4.4.4 Other Fuels in Respiration

Question 1

fats and proteins

Answer 1

• broken down into units that can enter various parts of the respiratory pathway, serving as an alternate fuel in respiration.

Question 2

note

Answer 2

• Respiration is controlled by allosteric feedback. For example, the allosteric enzyme phosphofructokinase is stimulated by AMP and inhibited by ATP.

Question 3

triglycerides

Answer 3

• a type of fat, are composed of glycerol and three fatty acids. When broken down, glycerol can enter glycolysis as glyceraldehyde phosphate. The fatty acids are broken down into two-carbon subunits that can easily be converted into acetyl CoA. One gram of fat has more than twice the energy as in one gram of glucose.

Question 4

amino acids

Answer 4

• usually used for the construction of proteins, but can be used for energy. In the liver, the amine group is removed and processed into urea, which is then excreted from the body. The rest of the amino acid that is left over may then enter the respiratory pathway at one of several different places.

Question 5

phosphofructokinase

Answer 5

• the third enzyme in glycolysis, serves as a major control point in respiration. The enzyme has a substrate binding site and an allosteric site where molecules can bind to inhibit or stimulate it. When ATP and/or citrate build up, they are able to inhibit phosphofructokinase. These are products of respiration, and when their levels get high it signals that it is not necessary to produce more product. As ATP is used, AMP levels build up. AMP is able to stimulate phosphofructokinase, allowing for the continued production of ATP.

Question 6

In order for proteins to be useful as an energy source for glycolysis and aerobic respiration, proteins must first

Answer 6

• be broken down into amino acids

Question 7

Regulation of glycolysis takes place by the

Answer 7

• allosteric inhibition of phosphofructokinase by excess ATP

Question 8

During the breakdown of fats for energy, glycerol

Answer 8

• enters glycolysis as glyceraldehyde 3-phosphate

Question 9

Before proteins can be used for fuel what must happen?

Answer 9

• The peptide bonds between amino acids must be broken and they must have their amino group removed

Question 10

In many organisms, ___________ can be used as an energy alternative to glucose.

Answer 10

• proteins, triglycerides, and fructose

Question 11

What compounds have an effect on the enzymatic activity of phosphofructokinase?

Answer 11

• ATP, citrate, AMP