1 Biology – Kevin Dees Biology Chapter 5 Biological macromolecules Biology – Kevin Dees Small molecules (like water and NaCl) have certain properties that arise from the bonds which hold atoms together in a particular arrangement. Many of the molecules that compose the cells in a living thing are huge and are often termed macromolecules. very large molecules - some proteins for examples contain thousands of covalently bonded carbon atoms
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Biology – Kevin Dees
Biology Chapter 5Biological macromolecules
Biology – Kevin Dees
Small molecules (like water and NaCl) have certain properties that arise from the bonds which hold atoms together in a particular arrangement.
Many of the molecules that compose the cells in a living thing are huge and are often termed macromolecules.
very large molecules- some proteins for examples contain
thousands of covalently bonded carbon atoms
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Biology – Kevin Dees
There are four categories of biological macromolecules:
1. Carbohydrates *
2. Lipids
3. Proteins*
4. Nucleic Acids*
* these three categories are composed of molecules that are formed as polymers
Biology – Kevin Dees
Polymers
• Polymers are long molecules consisting of many similar or identical building blocks linked by covalent bonds.
• These basic units (or building blocks) are known as monomers.
• As we will see, the monomers of each of the three different macromolecules are different , but the chemical mechanism to build polymers from these monomers is very similar.
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Synthesis and breakdown of polymers
• Each monomer molecule will be connected to an adjacent monomer by a chemical reaction known as dehydration synthesis
• When a covalent bond forms between the two monomers, each monomer contributes a part of a water molecule
• the H+ (hydrogen ion)
• OH- (hydroxide group)
Biology – Kevin Dees
• These reactions are building reactions (anabolic reactions) and require the input of energy.
• Enzymes are used to help speed up these reactions by lowering the activation energy of the reaction.
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• Polymers may also be broken down into smaller units by a catabolic reaction.
• This process requires the addition of water and is known as hydrolysis.– Split with water
– The reverse of dehydration synthesis
– Also requires enzymes to activate
Biology – Kevin Dees
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Biology – Kevin Dees
1. Carbohydrates
• Functions:– Quick energy source (fuel)
– Structural building materials
• Sugars (monosaccharides) form the basic monomers of polysaccharides.
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monosaccharides• Glucose is the most common
(most sugar names end in –ose)
• Glucose is important in the cellular respiration reaction
• “easy to catabolize”
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Glycosidic linkages• Covalent bonds formed by dehydration
synthesis linking monosaccharides
Glucose Fructose Sucrose – a disaccharide
Other disaccharides:
maltose – found in beer
Lactose – found in milk
Biology – Kevin Dees
Large polysaccharides
• Macromolecules of a few hundred to a few thousand monosaccharides.
• Used for storage – may be catabolized by hydrolysis to create monosaccharides for fuel.
• Used for building materials for cells
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Polysaccharide examples
• Starch – storage polysaccharide in plants– Glucose bank for plants
– Most animals have enzymes that can hydrolyze starch
• Glycogen – storage polysaccharide in animals
– Stored in liver and muscle tissue
– Used when demand for sugar increases; only a day’s worth of stored energy
Biology – Kevin Dees
• Cellulose - the most abundant organic compound on earth– Structural polysaccharide –
found only in plants
– Found in the cell wall of plant cells
– Very strong
– Forms long fibers
– Most animals do not have enzymes to hydrolyze cellulose
• Termites and cows use symbiotic microorganisms
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• Chitin – structural polysaccharide found in arthropods– Insects, crustaceans, arachnids
– Composes the exoskeleton
– Also found in some fungi
– Used to make surgical thread – very thin, very strong and decomposes easily.
Biology – Kevin Dees
2. Lipids
• Do not consist of polymers
• Grouped together because they are hydrophobic – little or no affinity for water
• Classes of lipids:– Fats
– Phospholipids
– Steroids
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Fats• Consist of a glycerol and fatty acids
• Are formed by dehydration synthesis
• Function - energy storage (2X sugar)- insulation in adipose tissue
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• Saturated fats – fatty acid tail does not have double bonds in the hydrocarbon chains– This makes them very stable and more difficult to
break down
– Solid at room temperature
– Most animal fats – lard, butter• increased risk of CV disease
• atherosclerosis
• Unsaturated fats – fatty acid tails have double bonds in hydrocarbon chains– Most plant oils – olive oil
– Liquid at room temperature
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Phospholipids
• Similar to fat but only has two fatty acid tails attached to glycerol and has a phosphate group (PO4) as well.
• Amphipathic -
hydrophobic and hydrophilic properties
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• When placed in water, forms phospholipid bilayer
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Steroids
• Cholesterol – fond in animal cells
• Some hormones – estrogen, testosterone
Biology – Kevin Dees
3. Proteins
• Very diverse group with many functions
• Monomers are amino acids – 20 naturally occurring– Amino group
– α carbon
– Carboxyl group
– R group (variable)
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• Linked during dehydration synthesis to form peptide bonds.
Biology – Kevin Dees
Functions of proteins
• Enzymes – catalysts in reactions– Digestive enzymes