Lecture 1: Cells? Flashcards
Prokaryote cell parts
- cytoplasm
- flagellum
- ribosomes
- nucleoid (DNA)
- plasma membrane
- cell wall
- capsule
- plasmid
- pili
Plant cell parts
- Rough ER
- Smooth ER
- Ribosomes
- central vacuole
- Tonoplast
- microfilaments
- Intermediate filaments
- microtubules
- chloroplasts
- plasmodesmata
- cell wall
- plasme membrane
- peroxisome
- mitochondria
- Golgi apparatus
- centrosome
- nucleus .. Chromatin, nucleolus, nuclear envelope
Animal cell parts
- Nucleus
- Nuclear envelope
- chromatin
- nucleolus
- glycosomes
- smooth ER
- cytosol
- mitochondrion
- centrioles
- centrosome matrix
- microvilli
- microfilament
- microtubule
- peroxisome
- secretion via exocytosis
- Golgi appaatus
- rough ER
- ribosomes
Centriole…
Organise spindle fibres in mitosis
Glycosome…
a peroxisome involved in glycogen storage & metabolism
Lysosome…
small vacuole
Eukaryotic cells are packed full of…
MEMBRANES. in 5ml of hepatocytes (teaspoonful) there are ~ 100m^2 of membranes
proteins in cells ____ of the volume of the cytosol
20-30%
Cytosol…
Aqueous component of the cytoplasm of the cell. Organelles & particles are suspended here
Why are cells so small?
- metabolism needs fuel from outside & produces waste products
- — exchange limited by surface area to volume ratios - smaller cells are easier to turn over/ replace
graph showing SA:V and side length of cube
shorter the side length of cube the higher the SA:V
Even small cells can have problems with SA for transports so…
in cells specialised for transport/exchanging materials, SA is dramatically increased and mitochondria abundant. E.g. microvilli in the intestine to absorb nutrients
Cell walls e.g. for root hair cells are…
all wiggly and folded = increased SA
a coenocytic structure =
multinucleate cells
some large cells do exist they often have…
a coenocytic structure with multiple nuclei and chloroplasts & a large vacuole
membranes allow,,,
compartmentation
why is compartmentation by membranes good?
- different environments (e.g. pH in vacuoles, mitochondria and cholorplasts)
- assists metabolic regulation by keeping enzymes, substrates and regulators separate
- locally high metabolite concentrations
- sequestration of toxic substances
- turnover of substances and organelles
- cells secrete and internalise large numbers of proteins -ER
Internal compartments of chloroplasts and mitochondria have an..
acidic pH to drive ATP synthesis
Nucleus contents:
genome, DNA replication, transcription, RNA processing, BUT translation is in the cytoplasm
Nucleus regulation:
Compartmenting the genome from the cytoplasm allows regulation of gene expression. (e.g. post-transcriptional processing, such as splicing (alternative)).
RNA splicing –>
RNA splicing is the process by which introns, regions of RNA that do not code for protein, are removed from the pre-mRNA and the remaining exons connected to re-form a single continuous molecule.
Nucleus Transport:
nuclear pore complexes transport RNA, ribosomes, proteins, carbohydrates, signalling molecules and lipids. Small particles (
Cytoskeleton:
- protein filaments and motor proteins
- protein filmanets form a 3D mesh -> rigidity, shape & structure
- movement (trackways)
In muscle cells, _____, comprises 10% of total cell protein, even in non muscle cells ___ forms 1-5% of cellular proteins
actin
Microtubules…
cylindrical tubes (20-25nm diameter) of tubular. Highly dynamic
Microfilaments…(& movements)
actin fibres (3-6nm diameter). Movements: gliding, contraction & cell cleavage. With myosin responsible for muscle contraction.
Microtubules…
determine cell shape, provide trackway for movement of cell organelles & vesicles. Spindle fibre sin mitosis inside flagella and cilia
Intermediate filaments…
(8-12nm diameter) anchor & position nucleus & give cell flexibility
cytoskeleton movers (motor proteins)
- all powered by ATP : Kinesin, dynein, myosin (muscle)
- molecules and cargo-containing vesicles (& organelles) are all moved around the cell by motor proteins
Kinesin…
travels towards the ‘plus’ end AWAY from the nucleus
Dynein…
travels towards the ‘minus’ and TOWARDS the nucleus
Actin filaments form…
trackways
E.g. of cytoskeleton movement..
Melanocytes. Melanophores used by fish, amphibians, crustaceans, cephalopods & reptiles to change colour. Motor proteins transport pigments in melanosomes along microtubule/actin tracks
Microtubules pattern for plant cell wall synthesis:
- Cortical microtubules form a template for deposition of cellulose in bands.
- Turgor-driven plant growth is constrained along the axis of elongation.
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prokaryote..
any cellular organism that has no nuclear membrane, no organelles in the cytoplasm except ribosomes, and has its genetic material in the form of single continuous strands forming coils or loops, characteristic of all organisms in the kingdom Monera, as the bacteria and blue-green algae.
