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What happens to fatty acids when they enter the body?
(*hint* making ATP & Krebs cycle)
Fatty acids are converted into acetyl CoA in the central matrix of a mitochondrion which then enters the Krebs cycle making ATP
What happens to amino acids when they enter the body?
Amino acids are converted into pyruvic acid allowing them to enter the pathway and release energy when they enter the Krebs cycle
Which releases the most energy when broken down: carbohydrate, fat or protein?
What is the energy balance equation?
Energy in - energy out = change in energy stores
If someone has a positive change in energy stores will they gain or lose weight?
A high energy diet and lack of activity leads to what? (In terms of energy stores)
Fat being stored by the body
If fat is regularly being stored by the body what could this lead to?
Obesity. Which causes an increase in LDLs therefore increasing the risk of CVD
A healthy low fat diet reduces the risk of CVD by around __%?
What are the 6 variables that affect energy expenditure?
- Basal metabolic rate
- Dietry induced thermogenesis
- Physical activity
- Composition of the diet
- Pregnancy and lactation
What is 'Basal Metabolic Rate'?
The energy expended in a resting, fasting state where the person does not need to thermoregulate. It is a measure of the energy required to carry out basic essential bodily funtions such as breathing and circultion of blood.
What factors affect BMR? And how do they affect it?
- Body size - the greater the mass, the more tissue, the more energy is required so BMR increases
- Body composition - Muscle is more metabolically active than fat tissue
- Gender - Men have higher BMR as they tend to have more muscle tissue than women (women have more fat)
- Age - BMR is proportionally higher in children as they are growing.
- Nutritional status - BMR is reduced by being on a low energy intake for any length of time. This helps animals survive in famine conditions for longer.
How do the additional energy expenditures above BMR affect energy expenditure?
- Physical activity above resting increases the additional energy and as the intensity and duration of the activity increase so does energy expenditure
- A colder climate increases additonal energy expenditure. As temperature decreases heat loss increases. The body increases its energy expenditure to generate more heat to maintain body temperature.
- Dietry induced thermogenesis is the additional energy expenditure needed to digest food. It depends on the type of food eaten.
- The composition of the diet also affects energy expenditure. High protein and high carbohydrate diets have high energy expenditure for digestion. High fat diets have low energy expenditure.
- During pregnancy there will be energy requirements for the growth of the foetus, placenta and breast tissue. Similarly, lactation requires energy for the synthesis of molecules for the milk.
Name and describe the three ways of measuring energy expenditure
- Direct calorimetry measures the heat released from the body in an airtight chamber, which is insulated to prevent heat loss. A person lives in the chamber for several days and the heat released from their body is found by comparing the temperatures of water entering and exiting a heat exchange. This is the most direct way of measuring energy expenditure.
- Indirect calorimetry is when oxygen consumption is measured over a period of time. The total volumes of oxygen inhaled and exhaled are compared. There is a direct correlation between oxygen consumption and energy expenditure.
- Measuring heart rate is the most indirect way of measuring energy expenditure. This is based on the correlation between heart rate and oxygen consumption. For this, the persons oxygen consumption and heart rate have to be found at various exercise workloads and even then the energy expenditure is estimated from the two correlations.