Chapter 25 Metabolism

Question 1

Metabolism

Answer 1

the sum of all chemical reactions in the body; catabolism + anabolism

Question 2

Heat

Answer 2

40% of the energy is captured to produce ATP from ADP and the remaining 60% escapes as…..

Question 3

Oxidation

Answer 3

the removal of electrons

Question 4

Reduction

Answer 4

the addition of electrons

Question 5

Substrate Level Phosphorylation

Answer 5

a high energy phosphate is transferred directly from a substrate to ADP thus forming ATP

Question 6

Oxidative Phosphorylation

Answer 6

electrons are transferred from an organic compound to a
cofactor carrier molecule (e.g. NAD+). The electrons are passed through other carriers (the electron transport chain) to a final acceptor (oxygen) and the passing of the electrons releases energy that is harvested to add a phosphate to ADP in a process called chemiosmosis.

Question 7

Carbohydrate Catabolism (two ways)

Answer 7

1. Cellular respiration
2. Fermentation

Question 8

ATP Production (two ways)

Answer 8

1. Substrate Level Phosphorylation
2. Oxidative Phosphorylation

Question 9

Aerobic Respiration of Gluecose (Three stages)

Answer 9

1. Glycolysis
2. Citric Acid Cycle
3. Electron Transport Chain

Question 10

Glycolysis

Answer 10

• anaerobic, occurs in cytoplasm
• 1 glucose oxidized and catabolized into 2 pyruvic acids
• 2 NADH produced by reduction of 2 NAD via oxidation of glucose
• 2 ATP produced by substrate level phosphorylation
• If no O2 available, pyruvic acid reduced to lactic acid (fermentation)
• Erythrocytes (RBCs): glycolysis only (no mitochondria!)
• Skeletal muscle: fermentation when no O2
• Neurons and cardiac muscle cannot ferment, need O2, must always do
  complete aerobic respiration of glucose

Question 11

Citric Acid Cycle

Answer 11

• 2 acetyl combined with 2 oxaloacetic acids creating 2 citric acids
• citric acid decarboxylated and oxidized producing 4 CO2, 6 NADH, 2 FADH2 - 2 ATP generated by substrate level phosphorylation

Question 12

Electron Transport

Answer 12

• aerobic, occurs on cristae of mitochondria
• NADH and FADH2 (reduced during glycolysis and citric acid cycle) are oxidized
• electrons (as H) are passed to the ETC (cytochromes), finally accepted by oxygen - 32 ATP generated by chemiosmosis / oxidative phosphorylation
• 12 H2O produced as waste from reduction of oxygen

Question 13

Decarboxylation

Answer 13

• 2 pyruvic acid decarboxylated and oxidized into 2 acetyl
  Co A + 2 CO2 with 2 NADH

Question 14

Lipolysis

Answer 14

The process of lipid catabolism hydrolyzes triglycerides, the storage form of fat, into glycerol and three fatty acids. The glycerol is converted into pyruvic acid in the cytoplasm and catabolized through the Citric Acid Cycle in the mitochondria. The fatty acids are catabolized by Beta-oxidation in the mitochondria to be entered into the Citric Acid Cycle as two-carbon fragments. For each two-carbon fragment of fatty acid produced by Beta-oxidation, the cell can generate 17 molecules of ATP. This is 1.5 times the energy production (when compared carbon to carbon) as with glucose. Although lipolysis generates more energy, it always requires oxygen and occurs much more slowly than equal carbohydrate metabolism.

Question 15

Protein and Amino Acid Catabolism

Answer 15

or proteins to be used for energy production, they must first be broken down into individual amino acids. Then for the amino acids to be used in the Citric Acid Cycle they must first have the amino group (NH2) removed in a process called deamination, which requires vitamin B6. The amino group is removed in conjunction with a hydrogen creating ammonia (NH3), which is very toxic. These reactions are carried out by cells of the liver. The liver must then convert the ammonia to urea, which is relatively harmless, for excretion by the kidney. The remaining amino acid carbon chains are then used at various stages in the Citric Acid Cycle to generate ATP. The amount of ATP produced varies with the type of amino acid, depending on which step into the Citric Acid Cycle it was entered.

Question 16

Nucleic Acid Catabolism

Answer 16

DNA is never catabolized for energy. RNA can be broken down into simple sugars and nitrogenous bases. The sugars are metabolized in glycolysis but only the pyrimidine bases, uracil and cytosine, can be processed into the Citric Acid Cycle. The purines, adenine and guanine, are deaminated and excreted as uric acid making RNA metabolism very inefficient. Typically nucleotides are simply recycled into new nucleic acid molecules and are not used for energy production.