Lecure 25

Question 1

Autotrophs

Answer 1

• organims that use carbon dioxide from atmosphere as source of carbon which they use to contrast their carbon containing molecules
• Some can also use N2 and convert to NH3 as sole source of N in their nitrogen-containing molecules

Question 2

Photoautotrophs

Answer 2

• use photosynthesis
• source of energy is sunlight
• examples: photosynthetic bacteria, green algae

Question 3

chemoautotrophs

Answer 3

• use reduced chemicals
• source of energy is H2, H2S, NH4+
• a few bacteria and archaea

Question 4

Heterotrophs

Answer 4

organisms that need a source of organic carbon

Question 5

Photosynthetic organisms

Answer 5

• utilize sunlight but need organic sources of C, N

examples: some bacteria

Question 6

Chemoheterotrophs

Answer 6

organisms that derive all energy from oxidation of organic molecules
-animals, fungi, many bacteria

Question 7

Biosphere: balance of carbon and nitrogen

Answer 7

carbon, oxygen, and nitrogen (inorganic compounds) are incorporated into organic compounds by autotrophs:

• photosynthetic organisms utilize CO2 to produce organic carbon/oxygen molecules
• nitrogen-fixing bacteria and archaea utilize N2 to produce NH4+ and NH3
• Heterotrophs use organic compounds as nutrient resources and release inorganic as end products

Question 8

Intermediary Metabolism

Answer 8

network of biochemical reactions carried into living cells that involve compounds not more than 1000 daltons in size

Question 9

Metabolites

Answer 9

are all of the compounds (substrates, intermediates, products) that are part of the metabolic pathway

Question 10

anabolic pathways

Answer 10

also called biosynthesis

• involve the use of small molecules and energy to build up large molecules
• ENERGY reserves are expanded

Question 11

Catabolic pathways

Answer 11

-involve the degradation of large molecules with recovery of energy

Question 12

What are the chemical energy reserves from catabolism built up as?

Answer 12

ATP
NADH
NADPH
FADH2
QH2

Question 13

What are five common themes in metabolism

Answer 13

1. Homeostasis- cells maintain specific concentrations of metabolites and enzymes. There are feedback mechanisms in the cell that regulate enzymes so they remain at constant levels
2. External energy sources are necessary
3. Metabolic pathways are specified by genes
4. an organism (and cell) responds to enviromental opportunities and limitations (environmental stresses)
5. constant turnover of enzymes, molecules and structure in a cell (multicellular-programmed cell death and new synthesis of cells)

Question 14

What are the reasons for the number of steps in anabolic biosynthesis reaction?

Answer 14

1) energy of formation is so large for a substance like glucose that thermodynamically, its formation would be unfavorable
2) Enzymes can do linked reactions to produce metabolites that have a higher energy, but there is a limit to this in any particular step

Question 15

What are the reasons for the number of steps in catabolic reactions?

Answer 15

1) energy released all at once cannot be captured biochemically efficient because the energy releases exceeds the energy that can stored in one particular high energy compounds

Question 16

How can a cell do both anabolic and catabolic metabolism?

Answer 16

1) anabolic and catabolic pathways are located in different parts of the cell. Therefore the concentrations of metabolites are different which allows a cell to progress through multiple pathways at once
2) There is at least one enzyme that is unique to each pathway
3) the key enzyme is subject to inhibition/regulation which controls the flow of the metabolites through the reaction