Energy balance 1 Flashcards
Each cell in the body needs energy to perform the functions essential for the cell’s survival:
Name some of these processes
- intracellular signaling.
- DNA and RNA synthesis.
- Active transportation across cell membranes.
- Cellular Repair.
Energy is also required to carry out specialised contributions towards maintaining homeostasis such as:
Gland secretions (pancreatic beta cells secrete insulin).
Muscle contractions.
Describe the process of Cellular Respiration
- Process that makes energy for all life on earth.
- it is the transfer of chemical bond energy of organic molecules to the chemical bond of energy of ATP.
- Remember:
- Making chemical bonds stores energy.
- Breaking chemical bonds releases energy.
•Respiration breaks the bonds of glucose, so it releases energy.
Harvesting Energy Stored in Food: cellular respiration
- breaking down food to produce ATP
- in mitochondria
- using oxygen (“aerobic” respiration)
- Usually digesting glucose, however could be other nutrient sources, fats, proteins or other sugars.
Draw a cellular respiration flow chart
Energy balance
Conversion of Nutrient Energy to Heat:
Can all energy in nutrient molecules can be harnessed to perform biological work?
How much energy derived from nutrients is used to make ATP?
What does all energy liberated from ingested food, not used to complete internal or external work, eventually become?
- Not all energy in nutrient molecules can be harnessed to perform biological work.
- Only 50% of energy derived from nutrients is used to make ATP.
- All energy liberated from ingested food, not used to complete internal or external work, eventually becomes body heat.
However this heat is not wasted, because much of it is used to maintain body temperature.
Describe the Importance of Maintaining Body Temperature
- Optimise enzyme activity.
- Maintain immunity.
- More specific effects, include disruptions to osmosis and oxygen dissociation.
Consequences:
- Heat exhaustion/Heat stroke.
- Hypothermia
Temperature Regulation:
What is internal core temperature is homeostatically maintained at?
What are the main sites for monitoring body temperature
•100°F (37.8°C)
–Sites for monitoring body temperature:
- Oral
- Axillary
- Rectal
- Eardrum
- Temporal
Define Basal Metabolic Rate
A measurement of the number of calories needed to perform your body’s most basic (basal) functions.
What does metabolic rate determine?
Metabolic rate determinations form the basis of weight loss/gain goals and even have diagnostic value
What is a calorie?
It is the basic unit of heat energy
•Amount of heat required to raise the temperature of 1g of H2O by 1°C
–Kilocalorie or Calorie: used when discussing the human body
•Equivalent to 1000 calories
How Do You Measure Metabolic Rate?
Method 1:
DIRECT CALORIMETRY
Direct calorimetry obtains a direct measurement of the amount of heat generated by the body within a structure large enough to permit moderate amounts of activity. These structures are called whole-room calorimeters.
Method 2:
INDIRECT CALORIMETRY
Indirect calorimetry (a type of whole body calorimetry where all gas consumption and gas exhalation are continuously monitored) can be used to determine energy expenditure through the use of equations relating total O2 consumption, CO2 expiration, and urinary nitrogen excretion to energy utilization
Direct vs In-direct Calorimetry
Direct calorimetry:
Advantages: Extremely accurate
Disadvantage: Expensive, difficult to operate and not suitable for large groups.
Indirect calorimetry:
Advantages: Much cheaper & easy to carry out.
Disadvantage: Not as accurate as direct calorimetry.
State the rate of energy expenditure for a 70kg (154 pound) person during different activities
What factors Factors Influence the Basal Metabolic Rate?
- Body size: weight, height, and surface area increase.
- Body composition: Fat vs Muscle.
- Gender:
- Age:
- Climate and body temperature:
- Hormonal levels Thyroxine (T4), and adrenalin (epinephrine)
- Health: Fever, illness, or injury may increase resting metabolic rate two-fold.
Energy consumed from food =
external work + internal heat production ± stored energy
What is crucial to maintain a neurtal energy balance?
Energy input must equal energy output to maintain a neutral energy balance
Energy balance states
- Neutral energy balance: energy intake equals output.
- Positive energy balance: energy intake exceeds output.
- Negative energy balance: energy intake is less than immediate requirements.
How Does The Body Know We Are Hungry?
- There are no calorie receptors, which signal to the body how much we have eaten, or need to eat.
- Chemical messengers are responsible for the body’s nutritional status.
- Adipose stores
- Feeding status
The control of food intake does not depend on changes in a single signal but is determined by the integration of many inputs that provide information about the body energy status.
Food Intake is controlled primarily by what part of the brain?
the hypothalamus
Food Intake is controlled primarily by the hypothalamus:
What is the role of the arcuate nucleus?
What gives rise to the sensation of hunger?
What is satiety?
What is neuropeptide Y (NPY)
What is the function of melanocortins?
- Arcuate nucleus: central role in long-term control of energy balance and body weight and short-term control of food intake from meal to meal.
- Feeding or appetite, signals give rise to the sensation of hunger.
- Satiety is the feeling of being full.
- Neuropeptide Y (NPY): potent appetite stimulator
- Melanocortins: suppress appetite, thus leading to reduced food intake and weight loss
What are some regulatory Inputs for food intake?
•Regulatory inputs to the arcuate nucleus in long-term maintenance of energy balance: leptin and insulin
–Adipokines: hormones secreted by adipose tissue that play important roles in energy balance and metabolism
–Leptin: essential for normal body-weight regulation
–Insulin: important role in long-term control of body weight
Beyond the arcuate nucleus:
What additional neuronal areas of the hypothalamus control dietary intake?
Lateral hypothalamic area (LHA)
Paraventricular nucleus (PVN)
•LHA = Contains neurons that synthesise Orexins: potent stimulators of food intake:
- NPY +
- Melanocortin –
•PVN = Secrete corticotropin-releasing hormone which are inhibitors of food intake:
- NPY –
- Melancortin +
