MCB Exam 2 (Ch. 7 and Ch.2A)

Macronutrients

carbon, nitrogen, phosphorus, sulfur, oxygen and hydrogen. potassium, sodium, magnesium, calcium, and iron

Micronutrients

(trace elements) Mn, Zn, Co, Mo, Ni, and Cu

What do all organisms require?

carbon, hydrogen, oxygen, and electrons

What is the backbone of all organic components present in a cell? 

carbon

What else is found in organic molecules?

hydrogen and oxygen

What plays a role in energy production? 

electrons 

Phototrophs

capture light energy to produce ATP

Chemotrophs

capture energy from oxidation of reduced organic or inorganic compounds

Organotrophs 

acquire their electrons from organic molecules 

Lithotrophs

‘rock-eaters’ that acquire their electrons from inorganic sources

Autotrophs 

assimilate carbon from inorganic sources 

Heterotrophs

assimilate carbon in preexisting organic from

Mixotrophs 

some organisms have great metabolic flexibility and alter their metabolism in response to environmental changes - can be advantageous 

Nitrogen

amino acids, purines, pyridines, some carbohydrates, lipids, enzyme cofactors, etc 

How does nitrogen get supplied?

metabolism of amino acids, nitrates, ammonia, from atmosphere OR nitrogen fixation

Phosphorus 

nucleic acids, phospholipids, coenzymes, some proteins, etc co

Common phosphorus sources

• inorganic phosphate

• organic molecules containing a phosphoryl group

Sulfur 

amino acids, coenzymes 

How is sulfur obtained?

• amino acids cysteine and methionine

• sulfate

  • assimilatory suflate reduction

Assimilatory sulfate reduction

sulfate —> sulfite —→ hydrogen sulfide

Growth Factors 

organic compounds that cannot be synthesized by an organism but are essential for growth 

3 classes of growth factors

1. amino acids - protein synthesis

2. purines/pyrimidines - nucleic acid synthesis

3. vitamins - enzyme cofactors, needed in very small amounts

Growth rate

dependent on amount of nutrients in the environment

What will dictate how much growth can occur over time? 

one key nutrient available in the lowest amount 

Aerobes

grow in the presence of oxygen

Obligaste aerobes

REQUIRE oxygen to grow

Microaerophiles 

grow best when there is less oxygen than normal 

Anaerobic

growth occurs without oxygen

Aerotolerant anaerobes

aren’t harmed by oxygen but don’t use it either

Obligate anaerobes 

cannot grow when oxygen is present 

Faculties anaerobes

CAN use oxygen but can also grow in the absence of oxygen

Effects of oxygen on microbial growth

often determined by what defenses are available against oxygen’s negative effects in the cell

What do Strict anaerobic microorganisms lack

• superoxide dismutase 

• catalase 

Strict anaerobic microorganisms

these microbes cannot tolerate O2 and must be grown without O2 (in an incubator)

Effects of pH on microbial growth on acidophiles

pH < 5.5

Effects of pH on microbial growth on neutrophiles 

pH 5.5 to 8.5 

Effects of pH on microbial growth on alkalophiles

pH > 8.5