Lecture 2A: Microbial Nutrients and Nutrient Uptake Flashcards
Membrane Transport, Nutrient Uptake and Protein Secretion
1
Q
Are required in large amounts (in culture media, usually represented in gram-amounts)
A
Macronutrients
2
Q
Are required in minute amounts (in culture media, usually represented in milligram-amounts)
A
Micronutrients
3
Q
O and H usually from H2O
Cell Nutrition
A
Macronutrients
4
Q
Other macronutrients needed by cells but typically in smaller amounts (4)
A
- Phosphorus (P)
- Sulfur (S)
- Potassium (K)
- Magnesium (Mg)
Please Stop Kissing My Giraffe
5
Q
Are essential nutrients for only a few organisms, such as the NaCl requirement of most marine microorganisms. (2)
A
- Calcium (Ca)
- Sodium (Na)
6
Q
Elements essential for all microorganisms (7)
A
- hydrogen (H)
- oxygen (O)
- carbon (C)
- nitrogen (N)
- phosphorus (P)
- sulfur (S)
- selenium (Se)
“HOy, COng, NAg-PAsok Siya ng Sili!”
7
Q
What element makes up the largest percentage of a cell’s dry weight?
A
Carbon (50%)
8
Q
What percentage of a cell’s wet weight is water?
A
75%
9
Q
What are the four main macromolecules in a cell? (4)
Indicate their building blocks
A
- Proteins: amino acid
- nucleic acids: nucleotides
- lipids: fatty acids
- polysaccharides: sugars
10
Q
How do most prokaryotic cells obtain carbon?
A
By breaking down polymeric substances or directly taking in monomeric constituents
11
Q
Essential Elements: _____ and _____ are next (combined, 25% of dry weight), and ____ follows (13%).
A
- Oxygen (O)
- Hydrogen (H)
- Nitrogen (N)
12
Q
Although required, ______________________ combine for less than ______ of a cell’s dry weight.
Essential elements in small amounts; percentage
A
- Phosphorus (P)
- Sulfur (S)
- Potassium (K)
- Magnesium (Mg)
- 5%
Please Stop Kissing My Giraffe
13
Q
At least ______ other elements either are required by one or more microorganisms or, if not required, are still metabolized in some way
A
50
14
Q
Essential cations/anions for most microorganisms (5)
A
- Sodium (Na)
- Magnesium (Mg)
- Potassium (K)
- Calcium (Ca)
- Chlorine (Cl)
Never Make King Charles Cry Loudly.
15
Q
Trace metals - some essential for microorganisms (Give only 5)
If you can name all 9 elements…
A
- Iron (Fe)
- Cobalt (Co)
- Copper (Cu)
- Nickel (Ni)
- Zinc (Zn)
other: Manganese (Mn), Molybdenum (Mo), Vanadium (V), Tungsten (W)
16
Q
Elements used for special functions in microorganisms (Give only 5)
If you can name all 11 elements…
A
- Boron (B)
- Fluorine (F)
- Silicon (Si)
- Arsenic (As)
- Strontium (Sr)
other: Barium (Ba), Cadmium (Cd), Lanthanum (La), Cerium (Ce), Praseodymium (Pr), Neodymium (Nd)
BF Si As Sr
17
Q
Elements unessential but metabolized (Give only 3)
A
- Lithium (Li)
- Beryllium (Be)
- Aluminum (Al)
LiBerAl
18
Q
Elements unessential and not metabolized (Give only 3)
A
- Helium (He)
- Neon (Ne)
- Argon (Ar)
- Krypton (Kr)
- Xenon (Xe)
- Radon (Rn)
19
Q
Macromolecular composition of a cell (6)
From highest to lowest dry weight percentage
A
- Protein (55%)
- RNA (20.5%)
- Lipid (9.1%)
- Polysaccharide (5.0%)
- Lipopolysaccharide (3.4%)
- DNA (3.1%)
PeaRL PauL’s Dick
20
Q
Which is more abundant in a cell, DNA or RNA?
A
RNA
21
Q
What is the most abundant macromolecule in a bacterial cell?
A
Protein
22
Q
Which macromolecule primarily stores genetic information?
A
DNA
23
Q
What macromolecule forms ribosomes and helps in protein synthesis?
A
RNA
24
Q
What macromolecule makes up the bacterial cell membrane?
A
Lipids
25
What macromolecule serves as an energy source and structural component in bacterial cells?
Polysaccharide
26
Carbon source from _____________ compounds for most prokaryotes
| Macronutrients
organic compounds
27
Cells obtain organic carbon from the breakdown of polymeric substances (________________) or from the direct uptake of their monomeric constituents: _________ (6)
| Macronutrients
* catabolism
- amino acids
- fatty acids
- organic acids
- sugars
- nitrogen bases
- aromatic and other compounts
28
Some microbes are ______________ and can synthesize their own organic compounds from carbon dioxide (CO2).
| Macronutrients
autotrophs
29
What are the three main sources of nitrogen for microorganisms?
Bulk of nitrogen available in nature is as ___________ _____ , _________, or ______________.
| Macronutrients
- ammonia (NH3)
- Nitrate (NO3-)
- Nitrogen gas (N2)
30
The process where bacteria convert atmospheric nitrogen (N₂) into a usable form.
Nitrogen fixation
31
What is the most important trace metal in cellular respiration?
| Micronutrients: Trace Metals and Growth Factors
Iron (Fe)
32
What is the primary function of trace metals in microbial cells?
| Micronutrients: Trace Metals and Growth Factors
act as enzyme cofactors
33
Growth factors are __, while trace metals are __.
| Micronutrients: Trace Metals and Growth Factors
- organic micronutrients
- inorganic
34
___________ (organic rather than metallic) such as vitamins, amino acids, purines, pyrimidines
| Micronutrients: Trace Metals and Growth Factors
Growth factors
35
What is the most commonly required type of growth factor?
| Micronutrients: Trace Metals and Growth Factors
Vitamins
36
What role do vitamins play in microbial cells?
| Micronutrients: Trace Metals and Growth Factors
function as enzyme cofactors
37
Name three types of organic molecules that can serve as growth factors. (3)
| Micronutrients: Trace Metals and Growth Factors
- Amino acids
- purines
- pyrimidines
| other: vitamins
38
Which bacterial genera have extensive vitamin requirements? (3)
| Micronutrients: Trace Metals and Growth Factors
- *Streptococcus*
- *Lactobacillus*
- *Leuconostoc*
39
Give examples of growth factors (4)
| Micronutrients: Trace Metals and Growth Factors
- PABA (paminobenzoic acid)
- Folic acid
- Biotin
- B12 (Cobalamin)
- B1 (Thiamine)
40
If a cell is to grow and divide, it must take up its __ and __ from the environment.
| Nutrient Transport through the Cell Membrane
- macronutrients
- micronutrients
41
- __________________of the cell membrane serves as a challenge for nutrient transport.
- Concentration of a given nutrient in the cytoplasm is often much __________ than its concentration in the environment for simple transport to occur
- Often, nutrient concentration in the environment of the cell is __
| Nutrient Transport through the Cell Membrane
- Impermeability
- higher
- low
42
1/2 Several possibilities have been suggested to account for the abnormally high membrane permeability of water:
1. Water is very small and so it just __ in bilayers better than larger solutes.
2. Due to its size, water can __ very small statistical pores (w4.2 Å in diameter).
3. Passage down __.
4. Water can be __ in acyl chains that result from acyl chain melting (“lipid melting”).
5. Water may rapidly cross membranes through __.
| Nutrient Transport through the Cell Membrane: Simple diffusion
1. dissolves
2. readily enter
3. water channels
4. carried down kinks
5. nonmollar regions (e.g. microbes, cubic or HII phased)
43
2/2 Several possibilities have been suggested to account for the abnormally high membrane permeability of water:
6. High water permeability will occur at regions of __.
7. Through __ or __ used to conduct ions.
8. Through specific water channels known as __.
| Nutrient Transport through the Cell Membrane: Simple diffusion
6. packing defect (e.g. surface of integral membrane proteins, boundary between membrane proteins)
7. pores or channels
8. aquaporins
44
- Non-charged solutes (small, hydrophobic molecules like O₂, CO₂, and lipophilic substances) can pass through
- The solute will be evenly distributed on both sides of the membrane.
- a passive process driven by the concentration gradient.
- Diffusion rate = gradient
| Nutrient Transport through the Cell Membrane
Simple diffusion
45
- requires transport proteins
- transport proteins can become fully occupied, causing the rate to level off.
- a passive process driven by the concentration gradient.
| Nutrient Transport through the Cell Membrane
Facilitated diffusion
46
What type of kinetics does facilitated diffusion follow?
| Nutrient Transport through the Cell Membrane
Michaelis-Menten saturation kinetics
47
What types of transport proteins are used in facilitated diffusion? (2)
| Nutrient Transport through the Cell Membrane
- Carrier proteins
- channel proteins
48
- A facilitated diffusion transporter that allows glucose to passively enter cells without using ATP.
- does not require ATP because it relies on the concentration gradient of glucose.
- occurs in almost all cells
- can be found in the cells lining the small intestine
- composed of 12 alpha helices
| Nutrient Transport through the Cell Membrane
Glucose-facilitated diffusion transporter GLUT-1
49
Why does glucose require GLUT-1 instead of simple diffusion?
| Nutrient Transport through the Cell Membrane
Glucose is **polar and large**, so it cannot pass freely through the lipid bilayer.
50
What kind of kinetic behavior does GLUT-1 follow?
| Nutrient Transport through the Cell Membrane
**Michaelis-Menten saturation kinetics**, meaning the rate of transport levels off when all GLUT-1 proteins are occupied.
51
Give the four (4) basic classes of Potassium Channels
1. Calcium-activated potassium channel
2. Inwardly rectifying potassium channel
3. Tandem pore domain potassium channel
4. Voltage-gated potassium channel
| Composition of almost all cells
52
What type of potassium channel is activated by intracellular calcium?
Calcium-activated potassium channel
53
Which potassium channel allows K⁺ to flow more easily into the cell than out?
Inwardly rectifying potassium channel
54
What type of potassium channel has two pore-forming domains per subunit?
Tandem pore domain potassium channel
55
What type of potassium channel opens in response to changes in membrane potential?
Voltage-gated potassium channel
56
What term describes a potassium channel composed of identical protein subunits?
Homotetramer
57
What term describes a potassium channel composed of closely related but not identical proteins?
Heterotetramer
58
What structure in the potassium channel is responsible for K⁺ selectivity?
Pore loop
59
What does the pore loop do to K⁺ ions before they pass through the channel?
Strips away water molecules
60
- A potent neurotoxin that blocks sodium channels but does not affect potassium channels.
- there is no known antidote.
| Sodium channels
tetrodotoxin (TTX)
61
Which animal is commonly associated with tetrodotoxin (TTX)?
| Sodium channels
Pufferfish (also known as "fugu")
62
- A potent neurotoxin that blocks sodium channels, similar to TTX.
| Sodium channels
saxitoxin (STX)
63
What organisms produce saxitoxin (STX)?
| Sodium channels
dinoflagellates (algae) such as golden diatoms.
64
They accumulate the toxin by feeding on dinoflagellates that produce it, thus become toxic with saxitoxin (STX).
| Sodium channels
snails and shellfish
65
- They serve as transmembrane water channels that allow water molecules to pass in single file.
- They are impermeable to charged molecules and exclude the passage of other solutes.
Aquaporins
66
Is there always water movement in and out of cells? Why?
Yes, because of osmotic gradients and the constant regulation of water balance.
67
Specialized aquaporins that facilitate the passage of small solutes like glycerol in addition to water.
aquaglyceroporins
68
Who discovered aquaporins?
| and what year? what did he won?
Dr. Peter Agre
| 1992; 2003 Nobel Prize in Chemistry for his discovery of aquaporins.
69
28-kDa protein was thought to be related to blood cell proteins, but later identified as a __.
water channel
70
- Small, lipid-soluble molecules of microbial origin that facilitate ion transport across membranes.
- Purpose: to conduct ions across membranes
- electrochemical gradient
Ionophores
71
What are the two basic types of ionophores? (2)
| Give an example each
1️⃣ Channel formers (e.g., Nystatin)
2️⃣ Mobile carriers (e.g., Valinomycin)
72
Who discovered valinomycin?
| When?
Bernard Pressman
| in the early 1960s.
73
- 12-unit (dodeca) depsipeptide where amino acid peptide bonds are alternated with amino alcohol ester bonds
- a macrocyclic molecule with the 12 carbonyl oxygens facing the inside of the ring where they chelate a single K+
Valinomycin
74
Valinomycin contains: (3)
- D- & L-valine
- Hydroxyvaleric acid
- Lactic acid
75
What is valinomycin known for? (3)
✅ Originally considered an antibiotic
✅ Now recognized as an ionophore
✅ Most potent agent against SARS-CoV
76
a channel-forming ionophore that creates a hydrophobic pore across a membrane
Nystatin
77
Nystatin allows for the __ of various ions that depend on the dimensions of the pore.
rapid facilitated diffusion
78
Nystatin binds to __ in fungal membranes, forming __ that cause __ & __.
- ergosterol
- transmembrane channels
- K⁺ leakage
- fungal death
79
Why is nystatin used in medicine? (3)
✅ Antifungal agent
✅ Targets fungi without harming host cells
✅ Used as prophylaxis for AIDS patients
| prophylaxis-action taken to prevent disease
80
Who proposed the three-domain system? (2)
- Carl Woese
- George Fox
81
Why must all Archaea metabolize sugars?
Structural backbone of cells
82
What major carbohydrate pathway is absent in Archaea?
Glycolysis
83
What alternative sugar-metabolizing pathway is modified in Archaea?
Pentose phosphate pathway
84
How do microbes obtain phosphorus, and what is its function?
- As phosphate (PO₄²⁻)
- required for nucleic acids and phospholipids
85
What are the main sulfur sources for microorganisms? (3)
- Sulfate (SO₄²⁻)
- sulfide (H₂S)
- organic sulfur compounds
86
What is the role of potassium (K) in microbial cells?
Required for enzyme activity
87
What is the role of magnesium (Mg)?
Stabilizes ribosomes, membranes, nucleic acids, and is needed for many enzymes
88
What is the function of the cytoplasmic membrane in transport?
Barrier to leakage
89
What process accumulates solutes against the concentration gradient?
Active transport
90
What are the three basic mechanisms of active transport? (3)
- Simple transport
- group translocation
- ABC transport
91
What drives simple transport?
Proton motive force
92
Solute and proton cotransported in one direction
symport reaction
93
Solute and proton transported in opposite directions
antiport reaction
94
What is an example of a symporter in *Escherichia coli*?
Lac permease (lactose transport)
95
What happens to the proton motive force when lactose enters the cell?
It is diminished
96
What are the two key differences of group translocation from simple transport?
- Chemical modification of transported substance
- energy from phosphoenolpyruvate
97
What sugars does the phosphotransferase system transport in *Escherichia coli*? (3)
- Glucose
- mannose
- fructose
98
What is the energy source for the phosphotransferase system?
| Group translocation
Phosphoenolpyruvate (PEP)
99
What modification is usually added to transported carbohydrates in PTS?
Phosphate group
100
What are the five proteins involved in the phosphotransferase system? (5)
- Enzyme I
- HPr
- Enzyme IIa
- Enzyme IIb
- Enzyme IIc
101
Which enzymes in the phosphotransferase system are nonspecific? (2)
- Enzyme I
- HPr
102
What type of transport system involves periplasmic binding proteins?
ABC transport
| ATP-Binding Casette Transport
103
What is the energy source for ABC transporters?
ATP
104
What are the three components of the ABC transport system? (3)
- Substrate-binding protein
- transmembrane transporter
- ATP-hydrolyzing protein
105
What type of transport system chemically modifies the transported substance?
Group translocation
106
What is the function of transmembrane proteins in transport?
Form channels for solute movement
107
What conformational change occurs in transmembrane proteins during transport?
Gate-like opening to sweep solute into the cell
108
What powers active transport systems? (3)
- Proton motive force
- ATP; or
- other energy-rich compounds
109
What structural feature do transmembrane transporters have?
12 α-helices forming a channel
110
How does transport occur through transmembrane proteins?
Conformational change
111
What energy source drives group translocation?
| Group translocation
Phosphoenolpyruvate (PEP)
112
What system is the best-studied example of group translocation?
| the most common example of group translocation in bacteria
Phosphotransferase system
113
What types of sugars are transported by the phosphotransferase system?
(3)
| Group translocation
- Glucose
- mannose
- fructose
114
How does phosphorylation occur in group translocation?
Phosphate transfer cascade
115
What does ABC stand for in ABC transport systems?
ATP-binding cassette
116
What is the main advantage of periplasmic binding proteins?
High substrate affinity
117
How do gram-positive bacteria transport substances without a periplasm?
Surface-bound substrate-binding proteins
118
What do Archaea primarily use ABC systems for?
Sugar transport
119
What property of the cytoplasmic membrane makes transport necessary?
Hydrophobic barrier
120
What structures allow passive diffusion through the outer membrane of gram-negative bacteria?
Porins
121
What types of molecules are excluded by porins?
Hydrophobic compounds
122
Which specific porin facilitates maltose transport?
Maltoporin
123
Which molecules can freely diffuse through bacterial membranes? (4)
- Oxygen
- carbon dioxide
- ammonia,
- water
124
Does facilitated diffusion require energy?
No
125
1. What is an example of a molecule transported by facilitated diffusion in *E. coli*? 2. Which protein transports this in *E. coli*?
3. What molecules can pass through GlpF? (3)
4. What charged molecules are excluded from GlpF transport? (2)
1. Glycerol
2. GlpF (glycerol facilitator)
3. polyhydric alcohols, urea, glycine
4. G3P, DOHAP (charged molecules)
126
What protein facilitates rapid water transport across membranes?
Aquaporin-Z (AqpZ)
127
What triggers mechanosensitive channel activation?
Changes in turgor pressure
128
What mechanosensitive channels in E. coli prevent membrane rupture? (2)
- MscL
- MscS
129
1. What solutes exit the cell via mechanosensitive channels? (3)
2. What enters the cell via mechanosensitive channels?
1. K+, glutamate, ATP
2. Na+, H+
130
What bacterial structure releases periplasmic binding proteins during osmotic shock?
Outer membrane (gram-negative bacteria)
131
1. ABC transporters are also called what due to their ATP-binding motifs?
2. Name the two ATP-binding motifs found in ABC transporters. (2)
3. What *E. coli* permease is a well-studied ABC transporter?
1. Traffic ATPases
2. Walker A box, Walker B box
3. Histidine permease
132
What powers chemiosmotic-driven transport?
Ion gradients (proton motive force, sodium motive force)
133
What are the three types of ion-driven transport? (3)
- Symport
- antiport
- uniport
134
What is an example of an antiporter in E. coli?
Na+/H+ antiporter (NhaA, NhaB)
135
What are the two major classes of ATP-linked ion motive pumps? (2)
- F-type
- P-type ATPases
136
1. What is the exception to the single-subunit structure of P-type ATPases?
2. What organism was Kdp ATPase first identified in?
1. Kdp ATPase
2. *Escherichia coli*
137
What molecules sequester iron in animal hosts? (3)
- Transferrin
- lactoferrin
- ferritin
138
What form does environmental iron take that makes it insoluble?
Ferric hydroxide (Fe³⁺)
139
1. What molecules do bacteria use to scavenge iron?
2. What is the major (1) of E. coli?
1. Siderophores
2. Enterochelin
140
1. What two general proteins are required for all PTS carbohydrates?
2. Which enzyme is carbohydrate-specific in PTS?
3. Which domain of EII forms the translocation channel?
1. Enzyme I, HPr
2. Enzyme II (EII)
3. IIC
