cell organisation Flashcards
3 divisions of the living world
- EuBacteria (prokaryotes)
- archaea (pro)
- eukaryotes (eukaryotes)
role of cells
- grow & divide
- obtain & use energy in specific chemical reactions = metabolism
- move & dynamic
- complex or simple
- whole organism or part
features all cells have
- enclosed by a membrane
- all carry nucleic acid
- nucleic acid provides the instructions to direct the construction of specific machinery to obtain energy from the environment
- ATP energy used to duplicate the nucleic acid & the cellular machinery
comparison between prokaryotes & eukaryotes
p
- no nuclei
- simple internal organisation
- plasma membrane
- nucleoid - bacteria DNA not in a membrane
- divide by binary fission
e
- more complex
- contain a nucleus
- contain other organelles
- divide by mitosis/meiosis
what is common between prokaryotes & eukaryotes
- similar plasma membrane
- same genetic code
- similar mechanisms for ‘decoding’ the genetic code
- many metabolic pathways are the same
- similar use of ATP for energy
- both cells can be unicellular organisms
what is contained in a eukaryotic cell
- Defined membrane bound nucleus & organelles
- The nucleus contains the genome (aside
from mitochondrial and chloroplast DNA),
and it is the principal site of DNA and RNA
synthesis - Extensive internal membranes that
make up organelles - Plasma membrane
- Cytoplasm – lies between plasma
membrane and nucleus
structure of nucleus
- contains nearly all DNA
- nuclear envelope formed by two membranes containing nuclear pores
- supported by the nuclear lamina
role of nuclear pores
molecules move between the nucleus & cytosol
define nuclear lamina
network of intermediate filaments, a thin felt-like mesh just beneath the inner nuclear membrane
organelles in eukaryotic cell
- nucleus
- cytoplasm
- cytoskeleton
- ER
- golgi apparatus
- mitochondria
- lysosome
- centrioles
- vesicles and vacuoles
role of cytoplasm
= main site of protein synthesis & degradation & also performs most of the cell’s intermediary metabolism
- around 50% of cells volume
role of cytoskeleton & its three main components
= gives cell its shape & structure & provides a framework for movement
- microfilaments
- intermediate filaments
- microtubules
role of endoplasmic reticulum (ER)
manufacturing system & cellular ‘factory’
role of smooth endoplasmic reticulum
- has no ribosomes so no protein synthesis but it produces & stores lipids & steroids
role of rough endoplasmic reticulum
- has ribosomes attached to its surface = mediates synthesis & packaging of proteins
ribosomes = where protein synthesis occurs
where does ER send proteins
sends newly synthesised proteins to Golgi to be sorted to their final destination
structure of endoplasmic reticulum
- smooth & rough ER form sacs called cisternae
- protein molecules are stored in cisternal space/lumen
- when enough proteins are present, they collect & are pinched off in vesicles
role of golgi apparatus
receives lipids & proteins from the ER & dispatches them to various destinations, usually covalently modifying them en route
role of mitochondria
generate most of the ATP that cells use to drive reactions requiring an input of free energy
role of lysosomes
= degrades old organelles & proteins
- lumen pH (4.5-5) for enzymes involved in hydrolysis
- extracellular material taken-up through endocytosis
- intracellular material is digested through autophagy
role of endosome system
delivers materials to lysosome or plasma membrane (originates from trans golgi network)
structure of centrioles
composed mainly of protein tubulin
- present in many eukaryotes but absent from some plant & fungal cells
role of centrosomes
form the microtubule organising centre from which microtubules grow & forms spindles which separates chromosomes during cell divison
where are centrioles located & role
centrosomes contain 2 at right-angles surrounded by protein to regulate the cell cycle
