Energy Use and Expenditure Flashcards
What is energy needed for?
- Muscle Contraction
- Protein Synthesis
- Tissue Repair
- Active Transport
- Maintain Body Temp
- Gluconeogenesis
What is Gluconeogenesis?
Gluconeogeneis is the transforming of pyruvate back into stored glycogen when there is no oxygen.
Glucose - Glycolysis - Pyruvate - 1.(aerobic) 2.(anaerobic)
1. Krebs Cycle
2. Lactate - pyruvate - glycogenesis (requires 6ATP) - glucose - stored glycogen
Describe energy balance.
When intake > expenditure = positive energy balance
When intake < expenditure = negative energy balance
When intake = expenditure = energy balance
What are the Kcal values for each key energy source?
Carbohydrates - 3.75kcal/g
Fats - 9kcal/g
protein - 4kcal/g
Alcohol - 7kcal/g
How can the total energy of any given meal be measured?
Weighed
What is the definition of obese?
Greater than 30 BMI
What are some health complications associated with obesity?
Cardiovascular disease Type 2 Diabetes Colon and breast cancer Problems with weight bearing joints Resp conditions due to excess chest weight Psychological
What are eating disorders?
Any unhealthy attitude to food which can lead to illness.
What are the four types of eating disorder?
- Anorexia nervosa
- Bulimia (binge eating followed by anorexia type behaviour)
- Binge eating disorder
- OSFED (anything else)
How much energy do a 25yr old male or female require?
Female - 2080kcal a day
Male - 2600kcal a day
What are the three dimensions of Energy Expenditure?
- Basal Metabolic Rate
- Physical Activity
- Thermic effect of food
What is Basal Metabolic Rate?
The minimal amount of energy expenditure needed to survive (heart rate, breathing, brain activity, active transport)
What % of total energy expenditure (TEE) is covered by Basal Metabolic Rate?
60-70%
What is physical activity?
Energy to move, standing fidgeting, exercise
What % of total energy expenditure (TEE) does physical activity account for?
15-30% though varies widely
What is the Thermic affect of food?
Energy expenditure increases after eating due to energy cost of digestion
What % of total energy expenditure does the thermic affect of food account for?
10% (varies according to composition of diet)
What are some factors affecting the basal metabolic rate?
Weight
Body composition
Age
How does weight affect basal metabolic rate?
As weight increases so does BMR as more tissue = more energy expenditure
How does body composition affect basal metabolic rate?
At any given weight the higher the fat % the lower the BMR as muscle has a higher BMR than fat.
How does age affect basal metabolic rate?
BMR is highest in childhood largely due to the cost of growth.
Post 18yr BMR drops 2% per decade due to changes in body composition
What are some additional factors affecting basal metabolic rate?
Genetics, thyroid function.
Pregnancy = higher BMR
How is the energy cost of activity measured?
Calorimetry
What are the two types of Calorimetry?
Direct and Indirect
What is direct calorimetry?
Energy expenditure is measured by heat given off by subject which raises the temperature of a nearby water supply. This is accurate but costly and awkward
What is indirect Calorimetry?
Measures energy expenditure using douglas bag or electronic respirators by measuring oxygen uptake which increases with expenditure. Much less awkward.
What is the Krebs cycle?
A set of linked chemical reactions that take place in the mitochondria.
What is produced in the Krebs cycle?
2 ATP
NADH
FADH
What are NADH & FADH as produced by the krebs cycle?
Energy rich - electron - donor substances
What do NADH and FADH do?
Donate electrons as part of the Electron Transport Chain and the energy released from this generates further ATP
How many molecules of ATP does the Electron transfer chain generate?
Using O2 the electron transfer chain generates 32 molecules of ATP
How many ATP molecules in aerobic glucose (carbohydrate) metabolism are generated in:
Glycolysis?
Krebs Cycle?
Electron Transfer Chain?
Glycolysis - 2
Krebs Cycle - 2
Electron Transfer Chain - 32
What is the Electron Transport Chain?
A controlled release of energy using carrier molecules known as Cytochromes to carry electrons.
Describe the process of electron in the electron transport chain?
The electrons once donated from NADH & FADH move from cytochrome to cytochrome from a high energy state to a low energy state. As they travel down this chain they release energy which is used for ATP synthesis
What is anabolism?
Biochemical reactions that synthesis new molecules like lipids of carbohydrates and in doing so consume energy
What is catabolism?
Biochemical reactions that breakdown molecules like proteins or lipids and in do so release energy
In simple terms what does energy metabolism do?
Following digestion and absorption of nutrients like protein, lipids, carbohydrates, our body via metabolism extracts the energy in these molecules. It uses this energy to create ATP which can then be broken down to release energy when needed.
Discuss the metabolism of carbohydrates.
Carbohydrate molecules absorbed following digestion in the form of GLUCOSE
Glucose undergoes GLYCOLYSIS.
This converts the GLUCOSE into (2) PYRUVATE. In doing so that generates 2 ATP.
If anaerobic then PYRUVATE converted to LACTIC ACID
If aerobic, Pyruvate converted to ACETLY-CoA
Discuss the metabolism of Lipids
Lipids molecules (Glycerol + 3 Fatty Acids) absorbed following digestion are broken down into FATTY ACIDS.
BETA OXIDATION (aerobic) occurs synthesising ACETYL CoA.
ACETYL CoA then enters Krebs cycle
NO OXYGEN THEN NO FAT METABOLISM
Discuss the metabolism of Proteins
Proteins molecules absorbed following digestion broken down in to AMINO ACIDS
DEANIMATION occurs synthesising ACETYL coA.
Deanimation produces nitrogen which is excreted in urea - urine.
Amino Acids can also enter krebs cycle directly.
What is ACETYLE CoA?
A key point in metabolism. In Aerobic conditions it is the entry point for the krebs cycle
How many ATP molecules are synthesised from a single lipid molecule with (3) 18carbon fatty acids?
18 carbon fatty acid gives 146 ATP
x3 = 438 ATP
Therefore a fat molecule gives far more ATP than a carbohydrate
What are the by products of metabolism?
Carbon dioxide
Oxygen
When would you see protein metabolism?
Intense exercise
Starvation (muscle breakdown)
What is the healthy BMI window?
Between 18.5 and 24.9.
Below this is underweight, above is overweight