L 3: Cell structure and function

Question 1

Fundamental traits of bacteria

Answer 1

Thick, complex outer envelope
Compact genome with little non-coding DNA
No membrane-bound nucleus
Tightly coordinated cell functions

Question 2

Biochemical composition of bacteria

Answer 2

Water
Essential ions (K+, Mg+2, Cl-)
Small organic molecules (lipids, sugars)
Macromolecules (DNA, RNA, protein)

Question 3

Total composition of bacteria

Answer 3

Ranked by concentration:
Water
Proteins
RNA
Lipids
DNA
Metabolites
Peptidoglycan
Inorganic ions
Polyamines

Question 4

What is the structure that defines the existence of a cell and what is it mostly composed of?

Answer 4

Cell membrane
>50% protein

Question 5

Functions of membrane proteins

Answer 5

Structural support for the cell
Detection of environmental signals
Secretion and virulence factors and communication
Ions transport and energy storage

Question 6

Passive transport

Answer 6

Molecules move down concentration gradient

Question 7

Active transport

Answer 7

Molecules move up concentration gradient

Question 8

What energy fuels active transport?

Answer 8

1. Cotransport of another substance down its gradient
2. Coupling transport to energy-yielding chemical reaction

Question 9

Which types of molecules require transport through specific protein transporters?

Answer 9

Polar and charged

Question 10

Membrane proteins

Answer 10

Hydrophilic and hydrophobic regions that lock the protein into the membrane

Question 11

Membrane lipid diversity

Answer 11

Phospholipids vary with respect to their phosphoryl head groups. Some groups combine more than one lipid

Question 12

Saturated fatty acids

Answer 12

No double bonds
Unkinked
Rigid
Ex. Solid butter

Question 13

Unsaturated fatty acids

Answer 13

Double bonds (increase fluidity)
Cyclic structures (decrease fluidity)
Ex. Liquid oil

Question 14

Hopanoids

Answer 14

Add strength to membranes by limiting motion of phospholipid tails and stiffening the membrane

Question 15

Hydrothermal characteristics of archaea

Answer 15

Ether: links between glycerol and fatty acids
Methyl branch: branch strengthens membrane by limiting movement of hydrocarbon chains, found in Terpenoids
Bilayer fusion: forms tetraethers so the membrane is a monolayer
Cyclopentane rings: stiffen membrane

Question 16

Outer layer of prokaryotes

Answer 16

Most species have a cell wall or at least one protective layer
A few prokaryotes have no wall and just a membrane

Question 17

Sacculus

Answer 17

A single interlinked molecule serving as the cell wall, helps cells withstand turgor pressure, cage-like structure is porus to ions and organic molecules

Question 18

Turgor pressure

Answer 18

Caused by osmosis, water rushing into the cell

Question 19

Components of bacterial cell wall

Answer 19

Peptidoglycan: made of polymers of disaccharides (N-acteylglucosamine and N-acetylmuramic acid) bound to a peptide, which then forms cross-bridges connecting to other peptide strands

Question 20

Antibiotics and cell walls

Answer 20

Penecillin and vancomycin block cross bridge reactions from forming, weakening the cell wall

Question 21

Different types of peptidoglycan growth

Answer 21

1. Dispersed zonal: grows in stripes and then splits (break apart cookie dough)
2. Septal zonal growth: from the middle of a circle, splits in half
3. Polar growth: from one end to the other of a bar (rainbow of dyes)

Question 22

Cell envelope types in bacteria

Answer 22

1. Gram-positive: thick cell wall (3-20 layers)
2. Gram-negative: thin cell wall (1-2 layers)
3. Mycobacteria: very complex, multilayered wall
   Spirochetes, cyanobacteria, and archaea are not in the above categories

Question 23

Gram-Positive cell envelope

Answer 23

Multiple layers of peptidoglycan threaded by negatively charged teichoic acids, which retain the gram stain
Capsule made of polysaccharides and glycoproteins, protects cells from phagocytosis bc they are sticky so the cell doesn’t dry out, can be seen using dark field microscopy or negative staining (also found in Gram-negative cells)

Question 24

Gram-negative cell envelope

Answer 24

Think peptidoglycan layer
Outer membrane protects the cells, contains lipopolysaccharides cross-linked by Mg2+ and porin diffusion channels
Inner membrane contains lipoproteins

Question 25

S-layer

Answer 25

Addition protective layer Crystalline layer of thick subunits made of protein Contributes to cell shape and helps protect from osmotic stress

Question 26

Which of the following is not a component of peptidoglycan? A. N-acetylmuramic acid B. N-acetylglucosamine C. Lipopolysaccharide D. Amino acids E. Peptide cross-links

Answer 26

C. Lipopolysaccharide On outer membrane, not cell wall

Question 27

Nucleus

Answer 27

Eukaryotic cells Surrounded by a membrane

Question 28

Nucleoid

Answer 28

Prokaryotic cells Throughout the cytoplasm Condensed circular chromosome with proteins and RNA (still organized)

Question 29

Prokaryotic transcription and translation

Answer 29

Coupled RNA polymerase transcribes DNA into mRNA, which is then bound by a ribosome for translation into a polypeptide

Question 30

Cell fission

Answer 30

Requires highly coordinated growth and expression of all cell parts, coordinated DNA replication and cell wall expansion

Question 31

DNA replication within a dividing prokaryotic cell

Answer 31

Two replication forks are generated in each circular chromosome (4 total spots) leading to 4 offspring

Question 32

Replisome

Answer 32

Protein complex that helps synthesize DNA with DNA polymerase

Question 33

Septation

Answer 33

Last step of cell division, replication of the termination site triggers growth of the septum, which divides the cell into two daughter cells

Question 34

Aging bacteria

Answer 34

Each cell is half new and half old, leading to asymmetry as the cell ages (polar aging)

Question 35

Thylakoids

Answer 35

Extensive folded intracellular membranes found in plant chloroplasts for photosynthesis

Question 36

Carboxysomes

Answer 36

Polyhedral bodies (only found in Rubisco) are packed with the enzyme Rubisco for CO2 fixation. This creates a bubble in the organism so it can float up closer to the sun

Question 37

Sulfur globules

Answer 37

Granules of Sulfur that can be used as an antioxidant and to avoid predation

Question 38

Pili and fimbriae

Answer 38

Straight filaments of protein used in attachment to other things Ex. Sex pili

Question 39

Stalks

Answer 39

Membrane-embedded extensions of the cytoplasm that attach to surfaces and secrete adhesions factors called holdfasts

Question 40

Nanotubes

Answer 40

Intercellular connections that pass material from one cell to another cell

Question 41

Rotary Flagella

Answer 41

If a prokaryote moves, it probably does so via rotary flagella (can be one from one spot, one from two spots, many from one spot, or many from many spots)

Question 42

Magnetosome

Answer 42

Membrane bound organelle that allows bacteria to navigate the Earth's magnetic field Swim along geomagnetic fields to find low oxygen environments because it is toxic to them

Question 43

Classes of organelles in bacteria

Answer 43

Membrane bound Protein bound Lipid monolayer Phase-defined

Question 44

Membrane bound organelles in bacteria

Answer 44

Chromatophores: light driven ATP synthesis Anammoxosomes: NH4 to N2 Magnetosomes: compass needle

Question 45

Protein bound organelles in bacteria

Answer 45

Carboxysomes: carbon fixation Metabolosomes: diverse enzymatic reactions Iron nanocompartments: protect from oxidation

Question 46

Lipid monolayer organelles in bacteria

Answer 46

Chlorosomes: light driven ATP synthesis Lipid bodies: lipid homeostasis

Question 47

Phase-defined organelles in bacteria

Answer 47

Cell makes membraneless organelle that would not survive outside of the cell