Structure and function of microbial cells Flashcards
if we look at different kind of cells, can we identify properties that are shared by all cells?
Yes
Properties of all cells: 3
metabolism: cells take up nutrients, transform them, and expel waste
growth: nutrients in the environment are converted into new cell material to form new cells
evolution: cells evolve to display new properties.
Name the two types of metabolism
genetic: replication, transcription, translation
catalytic: energy biosynthesis
How would you capture evolutionary relationships?
Phylogenetic
Name properties that some cells have in common:
differentiation: some cells can form new cell structures such as pores
communication: cells interact with each other by chemical messenger
genetic exchange: cells can exchange genes by several mechanisms (donor->recipient)
motility: self-propulsion (flagellum)
whats is the genetic function of cells?
multiply and encode DNA=> DNA replication to make new proteins and DNA transcription of RNA than translation to make new proteins
what is the catalytic functions of cells?
energy conservation: ADP+Pi=>ATP
metabolism: generation of precursors of macromolecules
enzymes: metabolic catalyst
How does the surface affect molecule exchange with the outside?
bigger the volume, the relatively less surface you have.
Surface/volume=…..
Procaryote vs Eucaryote Internal structure of cells
cell wall, cytoplasmic membrane, ribosome, nucleoid, cytoplasm, plasmid
vs.
cell wall, cytoplasmic membrane, ribosome, cytoplasm, mitochondrion, nuclear membrane, nucleus, endoplasmic reticulum, Golgi complex
name and explain 3 characteristics of the membrane
permeability: prevents leakage and functions as a gateway for for transport nutrient into, and waste out of, the cell
protein anchor: site of many proteins that participate in transport bioenergetics, and chemotaxis
energy conservation: site of generation and use of the proton motive force
name 4 protein anchors
Sensors
• Adhesins
• Transporters
• Enzymes
whats the Ratio proteins/lipids
50% or less
what is the membrane mad of?
phospholipid bilayer=> PHOSPHATIDYLETHANOLAMINE=> 2 FA+glycerol+phosphate+ethanolamine
what type of bond do you find in bacteria eukaria and archaea
double ester bond and single ester bond respectively
what is the archaeal lipid chain made of?
Isoprene
what are the 5 variation of the Membrane of Archaea?
glycerol diether: glycerol+phytanyl (CH3 groups and isoprene units)
diglycerol tetraethers: 2 glycerol + biphytanyl
crenarchaeol:
lipid bilayer: glycerolphosphate+phytanyl+membrane protein
lipid monolayer: biphytanyl+membrane protein
In eukaryotes, the lipid bilayer is stabilized by…
a sterol, which consists of a polar head, a rigid planar steroid ring structure and a nonpolar hydrocarbon tail.
name 3 types of sterols found in eukaryotes
– Cholesterol – Animal cells
– Ergosterol – Fungi
– Stigmasterol – Plant cells and some protozoans
In bacteria the membrane is stabilized by …
hopanoids.
Are there any sterols in the membrane of a bacteria
almost always absent.
Storage of DNA in Bacteria and Archaea:
– Circular molecule, double
stranded.
– Generally haploid (one copy)
– Packaged with proteins (H‐NS and other Histone‐like protein), aggregates to form the nucleoid), = the chromosome
– DNA in the cytoplasm, ribosomal RNA encoded on the chromosome
– May also contain plasmids
Storage of DNA in Eukaryotes:
– Linear molecules, double‐
stranded.
– Generally diploid (two copies)
– Packaged with proteins (Histones) to form chromatin fibers, = the chromosome.
– DNA in the nucleus
– Nucleolus: (dense DNA that codes for ribosomal RNA, ribosomal proteins, immature ribosome)
How do all living things produce protein from DNA ?
Replication by DNA polymerase
Transcription of bottom strand by RNA polymerase to make RNA
Translation by Ribosome to make protein
what is the ribosome composed of?
Composed of ribosomal RNA and proteins
What is the role of the ribosome?
location in Eukaryotes
location in Procaryotes
Role is to translate mRNA into amino acid chains in order to form proteins.
– Prokaryotes: ribosomes are free in the cytoplasm or attached to cytoplasmic membrane.
– Eukaryotes: ribosomes are free in the cytoplasm or bound to the endoplasmic reticulum.
What is the S equation of Procaryotes and Eukaryotes?
Prokaryotes: 70S ribosome = 30S + 50S subunits
Eukaryotes: 80S ribosome = 40S + 60S subunits
What is the last common universal ancestor?
LUCA
The eukaryotic cell has organelles, which are they?
Organelle Function
Nucleus The “brains” of the cell, the nucleus directs cell activities and contains genetic material called chromosomes made of DNA.
Mitochondria Make energy out of food
Ribosomes Make protein
Golgi Apparatus Make, process and package proteins
Lysosome Contains digestive enzymes to help break food down
Endoplasmic Reticulum Called the “intracellular highway” because it is for transporting all sorts of items around the cell.
Vacuole Used for storage, vacuoles usually contain water or food. (Are you are thirsty? Perhaps your vacuoles need some water!)
*learn drawing
The eukaryotic cell wall function
A cell wall surrounds cell of plants, algae, fungi, but is absent in animals and most protozoa.
The cell wall forms a tough, rigid barrier that helps protect the cell and give its shape
The eukaryotic cell wall composition
The cell wall of eukaryotes is usually composed of polysaccharides.
• Diversity of cell wall molecules:
– Plants, algae and some fungi: cellulose (polymer of glucose).
– Fungi: chitin (polymer of N‐acetylglucosamine).
– Also cell walls made of galactose, mannose, etc.
How is the DNA stored in the nucleus?
Summary: DNA wraps around histones, which form loops of DNA called nucleosomes. These nucleosomes coil and stack together to form fibers called chromatin. Chromatin in turn forms larger loops and coils to form chromosomes
Euchromatin vs Heterochromatin
- Euchromatin: loosely packed, actively transcribed.
* Heterochromatin: densely packed, low level of transcription.
Translation for cytoplasmic proteins vs membrane proteins, secreted proteins or vesicular proteins
- In the case of cytoplasmic proteins: ribosome‐mRNA complex stays free in the cytoplasm.
- In the case of membrane proteins, secreted proteins or vesicular proteins: ribosome‐mRNA complex is directed to the ER.
The endoplasmic reticulum, what is it?
The endoplasmic reticulum (ER) is a system of membranous channels. The membrane is composed of a bilayer of phospholipid.
rough vs smooth ER
- Rough ER: studded with ribosomes, important for protein synthesis.
- Smooth ER: no ribosomes, involved in synthesis of lipid.
What happens in the rough ER? 6 steps
- mRNA leaves nucleus, and attaches to ribosome; protein synthesis begins
- Signal recognition particle (SRP) binds to signal peptide
- SRP attaches to receptor translocation channel opens; polypeptide enters ER.
- A signal peptidase removes the signal peptide.
- Ribosome subunits and mRNA break away.
- Protein folds into final shape
Function of ER (2)
protein synthesis and protein modification (e.g. glycosylation, and maturation)
What is the Golgi body?
The Golgi body is a set of membrane compartments involved in further processing of proteins and their distribution. Proteins are packaged in vesicles and transported to where they are required.
What are lysosomes and how are they brought in?
lysosomes are internal vesicles that contains hydrolytic enzymes required for degradation of materials brought in by phagocytosis and endocytosis.
Mitochondria function
Produce most of the ATP required by the cells.
Outer membrane of mitochondria composition and function
Outer membrane: many porin proteins, makes this membrane very permeable to small molecules.
Inner membrane of mitochondria composition and function
Inner membrane: 75% proteins, 25% lipids.
Transport proteins (regulated transport),
enzymes, cytochromes, ATPases. (Similar proteins are found in the membrane of XH2 bacteria and archaea)
matrix of mitochondria composition and function
enzymes (citric acid cycle), DNA, ribosomes (70S).
can mitochondria synthesize their own proteins?
Yes, but the remaining ones are imported from the cytoplasm of the cell (they are encoded on its genome).
Chloroplast: where is it present?
Present in phototrophic eukaryotes (plants, algae).
Chloroplast outer membrane: composition and function
Outer membrane: porins, similar to mitochondria (makes this membrane very permeable to small molecules)
Chloroplast inner membrane: composition and function
Inner membrane: transport proteins (regulated transport).
Chloroplast Stroma: composition and function
Stroma: circular DNA, 70S ribosomes, enzymes of the Calvin cycle (assimilation of CO2, biosynthesis).
Chloroplast Thylakoids: composition and function
Thylakoids: closed system of interconnecting sacks and tubules.
Contain enzymes and pigments that harvest light energy and the membrane‐ bound ATPases that use this energy to produce ATP.
Similar proteins are found in many photosynthetic prokaryotes, usually in the cytoplasmic membrane.
can chloroplast synthesize their own proteins?
Chloroplasts are able to synthesize some of their own proteins (their own circular DNA!), the remaining ones are imported from the cytoplasm of the cell.
Eukarya vs Archaea evolution
nucleus formed in eukarya
Acquisition of mitochondria and chloroplasts: what theory supports this?
“Endosymbiotic theory”
Eukaryotic cytoskeleton composition and function
The cytoplasm contains a complex network of protein filaments that helps organize the cytoplasm and give the cell its shape.
Proteins found in cytoplasm that form the cytoskeleton
- Microtubule: α‐tubulin, β‐tubulin.
- Actin filament: actin.
- Intermediate filament: keratin, desmin, vimentin.
- Similar proteins are found in several non‐spherical prokaryotes.
where do microtubules grow from?
centrosome
what do intermediate filaments in the microtubule do?
anchor the nucleus
function of microtubules
Microtubules serve as “highways” for the transport of organelles and vesicles around the cytoplasm. Kinesin and dynein are two proteins that attach to vesicles or organelles and “walk” on microtubules, transporting their cargos to where they are required.
how many step microtubules need to take to cross whole cell?
Max 5 s to cross the whole cell
what does one alpha and beta tubule form?
doublet microtubule
how many doublet microtubules in eukaryotes?
- 9 sets of microtubule doublets.
* 9 + 2 construction
what covers the cilliim and surrounds the microtubule?
plasma membrane
how does the dynein create movement?
The dynein arms slide the doublets past each other, creating movement.
how do bacteria move around?
flagella and cilia
