Exam 2: Microbial Metabolism-Intro and Cellular Respiration

Question 1

Why is it important to understand metabolism in general, and microbial metabolism in particular?

Answer 1

Microbes are critical to nutrient cycling helpful in bioremediation, important factories in the synthesis of various important products, and disrupting key metabolic processes is important in controlling the growth of microbes.

Question 2

What is metabolism, and what is a metabolic pathway?

Answer 2

Metabolism is collection of controlled biochemical reactions occurring within an organism and specific tasks are accomplished through metabolic pathways.

Question 3

Describe and compare catabolism and anabolism, showing the relationship between the two.

Answer 3

Anabolism is reactions constructing larger molecules from smaller molecules, which requires energy input. Coupled by catabolism which breaks larger molecules into smaller molecules releasing energy. Energy is commonly stored and derived from ATP.

Question 4

What are precursor metabolites? Why are they important?

Answer 4

Smaller molecules used as starting material in anabolic pathways, used in synthesis of larger organic molecules. Important because they are the building blocks for everything else.

Question 5

In what ways is the ATP cycle like the cycling of NADH?

Answer 5

The same quantity of free energy is released per molecule of ATP or NADH. Both molecules are oxidized by molecular oxygen (O2) in reactions that release energy for use by the cell. Both compounds function as mobile energy carrier molecules in a cell.

Question 6

List and describe the three ways in which ADP can be phosphorylated.

Answer 6

1) Substrate- level: Transfer of Pi from a phosphorylated compound to ADP

2)Oxidative: Energy from redox reactions is used to attach Pi to ADP

3) Photophosphorylation: Light energy is used to attach Pi to ADP

Question 7

Why do all living organisms require energy at all times, even if they are not always growing or moving?

Answer 7

For maintenance everything simply being alive requires energy.

Question 8

In a single sentence, summarize the process of aerobic cellular respiration.

Answer 8

Glucose reacts with oxygen, forming ATP that can be used by the cell.

Question 9

What groups of organisms perform aerobic respiration? Do animals? How about plants?

Answer 9

All multicellular organisms including animals, plants, and other living organisms.

Question 10

What is the general formula for aerobic cellular respiration? (Do not bother balancing the formula.)

Answer 10

Glucose + O2 🡪 CO2 + H2O + energy

Question 11

What is the general formula for the burning of gasoline in your car’s engine? (Do not bother balancing the formula.)

Answer 11

C8H18+12.5O8→ 8CO2+9H2O

Question 12

What is the general formula for the burning of natural gas in your furnace? (Do not bother balancing the formula.)

Answer 12

CH4+O2→ CO2+H2O

Question 13

What are the two processes by which carbohydrates are catabolized?

Answer 13

Aerobic cellular respiration and Fermentation

Question 14

What are the three stages of cellular respiration? Where within a eukaryotic cell does each occur?

Answer 14

Glycolysis- cytosol
Krebs cycle - mitochondria
Electron transport pathway- mitochondria

Question 15

Do all organisms capable of aerobic cellular respiration possess mitochondria? Explain.

Answer 15

No, bacteria and other prokaryotic organisms don’t have mitochondria, but some of them are still capable of cellular respiration because they produce the proteins involved in aerobic cellular respiration.

Question 16

Describe the endosymbiotic origin of mitochondria.

Answer 16

Bacteria cells engulfed by early eukaryotic cells. Maintained rather than being digested. Started off parasitic but tired symbiotic. Both components bacterium and host benefited from the relationship and bacteria lost their ability to exist independently.

Question 17

What part of a mitochondrion corresponds to the ancestral bacterium’s cytoplasm?

Answer 17

Matrix

Question 18

What part of a mitochondrion corresponds to the ancestral bacterium’s cell membrane?

Answer 18

Inner Membrane

Question 19

Where within a cell does glycolysis take place?

Answer 19

cytosol/ cytoplasm

Question 20

List the three stages of glycolysis and describe generally what occurs in each.

Answer 20

1) Energy Investment Stage: 2ATP invested to split glucose into 3-carbon molecules. Each ATP loses a phosphate and binds to either end of the glucose. The Result is a 6-carbon molecule.

2) Lysis Stage: The now 6 carbon glucose is split into 2 3-carbon molecules.

3) Energy Conserving stage: 3-carbon molecule oxidized to form pyruvate. Result 4 ATP and 2 NADH.

Question 21

When glucose is broken down during glycolysis, what are the products? What high-energy molecules are made? How many of each are made? By what processes are they made?

Answer 21

Total products are 4 ATP and 2 NADH, net gain is 2ATO and 2 NADH. NADH is produced through redox reactions (transfer of electrons). ATP is generated through substrate-level phosphorylation.

Question 22

Where within the cell does the transition step take place? (The answer is more complex than a simple word or two.)

Answer 22

Pyruvate, the byproduct of glycolysis which occurs in the cytosol, needs to be moved into the mitochondria across the double membrane.

Question 23

In what way are pyruvate molecules modified as they are transported into the mitochondrion? What high-energy molecules are produced during this step, and how many are made? Are any waste products made? Explain.

Answer 23

Converted acetyl CoA by removing ⅓ carbons (removed as CO2). The remaining 2 carbons are transported and converted. Products 2 NADH, 2 acetyl groups, 2 CO2.

Question 24

Are the pyruvate molecules produced in glycolysis always transported into the mitochondria? Explain.

Answer 24

No, it can be turned into many other things. Not every single pyruvate is transported into the mitochondria, it has other uses. One example is it can be used to produce non-essential amino acids (if not obtained through diet can be built). It’s a precursor metabolite.

Question 25

In what part of a mitochondrion does the Krebs cycle take place?Eukaryotes vs prokayotes.

Answer 25

Mitochondrial matrix of eukaryotes. Cytosol of prokaryotes.

Question 26

By what two other names is the Krebs cycle known? To hell with standardization, why not make science unnecessarily complex?

Answer 26

Citric acid cycle, or TCA cycle.

Question 27

What high-energy molecules are made as acetyl groups are completely oxidized during the Krebs cycle, and how many of each are made? By what processes are they made? Are any waste products made? Explain.

Answer 27

6 NADH, 2 ATP, 2 FADH2. Enzymes catalyzed reactions through a multi step metabolic pathway. Wates product is 4 CO2.

Question 28

What high-energy molecules are made as glucose is fully oxidized to carbon dioxide, and how many of each are made? Is the energy in all these molecules equally available to perform cellular work? Explain.

Answer 28

4 ATP, 10 NADH, 2 FADH2. No, only ATP readily usable to perform cellular work. The NADH and FADH2 are in the form of reduced coenzymes.

Question 29

In what part of a mitochondrion does the electron transport chain reside? Describe the origin of this part of the mitochondrion.

Answer 29

Inner mitochondrial membrane, membrane of bacterial origin.

Question 30

Do any prokaryotes possess electron transport chains? If so, where do they reside?

Answer 30

Yes, cell membrane of prokaryotes.

Question 31

Describe the composition of the electron transport chain? Is its composition fundamentally the same in all organisms? Is its composition identical in all organisms? Explain.

Answer 31

Membrane bound carrier molecules accept the high energy electrons from the reduced coenzymes. Electrons are passed from one to the next. As they are passed the inherent energy of the electrons decreases and that energy is exported.

  Energy used to pump H+ from NADH across the membrane via active transport. Result is NAD+. This is a proton gradient which has high potential energy. 
 Membrane acts as a dam with H+ build up on one side creating build up of energy.
	 
	 Fundmentallythe smame in all organisms but not identical.

Question 32

When a single NADH molecule donates its electrons to the electron transport chain, approximately how many ATP molecules are synthesized?

Answer 32

3 ATP

Question 33

When a single FADH2 molecule donates its electrons to the electron transport chain, approximately how many ATP molecules are synthesized?

Answer 33

2 ATP

Question 34

What is the role of oxygen in the electron transport chain?

Answer 34

It’s the trash can for the energy depleted electrons.

Question 35

What happens to the electron transport chain when oxygen is not present?

Answer 35

the electrons will be backed up, eventually causing the electron transport chain to halt. This will cause the products of glycolysis to go through fermentation instead of going to the citric acid cycle.

Question 36

Describe the function of the electron transport chain, now including a discussion of proton gradients, ATP synthase, and chemiosmosis.

Answer 36

Electron transport chain creates a proton gradient with high concentration on H+ on one side of the membrane against the gradient. ATP synthase complex is the gateway for H+ to pass through to the other side of the membrane. The ATP synthesis uses the H+ and the kinetic energy of this movement creates 2 ATP via oxidative phosphorylation.The ATP generation part of this is called chemiosmosis.

Question 37

Total theoretical yield of all products of aerobic respiration.

Answer 37

4 ATP
10 NADH-> 30 ATP
2 FADH2-> 4 ATP
So…..38 ATP total yield.

Question 38

What is the theoretical ATP yield of aerobic respiration?

Answer 38

38 ATP

Question 39

List four reasons why this theoretical yield is never reached.

Answer 39

1) Intermediates in the pathways are removed as precursor metabolites for biosynthesis. Here and there some of the intermediates are used for other things.

2) Each NADH yields slightly less than 3 ATP (2.6/2.7 ATP).

3) Electrons of NADH generated during glycolysis are shuttled into the mitochondria as FADH2. Which uses ATP as energy.

4) Some of proton motive force of the H+ gradient is used to drive other work.

Question 40

What is the main goal of the electron transport chain?

Answer 40

Main goal of the electron transport chain is to convert NADH and FADH2 into the more easily used ATP.

Question 41

What types of organisms possess the Entner-Doudoroff pathway?

Answer 41

Used by some bacteria and archaea. Can be used instead of glycolysis or in addition to glycolysis. Alternative way to catabolize glucose to pyruvate.

Question 42

How is the Entner-Doudoroff pathway like glycolysis, and how is it different?

Answer 42

Uses different enzymes and slightly less yield than glycolysis.

Question 43

Why do you think multiple “roughly equivalent” pathways exist?

Answer 43

To make the most use of the glucose available and to have alternative pathways if something needed is missing from another pathway.

Question 44

How might an organism have gained both glycolysis and the Entner-Doudoroff pathway?

Answer 44

analogous structures

Question 45

What types of organisms possess the pentose phosphate pathway?

Answer 45

Wide range of prokaryotes and eukaryotes (including humans).
Functions in conjunction with glycolysis and or entner-doudoroff.

Question 46

How is the pentose phosphate pathway like glycolysis, and how is it different?

Answer 46

uses different enzymes, slightly less yield, produces ATP, NADH, and precursor metabolites.

Question 47

Though the pentose phosphate pathway is a catabolic process, its primary function is anabolic. Explain.

Answer 47

Primary function is the production of precursor metabolites used in anabolic reactions (notably 5 carbon sugars).

Question 48

Might it be of benefit to an organism to be capable of both glycolysis and the pentose phosphate pathway? Explain.