Metabolism

Question 1

What is metabolism?

Answer 1

The sum of every chemical reaction that happens in a cell.

Question 2

What is catabolism?

Answer 2

Large molecules are broken down into smaller ones. This process releases energy.

Question 3

What is anabolism?

Answer 3

Small molecules are put together to make larger molecules. This process uses energy.

Question 4

Why are both catabolism and anabolism needed by cells?

Answer 4

Both of these processes are needed in the cell to keep its energy balance. The bonds broken by catabolism release the energy that is required for anabolism to take place.

Question 5

What is a heterotroph?

Answer 5

gets their carbon from organic molecules. These compounds are first given to them by autotrophs

Question 6

What is an autotroph?

Answer 6

make organic carbon compounds through the conversion of inorganic carbon dioxide.

Question 7

What is a phototroph?

Answer 7

an organism that obtain their energy for electron transfer from light

Question 8

What is a chemotroph?

Answer 8

an organism that gets their energy for electron transfer by breaking chemical bonds

Question 9

What is a lithotroph?

Answer 9

chemotroph that obtains its energy from inorganic compounds

Question 10

What is a organotroph?

Answer 10

chemotroph that gets its energy from organic compounds

Question 11

What are the major steps of glycolysis?

Answer 11

energy investment phase:
1) energy from two ATP molecules is used to phosphorylate a glucose molecule and break it into two glyceraldehyde 3-phosphate molecules.
energy payoff phase:
2) energy is taken when it oxidizes G3P to pyruvate. When this occurs, four ADP molecules phosphorylate to ATP molecules and two molecules of NAD+ are reduced to NADH
- glycolysis produces two ATP, two NADH molecules, and two pyruvate molecules.

Question 12

Where does glycolysis take place in cells?

Answer 12

cytoplasm (both prokaryotic and eukaryotic cells)

Question 13

What are examples of other glycolytic pathways?

Answer 13

1) Entner-Doudoroff pathway for prokaryotes
2) Pentose phosphate pathway (aka phosphogluconate pathway or hexose monophosphate shunt).

Question 14

What are the main steps of the transition reaction (pyruvate oxidation/bridge reaction)?

Answer 14

pyruvate dehydrogenase converts pyruvate into an acetyl group by removing a carboxyl group (decarboxylated). This process releases carbon dioxide. An electron is also transferred to an NAD+ reducing it to NADH. The acetyl then is attached to coenzyme A. The transition reaction results in the formation of acetyl CoA.

Question 15

Where does the transition reaction take place in cells?

Answer 15

cytoplasm (in prokaryotes), mitochondrial matrix (eukaryotes)

Question 16

What are the main steps of the Kreb’s cycle (Cyclic acid/TCA cycle)?

Answer 16

The acetyl CoA that was formed by the transition reaction is fed into the Kreb’s cycle. Acetyl CoA gets oxidized. Three NAD+ are reduced into 3 NADHs, an FAD is reduced into an FADH, and two carbons get oxidized into carbon dioxides. An ADP or GDP is also phosphorylated into ATP or GTP. This cycle produces one ATP or GTP, one FADH2, and three NADH. The Krebs cycle ends and begins with the formation of the same compound.

Question 17

Where does the Kreb’s cycle occur in cells?

Answer 17

cytoplasm (in prokaryotes), mitochondrial matrix (in eukaryotes)

Question 18

What are the main steps of the electron transport system?

Answer 18

It is a succession of ion pumps and electron carriers that are used to pump H+ ions (protons) from inside the cell to the outside across the membrane. Energy is sucked out of electrons as they are transferred through the electron transport system. This energy is used to pump the H+ ions across the membrane. This process takes advantage of the concentration gradient as it takes the energy and converts it to ATP. The H+ ions then use ATP synthase to go back through the membrane. This process catalyzes the formation of ATP.

Question 19

Where does the electron transport system occur in cells?

Answer 19

inner mitochondrial matrix (eukaryotes), cytoplasm (prokaryotes)

Question 20

What is PMF?

Answer 20

Proton motive force is the electrochemical gradient that is made by the accumulation of protons (H+) on one side of the membrane compared to the other side.

Question 21

What is chemiosmosis?

Answer 21

the movement of H+ ions (protons) across the membrane through ATP synthase.

Question 22

Compare and contrast aerobic vs anaerobic respiration.

Answer 22

In anaerobic respiration, a non-oxygen inorganic molecule is the final electron acceptor at the end of the ETS. Some non-oxygen inorganic molecules anaerobic respiration uses include carbon dioxide, nitrate, sulfate, or oxidized iron. Through anaerobic respiration, there is less ATP formed. In aerobic respiration, the final electron acceptor of the electron transport system is an oxygen molecule. Aerobic respiration results in the formation of more ATP. Both aerobic and anaerobic respiration need glucose and use glycolysis. Both of them also make energy for the cell.

Question 23

What is fermentation

Answer 23

regenerates NAD+ from NADH by using an organic molecule as a final electron acceptor. This regeneration is used in order for glycolysis to continue.

Question 24

What are some of the products of fermentation in different organisms?

Answer 24

1) Lactic acid fermentation produces lactic acid.
- Examples of organisms that use this are streptococcus, lactobacillus, and Homo sapiens.
2) Alcohol fermentation produces ethanol and carbon dioxide.
- Microbes that use this type of fermentation are yeasts such as saccharomyces and candida.
3) E.coli uses many types of fermentation that can produce lactic acid, acetic acid, formic acid, ethanol, hydrogen gas, and carbon dioxide.
4) Enterobacter uses fermentation to produce formic and lactic acid, 2,3, butanediol, ethanol, and hydrogen gas.
5) Fermentation is used by Propionibacterium to produce acetic acid, carbon dioxide, and propionic acid.
6) Clostridium use fermentation to produce acetone, butyric acid, carbon dioxide, butanol, and ethanol.

Question 25

Compare and contrast cell respiration (aerobic and anaerobic) and fermentation.

Answer 25

The final electron accepter for aerobic respiration is oxygen while it is a non-oxygen and inorganic molecule in anaerobic respiration. For fermentation the final electron acceptor is pyruvate. Both aerobic respiration and fermentation use an organic electron acceptor. Both anaerobic respiration and fermentation produce less ATP than aerobic respiration. Cell respiration and fermentation both require glycolysis to occur.

Question 26

How are lipids catabolized?

Answer 26

Lipids such as triglycerides are broken down by releasing fatty acid chains. Lipases catalyze triglycerides. Phospholipids are broken down by releasing the phosphorylated head group via phospholipases. These parts are released from the three-carbon glycerol backbone. The final products of the catabolism of lipids are fatty acids and glycerol. Glycerol can be broken down further. It can be phosphorylated to create glycerol-3-phosphate that can then go through glycolysis. The fatty acids can be catabolized to remove their acetyl groups. The acetyl groups produced can be carried by coenzyme A to go through the Kreb’s cycle.

Question 27

How are proteins catabolized?

Answer 27

Protease enzymes degrade proteins. Extracellular proteases internally cut proteins to break them down into smaller peptides. These smaller peptides can be taken by cells. Intracellular proteases can then break down the smaller peptides into individual amino acids. These amino acids can be deaminated by removing the amino group. The final molecules can then go through the Krebs cycle or the transition reaction.

Question 28

What is the difference between oxygenic and anoxygenic photosynthesis?

Answer 28

In anoxygenic photosynthesis oxygen is not generated. Other reduced compounds function as the electron donor. Compounds that can serve as the electron donor include hydrogen sulfide or hydrogen gas. This type of photosynthesis is carried out by some types of bacterial phototrophs. Oxygenic photosynthesis involves using water as the electron donor. This type of photosynthesis is called oxygenic because oxygen is released and generated as a byproduct.

Question 29

How is bacterial metabolism critical in the nitrogen cycle?

Answer 29

Bacterial metabolism is critical in the nitrogen cycle because it is required to fix nitrogen and for denitrification. Bacteria can take nitrogen and fix it and turn it into organic molecules. It takes up atmospheric nitrogen and makes it available for other living organisms. For instance, cyanobacteria fix nitrogen into ammonia. Bacteria also contribute to the cycle back up as they are important in the process of denitrification. Bacteria in the soil use nitrate and convert it into nitrogen gas. They release the nitrogen back out as nitrogen gas to the atmosphere.

Question 30

How is bacterial metabolism critical in the sulfur cycle?

Answer 30

Bacterial metabolism is critical in the sulfur cycle as they convert hydrogen sulfide into sulfur then sulfate. Bacteria can use hydrogen sulfide and oxidize it to become sulfur and then sulfate. Bacteria can also remove sulfur groups from amino acids to produce hydrogen sulfide. This process causes the return of inorganic sulfur to the environment.