Junctions/ Gap Junctions
Selective diffusion
Each junction is a circular patch studded with several hundred pores
Connexon proteins
Found in epithelia and also some smooth muscle and cardiac muscle (excitation spread)
Junctional Complex
Close association of several types of junctions found in certain epithelial tissues
ZO –> ZA –> MA
Transport in and out of the cell
Diffusion
Transport Proteins - pumps or channels
Vesicles - endocytosis, phagocytosis
Endocytosis
From extracellular space to intracellular space of the cell
Membrane invaginates, fuses and newly made endocytotic vesicle buds into the cell
Receptor-mediated
Exocytosis
Material moves from the intracellular space to the extracellular space
Phagocytosis
Bacteria or larger material from extracellular space incorperated into cell
Bacterium binds to cell surface receptors –> cell extensions –> Engulfment of bacterium –> Phagosome –> Binds to Lysosome –> Phagolysosome
