Module 3 - Macromolecules, Cellular Chemistry, Microbial Growth, and Nutrition

Question 1

What are the most common receptors on the surface of cells?

Answer 1

1) Glycoprotein
2) Glycolipids

Question 2

What’s the relation between bacteria and the concept of Ligand-Receptor

Answer 2

Bacteria can use receptors and bind and gain access to the cell

Question 3

What is culture media?

Answer 3

Contains all the nutrients required by the organism for growth

Question 4

What do you need to promote bacterial growth?

Answer 4

1) A carbon source
2) A nitrogen source
3) Phosphate source
4) pH (buffering capacity)

Question 5

What is the difference between defined and complex media?

Answer 5

Defined - all chemicals are known (you control what to put in)
Complex - all chemicals are unknown and made of extracts

Question 6

What are the different types of media?

Answer 6

Defined vs Complex and Selective vs Differential

Question 7

What are the different mechanisms of selective and differential media?

Answer 7

1) Blood agar - supports the growth of many fastidious bacteria and can be differentiated based on their ability to produce hemolysins (proteins that lyse red blood cells)
2) Eosin methylene blue (EMB) agar - inhibits the growth of Gram-positive bacteria
3) MacConkey (MAC) agar - has selective components such as bile salts and crystal violet (CV), which inhibit the growth of Gram-positive bacteria (specifically lactose vs non-fermenters)
4) Mannitol salt agar - has a concentration of NaCl that selects for the growth of staphylococci

Question 8

What is the growth curve?

Answer 8

A microorganism’s pattern of growth that’s observed when microorganisms are cultivated in batch culture

Question 9

How are growth curves usually plotted?

Answer 9

Usually plotted as the logarithm of cell number vs time

Question 10

What are the different phases of the growth curve?

Answer 10

1) Lag phase - phase where microorganisms try to figure out what’s available to use (carbon source, nitrogen source, etc)
2) Log phase - cells multiply exponentially and go through doubling
3) Stationary phase - nutrients become less and less, and the # of cells dying equals to the # of cells multiplying
4) Death phase - well… death

Question 11

What is the generation time in a growth curve?

Answer 11

The time is takes for the population to double in size

Question 12

What affects the growth of microorganisms?

Answer 12

pH and temperature

Question 13

What are hyperthermophiles?

Answer 13

Grows in extremely hot environments. Also called extremophiles.

Question 14

What are thermophiles?

Answer 14

Grows in hot temps

Question 15

What are mesophiles?

Answer 15

Grows in earth temp (room temp. Most organisms prefer this.

Question 16

What are psychrotrophs?

Answer 16

can grow and survive in cold and room temps

Question 17

What are psychrophiles?

Answer 17

like colder temps

Question 18

What domain do most extremophiles belong to?

Answer 18

Archaea

Question 19

What are the cardinal growth temperatures?

Answer 19

1) Minimal - the lowest temp microorganisms can survive
2) Maximal - the highest temp microorganisms can survive (after that = death)
3) Optimum = temp that the microorganisms grow the best (optimal growth rate)

Question 20

What is the oxygen concentration of a facultative anaerobe?

Answer 20

• Only survives with the presence of oxygen
• Has enzymes to neutralize free radicals

Question 21

What is the oxygen concentration of a facultative anaerobe?

Answer 21

Can grow with or without oxygen, but prefers oxygen

Question 22

What is the oxygen concentration of a strict anaerobe?

Answer 22

Cannot tolerate oxygen and dies in the present of it because they don’t have the right enzyme

Question 23

What are the biosafety levels?

Answer 23

• BSL-1: least protection
• BSL- 2
• BSL- 3
• BSL- 4: most protection

Question 24

What are biofilms?

Answer 24

Microbial communities that form sline or hydrogels that adhere to surfaces - acts as a protection

Question 25

Define osmosis.

Question 26

What is an isotonic solution?

Answer 26

No net movement of water occurs - the solute outside the cell is the same as the inside

Question 27

What is a hypotonic solution?

Answer 27

Water moves into the cell. If the cell wall is strong enough, it contains the swelling. If not, the cell wall is weak or damaged, and the cell bursts (osmotic lysis)

Question 28

What is a hypertonic solution?

Answer 28

Water moves out of the cell, causing its cytoplasm to shrink (plasmolysis)

Question 29

What is the only thing that can pass through the cell membrane?

Answer 29

Small, non-polar, fat-soluble compounds

Question 30

What protects the cell wall from osmotic stress and prevents the cell from bursting because of too much water entering?

Answer 30

Cell wall

Question 31

What is diffusion?

Answer 31

Molecules can pass through with NO ENERGY NEEDED because it follows a concentration gradient (goes from high to low)

Question 32

What are the two types of diffusion?

Answer 32

1) Passive - molecules can squeeze between the phospholipids 2) Facilitated - requires some kind of carrier across the membrane, no energy required, follows a concentration gradient

Question 33

What are the different types of membrane transport systems?

Answer 33

1) Facilitated diffusion 2) Active transport 3) Group translocation

Question 34

What are the membrane transport systems used for?

Answer 34

Used to move nutrients and waste products across the membrane

Question 35

In facilitated diffusion, does it stop or continue once equilibrium is reached?

Answer 35

Stop

Question 36

What is active transport?

Answer 36

Requires energy and can work AGAINST the concentration gradient

Question 37

What does active transport use as its energy source?

Answer 37

Uses proton motive force (PMF) as the energy source - EX: proton gradients and ion (charge) gradient

Question 38

What is group translocation?

Answer 38

A form of active transport that requires energy and allows bacterial cells to import glucose. Glucose is then modified into glucose-phosphate.

Question 39

What energy does group translocation use?

Answer 39

Comes from phosphoenolpyruvate (PEP)

Question 40

What are ABC transporters?

Answer 40

A form of active transport that requires energy and can concentrate AGAINST the concentration gradient. It does NOT modify any molecules coming in.

Question 41

What energy do ABC transporters use?

Answer 41

ATP

Question 42

What is the microbiome?

Answer 42

A group of microbes that live stably on/in the human body

Question 43

What does the microbiome do?

Answer 43

1) Helps to maintain good health 2) Can prevent the growth of pathogenic microbes 3) May help train the immune system to discriminate threats

Question 44

Fun fact: An adult human is composed of _______________ body cells.

Answer 44

30 trillion

Question 45

When do we begin to acquire our microbiome?

Answer 45

Begin to be acquired as newborns

Question 46

What kind of growth factors does normal microbiota produce?

Answer 46

Vitamins B and K

Question 47

What is dysbiosis?

Answer 47

Having an imbalanced microbiome