Chapter 6 Microbial Metabolism

Question 1

Metabolism

Answer 1

• Sum of all chemical reactions that take place in an organism
• Can be divided into two classes:
  1) Reactions requiring energy = anabolic
  2) Reactions generating energy = catabolic

Question 2

Anabolism (biosynthesis)

Answer 2

• The building of complex organic molecules into simpler ones
• Example: Proteins broken down into amino acids; energy released

Question 3

ATP

Answer 3

• Energy is stored in the form of Adenosine Tri Phosphate (ATP)
• High energy bond is broken: energy released is used as the driving force for other reactions
• ATP => ADP + pi
• ATP is generated using energy from catabolic reactions

Question 4

ATP has two key functions within the cell

Answer 4

1) Energy currency of the cell by releasing energy when hydrolysed to ADP (powers cell metabolism)
2) It may transfer the released phosphate group to other organic molecules, rendering them less stable and more reactive

Question 5

ATP is synthesized from ADP using energy derived from one of two sources:

Answer 5

1) Solar energy- photosynthesis converts light energy into chemical energy that is stored as ATP
2) Oxidative processes - Cell respiration breaks down organic molecules to release chemical energy that is stored as ATP

Question 6

Oxidation - Reduction (Redox) Reactions

Answer 6

• Oxidation - removal of electrons from a molecule
• Reduction - addition of electrons to a molecule
• In a redox reaction: One molecule gets oxidized, and another molecule gets reduced

Question 7

Nicotinamide Adenine Dinucleotide (NAD+, NADH + H+)

Answer 7

• An electron carrier
• Removes 2 electrons from a substrate, then gives them to another substrate
• 2 protons (H+) are also transferred
• FIND FORMULA (Reducing Power)

Question 8

Collision Theory

Answer 8

• Atoms/ molecules are continuously moving and colliding
• Old chemical bonds can be broken
• New bonds can be formed
• Collision energy needed for chemical reactions = activation energy
• To increase reaction rate: increase temp., increase pressure, enzymes

Question 9

Enzymes

Answer 9

• Serve as catalysts - speed up a chemical reaction without being permanently altered
• Acts on specific substrates - each enzyme catalyzes only one reaction
• Lowers the activation energy

Question 10

Carbohydrate Catabolism

Answer 10

• Glucose is the most common carbohydrate used for energy
• Two processes can be used to break down glucose:
  1) Cellular Respiration
  2) Fermentation

Question 11

Substrate Level Phosphorylation

Answer 11

ATP is formed when enzymes transfers a phosphate group from a substrate to ADP

Question 12

Oxidative Phosphorylation

Answer 12

1) Uses O2 to oxidize the electron carriers NADH and FADH2 in order to generate ATP
2) ATP is made by a mechanical process, ADP and Pi are smashed together in ATP synthase
3) Occurs in electron transport chain on the mitochondrial inner membrane
4) Water is produced in this process as O2 is reduced

Question 13

Cellular Respiration (Stages)

Answer 13

1) Glycolysis (Splitting of Sugar)
2) The TCA Cycle (Kerbs Cycle)
3) Electron Transport Chain

Question 14

Glycolysis

Answer 14

• Sequence of 10 reactions
• 1 Glucose is converted into 2 molecules of pyruvate
• Small amount of energy is released – 2 ATP + 2 NADH
• Does not require oxygen

Question 15

TCA cycle (Kerbs Cycle)

Answer 15

• Pyruvate is broken down completely to CO2
• More ATP and NADH produced (2 ATP, 8 NADH, and others)
  -The TCA cycle occurs in the:
  Cytoplasm of a bacterial cell
  Mitochondria of a eukaryotic cell

Question 16

Election Transport Chain

Answer 16

• NADH electrons are transported through a series of electron carriers
• Occurs in the cell membrane of bacteria
• In the mitochondrial membrane of eukaryotic cells
• Energy released during each transfer is used to make ATP
• Makes 2-3 ATP per NADH
• Cellular respiration produces about 32-38 ATP per glucose

Question 17

Fermentation

Answer 17

• Also starts with Glycolysis
• No TCA cycle
• No electron transport chain
• Does not require oxygen
• Very inefficient: produces only 2 ATP per glucose
• At the end of glycolysis, pyruvate is converted into a fermentation product

Question 18

Examples of Fermentation

Answer 18

1) Lactic Acid Fermentation
- Pyruvate is converted to lactic acid as a waste product
- Example: Yogurt is produced when bacteria ferment the sugars in milk to produce lactic acid
2) Alcohol Fermentation
- Carried out by yeast (fungi) and some bacteria
- Waste products are ethanol and CO2

Question 19

Food Catabolism

Answer 19

• Because bacteria don’t eat just glucose
  1) Carbohydrates
  2) Lipids
  3) Proteins

Question 20

Carbohydrates (Food Catabolism)

Answer 20

• Polysaccharides are broken down into component sugars

- Converted to glucose

Question 21

Lipids (Food Catabolism)

Answer 21

Broken into components: fatty acids and glycerol by the enzyme - Lipase

Question 22

Proteins (Food Catabolism)

Answer 22

• Broken into amino acids, by enzymes - proteases

- These intermediates can than be catabolized using glycolysis and TCA

Question 23

Anabolism (biosynthesis)

Answer 23

Components of glycolysis and TCA cycle usually serve as starting point:

1) For amino acid, lipid and nucleotide production
2) Called: precursor metabolites