Module 2 (cell structure and function) Flashcards
Cell membrane structure
Arranged as a phospholipid bilayer around cytoplasm; two rows of polar hydrophilic heads (phosphate, face exteriors) and lipid hydrophobic tails (fatty acids, face each other); embedded with proteins; dynamic
Cell membrane functions
Selectively permeable barrier which controls passage of substances into and out of the cell
Cell membrane proteins and functions
Often amphipathic (hydrophobic and hydrophilic regions); can be integral or peripheral; are cell specific and dynamic; allow transport, enzymatic activity, cell to cell recognition, intercellular joining, signal transduction and attachment to cytoskeleton and ECM
Integral proteins
Embedded partially or fully into the membrane (e.g. transmembrane proteins span the entire membrane, contact extracellular and cytoplasmic areas)
Peripheral proteins
Associated with the membrane but are not actually embedded in it
Nucleus description and components
Largest organelle; enclosed by a double lipid bilayer (nuclear envelope) which is continuous with the RER; nuclear pores and nucleolus
Nucleus function
Houses/protects DNA in eukaryotic cells; nuclear pores are tightly regulated channels which allow entry and exit of substances (e.g. protein, mRNA); nucleolus makes RNA and assembles proteins; molecule segregation allows temporal and spatial control of cell function (things can happen fast and be directed to different parts of the cell)
DNA
Deoxyribonucleic acid; double helix made up of nucleotides (nitrogenous base, phosphate group and pentose sugar); forms inherited genetic material
RNA
Ribonucleic acid (mRNA, rRNA and tRNA); relays information from genes to guide synthesis of proteins from amino acids
Fluid mosaic model
Plasma membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids
Cytoplasm
Everything inside the plasma membrane including the organelles (not nucleus); fluid portion is the cytosol which is water and dissolved/suspended substances (e.g. ions, proteins, ATP, lipids)
Endomembrane system
Nucleus, smooth and rough ER, golgi apparatus and lysosomes; along with plasma membrane share membrane structures which allows formation, shipping and movement of compounds around cell
Which major organelles are not a part of the endomembrane system?
Mitochondria, have membranes but don’t share messages between other structures in cells; ribosomes, no membranes
Ribosomes structure
Large and small subunits (rRNA in complex with many proteins) made in nucleolus and leave through nuclear pores and come together in cytoplasm
Ribosomes function
Sites of protein synthesis (translation); some found associated with RER - make non-cytosolic proteins/endomembrane and others found free in cytoplasm making proteins to be used in cytosol (non-endomembrane destinations)
Rough ER structure
Continuous with the nuclear envelope, folded into a series of flattened sacs; outer surface studded with ribosomes
Rough ER function
Produces secreted proteins, membrane proteins and organelle proteins; proteins enter RER for folding; RER surrounds protein to form transport vesicles destined for golgi
Smooth ER structure
Extends from the RER to form a network of membrane tubules and lacks ribosomes;
Smooth ER function
Does not make proteins, but synthesises lipids (including phospholipids and steroids); stores cell-specific proteins (not all cells make all proteins); tissue-type/cell specific
Smooth ER cell-specific examples
Liver cells: houses enzymes for detoxification and glucose release; liver, kidney and intestinal cells: houses enzymes which removes the phosphate group from a glucose molecule so glucose can enter bloodstream; muscle cells: release calcium ions which trigger contraction
Golgi apparatus structure
‘Warehouse’ which is made up of 3-20 flattened membranous sacs with bulging edges (cisternae) stacked on top of each other; more extensive in cells that secrete proteins
Golgi apparatus function
Modifies, sorts, packages and transports proteins received from RER; forms secretory vesicles (proteins for exocytosis), membrane vesicles (PM molecules) and transport vesicles (molecules to other organelles)
Golgi apparatus process
Entry (cis) face faces RER, exit (trans) face faces plasma membrane; each sac/cisternae contains enzymes of different functions where modifications occur; proteins move cis to trans from sac to sac, mature at the exit cisternae and travel to their destination
Lysosomes structure
Contain powerful digestive enzymes; vesicles formed from golgi apparatus