7.3 Energy use Flashcards
Energy use
All living organisms require energy to survive.
This energy comes from an essential chemical reaction that takes place in all living cells called respiration.
Glucose is a reactant for respiration that stores chemical energy.
When glucose is broken down during respiration the energy is released in a usable form.
To get glucose into the body it must be consumed in the food we eat.
Energy is measured in calories and has the unit Kcal.
Different people have different day-to-day energy requirements.
Energy consumptions
Age - Young children require a lot of energy because they are very active and use energy for growing.
Adults require less energy because as you age, your body replaces muscle with fat and fat burns fewer calories.
Gender - The average adult male requires 2,500 Kcal/day.
The average adult female requires 2,000 Kcal/day.
Height - Taller people require more energy than shorter people because they have more body cells that are respiring.
Energy expenditure - Exercise burns calories.
The more exercise a person carries out, the higher the energy requirement
People who live a sedentary lifestyle require very little.
Balanced diet
A balanced diet provides all the necessary nutrients required for good health.
To achieve a balanced diet, each person must consume a variety of different food types to gain all the different required nutrients.
No single food contains all the nutrients required by the human body
The required nutrients are: Carbohydrates, Proteins, Fats, Fibre, Vitamins, Minerals and Water.
Importance of a balanced diet
Consuming too much saturated fats can lead to excess fats being stored in the body. Over time and in excess this can lead to obesity.
Carbohydrates and sugary foods provide glucose for respiration, increasing the energy available for sporting activities.
Different nutrients are required for the basic metabolism (chemical reactions) in all cells - these include things like growth and water balance in cells.
Nutrients
Carbohydrates - Provide glucose for respiration, which releases energy in the body for all types of exercise of all intensities.
Large carbohydrates like starch break down slower than sugars and so release their energy over a longer period of time.
A typical balanced diet is made up of: 55–60% carbohydrate.
Fat - Also acts as an energy source but is only used when there are not enough carbohydrates available to meet the demand for energy.
It provides more energy than carbohydrates at low-intensity exercise.
A typical balanced diet is made up of: 25–30% fat.
Protein - Needed for growth and building/repairing of muscles.
A typical balanced diet is made up of: 15–20% protein.
Vitamins and minerals - Needed for aiding in the functioning of body systems and the overall health of the body.
Dehydration
Dehydration is the excessive loss of body water, interrupting the functioning of the body.
It occurs when the body does not take in enough water to supply the needs of the body’s metabolism and to resupply the water that is lost via excretion (e.g. sweat).
Consuming water in food and drinks (hydrating) is essential for preventing dehydration.
This is particularly important during exercise when increased sweat is lost to the environment.
Consequences of dehydration
The slowing down of blood flow due to ‘thicker’ blood with high viscosity. This reduces the delivery of essential chemicals like glucose and oxygen to the cells.
Heart rate increases to try and counteract the effect of the slow-flowing blood.
Sweating is a very important mechanism for cooling the body down. Without excess water for sweat, the body can easily overheat.
The reduction in blood flow to the brain and muscles can also increase reaction times and lead to poor decision-making.
This can have a particular impact on sporting ability and success in competitive environments.
Muscle fatigue and cramps are also common symptoms of dehydration as muscles suffer from a lack of oxygen due to slow blood flow.
