Transcript Nutrition - Dr Rob's A

Biological Compounds
Macronutrients
‘BIG’ nutrients – these are complex ‘chemicals’
XS stored
as FAT
Broken down into
glucose
Stored as glycogen
Carbohydrates
Cellular respiration
Glucose + oxygen  water + carbon dioxide + ENERGY
ENERGY
Other macronutrients…
Lipids:
ENERGY
stored in body fat
and found in membranes
Proteins:
growth and repair
Micronutrients
The body only needs VERY SMALL amounts of these
Inorganic Ions:Calcium (Ca2+) for teeth, muscles, bones, blood clotting
Sodium (Na+) for nerves, heartbeat, muscle contraction
Magnesium (Mg2+)
Iron (Fe2+)
Phosphate (PO43-)
Vitamins: complex organic substances
water soluble (in blood) e.g. vit C
fat soluble e.g. vit A
Vitamin C
Vitamin C:
connective tissue, bones, skin, teeth, endothelial cells
deficiency can lead to scurvy
can contribute to CVD
Water & fibre: (roughage)
holds water
provides bulk for intestinal muscles to work on
Organic Molecules
Carbohydrates
Carbon Chemistry!
2D version
Long chain of C atoms
The very lazy
scientist….
Branched chain carbon polymer
Carbon ring structures
Buckminsterfullerine (‘Buckyball’)
Carbon Chemistry KEY FACTS
Organic molecules contain: Carbon, hydrogen, oxygen, (sulphur, nitrogen, phosphrous)
One carbon atom can bond with four other atoms forming a TETRAHEDRAL shape
The bits of the body that are not WATER are ORGANIC molecules
Carbon can form long chains, branched chains or ring structures
They can ‘fold-up’ to make three-dimensional structures
Carbohydrates (CHO’s)
Sugars: sucrose (white crystalline ‘sugar’)
glucose (energy supplier – sports drinks)
starch (flour, potatoes)
Carbohydrates fall into four main groups:
1. Monosaccharides (one ‘sugar-structure’)
2. Disaccharides
(two ‘sugar-structures’)
3. Oligosaccharides (3-11 ‘sugar-structures’)
4. Polysaccharides (over 11 ‘sugar-structures’)
Monosaccharides (‘simple’ sugars)
triose
Just one sugar-structure
Have an empirical formula of (CH2O)n
Triose – found in mitochondria
ribose
Pentose – found in DNA or RNA
Hexose – glucose
galactose
fructose
Empirical formula for hexoses is C6H12O6
glucose
Isomerism
C 3 H 6 O3
H
C
H
O
H
H
C
OH
H
C
OH
H
H
C
OH
C
O
C
OH
H
GLYCERALDEHYDE
DIHYDROXYACETONE
Ribose & Deoxyribose
C5H10O5
Glucose
Monosaccharides you need to know…
SIDE CHAINS AFFECT THE WAY IN WHICH THE MOLECULE IS
USED BY THE BODY
 all of the carbon atoms are numbered 1-6
 α-glucose has a side chain at position 6
 fructose has a side chain at position 1 and position 6
Disaccharides
Disaccharides
 These are 2 monosaccharides JOINED TOGETHER
 glucose + glucose makes MALTOSE
 glucose + fructose makes SUCROSE
 glucose + galactose makes LACTOSE
Monosaccharides join together by CONDENSATION
REACTION and the bond that joins them together is a
GLYCOSIDIC BOND
Building a disaccharide
Disaccharide summary
The three common disaccharides you need to know:
All of these are formed by CONDENSATION REACTION
(the one you need to be able to draw and label is maltose!!!)
Challenge!
• See if you can draw the structure of
Lactose
(that’s glucose + galactose)
Breaking apart disaccharides (and polysaccharides)
Disaccharides – KEY FACTS
Disaccharides are formed from two monosaccharides
 glucose + glucose makes MALTOSE
 glucose + fructose makes SUCROSE
 glucose + galactose makes LACTOSE
The reaction that joins two monosaccharides is called a
condensation reaction
(break them up with hydrolysis)
The bond formed between two monosaccharides is called a
GLYCOSIDIC BOND – the number of the carbon atoms nearby that
are joined gives the bond its name e.g. 1,4 glycosidic bond for maltose
Polysaccharides
What are they?
• Macromolecules
• Polymers
– Made up of monosaccharide monomers
Covalently bonded by Condensation
Polymerisation
Common ones
•
•
•
•
Starch
Glycogen
Cellulose
Chitin
• All made from glucose
Different properties depend on which ISOMER and
the type of GLYCOSIDIC bond
Polysaccharide Monomer
Starch
α-glucose
(amylose)
α-glucose
Starch
Glycogen
Cellulose
(amylopectin
)
α-glucose
β-glucose
Glycosidic Molecule
Bond
Shape
1,4
Unbranched
wound into a
helix
1,4 with some
1,6
Tightly
packed
branched
chain
1,4 with more
1,6 than
amylopectin
1,4
Very
branched
compact
molecule
Unbranched
straight
chains
Starch
• Mixture of amylose (30%) and amylopectin
(70%)
• Amylose:
– unbranched chains
– 1,4 glycosidic bonds
– >300 glucose monomers, helical shape
– coils have 6 monomers/turn held together by
hydrogen bonds
Starch
• Amylopectin:
– Glucose monomers
– 1,4 glycosidic bonded chains
– Branches in chains due to 1,6 glycosidic bonds
– Branches every 20-30 residues
– Molecule several 1000 monomers, very
branched and coiled compactly
Starch
• Functions as storage in plants:
– Compact
– Insoluble
– No osmotic effects
– Doesn’t interfere in cell reactions
– Easily hydrolysed to sugars when required
• Build up into grains in structures called
amyloplasts in plant cytoplasm
Polysaccharides
Complex carbohydrates – many monosaccharides joined together by
glycosidic bonds
In plants strings of α-glucose joined by glycosidic bonds form starch,
which is made up of amylose & amylopectin
Amylase breaks the glycosidic bonds from the ends of amylose, and
amylopectin (branched) which releases energy
Glycogen
• Polymer of α-glucose with 1,4 and 1,6 glycosidic bonds
• Very similar to amylopectin but it branches more often,
every 8 – 12 residues.
• Very compact
• Energy storage in animals –liver and muscle cells
• Cytoplasm of bacteria
• Well suited to its role
– Compact
– Rapidly hydrolysed to sugars when needed
Page 6 of molecules handout
Question pack
Cellulose
• Polymer of β-glucose
• 1,4 glycosidic bonds forming straight
unbranched chains
• 1000’s of monomers
• Major constituent of the plant cell wall
• Hydrogen bonding
can occur between OH groups on
adjacent chains
holding it together
Cellulose cont.
• Up to 2000 chains can be held together
– form microfibril giving high tensile strength
Cellulose cont.
• Microfibrils embedded in a matrix (like a cement)
making it a composite material
• Few organisms can break it down (digest) using
enzyme cellulase
– A few prokaryotes and fungi can
• What is cellulose called in the field of
nutrition?
– fibre
• Can mammals break down cellulose?
– Ruminant mammals have bacteria in gut to
do it
Anaerobic bacteria in caecum and appendix
Chitin
• Chitin is used structurally
• HOMEWORK – find out more!
• Hand in a ‘fact sheet’ on Chitin
• Maximum of one side
Polysaccharides – key facts
Complex carbohydrates – many monosaccharides joined together by
glycosidic bonds
They often fold-up on themselves to become more complex or are
branched
The body/plants uses polysaccharides as storage – these molecules
can be broken down into smaller components
Breaking glycisidic bonds is referred to as HYDROLYSIS and
releases a lot of ENERGY
Polysaccharides are INSOLUBLE so do not interfere with other
chemical functions of the cell and have little impast on osmosis
Starch is a polysaccharide found in plants
Glycogen is a polysaccharide found in animals
Lipids
Fats, Oils and Waxes
• Organic compounds
• Insoluble in water
• Soluble in organic solvents (eg acetone, ether)
• Relatively small
(compared to polysaccharides)
• Tend to form together into globules
Due to not being soluble
• Naturally occurring fats and oils are esters
• Formed by condensation reactions
between glycerol (an alcohol) and fatty
acids
Glycerol + Fatty acid
Ester +
3 H2O
H
• Glycerol
– C3H8O3
H
H
H–C–C–C–H
OH OH OH
– 3 hydroxyl groups
each can undergo condensation reaction
with a fatty acid.
Produces an ester called a triglyceride
(triacylglycerol)
Fatty Acid
Long non-polar Hydrocarbon chain
Polar carboxyl (COOH) end
Condensation Reaction
Triglycerides
Triglycerides containing saturated fatty acids have a
high melting point and tend to be found in warmblooded animals. At room temperature thay are solids
(fats), e.g. butter, lard.
Triglycerides containing unsaturated fatty acids have
a low melting point and tend to be found in coldblooded animals and plants. At room temperature
they are liquids (oils), e.g. fish oil, vegetable oils.
Triglycerides
They are used for storage, insulation and protection in
fatty tissue (or adipose tissue) found under the skin (subcutaneous) or surrounding organs.
They yield more energy per unit mass than other
compounds so are good for energy storage.
Water released in oxidisation called metabolic water,
important to organisms in dry climates
Carbohydrates can be mobilised more quickly, and
glycogen is stored in muscles and liver for immediate
energy requirements.
Phospholipids
• Like lipids, are esters of glycerol and fatty acids. BUT,
one of the fatty acid chains is replaced by a polar
phosphate group
Phospholipid
Phospholipids
• Polar (phosphate) group is soluble in water
• The fatty acid chains are not
• So at air-water or oil-water interfaces,
phospholipids orientate so the polar head is
in the water.
• Important constituent in cell membranes.
Fats and health.
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Saturated or unsaturated? Which is best?
What are the risks of the wrong type?
How much is too much?
Who says?
What’s BMI?
Question Pack