Cells Flashcards
what is the basic definition of cells
-cells are the basic unit of life
-can have diff structures to reflect the range of functions
-they interact with each other and the extracellular matrix
three types of cells
-prokaryotes: no nucleus or membrane bound organelles
-eukaryotes: defined nuclear structure
-viruses: require host to replicate
basic regulation of cells is….
they replicate themselves
-aquire and metabolise nutrients
the molecular composition of cells (solvent)
-water is the main solvent in cells where chemical reaction of cells
-cytosol: represents the water containing inorganic ions and small organic molecules this accounts for 70-80% of the weight of a living cell
-macromolecules account for the remaining weight
cytoplasm: semisolid fluid that defines all components outside the nucleus and within the cytoplasmic membrane
Macromolecules in a cell examples
-protiens
-polysaccharides
-lipids
-DNA /RNA
generalised structure of a eukaryotic human cell
-Highly organized and most have similar sub-cellular components, such as organelles that define the individual cell
-Most cells have direct, specific interactions with neighbouring cells and/or the extra-cellular matrix/environment
-drugs target specific cellular components
the nucleus
-DNA packaged into chromosomes within a nuclear matrix
-DNA packaged with proteins into super-coiled structure to form chromatin
-also contains enzymes and proteins for regulation of DNA
-regions of RNA and a protein called nucleoli
-surrounded by a double membrane the envelope is connected with ER
-nuclear pores facilitates movement of small molecules
different types of nucleuses in cells
-some cells have several nuclei
-some have lobular
-some have ovoid structure
the endoplasmic reticulum
-network of membranes that fold into cisternae
-with interconnected lumen that links to the nuclear membrane
-protiens synthesised on the ER can undergo modification there and then is passed to the Golgi complex and lysomes for further processing
-is a store of Ca2+ in muscle cells
-involved in the synthesis of lipids and steroids and detoxification of drugs in liver cells
Golgi apparatus
-golgi complex derived from ER but not connected
-stacks of smooth membrane sacs and vesicles
-Cis (Faces the ER) and receives the protiens and lipids
-trans face (faces cytoplasmic membrane) targets delivery of protiens
- process and sorts protiens and packages
-more modification
mitochondrion
-source of ATP
-double membrane,
-Enzymes of ETC embedded in inner membrane
-enzymes for Krebs and fatty acid oxidation are in the matrix
-has its own circular DNA, RNA and ribosomes
-interhrited maternally
lysosomes
Lysosomes are derived from Golgi complex and contain various enzymes that work in an acidic environment, around pH 5.0
Involved in breakdown of proteins, carbohydrates and lipids
Endosomes
are structures formed by pinching off part of cytoplasmic membrane when material like lipoproteins or ‘foreign bodies’ are brought inside cell
Phagosomes
are found in specialized cells like macrophages and breakdown ‘foreign bodies’ e.g., bacteria and involve the cytoplasmic membrane engulfing and pinching off inside the cell, creating a specialized microenvironment within the cell where enzymes and reactive oxygen species/free radicals contribute to killing / breaking up of the particle/bacterium
Peroxisomes
are organelles involved in oxidation – reduction reactions
ribosomes
-site of protein synthesis translation
-consists of two sub units
-Eukaryotes – 80S ribosome
Prokaryotes – 70S ribosome
cytoskeleton
-Consists of
-microfilaments: actin provide mechanical support and transmit signals
intermediate filaments: resistance to shear stress
microtubule: tubular movement snd separation of chromosomes, movement of cilia and flagella
cytoskeleton in muscles
-specific protein fibres actin and myosin facilitate contractile forces
-fibres are arranged in sarcomeres in skeletal and cardiac muscle
-smooth muscle have actin arranged diagonally within the cytoplasm cause contraction in a twisting manor when they interact with myosin
the cytoplasmic membrane
-phospolipid bialayer
-controls what come in and out of the cell
-interacts with other class
prokaryotes example bacteria
-DNA in circular nucleoid
-have a smaller genome and often haploid
-more rapid replication and regulation of DNA
-extra chromosomal DNA in plasmids
-smaller ribosomes
-ETC in cytoplasmic membrane
-some have cell walls like peptidoglycan
anatomy of virus
-caspid protects genome
-capsomers are the viral proteins that protect the genomic material
-capsomers bind to receptors on host cell which cause the invasion
naked viruses vs enveloped viruses
-naked: caspid only polio
- envelope viruses : caspid has a lipid bilayer derived from host. this contains viral proteins
HIV
