Cells Flashcards
brief history of cells:
Robert Hooke: referred to cells
- Leeuwenhoek ‘father of microbiology’
- Schleiden and Schwann formulated cell theory:
- all organisms made of cells
- cell most basic unit of life
- all cells arise from pre-existing cells
microscopy:
- cells too small to be seen with unaided eye
- light microscope magnify 1000x
- but most subcellular structures (organelles) too small to be seen using light microscope
eg of electron microscopy:
TEM: transmission electron microscopy
- electron beam through slice of specimen
- 0.05 nm
SEM: scanning electron microscopy
- scans surface of specimen using electron beam
- 0.4 nm resolution
plasma membrane features:
- selective plasma membrane allows sufficient passage of oxygen, nutrients and waste
- phospholipid bi-layer
organelles found in animal cells only:
- lysosomes
- centrosome with centrioles
organelles found in plant cells only:
- chloroplast
- central vacuole
- cell wall
- plasmodesmata
features: nucleus
- nuclear DNA
- nuclear double membrane
- each layer lipid bilayer
- pores regulate entry/exit of molecules from nucleus
how is nucleus shape maintained? + nucleolus
- nuclear lamina
- protein
- genetic material called chromatin (protein + DNA)
- nucleolus synthesises rRNA (which joined to proteins form ribosome subunits)
features: ribosomes
factory of the cell
- rRNA + protein
- carry out protein synthesis in:
- cytosol (free ribosomes)
- on RER or nuclear envelope (bound)
list components of endomembrane system:
- nuclear envelope
- endoplasmic reticulum
- golgi apparatus
- lysosomes
- vacuoles
- plasma membrane
how are the endomembrane system related?
either continuous or connected via vesicles
features: endoplasmic reticulum
- more than half of total membranes in most eukaryotic cells
- continuous with nuclear envelope
- Smooth ER vs Rough ER
detail: RER vs SER
ER is a biosynthetic factory:
smooth:
- lipid synthesis
- carb metabolism
- detoxification of poison
- calcium storage
rough:
- glycoprotein synthesis
- membrane production
features: golgi apparatus
- flattened membranous sacs (cisternae)
- modification of ER products
- manufactures certain macromolecules
- package materials into transport vesicles
features: lysosomes
membranous sac of hydrolytic enzymes- digest macromolecules
- lysosomal enzymes can hydrolyse proteins, fats, polysaccharides and nucleic acids
lysosomes: phagocytosis + autophagy
- some cells can engulf another via phagocytosis
- which forms food vacuole
- lysosome fuses with food vacuole to digest molecules
- lysosomes also use enzymes to recycle organelles and macromolecules of the cell, via autophagy
features: vacuole and egs.
- plant/ fungal cell may have several
- food vacuoles formed by phagocytosis
- contractile vacuoles: pump excess water out of cells (freshwater protists)
- central vacuoles found in mature plant cells hold organic compounds + water
features: mitochondria
- in nearly all eukaryotic cells
- cellular respiration
- smooth out membrane and inner folded one (cristae)
- forms intermembrane space + mitochondrial matrix
- large SA for enzymes to synthesis ATP
features: chloroplasts
- photosynthesis
- chlorophyll reside in thylakoid membranes
features: cytoskeleton + types
- network of fibres extending throughout cytoplasm
- organises cell structures, anchoring organelles
- microtubules
- microfilaments
- intermediate filaments
cytoskeleton contd. function + interactions
- support
- mobility and regulation
- maintains shape
- motor proteins interact to produce motility
- inside cell, vesicles can ‘walk’ along ‘monorails’ provided by cytoskeleton
microtubules: function
thickest of the 3
- hollow rods 25nm diameter
- grow from centrosome near nucleus
- shapes cell
- guide movement of organelles
- separating chromosomes during cell division
microfilaments: function
aka actin
- thinnest component
- rods 7nm diameter,
- twisted double chain of actin subunits
- bears tension, resist pulling forces of cell
- forms 3D network, support shape
- interacts with myosin for movement
intermediate filaments: function
middle fibres
- 8-12 nm diameter
- support cell shape, fix organelles in place
- variety of different proteins
- more permanent than microtubules and microfilaments
microtubules: cilia and flagella
- components of cilia and flagella
- motor proteins (dyenin) ‘walk’ along microtubule
- cross links limit sliding = bending of cilia or flagella
eg of each cytoskeleton:
microtubule: tubulin dimer
- intermediate filament: keratin protein
- microfilament: actin subunit
