Cell Morphology, Membrane Structure and Nutrient Transport.

Question 1

What are the three cell morphology shapes? What are examples of each?

Answer 1

Rods (bacilli)- E. coli
Cocci- Streptococcus pyogenes
Spirilla- Spirillum volutans

Question 2

What are three unusual cell morphology shapes? What are examples of each?

Answer 2

Spirochete (spaghetti)- Treponema pallidum
Budding and Appendage Bacteria (sperm shaped)- Caulobacter crescentus
Filamentous Bacteria- Streptomyces griseus

Question 3

True or False: Morphology typically does not predict physiology, ecology, phylogeny, etc. of a prokaryotic cell.

Answer 3

True

Question 4

What are the advantage(s) to cell having a different shape?

Answer 4

Optimization for nutrient uptake (small cells and those with high surface-to-volume ratio)
Swimming motility in viscous environments or near surfaces (helical or spiral-shaped cells)
Gliding motility (filamentous bacteria)

Question 5

What is the average size of a prokaryote? What are some example(s) of organisms this size?

Answer 5

Average: 1 um
E. coli ~ 1.0 x 3.0 µm
Staphylococcus aureus ~ 1.0 µm diameter

Question 6

What is a very small size of a prokaryote? What are some example(s) of organisms this size?

Answer 6

Very small: 0.3 um

Mycoplasma genitalium ~ 0.3 µm

Question 7

What is a very large size of a prokaryote? What are some example(s) of organisms this size?

Answer 7

Very large: 80 x 600 um

Epulopiscium fishelsonii ~ 80 x 600 µm.

Question 8

Why is it an advantage to be small, rather than being large?

Answer 8

A smaller cell has a greater surface area to volume ration than a cell with a larger size, leading to optimal nutrient uptake and faster growth.

Question 9

Cells smaller than ___ are unlikely, due to there not being enough space to fit all the organs.

Answer 9

<0.15 um

Question 10

Where are most small cells (0.2-0.4 um) usually found?

Answer 10

The ocean.

Question 11

Why are most pathogenic bacteria also small?

Answer 11

Because any genes missing are supplied by their host.

Question 12

What are the characteristic(s) of a plasma membrane?

Answer 12

Thin structure that surrounds the cell
Vital barrier that separates cytoplasm from environment
Highly selective permeable barrier- enables concentration of specific metabolites and excretion of waste products

Question 13

The main structure of a plasma membrane is the phospholipid bilayer. What component(s) make up this layer?

Answer 13

The phospholipid bilayer is made up of hydrophobic (fatty acid) and hydrophilic (glycerol-phosphate) components.

Question 14

True or False: the phospholipid bilayer can only exist in one form and is always attached to a glycerol backbone.

Answer 14

False: The phospholipid bilayer can exist in many different forms and is always attached to a glycerol backbone.

Question 15

Which way to the fatty acids and glycerol-phosphates face in relation to the inside and outside of the cell?

Answer 15

The fatty acids face in towards the cell because they are hydrophobic, and the glycerol-phosphates face out of the cell because they are hydrophilic.

Question 16

Still referring to the phospholipid bilayer, what is an ester linkage composed of?

Answer 16

Consist of: glycerol

• 2 Fatty acids
• Phosphate
• Side chain (optional)

Question 17

Having both polar and non-polar characteristics means an organism has __________ characteristics.

Answer 17

Ampithatic

Question 18

True or False: if something is polar it is usually hydrophilic, and if something is non-polar it is usually hydrophobic.

Answer 18

True

Question 19

How wide is the plasma membrane? What is it stabilized by?

Answer 19

8-10 nm

The membrane is stabilized by hydrogen bonds and hydrophilic bonds.

Question 20

What cations form ionic bonds with the negative charges of the phospholipids?

Answer 20

Mg2+ and Ca2+

Question 21

The plasma membrane is embedded with proteins. What do proteins interacting with the inside of the membrane deal with?

Answer 21

Deal with energy-yielding reactions and other important cell reactions.

Question 22

In gram-negative bacteria, what proteins bind substrates or process large molecules for transport?

Answer 22

Periplasmic Proteins

Question 23

A protein that is firmly embedded in the plasma membrane is what kind of membrane protein?

Answer 23

Intgral membrane protein

Question 24

A protein where one portion is anchored into the membrane is what kind of membrane protein?

Answer 24

Peripheral membrane protein

Question 25

True or False: Eukarya, bacteria and archaea all have the same kind of ester linkage.

Answer 25

False: Archaea have a different ester linkage than bacteria and eukarya because they live in more extreme environments.

Question 26

In an archaea plasma membranes, what is different about the lipids?

Answer 26

Archaea lack fatty acids, and have isoprenes instead- they have 5 carbon tails.

Question 27

What are the major lipids in an archaea plasma membrane?

Answer 27

Diethers (2O + ester linkage) and tetraethers (contains 4 ether functional groups)

Question 28

In archaea plasma membranes what kind of structures can the lipids exist as?

Answer 28

Monolayers, bilayers or a mixture.

Question 29

True or False: lipid bilayers are extremely heat resistant.

Answer 29

False: lipid monolayers are extremely heat resistant.

Question 30

Where are archaea lipid monolayers usually found?

Answer 30

Hyperthermophilic Archaea (grow best at temperatures above 80 C)

Question 31

What are the membrane function(s)?

Answer 31

Permeability barrier
-Polar and charged molecules must be transported
-Transport proteins accumulate solutes against the concentration gradient
Protein anchor
-Holds transport proteins in place
Energy conservation
-Generation of proton motive force

Question 32

What type of system do prokaryotes use to transport nutrients? What is its restriction?

Answer 32

They use carrier-mediated transport systems. They can only take one substance at a time.
-like leading someone by the elbow

Question 33

What is the saturation effect?

Answer 33

Transport stops when the concentration of solute is equal on both sides. Rate of transport = External solute concentration. No saturation effect.

Question 34

What are the major classe(s) of transport systems in prokaryotes?

Answer 34

Simple transport
Group translocation
ABC system

Question 35

What are the driving energy forces for the nutrient transport system(s)?

Answer 35

Simple transport- proton motive force
Group translocation- phosphoenolpyruvate
ABC system- ATP

Question 36

What three transport events in simple transport are possible? What do they do?

Answer 36

Symport- function as co-transporters.
Uniport- transport in one direction across the membrane.
Antiport- transport molecules at the same time in opposite directions.

Question 37

Give an example of simple transport, what it is transporting, and how is it accomplishing this?

Answer 37

Lac permease of Escherichia coli •
Lactose is transported into E. coli by the simple transporter lac permease, a symporter
Activity of lac permease is energy-driven
Transports lactose and a H+ into the cell simultaneously

Question 38

Give an example of group translocation, what is it transporting and how is it accomplishing this?

Answer 38

Phosphotransferase system in E. coli
Sugar is phosphorylated during transport across the membrane
Moves glucose, fructose, and mannose Phosphoenolpyruvate (PEP) donates a P to a phosphorelay system
P is transferred through a series of carrier proteins and deposited onto the sugar as it is brought into the cell

Question 39

What does “phosphoroylate” mean?

Answer 39

To have a phosphate group introduced to the molecule or compound.

Question 40

What do ABC (ATP-binding cassette) transport systems usually transport? Give examples.

Answer 40

Organic compounds 
-sugars, amino acids, 
inorganic nutrients  
-sulfate, phosphate
trace metals

Question 41

How do gram negative bacteria use the ABC transport system?

Answer 41

They employ periplasmic-binding proteins and ATP-driven transport proteins.

Question 42

How do gram positive bacteria use the ABC transport system?

Answer 42

Employ substrate-binding lipoproteins (anchored to external surface of cell membrane) and ATP-driven transport proteins.

Question 43

In ABC transport in gram negatives, where is a solute binding protein found and what does it do?

Answer 43

It is found in the periplasm and it binds to specific substrates.

Question 44

What is the function of an ATP-hydrolyzing protein?

Answer 44

To supply energy for transport events.