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Nutrition
and diet
Adrian
Whyte and Joanna Johnson, Contributor
NUTRITION
IS the process by which organisms require
energy, in the form of food, to carry
out growth, development, maintenance
and repair.
There
are two main types of nutrition:
1)
Autotrophic nutrition: In this
type of nutrition organisms are able
to synthesise complex organic molecules
from simpler inorganic molecules.
Examples
of this process are photosynthesis
and chemosynthesis.
2)
Heterotrophic nutrition: In
this type of nutrition, organisms
(animals and fungi) feed on organic
substances that have been produced
by other organisms. Examples of this
are holozoic nutrition and filter
feeding.
AUTOTROPHIC
NUTRITION IN GREEN PLANTS
All
green plants are autotrophic and utilise
light as a source of energy for synthesis
(photosynthesis).
Photosynthesis
is a chemical process by which green
plants synthesise organic compounds
from water and carbon dioxide in the
presence of light energy. This process
occurs in the chloroplast.
THE
STAGES OF PHOTOSYNTHESIS
There
are two reaction stages of photosynthesis:
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The light-dependent reaction,
where light energy is absorbed by
the chlorophyll in the chloroplast
and used to split water into
hydrogen and oxygen atoms.
*
The light-independent reaction
(dark reaction), which occurs without
the use of light. This is where the
hydrogen atom that was split
from water is used to join with carbon
dioxide to form glucose.
Q1.
What are the conditions necessary
for photosynthesis?
Answer:
Carbon dioxide, water, sunlight, chlorophyll,
enzymes, minerals and an
appropriate temperature.
IMPORTANT
MINERALS REQUIRED BY PLANTS
Minerals
are required by plants for healthy.
growth and development. Any shortage
of a particular mineral can adversely
affect the plant.
HETEROTROPHIC
NUTRITION IN HUMANS
The
type of nutrition that humans exhibit
is holozoic nutrition. This means
feeding on large pieces of food, which
are then digested in an alimentary
canal outside of the cells.
A
key term when dealing with human nutrition
is diet.
WHAT
IS A DIET?
This
is simply the food requirements of
an organism. A diet should include
certain substances known as nutrients.
These include: vitamins, minerals,
dietary fibre as well as water, lipids,
carbohydrates, and proteins.
A
balanced diet contains the correct
proportions of these nutrients, which
will vary depending on the age, sex,
body size and level of activity of
an individual.
Some Nutrients Needed By Man for
Heath
| Nutrients |
Functions |
Dificiency
disease |
Macromolecules/
nutrients |
|
|
| Carbohydrates |
Primary
source of energy. |
General
weakness |
| Proteins |
Repair
of muscle and growth |
Kwashiorkor |
| Fats/Lipids |
- Energy
storage
- Insulation
especially in artic animals.
|
|
| Vitamins |
|
|
| A |
- Keep
cells along the respiratory
system healthy.
- To
Make the pigment in the rods
of the eye needed for seeing
in dim lights
|
Resoiratory
infections and night blindness
Xerophthalmia |
| B
(there are about 12 kinds) |
Involved
in many metabolic reactions |
Beriberi
- weak and painful muscles, depression
irritability |
| C |
Keeps
tissue healthy |
Scurvy
- bleeding gums |
| D |
- Control
calcium and phosphoros absorption
- Important
in bone and teeth formation.
|
Rickets
- lack of calcium in bones causes
'bow legs' in children
or 'knock knee' |
| Minerals |
|
|
| Calcium
(Ca) & Phosphorous (P) |
For
strong bones and teeth |
Brittle
bones and teeth |
| Iron |
Formation
of haemoglobin |
Anaemia
- 'weak blood' tiredness, lack
of energy since there will be
less red blood cells |
| Iodine |
Formation
of the hormone Thyroxin |
- Goitre
(Adults) - reduced
metabolic rate, swelling of
the thyroid gland.
- Cretinism
(children) - Physical
and mental retardation
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| Nutrition
in humans involves the following
processes. |
Ingestion
Digestion
Absorption
Assimilation
Egestion |
|
|
| Ingestion |
Process
by which food is taken in. |
| Digestion |
the
breaking down of ingested food
into chemical simpler forms. |
| Absorption |
movement
of dissolved substances accross
cell membrane into the lining
of the alimentary canal. |
| Assimilation |
the
utilization of the absorbed food. |
| Egestion |
removal
of the undigested materials from
the gut. |
*
Adrian Whyte and Joanna Johnson
teach Biology at Ardenne High School.
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