Nutrition Science and Everyday Application - beta v 0.1

PROTEIN FUNCTIONS 329
ENERGY PRODUCTION
Some of the amino acids in proteins can be disassembled and used to make energy. Only
about 10 percent of dietary proteins are catabolized each day to make cellular energy. The
liver is able to break down amino acids to the carbon skeleton, which can then be fed into
the citric acid or Krebs cycle. This is similar to the way that glucose is used to make ATP. If
a person’s diet does not contain enough carbohydrates and fats, their body will use more
amino acids to make energy, which can compromise the synthesis of new proteins and
destroy muscle proteins if calorie intake is also low.
Not only can amino acids be used for energy directly, but they can also be used
to synthesize glucose through gluconeogenesis. Alternatively, if a person is consuming a
high protein diet and eating more calories than their body needs, the extra amino acids will
be broken down and transformed into fat. Unlike carbohydrate and fat, protein does not
have a specialized storage system to be used later for energy.
Self-Check
An interactive H5P element has been excluded from this version of the text. You can view it online here:
https://openoregon.pressbooks.pub/nutritionscience/?p=468#h5p-15
Attributions:
• “Protein Functions”, section 6.4 from the book An Introduction to Nutrition (v. 1.0),
CC BY-NC-SA 3.0
Image Credits:
• Fig 6.9. ”Enzyme , antibody, and hormone” from “Protein Functions”, section 6.4
from the book An Introduction to Nutrition (v. 1.0), is licensed under CC BY-NC-SA
3.0
• Table 6.2. “Protein types and functions” by Tamberly Powell is licensed under CC
BY-NC-SA 2.0
• Fig 6.10. “Collagentriplehelix” by JWSchmidt is licensed under CC BY-SA 3.0
• Fig 6.11. “Enzyme activity” from “Protein Functions”, section 6.4 from the book An