Bio-chemistr
yStructures / Functions of Biomolecules
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MacroMoleculesMacro = largeMolecules = 2 or more atoms
covalently bondedUsually referred to as polymers
Like a chainMade from several repeating subunits
The repeated subunits are called monomers.
Like links in a chain
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Types of Macromolecules
There are four of them.1. Carbohydrates2. Lipids3. Proteins4. Nucleic acids
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• Monomer – monosaccharide• Chemical formula: (CH2O)n
• Carbon chains or rings with H’s, OH groups and a C=O or carbonyl group. Depending on the placement of the carbonyl group they may be aldoses or ketoses.
Carbohydrate Structure
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• Most monosaccharides have 3, 5, or 6 carbons.– 3 carbons = triose– 5 carbons = pentose– 6 carbons = hexose
• Different placement of the OH groups creates several different monosaccharides with the same chemical formula.
Carbohydrate Structure
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• Polysaccharides consist of many monosaccharides joined together by glycosidic bonds.
• One function of polysaccharides is energy storage – it is hydrolyzed as needed.
• Other polysaccharides serve as building materials for the cell or whole organism.
• Common polysaccharides:-StarchGlycogenCellulose Chitin
Carbohydrate Structure
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• Starch is a storage polysaccharide composed entirely of glucose monomers– Great big chain of glucose molecules
Carbohydrate Structure
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Biological Uses of Polysaccharides
• Plants store starch within plastids, including chloroplasts.
• Plants can store surplus glucose in starch and withdraw it when needed for energy or carbon.
• Animals that feed on plants, especially parts rich in starch, can also access this starch to support their own metabolism.
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Functions of Carbohydrates
• Energy production (glucose and fructose) and storage (glycogen and starch).
• Cell identity markers – carbohydrate chains attached to cell membrane proteins identify the type of cell.
• Building blocks for other molecules such as, DNA and RNA, amino acids and lipids.
• Structural - cellulose, chitin, peptidoglycans.
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Lipids• Lipids are an exception among macromolecules
because they do not have polymers.– Though lipid structure is easily recognized
• Lipids all have little or no affinity for water.• Lipids are highly diverse in form and function.
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Lipids - Diverse Hydrophobic
Molecules1. Fats store large amounts of energy.2. Phospholipids are major components of cell
membranes.3. Steroids include cholesterol and certain hormones.
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1. Fats store large amounts of energy• Although fats are not strictly polymers, they are large
molecules assembled from smaller molecules by dehydration reactions.
• A fat is constructed from two kinds of smaller molecules, glycerol and fatty acids.
Structures and functions lipids
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• Glycerol consists of a three carbon skeleton with a hydroxyl group attached to each.
• A fatty acid consists of a carboxyl group attached to a long carbon skeleton, often 16 to 18 carbons long.
Structures and functions lipids
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• The many nonpolar C-H bonds in the long hydrocarbon skeleton make fats hydrophobic.
• In a fat, three fatty acids are joined to glycerol by an ester linkage, creating a triacylglycerol.
Structures and functions lipids
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• The three fatty acids in a fat can be the same or different.• Fatty acids may vary in length (number of carbons) and in
the number and locations of double bonds.• If there are no carbon-
carbon double bonds, then the molecule is a saturated fatty acid - a hydrogen at every possible position.
Structures and functions lipids
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• If there are one or more carbon-carbon double bonds, then the molecule is an unsaturated fatty acid - formed by the removal of hydrogen atoms from the carbon skeleton.
• Saturated fatty acids are straight chains, but unsaturated fatty acids have a kink wherever there is a double bond
Structures and functions lipids
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Saturated vs. Unsaturated• Fats with saturated fatty acids are saturated fats.
– Most animal fats– solid at room temperature.– A diet rich in saturated fats may contribute to cardiovascular
disease (atherosclerosis) through plaque deposits.
• Fats with unsaturated fatty acids are unsaturated fats.– Plant and fish fats, known as oils– Liquid are room temperature.
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2. Phospholipids are major components of cell membranes
• Phospholipids have two fatty acids attached to glycerol and a phosphate group at the third position.
• The “head” likes water• The “tail” hates water
Structures and functions lipids
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• The interaction of phospholipids with water is complex.– The fatty acid tails are hydrophobic, but the phosphate group
and its attachments form a hydrophilic head.
Structures and functions lipids
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• At the surface of a cell phospholipids are arranged as a bilayer.– the hydrophilic heads are on the outside in contact with the aqueous
solution and the hydrophobic tails form the core.– The phospholipid bilayer forms a barrier between the cell and the
external environment.
• They are the major component of cell membranes.
Structures and functions lipids
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3. Steroids include cholesterol and certain hormones.• Steroids are lipids with a carbon skeleton
consisting of four fused carbon rings.– Different steroids are created by varying functional groups
attached to the rings.
Structures and functions lipids
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• Proteins are instrumental in about everything that an organism does.– structural support,– storage– transport of other substances– intercellular signaling– movement– defense against foreign substances– Proteins are the main enzymes in a cell and regulate
metabolism by selectively accelerating chemical reactions.• Humans have tens of thousands of different proteins,
each with their own structure and function.
Proteins
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Proteins
1. A polypeptide is a polymer of amino acids connected to a specific sequence .
2. A protein’s function depends on its specific conformation.
Many Structures, Many Functions
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• Proteins are the most structurally complex molecules known.– Each type of protein has a complex three-
dimensional shape or conformation.• All protein polymers are constructed from the same
set of 20 monomers, called amino acids.• Polymers of proteins are called polypeptides.• A protein consists of one or more polypeptides
folded and coiled into a specific conformation
Proteins
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A polypeptide is a polymer of amino acids connected in a specific sequence
• Amino acids consist of four components attached to a central carbon, the alpha carbon.
• These components include a hydrogen atom, a carboxyl group, an amino group, and a side chain.
• Polypeptides are made of amino acids – Amino acids CONTAIN NITROGEN (N)
Proteins
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• The repeated sequence (N-C-C) is the polypeptide backbone.
• Attached to the backbone are the various R groups.• Polypeptides range in size from a few monomers to
thousands.
Proteins
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Nucleic Acids• Contain genetic information– Provides instructions for making polypeptides
• Each monomer is a nucleotide• Nucleotides are composed of
1. 5 carbon sugar Deoxyribose ribose
2. Phosphate group3. Nitrogenous base
Adenine (A) Thymine (T) in DNA, Uracil (U) in RNA Guanine (G) cytosine
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• Deoxyribonucleic acid (DNA)– Sugar is deoxyribose– Shape is a double helix
• Ribonucleic acid (RNA)– Sugar is ribose– Uses a different nitrogenous base– Uracil (U) instead of thymine (T)– Shape may be a single or double helix
Nucleic Acids
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