Bacterial & Eukaryotic Cell Structure Flashcards
Do bacteria contain membrane-bound organelles?
No
What cellular components do bacteria have?
Cell wall, cell membrane, fimbrae, flagella, cytoplasm, ribosomes, DNA in a nucleoid region
How does compartmentalization differ between eukaryotic and prokaryotic cells?
Eukaryotes have compartmentalization
How does a bacterial flagellum move?
i) rotates like a corkscrew to allow movement
ii) rotation about hook causes movement
iii) basal apparatus anchors flagellum into the cell
What is a polymer of flagellin?
A filament
What is the basal apparatus?
Anchors a bacterial flagellum onto the cell and contains a gear system that drives the hook
Where does energy come from to power the basal apparatus?
Energy for rotation comes from the H+ gradient
What is the difference between a Gram-positive and a Gram-negative cell?
Gram-positive has a thick layer of peptidoglycan whereas Gram-negative cells have a thin layer and an extra outer membrane
What is a Gram-positive cell?
A bacterial cell with a thick layer of peptidoglycan
What is peptidoglycan?
A polymer of NAG:NAM sugars (polysaccharide)
What molecule links the layers of peptidoglycan together?
Teichoic acid
What molecule links peptidoglycan to the cell membrane?
Lipoteichoic acid
What molecule forms cross-bridges in peptidoglycan?
Peptides
What is a Gram-negative cell?
A bacterial cell with a thin layer of peptidoglycan and an outer membrane
What is the outer membrane of a Gram-negative cell composed of?
Inner phospholipids are regular but facing the outside, there are lipopolysaccharides that are negatively charged
What prevents repulsion between negatively charged lipopolysaccharides in a Gram-negative cell?
The association of divalent cations such as Mg2+
What is a substance that kills bacterial pathogens by targeting bacterial-specific structures?
An antibiotic
How do antibiotics work?
Disrupts the formation of bacterial ribosomes (protein synthesis) or bacterial cell wall (peptidoglycan)
What are hair-like structures that allow attachment in bacterial cells?
Fimbrae
What is biofilm (slime cities)?
Bacterial cells secrete a mucous that surrounds the cell known as the capsule
What is the function of biofilm?
Protects the cell from dehydration and allows attachment
What is the microbiome?
The collection of organisms normally found on our body
How does the colonization of bacteria begin at birth?
Through the birth canal and feeding
What is normal flora in our microbiome?
It is the “good bacteria” living on our body that produce inhibitory compounds like toxins and organic acids that prevent the growth of pathogens
What are some functions of normal flora?
i) prevents the growth of pathogens
ii) required for developmental processes
iii) provides vitamins and nutrients
iv) helps train immune system to distinguish harmful vs friendly
What is the hygiene hypothesis?
Exposure to microbes help maintain a healthy immune system
What was the reason why adaptation was necessary 2.4 billion years ago?
O2 was accumulating in the atmosphere and it is toxic to all cells
Where did organelles come from?
The endomembrane system and the endosymbiotic organelles
What is the endomembrane system?
Infoldings that fused to create internal membranes (outer nuclear membrane, ER, Golgi, and lysosome)
What are endosymbiotic organelles?
The mitochondria and chloroplast which arose from a primitive prokaryote living inside a primitive eukaryote (archean relative)
What is the endosymbiont hypothesis?
The mitochondria have very efficient metabolism and the archeal cell had space and protection from O2. In eukaryotic cells, mt and cp have prokaryote-like ribosomes and gene organization
What are the functions of the nucleus?
To store DNA and it is the site of gene expression
What is the structure of the nucleus?
Double membrane-bound sphere and the outer membrane is continuous with the ER
What are the nuclear pore complexes?
Transmembrane complexes that span both bilayers of the nucleus which allow non-selective transport
Where is the site of ribosomal assembly?
Nucleolus
How are ribosomes formed in the nucleolus?
Ribosomal subunits independently enter NPCs and the subunits form complexes with rRNA at the nucleolus and leave together for translation
What is the function fo the nuclear envelope?
To separate the nucleoplasm from the cytoplasm (2 layers)
What lines the inner membrane of the nuclear envelope and provides structural protection?
Nuclear lamina
What is chromatin packaging?
Packages and protects DNA
What are the four orders of chromatin packaging?
i) nucleosome: DNA wraps around a histone octomer
ii) solenoid/30 nm fibre: nucleosomes stack with help of Histone H1
iii) looped domains: 30 nm fibre loops off a non-histone protein scaffold
iv) mitotic chromosome: fully condensed chromosome
What is a histone octomer?
Contains 2 of each: H2A, H2B, H3, H4 positively charged proteins
What is the difference between the rough and smooth ER?
Rough has ribosomes and smooth does not involve any protein synthesis at all
What are bound ribosomes?
Ribosomes that make proteins for exports or endomembrane system
What are free ribosomes?
Ribosomes that make proteins for cytoplasm or nucleoplasm
What are the functions of the SER?
i) ion storage (Ca2+)
ii) phospholipid synthesis
iii) steroid synthesis
iv) detoxification of drugs and alcohol
What is the structure of the Golgi?
A set of flattened membrane-bound compartments called cisternae
What is the function of the Golgi?
i) receives cargo from the ER
ii) sorts cargo according to destinations (lysosome, membrane, or back to ER)
iii) packages cargo into vesicles
What are the two models of Golgi Trafficking?
Vesicle Trafficking and Cisternae Maturation
What is vesicle trafficking in the Golgi?
Small vesicles are associated with the Golgi and they carry cargo between cisternae
What is cisternae maturation in the Golgi?
The fusion of vesicles from the ER form cis-cisternae and they go down the Golgi never leaving their cisternae as the bottom ones vesiculate
What is the function of the lysosome?
Involved in the digestion of macromolecules from endocytosis
What does the lysosome contain?
Contains hydrolytic enzymes that function best at pH 5.0
How does the lysosome maintain its pH?
It actively pumps in H+ to maintain low pH
What is the term for cell suicide?
Autophagy
How can a cell commit suicide?
By rupturing its lysosomes
