biochem overview Flashcards
List the components of the energy balance equation including components of energy expenditure.
Total energy expenditure: resting metabolic rate (75%) + thermic effect of food (8%) + energy expended in physical activity (up to 30-40%)
primary determinant of resting metabolic rate
fat free mass (lean body mass)- organs such as the liver, heart, kidney, brain and skeletal muscle are the most metabolically active
ways to measure resting metabolic rate
- Measure via indirect calorimetry: device that measures respiratory gas composition and flow rates to estimate O2 consumption and CO2 production. This is an indirect measure of energy. 2. Estimated via formula using age, sex, height and weight. Lean body mass can be added if known.
what is thermic effect of food
Energy cost of digesting and distributing nutrients from the diet to tissues of the body. Protein > carbohydrates > fat
Non exercise activity thermogenesis
component of energy expended in physical activity- This is energy expended in movement that is “unconscious” or unplanned. Some people call this “fidgeting” or movements that we all do while we are doing other things.
ways to measure total energy expenditure
doubly labeled water- measures oxygen consumption in free living individuals over a period of weeks.
Estimate the pool sizes of stored fat, carbohydrate and protein in the body.
In a 70kg person- fat: 13kg (120,000kcal, 9 kcal/g), plus 450kcal in liver and 3000kcal in muscle. Carb (glycogen): 400g (1600kcal, 4kcal/g) in muscle, 100g (400kcal, 4kcal/g) in liver . Protein: no readily accessible pool of protein in the body
what is the most accurate way to measure body composition
DEXA- dual energy x-ray absorptiometry
List the hierarchy of fuels for oxidation. Discuss how this relates to weight gain
Protein excess: oxidized to form carbohydrate or fat. Carb and fat excess: carbs preferentially oxidized and fat stored. individuals in positive energy balance will tend to accumulate body fat.
hierarchy of fuels during fasting state
Brain is most important organ to sustain- requires glucose. Glycogen is broken down, protein in muscles breaks down into aa which are converted to glucose.
Identify the structures of glucose, fatty acids and amino acids.
glucose: hexose ring. Fatty acid: hydrocarbon chain with carboxy group at end. Amino acid: amino group (NH2), carboxylic group (COOH), side chain (R ) and alpha carbon with H
fasted vs fed state
In the fed state insulin is high, glucagon is low and the task of the body is to assimilate ingested nutrients. In a fasted state, insulin is low, glucagon is high and the body is relying on previously stored nutrients
anabolic vs catabolic state
“Anabolic” refers to processes of building polymers from monomers as opposed to catabolic processes which refer to pathways that break down complex molecules into their constituent parts.
positive vs negative energy balance state
similar to fed versus fasted, but are broader including states like exercise where there is a need to acutely access stored nutrients. Positive energy state is similar to fed state
list main biochemical pathways involved in carbohydrate metabolism
glycolysis, TCA cycle, electron transport, gluconeogenesis, glycogen formation and breakdown and pentose phosphate pathway (hexose monophosphate shunt)
