Cell Structure Flashcards
Describe the plasma membrane?
Is a phospholipid bilayer. Purpose is similar in eukarya and prokaryotes. Selective barrier through which materials exit and enter
Describe the cytoplasm.
Includes everything inside the plasma membrane with the exception of the nucleus
Describe the generic eukaryotic cell
Flagellum Mitochondria Ribosomes Nucleus Nucleolus Plasma membrane
Describe the generic prokaryotic cell
Ribosomes Fimbria Nucleoid Cytoplasm Flagellum
Describe the cell structure of the prokaryote
One circular chromosome, not in a membrane No histones No organelles Peptidoglycan walls is bacteria Pseudomurin cell walls if archaea Binary fission Ribosomes size 70s
Describe the cell structure of the eukaryote
Paired chromosomes, in nuclear membrane Histones Organelles Polysaccharide cell walls if plants Chintinous cell walls if fungi Mitotic spindle/ mitosis/ meiosis Ribosomes size 80s
What is the average size of prokaryotic cells?
0.2 - 1.0 um to 2 - 8 um in length
Most bacteria are monomorphic (one shaped)
A few are pleomorphic (many shaped)
What are the 3 names for bacterial shapes?
- Bacillus (rod shaped)
- Coccus (spherical)
- Spiral, which can be vibrio with one bend, spirillum with 2 bends or spirochete with multiple bends
What are some of the cell arrangements for bacteria?
Pairs - diplococci (round) or diplobacilli (rods)
Clusters - staphylococci. Clusters of spherical cells
Chains. Streptococci (chains of spherical cells) or streptobacilli (chains of rod shaped cells)
Tetrads (4’s)
Sarcinae (8’s)
Describe the structure and function of the glycocalyx
Outside cell wall - sticky slime layer, unorganised and loose.
Capsule - neatly organised.
Extracellular polysaccharide allows cell to attach
Capsules prevent phagocytosis - evading immune systems macrophages
E.g plaque on teeth
Describe the structure of prokaryotic flagellum.
Rotates Outside cell wall Made of chains of protein - flagellin Attached to a protein hook Anchored to the wall and membrane by the basal body
What are the 4 types of bacteria flagella arrangements?
- Peritrichous - around, all over the cell
- Monotrichous and polar - being one flagella. Polar being one or at both ends
- Lophotrichous - a tuft of flagella. May be polar as well. Either at one or both ends.
- Amphitrichous - at both ends or polar.
What are axial filaments?
Bundles of fibrils that arise at the ends of the cell. Also called endoflagella
They are in spirochetes
Anchored at one end of a cell.
Rotation causes cell to move
What are fimbriae?
Generally many small projections not visible under light microscopes.
Facilitate attachment to surfaces or cells
What are pili?
Hair like appendages. Shorter, straighter and thinner.
Tube like for sex. Composed of protein pilin
What is conjugation pili?
DNA passed from one cell to another through these tubs. Can pass genetic determinants
Describe the function and main parts of the bacterial cell wall.
Prevents cell rupturing, shape and point of anchorage for flagella.
Prevents osmotic lysis
Made of peptidoglycan - in bacteria
Synthesis is inhibited by the antibiotic penicillin
Describe the repeating disaccharide that makes up peptidoglycan
It’s a polymer consisting of
N-acetylglucosamine (NAG)
N-acetylmuramic acid (NAM)
What is gram staining?
A technique used to differentiate between bacterial types based on the composition of their cell walls
Describe gram positive cell walls.
Retain crystal violet stain - thick peptidoglycan in wall.
NO outer membrane
Teichoic acid crosslinks
More susceptible to penicillin which blocks synthesis or peptidoglycan - cells lose
Describe gram negative cell walls
Outer membrane blocks purple dye
Thin layer of peptidoglycan
Periplasmic space - turns red after wash
Outer membrane contains lipopolysaccharide
What are the basics of endosymbiotic theory?
Prompted by Lynn Marguilis
Mitochondria and chloroplast have prokaryotic features. They also have their own piece of DNA which allows them to self replicate, independent of cell replication
Suggested - prokaryotes were engulfed by an ancient eukaryote, or alternatively, invaded by one
Then 2 organisms had a selective advantage, eg, survive and reproduce in their niche.
What organelles are linked to the endosymbiotic theory?
Mitochondria and chloroplasts
Describe the structure and function of the nucleus. Eukaryote cell.
S -bound by a double membrane called the nuclear envelope.
F - DNA storage and RNA synthesis
