1.2 cell structure Flashcards
what kingdom are prokaryotes?
Monera
what are the 2 domains of prokaryotes?
Archaebacteria – found in extreme environments like high temperatures, salt concentrations or pH (i.e. extremophiles)
Eubacteria – traditional bacteria including most known pathogenic forms (e.g. E. coli, S. aureus, etc.)
how do prokaryotes reproduce?
via binary fission
describe the process of binary fission
- The circular DNA is copied in response to a replication signal
- The two DNA loops attach to the membrane
- The membrane elongates and pinches off (cytokinesis), forming two cells
prokaryotic features (9)
Cytoplasm, nucleoid, plasmids, ribosomes, cell membrane, cell wall, slime capsule, flagella, pili
compartmentalization
having membrane-bound organelles
benefits of compartmentalization
efficiency of metabolism
localised conditions (pH, osmolarity, etc.)
number and location of organelles can be changed.
how did eukaryotes evolve from prokaryotes
via endosymbiosis
4 kingdoms of eukaryotes
protista, fungi, plantae, animalia
universal organelles (prokaryote & eukaryote)
ribosomes, cytoskeleton, plasma membrane
eukaryotic organelles (plant & animal)
nucleus, ER, golgi apparatus, mitochondrion, peroxisome, centrosome
plant-cell-only organelles
chloroplast, vacuole, cell wall
animal-cell-only organelle
lysosome
ribosomes
Structure: Two subunits made of RNA and protein; larger in eukaryotes (80S) than prokaryotes (70S)
Function: Site of polypeptide synthesis (this process is called translation)
cytoskeleton
Structure: A filamentous scaffolding within the cytoplasm (fluid portion of the cytoplasm is the cytosol)
Function: Provides internal structure and mediates intracellular transport (less developed in prokaryotes)
plasma membrane
Structure: Phospholipid bilayer embedded with proteins (not an organelle per se, but a vital structure)
Function: Semi-permeable and selective barrier surrounding the cell
nucleus
Structure: Double membrane structure with pores; contains an inner region called a nucleolus
Function: Stores genetic material (DNA) as chromatin; nucleolus is site of ribosome assembly
endoplasmic reticulum
Structure: A membrane network that may be bare (smooth ER) or studded with ribosomes (rough ER)
Function: Transports materials between organelles (smooth ER = lipids ; rough ER = proteins)
golgi apparatus
Structure: An assembly of vesicles and folded membranes located near the cell membrane
Function: Involved in the sorting, storing, modification and export of secretory products
mitochondrion
Structure: Double membrane structure, inner membrane highly folded into internal cristae
Function: Site of aerobic respiration (ATP production)
peroxisome
Structure: Membranous sac containing a variety of catabolic enzymes
Function: Catalyses breakdown of toxic substances (e.g. H2O2) and other metabolites
centrosome
Structure: Microtubule organising centre (contains paired centrioles in animal cells but not plant cells)
Function: Radiating microtubules form spindle fibres and contribute to cell division (mitosis / meiosis)
chloroplast
Structure: Double membrane structure with internal stacks of membranous discs (thylakoids)
Function: Site of photosynthesis – manufactured organic molecules are stored in various plastids
vacuole
Structure: Fluid-filled internal cavity surrounded by a membrane (tonoplast)
Function: Maintains hydrostatic pressure (animal cells may have small, temporary vacuoles)
cell wall
Structure: External outer covering made of cellulose (not an organelle per se, but a vital structure)
Function: Provides support and mechanical strength; prevents excess water uptake
lysosome
Structure: Membranous sacs filled with hydrolytic enzymes
Function: Breakdown / hydrolysis of macromolecules (presence in plant cells is subject to debate)
draw a prokaryotic cell
see ipad
what does the S in 70S and 80S ribosome stand for?
Svedberg units
What type of DNA replication takes place during binary fission?
semi-conservative
resolution
Resolution is the ability to distinguish between two points in a microscope’s field of view.
What is the difference between prokaryotic and eukaryotic DNA?
Eukaryotic DNA is associated with histones, whereas prokaryotic DNA is not.
disadvantage of using an electron microscope to observe organisms and cells
Specimens cannot be viewed in full, natural colour.
which has a higher resolution: light or electron microscope?
electron microscope
What is the destination of a protein synthesised by free ribosomes?
cytoplasm, lysosomes, mitochondria, chloroplasts and the nucleus
The smooth endoplasmic reticulum is responsible for the synthesis and storage of:
lipids and steroids
