Components of the cell (II) Flashcards
What are the 2 groups of bacteria?
Archaebacteria, Eubacteria
What are the 3 common shapes of bacteria?
- Rod shape called bacillus (bacilli)
- Spiral shape
- Sphere shape called coccus (cocci)
What are the components of a prokaryotic cell? (8)
Cell wall Cell/cytoplasmic membrane Capsule Cytoplasm Chromosomal DNA Ribosome Flagella Pili
Describe the structure of the cell wall
Contains tiny pores
Works like a filter
Tough flexible and sometimes rigid
What is the function of the cell wall?
Allows wastes to flow out
Maintains cell shape
Allow water and dissolved substances to flow into the cell
Provides cell with structural support, protection and filtering mechanism
What is the key chemical component in bacteria cell?
Peptidoglycan
Gram positive and Gram negative
2 large groups of bacteria (gram positive and negative) are differentiated based on their different cell wall constituents
Differences between gram positive and gram negative bacteria:
Gram positive
purple stain
thick layer of peptidoglycan
Teichoic acid is present
Outer membrane is absent
Lipopolysaccharide (endotoxin) is absent
Porin protein is absent (unnecessary as there is no outer membrane)
Gram negative
pink stain
thin layer of peptidoglycan
Teichoic acid is absent
Outer membrane is present
Lipopolysaccharide (endotoxin) is present
Porin protein is present (allow molecules to pass through outer membrane)
Examples of gram positive bacteria:
Rods:
Bacillus
Clostridium
Diphtheria
Cocci:
Staphylococci
Streptococci
Entercocci
Examples of gram negative bacteria:
Rods:
Proteus
E coli Escherichia
Salmonella
Cocci:
Neisseria
Moraxella
Describe the structure of the cell membrane:
composed of 2 layers of flexible (fluid like) lipid molecules (phospholipid bilayer)
- polar heads facing watery medium
- non polar tails face each other
What is the function of the cell membrane?
-Separates the cell’s contents from its surrounding fluids
-Selectively permeable, allows easy diffusion of small, non polar molecules
-Regulates passage of larger or charged molecules
different to eukaryotic cell: they have sterols cholesterol
What is the function of the capsule?
[] Polysaccharide layer that lies outside the cell envelope
- Thick covering of cell wall that protect bacteria from white blood cells, chemicals and dehydration
- Sticky nature allows it to adhere to other cells or surfaces
Describe the structure and function of the cytoplasm:
[] Semi fluid (jelly like solution) that fills the cell
- contain cytosol and insoluble components
- composed of 65 % water (favourable conditions for chemical reactions to occur)
function: responsible for cell growth, metabolism, elimination of waste and replication (reproduction) of the cell.
What is chromosomal DNA?
It is also called nucleoid (nucleus like). It consists of only DNA
- Not enclosed by a membrane
- Located within the cytoplasm
Describe the structure of Bacterial DNA:
Composed of 1 single coiled chromosome located in nucleoid region and multiple copies of circular DNA (plasmids)
What are plasmids?
short def: naturally occurring extrachromosomal DNA molecules, small, circular and double stranded
-often associated with conjugation, a mechanism of horizontal gene transfer
function:
- carry genes that build resistance against antibiotics or poisons
- code for protein that can kill other bacteria
- enable digestion of unusual substances
- turn the host of the plasmid into a pathogen
Function of ribosome:
- only organelle in prokaryotes
- protein factory, site for synthesis of proteins
Function of the Flagella:
Main role is locomotion (movement of bacteria)
serves as a “sensory unit”
“choose” to move forward towards a favorable environment or away from a hostile
-most cocci don’t have this, they are non mobile
Name an application of plasmids in real life:
production of human insulin in bacteria by inserting insulin genes into plasmid vector then transfer them into bacterial cells for mass production of insulin
Steps to using plasmids as a vector for production:
- cut plasmid using restriction enzymes
- insert gene/ plasmid into vector
- ligase joins them together
- plasmid vector- bacterial cells mass production
Describe how the structure of Pili serves its function:
- Hair like projections surrounding the outer layer of the cell
- Enables bacteria to stick on surfaces or latch on other cells
- Also involved in process called “conjugation” where genetic material is transferred from 1 bacterium to another
What do you call a bacteria with one or more pilis?
one pili- monotrichous
two- amphitrichous
four-lophotrichous
more… peritrichous
What components of plant cell is not in animal cell?
- central vacuole
- cell wall
- chloroplast
