Bacterial & Eukaryotic Cell Structure Flashcards by Jenna Davidson

Do bacteria contain membrane-bound organelles?

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What cellular components do bacteria have?

Cell wall, cell membrane, fimbrae, flagella, cytoplasm, ribosomes, DNA in a nucleoid region

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How does compartmentalization differ between eukaryotic and prokaryotic cells?

Eukaryotes have compartmentalization

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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

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What is a polymer of flagellin?

A filament

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What is the basal apparatus?

Anchors a bacterial flagellum onto the cell and contains a gear system that drives the hook

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Where does energy come from to power the basal apparatus?

Energy for rotation comes from the H+ gradient

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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

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What is a Gram-positive cell?

A bacterial cell with a thick layer of peptidoglycan

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What is peptidoglycan?

A polymer of NAG:NAM sugars (polysaccharide)

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What molecule links the layers of peptidoglycan together?

Teichoic acid

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What molecule links peptidoglycan to the cell membrane?

Lipoteichoic acid

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What molecule forms cross-bridges in peptidoglycan?

Peptides

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What is a Gram-negative cell?

A bacterial cell with a thin layer of peptidoglycan and an outer membrane

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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

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What prevents repulsion between negatively charged lipopolysaccharides in a Gram-negative cell?

The association of divalent cations such as Mg2+

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What is a substance that kills bacterial pathogens by targeting bacterial-specific structures?

An antibiotic

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How do antibiotics work?

Disrupts the formation of bacterial ribosomes (protein synthesis) or bacterial cell wall (peptidoglycan)

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What are hair-like structures that allow attachment in bacterial cells?

Fimbrae

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What is biofilm (slime cities)?

Bacterial cells secrete a mucous that surrounds the cell known as the capsule

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What is the function of biofilm?

Protects the cell from dehydration and allows attachment

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What is the microbiome?

The collection of organisms normally found on our body

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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