BIOGEOSPHERE
Bilingual Biology and Geology
I.E.S. "J.S.Elcano (Sanlúcar Bda.)
2. Nutritional needs
We need food to satisfy three types of needs: energetic, structural, and functional and regulatory.
a) Energetic needs
To maintain the activity of all our cells, tissues and organs and do some physical activity our bodies need energy.
We obtain the energy we need from energy-giving nutrients (sugars and fats) and when these are lacking, also from proteins. This process happens as a result of cellular respiration, which is a combination of metabolic reactions that take place in cells.
Different nutrients have different calorific values:
- one gram of fat gives you 9 kcals
- one gram of sugars gives you 3.75 kcals
- one gram of protein gives you 4 kcals
Even when our bodies are resting, they need a minimal amount of energy. This is called the basal metabolic rate and is the energy required to keep our vital functions going: breathing, blood flow, etc.
The basal metabolic rate is measured after resting in one place with an average temperature (about 20°C) and after not eating for 12 or more hours.
The value of the basal metabolic rate is expressed in kilocalories (kcal) per day and is different for different people. It depends on body mass, size, age and sex. Its average value is between 1800 and 1600 kcal/day.
The daily basal metabolic rate can be calculated approximately like this:
Men
66.5 + [13.7 x body mass (kg)] + [5 x height (cm)] - [6.7 x age (years)]
Women
55 + [9.5 x body mass (kg)] + [4.8 x height (cm)] - [4.7 x age (years)]
To the basal rate we add the energy expended corresponding to the physical activity that has been done. Its average value is between 2000 and 3000 Kcal/day.
Basal rate = Basal metabolic rate + Physical activity
b) Structural needs
As well as providing energetic nutrients, food also provides the body with essential substances to build and repair biological structures.
The most important structural nutrients are proteins, but some lipids and mineral salts also have this function. We need 0.8 grams of proteins daily per each kilogram of weight at less to be healthy.
c) Functional and regulatory needs
Our body needs other kinds of nutrients like vitamins and some minerals in order to function properly. These ensure that metabolic reactions happen effectively, organs function normally and all parts of our body work well together.
Although our body needs less of these types of
nutrients than the other types, they are still
essential.
READING ACTIVITIES
After reading the text, copy and answer the following questions into your notebook:
Remember: you must make complete sentences.
2.1. Define basal metabolic rate. What factors does it depend on?
2.2. Calculate your basal metabolic rate (use the formula in the text
to do it). Is this all the energy that you need during a day? Why?
2.3. Knowing how much energy gives us each type of nutrient, calculate:
a. How much energy give us a ham sandwich that contains 100 g of bread (consider that all the bread is glucid) and 50 grams of ham, of which 15 grams are fats.
b. How much energy gives us 250 grams of rice that contain 65% of glucids, 5% of proteins and 1% of lipids. What type of nutrients corresponds to the percentage remaining?
2.4. What happen with the nutrients we take in excess, the ones that cells
do not consume? What consequences can have it to the health?
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Eva Mª
López Rodríguez
Departamento
Biología y Geología
IES " J. S. Elcano"
Sanlúcar de Barrameda