Nutrition
Nutrition is the
uptake and storage of organic and inorganic substances needed to give energy
and raw materials for growth and repair.
-
Organic: made of central chains
of carbon. E.g. carbohydrates, proteins and fats = CHO
-
Inorganic: contain no carbon and
tend to be small. E.g. water, vitamins, and inorganic ions such as Na+,
K+, H+
We need food for energy, growth and repair
and to protect us from disease.
An
autotroph is an organism that creates its own food through photosynthesis or
chemosynthesis. E.g. plants.
A
heterotroph is like a human or other animal; they cannot produce their own food
and must eat other organisms to live.
A balanced diet is one that contains adequate amounts of all the necessary nutrients required for healthy growth and activity.
Nutrient
|
Function
|
Examples
|
Carbohydrates
|
To give us
energy
|
Pasta, bread,
cereal
|
Proteins
|
For growth and
repair of tissues.
|
Fish, meat, eggs
|
Fats
|
Help to keep us
warm and to make cell membranes. Also for insulation and buoyancy.
|
Butter,
chocolate, oil
|
Vitamins (in
small amounts)
|
For cells to
work properly.
|
Carrots (Vit.C)
|
Minerals (in
small amounts)
|
To make body
chemicals. (Calcium for healthy teeth and bones. Iron for blood.)
|
In a variety of
foods such as meat, dairy and fruits.
|
Fibre
|
For peristalsis
and healthy bowel function.
|
Bread, nuts,
fruit
|
Water
|
Enables chemical
reactions and transports nutrients around the body.
|
Carbohydrates
Carbohydrates (also called saccharides) are molecular
compounds made from just three elements: carbon, hydrogen and oxygen.
The carbohydrates
with the smallest and simplest molecules are sugars. These are called
monosaccharaides.
·
Glucose is a monosaccharide:
has 1 ring of carbon atoms, which has hydrogen and oxygen atoms, attached to
it.
·
Maltose is a disaccharide:
has 2 rings.
·
Starch, cellulose and glycogen are polysaccharides:
have 4 rings.
Proteins are made of long chains of amino acids chemically bonded together.
Amino acids are made of carbon, hydrogen, oxygen, nitrogen and sometimes sulfur. In nature there are thousands of different
proteins, but there are only 20 different types of amino acids.
Examples of very important proteins :
- haemoglobin
|
- enzymes
|
- antibodies
|
- keratin
|
- collagen
|
- insulin
|
Examples of structural
proteins :
- hair
|
- fingernails
|
- muscles
|
- skin
|
- ligaments
|
Fats are made up
of fatty acids
and glycerol.
Fats contain carbon, hydrogen and oxygen.
o
Saturated fats: liquid at room temperature; regular shape (more
efficient)
o
Unsaturated fats: solid at room temperature; irregular shape
(less efficient); more double bonds.
Where are fats
found?
o
In
animals : fish, meat, eggs, bacon, milk…
o
In
plants : cocoa, coconut, sugar, nut, oil…
Substance
|
Test
|
Positive Result
|
Starch
|
Iodine
|
Dark
blue/ black
|
Glucose
|
Benedict’s solution then heat
|
Orange/ yellow/
brick
red
|
Protein
|
Biuret reagent
|
Purple/
Lilac
|
Fat
|
Ethanol + Water
|
Cloudy
precipitate
|
Fibre
- Fibre is made up of a number of complex
carbohydrates.
- There are no calories, vitamins or minerals
in fibre.
- It is ONLY found in the cell walls of
plants (consists mainly of cellulose)
- We have no enzymes that can digest
cellulose, so fibre is not digested when we eat it. (Does not enter the blood
or other parts of the body).
- The presence of cellulose inside the
alimentary canal stimulates the muscles in its walls to squeeze the food along
(peristalsis).
- Fibre is essential for healthy bowel
function.
- Too much fibre can lead to diarrhea.
- Too little fibre can lead to constipation,
piles or cancer of colon.
Vitamins and Minerals
Vitamins
and minerals
|
Examples
of foods
|
Function
|
Deficiency
symptoms
|
Vitamin C
|
Fresh fruits and
vegetables
|
- Holds cells
together
- For healthy
teeth, gums and blood vessels
- Improves iron
absorption and resistance to infection
|
SCURVY
- Pale skin full
of bruises
- Sunken eyes
- Bleeding gums
- Loss of teeth
|
Vitamin D
|
Milk, fish, eggs
and light (skin cell can make Vitamin D when sunlight falls on them)
|
- Helps absorb
calcium from the food we eat.
|
RICKETS
- Weak teeth and
bones. They may bend and grow into a permanently bent shape.
|
Iron
|
Spinach, red
meat, lentils
|
- Needed for
making hemoglobin, the blood-carrying molecule.
|
ANAEMIA
- Less energy
produced causing fatigue.
|
Calcium
|
Dairy products,
salmon
|
- Used in
building bones and teeth.
- Needed for
blood clotting.
|
RICKETS
- Weak teeth and
bones.
|
Problems of world food supplies
- Climate: not enough rainfall to allow crops to grow
well.
- Poor
soil: soil needs to be
fertile for crops to grow well.
- Natural
disasters: Earthquakes,
volcanoes, floods and drought prevent or destroy food production.
- Lack
of money: People don’t
have enough money to grow/ buy enough food.
- Wars: When people fight with each other, it is
dangerous to farm.
- Increase
of population: The
population increases much faster than food can grow.
- Urbanization: As more people move to the city, there are
less people left in the countryside to grow crops.
Food additives
Food additives
have no nutrient value but are added to food to improve the appearance, flavor,
texture and/or storage properties of food:
Preservatives: keep the food fresh and prevent decay
Flavorings
and colorings: add to the
taste and visual appeal of food. (E.g. carotene in tomatoes).
Antioxidants: Stop components of the food combining with
oxygen.
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