Nutrition :)

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Humans
. 2.23 understand that a balanced diet should include
appropriate proportions of carbohydrate, protein,
lipid, vitamins, minerals, water and dietary fibre
. 2.24 identify sources and describe functions of
carbohydrate, protein, lipid (fats and oils), vitamins A, C
and D, and the mineral ions calcium and iron, water and
dietary fibre as components of the diet
. 2.25 understand that energy requirements vary
with activity levels, age and pregnancy
. 2.26 describe the structures of the human alimentary
canal and describe the functions of the mouth,
oesophagus, stomach, small intestine, large intestine and
pancreas
. 2.27 understand the processes of ingestion, digestion,
absorption, assimilation and egestion
. 2.28 explain how and why food is moved through the gut
by peristalsis
. 2.29 understand the role of digestive enzymes, to include
the digestion of starch to glucose by amylase and
maltase, the digestion of proteins to amino acids by
proteases and the digestion of lipids to fatty acids and
glycerol by lipases
. 2.30 understand that bile is produced by the liver and
stored in the gall bladder, and understand the role of bile
in neutralising stomach acid and emulsifying lipids
. 2.31 describe the structure of a villus and explain how
this helps absorption of the products of digestion in the
small intestine
. 2.32 describe an experiment to investigate the
energy content in a food sample.

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Nutrition
Human
A balanced diet should include:
Carbohydrates
Contain the elements carbon, hydrogen and oxygen
Starch, glycogen are complex long chained carbohydrates made
up of smaller units (glucose/maltose)
Provide energy for respiration
Found in pasta, rice, sugar
Proteins
Long chains of amino acids
Contain carbon, hydrogen, oxygen and nitrogen atoms
Growth and repair of tissue
Provide energy in emergencies
Found in meat, fish
Lipids (fats/oils)
Built from fatty acids and glycerol
Contain carbon, hydrogen and oxygen atoms
Provide energy and insulation
Act as an energy…read more

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Aids the movement of food through the gut
Found in whole meal bread
Energy requirements
Activity level
Active people (physical jobs: builders) need more energy
than non-active people (office jobs)
Age
Children and teenager need more energy for growth
Pregnancy
Pregnant women need more energy to provide the energy
for the development of the fetus
Especially calcium and iron
Digestive enzymes
Digestive enzymes break down big molecules into smaller molecules
Amylase
Starch Maltose
Maltase
Maltose Glucose
Protease
Protein amino acid
Lipase
Lipid glycerol/fatty acids
Bile…read more

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Structure of the human alimentary canal (gut)
Mouth
Salivary glands in the mouth produce amylase in the saliva
Food is broken into smaller pieces by the teeth (mechanical digestion)
The tongue molds the small food pieces into a bolus (easy to swallow)
Oesophagus
A muscular tube that connects the mouth and stomach
Epiglottis
Covers the trachea so food doesn't go down it (choking)
Stomach
Produces protease, pepsin
Contains hydrochloric acid
Provides the optimum pH for stomach enzymes
Kills bacteria
The stomach wall is made up…read more

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Excess water is absorbed into the blood by osmosis
Peristalsis
Food moves along the gut by contracting and relaxing the muscles in the gut
wall
The circular muscles contract and the longitudinal muscles relax
(narrow)
The circular muscles relax and the longitudinal muscles contract (wide)
The structure of a small intestine
A small intestine is very long
Longer time for absorption to occur
Contains villi
Increases the surface area for absorption
Have microvilli which further increases the surface area
Contain lots of blood capillaries- maintain…read more

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Villi are one cell thick- diffusion is quick
Five main stages of Digestion
Ingestion
Taking food into the body (mouth)
Digestion
The breakdown of large insoluble food molecules into small soluble food
molecules
Absorption
Digested molecules enter the blood stream via diffusion through the
walls of the intestines
Food molecules- small intestine
Water- large intestine
Assimilation
When cells use the digested food
Amino acid is used to make proteins
Egestion
Producing faeces (fiber, dead cells)
An experiment to investigate the energy content in a food…read more

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