ENERGYENERGY

ABILITY TO DO WORKABILITY TO DO WORK

© PDST Home Economics

EnergyEnergy

Energy is the ability to do a taskEnergy is the ability to do a task

The food we eat gives the body energyThe food we eat gives the body energy

Food is the fuel for the bodyFood is the fuel for the body

Measuring EnergyMeasuring Energy

Energy is measured in calories or joulesEnergy is measured in calories or joules

We usually refer to kilocalories or kilojoules We usually refer to kilocalories or kilojoules because a calorie or a joule is a very small because a calorie or a joule is a very small amount amount

A kilocalorie is the amount of heat energy it takes A kilocalorie is the amount of heat energy it takes to raise a litre of water by 1to raise a litre of water by 1ºCºC

1kilocalorie = 4.2 kilojoules1kilocalorie = 4.2 kilojoules

Getting energy from foodGetting energy from food

Energy is got from food in a process called Energy is got from food in a process called cellular respiration (oxidation).cellular respiration (oxidation).

Digested food and oxygen go into the body cells Digested food and oxygen go into the body cells and react together to produce energyand react together to produce energy

Food + Oxygen → Energy + water + COFood + Oxygen → Energy + water + CO22

Food labels tell us how much energy 100g of a food will give us.

Energy Content of FoodEnergy Content of Food

All foods give us energy.All foods give us energy. Some food will give more energy than Some food will give more energy than

others it depends on the kind of nutrients others it depends on the kind of nutrients in the food.in the food.

Protein, Fats and Carbohydrates give a lot Protein, Fats and Carbohydrates give a lot of energy but Water, Minerals and of energy but Water, Minerals and Vitamins give very littleVitamins give very little

100g Cabbage = 22 kilocalories100g Cabbage = 22 kilocalories 100g Cheddar cheese = 412 kilocalories100g Cheddar cheese = 412 kilocalories Fats give the most energyFats give the most energy

Energy Value of NutrientsEnergy Value of Nutrients

1g Protein = 4 kilocalories or 17 kilojoules of 1g Protein = 4 kilocalories or 17 kilojoules of energyenergy

1g Carbohydrate = 4 kilocalories or 17 kilojoules of 1g Carbohydrate = 4 kilocalories or 17 kilojoules of energyenergy

1g Fats = 9 kilocalories or 38 kilojoules of energy1g Fats = 9 kilocalories or 38 kilojoules of energy

Amount of energy neededAmount of energy needed

A basic amount of energy is needed just to keep A basic amount of energy is needed just to keep the body alive ….. Heart, Lungs, Brain.the body alive ….. Heart, Lungs, Brain.

This basic amount of energy is called the Basal This basic amount of energy is called the Basal Metabolic Rate (BMR).Metabolic Rate (BMR).

Energy NeedsEnergy Needs

Everyone needs a different amount of energy.Everyone needs a different amount of energy.

The factors that decide how much energy you need areThe factors that decide how much energy you need are AgeAge SizeSize ActivityActivity GenderGender ClimateClimate Pregnancy/ breast feedingPregnancy/ breast feeding

Energy BalanceEnergy Balance

To keep your body at the same weight, the To keep your body at the same weight, the amount of energy you take in must equal the amount of energy you take in must equal the amount of energy you use upamount of energy you use up

If you eat more calories then you use you gain If you eat more calories then you use you gain weightweight

If you eat less calories than you use you loose If you eat less calories than you use you loose weightweight

Functions of EnergyFunctions of Energy

All activities, including working internal organsAll activities, including working internal organs

Keeping body temperature at 37Keeping body temperature at 37ºCºC

Working of cells and nervesWorking of cells and nerves

Making new cells … growthMaking new cells … growth

How much Energy do you needHow much Energy do you need

Girls 9 – 18 need 2300 kcals. per dayGirls 9 – 18 need 2300 kcals. per day

Boys 12 – 15 need 2800 kcals. per dayBoys 12 – 15 need 2800 kcals. per day

Boys 15 – 18 need 3000 kcals per dayBoys 15 – 18 need 3000 kcals per day

How much energy?How much energy?

Activity done for 1 hourActivity done for 1 hour

Sleeping - 70 kcalsSleeping - 70 kcals

Writing - 115 kcalsWriting - 115 kcals

Housework - 250 kcalsHousework - 250 kcals

Walking fast - 400 kcalsWalking fast - 400 kcals

Swimming - 700 kcalsSwimming - 700 kcals

Running - 900 kcalsRunning - 900 kcals