Cell types & specialisation Flashcards
What are the essential features of a cell?
- Exterior plasma membrane (phospholipid bilayer)
- Nuclear region w DNA
- Interior cytoplasm (semifluid matrix)
What are the 2 cell types?
- Prokaryotic
- Eukaryotic
What are prokaryotic cells like?
No nucleus, little defined internal structure & unicellular - v small ~5-2.0um diameter
What are eukaryotic cells like?
Contain nuclei, more complex w specialised organelles
May be unicellular or multicellular (animals, plants or fungi)
What are the 3 divisions in the tree of life?
- Eukaryotes
- Bacteria - prokaryotes
- Archaea - “”
What type of cells are eubacteria?
Prokaryotes
They are the most commonly encountered of the prokarya
What features are most commonly found in eubacteria?
- Plasma membrane (PM)
- Rigid cell wall - composed of peptidoglycan (carb/protein polymer) external to PM
Simple internal organisation & lack of differentiation
Genomic DNA presented in ‘nuclei’ region - not steerage for cytoplasm
What are the types of bacteria?
- Gram-positive
- Gram-negative
What is Gram+ bacteria like?
Has plasma membrane and cell wall
What is Gram- bacteria like?
Has extra periplasmic space outside of the plasma membrane & cell wall
Name a type of gram- bacteria
E.coli
What are the main ways that bacterial cells are diverse?
- Cell shape
- Cell appendages
- Some have infoldings of the plasma membrane
Why do some bacteria have infoldings in the plasma membrane?
(Give an example)
To allow photosynthesis
e.g. Cyanobacteria (blue green) with apparent internal membranes
What are the various cell shapes found in bacterial cells?
Round, oval, spiral, curved, rods, chains etc
Give some examples of bacterial cell appendages that allow for specialisation
- Some have rotating flagella on surface for motility
- Many Gram- have short ‘fimbriae’ for attachment to surfaces and ‘pili’ for attachment to bacteria
What are some features of archaea (prokaryote)?
- Have many similar features to bacterial cell structure
- Have some unique cell shapes - beached, flat & square
- Have distinct biochemistry - incl cell membranes, DNA molecular differences
- Lack peptidoglycan cell wall
- Found in hostile environments
How are bacterial and archaea cells similar?
Similar:
- Size range
- Shape (rods, round)
Have external flagella and pili
DNA present in nucleoid region, not sep. from cytoplasm
What do archaea cells have instead of the peptidoglycan wall which they lack?
They instead have very diverse outer surface layers
Archaea can be found in hostile environments, give some examples
- Hot volcanic springs
- Airless marine sediments
- Salt lakes
What are eukaryotes like?
Wide variety
Structurally more complex than Prokaryotic cells
What are the features of eukaryotic cell structure?
- Plasma membrane (PM)
- DNA cont in a nucleus, separated from cytoplasm by membrane - DNA present on chromosomes
- Cytoplasm is compartmentalised - features organelles
- Complex cytoskeletal system to maintain cell integrity e.g. microtubules & intermediate & acting filaments
What is the role of the plasma membrane in eukaryote cells?
It delineates the edge of cell cytoplasm
Give some examples of eukaryote cell diversity?
Animal, plant, protist, fungal cells
What are the main constituents in an animal cell?
- Nucleus
- Organelles: mitochondria, Golgi body, peroxisomes, RER & SER, small vacuoles
- Ribosomes
- CENTRIOLES
- Cytoskeleton
What are the main constituents of a plant cell?
- Nucleus
- Organelles: mitochondria, Golgi body, peroxisomes. RER & SER & chloroplasts
- Ribosomes
- Cytoskeleton
- SINGLE LARGE VACUOLE
- RIGID CELLULOSE CELL WALL
What is a model protist cell like?
- Mainly unicellular
- Flexible cell surface with supportive ‘pellicle’
- Some have contractive vacuole
What is a model fungal cell like?
- Unicellular yeasts or filamentous hyphae
- Can contain multiple nucleus per compartment
- Rigid chitin wall
How is multicellularity useful to eukaryotes?
It allows specialisation - cells have different functions within whole organism
The cell structure & biology varies according to the function of the cell
Why do cells differentiate?
As a result of the expression of subsets of genes within the genome
Give 4 examples of specialised functions of cells?
- Movement
- Signalling
- Transport
- Reproduction
How are some cells specialised to movement?
- Some have external projection from the cell surface which undulate to cause movement
e.g. flagella (few & large) or cilia (small & numerous)
Where are flagella and cilia generally found?
Found in unicellular protists/fungi for propulsion & vertebrate tissues incl airways & ears
How are some cell specialised to signalling?
(Neurones)
Nerve cells (neurones): have a central cell body with terminal dendrites & long axon transmitting electrical signals
Length may be > 1 metre
How are some cells specialised for transport?
(RBCs)
RBCs (erythrocytes) specialised for gas transport; lack nucleus & organelles when mature & instead packed full of haemoglobin
Are small (8um) for passage through capillaries
How are some cells specialised for reproduction?
Sperm cells have a flagellum for swimming
Mushroom spores are produced on gills by specialised ‘basidia’ swollen reproductive cells
