Transcript Nutrients

Unit 2A
Human Form & Function
Cells, metabolism & regulation
Nutrition
Nutrients
• Nutrients are the chemical
compounds that make up foods and
which are essential for life.
• Nutrients include:
• Carbohydrates
• Lipids
• Protein
• Vitamins
• Minerals
Carbohydrates
Carbohydrates
• Typical examples are sugars &
starches
• They all contain the elements C,
H, O roughly in the proportion of
1C:2H:1O
• The building blocks are simple
(monosaccharide) sugars (e.g.
glucose)
Main uses
• Carbohydrates are used mainly
as an energy source for cellular
respiration
• Some combine with other
substances – e.g. glycoproteins in
the cell membrane
• Can be stored in the liver and in
muscle cells as glycogen
Sugars
• Sugars are relatively small
carbohydrate molecules – either a
single sugar molecule
(monosaccharides or simple
sugars) or double sugar molecules
(disaccharides or double sugars)
• Sugars are water soluble and most
are sweet
Sugars
• Examples of
monosaccharide
sugars - glucose
(dextrose), fructose,
galactose and ribose
• Examples of
disaccharide sugars sucrose, maltose and
lactose
Polysaccharides
• Starch is a good example of a
polysaccharide (glycogen is a
polysaccharide that occurs in animals)
• Polysaccharides are long chains (or
polymers) of simple sugars
• Polysaccharides are not sweet and do
not dissolve in water
• Starch represents a large part of our
carbohydrate intake
Carbohydrate –rich foods
• Foods rich in starch – Cereal-based
foods (e.g. bread, pastry, pasta,
noodles, rice)
Some vegetables (e.g. potatoes, beans
& corn), nuts
• Foods rich in sugars – cakes, biscuits,
lollies, many processed foods, fruit
(dried fruit, stone fruit, bananas, citrus),
sweetened drinks (fruit juice, flavoured
milk, carbonated drinks)
Lipids
Lipids
• Typical examples are fats & oils
• They all contain the elements C, H, O - a
smaller proportion of O than in
carbohydrates
• The building blocks are fatty acids &
glycerol
• Some fatty acids (e.g. omega-3 & omega6) are essential fatty acids
Triglycerides
• Most lipids are
triglycerides – i.e. one
glycerol molecule attached
to three fatty acid
molecules.
• The way in which the C &
H atoms in the fatty acids
are bonded determines
whether a fat is ‘saturated’
or ‘unsaturated’.
Glycerol
Fatty acids
Lipid classification
• Low density lipids (LDL) carry cholesterol from
the liver to the tissues. LDL can start the
formation of plaque and increased levels are
associated with cardiovascular disease. For this
reason, cholesterol inside LDL is often called
‘bad’ lipids.
• High density lipids (HDL) collect cholesterol from
the tissues, and bring it back to the liver.
Sometimes referred to as the ‘good’ lipids.
Main uses
• An energy source – lipids contain twice as much
energy as carbohydrates
• Energy storage
• Insulation
• Protection of organs
• Structural functions (e.g. cell membrane, myelin
sheath
• Metabolic functions (e.g. cholesterol, steroids)
• Chemical messengers (e.g. prostaglandin,
hormones)
Lipid-rich foods
• Dairy foods (e.g. cream, butter,
cheese), pastry, fried foods, meat
(fat on), poultry (skin on), oily fish,
avocado, olives, nuts
Proteins
Proteins
• They all contain the elements
C, H, O, N – (some contain
elements such as iron, sulphur
and phosphorus)
• The building blocks are amino
acids
Main uses
• Structural functions (e.g. actin &
myosin in muscles, collagen in
connective tissues)
• Metabolic functions (e.g. enzymes)
• Oxygen transport (haemoglobin)
• Protection (antibodies, blood
clotting)
• Energy source (in emergencies)
Essential amino acids
• Essential amino acids are the
eight (possibly nine) amino acids
that cannot be produced by the
body and must therefore be
obtained from the diet.
• Complete proteins (animal
proteins, such as most meats,
eggs & milk) contain the full range
of amino acids.
• Incomplete proteins (mainly plant
proteins, such as grains &
legumes) contain low levels of
one or more of the essential
amino acids.
Protein-rich foods
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Dairy foods (e.g. milk, cheese, yoghurt)
Eggs
Lean Meats, Fish, and Poultry
Soy Milk
Beans, Tofu, Lentils, and other
Legumes
• Grains, including bread and pasta
• Nuts and Seeds
Vitamins
• Vitamins are organic substance
essential in small quantities for
normal health.
• Most vitamins act as coenzymes
or help regulate metabolic
processes.
• There are 13 known vitamins,
most of which are present in
foods - some are produced within
the body.
Solubility
• Vitamins are often classified as water
soluble or fat soluble
• Vitamins B & C are water soluble.
These are easily excreted from the
body.
• Vitamins A, D, E & K are fat soluble
and are absorbed from the gut with
the help of lipds.
Vitamin deficiency diseases
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A – night blindness
B1 – beriberi
B3 – pellagra
B6 & B12 – anaemia
B9 – (folic acid) miscarriage, neural
tube defect
• C – scurvy
• D - rickets
Dietary minerals
• Dietary minerals are the chemical
elements required by living
organisms, other than the four
elements Carbon, Hydrogen,
Nitrogen, and Oxygen.
• Dietary minerals occur in all
natural foods.
Macrominerals & trace minerals
• Macrominerals are those, such as
Na, Mg, K, Ca, Fe, P, S & Cl,
required in relatively large
amounts.
• Trace minerals are those required
relatively in small amounts (see
table).
Functions
• Dietary minerals have many functions
e.g.
• Ca is needed in bones and muscles
• Na & K are important electrolytes
• Fe is needed in haemoglobin
• P is an essential element in nucleic
acids (DNA & RNA)
A balanced diet
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USDA food pyramid