The Structure and Function of Macromolecules

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The Structure and Function of Macromolecules

• AP Biology Chapter 5

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Macromolecules

• Macromolecules are giant molecules .
• Four main classes of macromolecules are
• Carbohydrates
• Lipids
• Proteins
• Nucleic Acids

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Polymers

• A polymer is a long molecule made of many similar
  or identical monomers (small molecules).
• Polymers are linked by covalent bonds.
• The covalent bonds occur through condensation
  reactions called dehydration.
• The polymers are disassembled by a hydrolysis
  reaction.

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Dehydration Reactions

• Condensation involves a dehydration synthesis
  because a water is removed (dehydration) and a
  bond is made (synthesis).
• When two monomers join, a hydroxyl (OH) group is
  removed from one monomer and a hydrogen (H) is
  removed from the other.
• This produces the water given off during a
  condensation reaction.

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Carbohydrates
Carbohydrates function

• in short-term energy storage
• as intermediate-term energy storage (starch for
  plants and glycogen for animals)
• as structural components in cells (cellulose in
  the cell walls of plants and many protists), and
  chitin in the exoskeleton of insects and other
  arthropods.

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Monosaccharides

• Monosaccharides are single (monoone) sugars.
• Sugars are structurally the simplest
  carbohydrates.
• They are the structural unit which makes up the
  other types of carbohydrates.
• Important monosaccharides include ribose,
  glucose, and fructose.

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Disaccharides

• Disaccharides are formed when two monosaccharides
  are chemically bonded together.
• Sucrose, a common plant disaccharide is composed
  of the monosaccharides glucose and fructose.
• Lactose, milk sugar, is a disaccharide composed
  of glucose and the monosaccharide galactose.

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Polysaccharides

• Polysaccharides are large molecules composed of
  individual monosaccharide units.
• A common plant polysaccharide is starch, which is
  made up of many glucoses.
• Glycogen is an animal storage product that
  accumulates in the vertebrate liver.
• Cellulose is a polysaccharide found in plant cell
  walls. Cellulose forms the fibrous part of the
  plant cell wall.

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Amylopectin
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Lipids

• Lipids are involved mainly with long-term energy
  storage.
• They are generally insoluble in polar substances
  such as water.
• Secondary functions of lipids are as structural
  components and as hormones that play roles in
  communications within and between cells.
• Lipids are composed of three fatty acids
  (usually) covalently bonded to a 3-carbon
  glycerol.

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Fatty Acids

• Fatty acids can be
• saturated (meaning they have as many hydrogens
  bonded to their carbons as possible) or
• unsaturated (with one or more double bonds
  connecting their carbons, hence fewer hydrogens).

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Fats

• A fat is solid at room temperature, while an oil
  is a liquid under the same conditions.
• The fatty acids in oils are mostly unsaturated,
  while those in fats are mostly saturated.

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Fats and Oils

• Fats and oils function in energy storage.
• Animals convert excess sugars into fats.
• Most plants store excess sugars as starch,
  although some seeds and fruits have energy stored
  as oils

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Fats

• Another use of fats is as insulators and
  cushions.
• The human body naturally accumulates some fats in
  the "posterior" area.
• Subdermal ("under the skin") fat plays a role in
  insulation.

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Phospholipids

• Phospholipids and glycolipids are important
  structural components of cell membranes.

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Waxes

• Waxes are an important structural component for
  many organisms, such as the cuticle, a waxy layer
  covering the leaves and stems of many land
  plants and protective coverings on skin and fur
  of animals.

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Cholesterol and Steroids

• Cholesterol and steroids Most mention of these
  two in the news is usually negative.
• Cholesterol has many biological uses, such as its
  occurrence in the cell membranes, and its role in
  forming the sheath of some neurons.

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Proteins

• Proteins are very important as control and
  structural elements.
• Control functions of proteins are carried out by
  enzymes and proteinaceous hormones.

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Enzymes

• Enzymes are chemicals that act as organic
  catalysts (a catalyst is a chemical that promotes
  but is not changed by a chemical reaction).

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Structural Proteins

• Structural proteins function in the cell
  membrane, muscle tissue, etc.

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Proteins

• The building block of any protein is the amino
  acid, which has an amino end (NH2) and a carboxyl
  end (COOH).
• The R indicates the variable component of each
  amino acid.

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Basic Amino Acid
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Amino Acids
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Evolutionary Significance

• All living things use various combinations of the
  same twenty amino acids. A very powerful bit of
  evidence for the phylogenetic connection of all
  living things.

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Peptide Bond

• Amino acids are linked together by joining the
  amino end of one molecule to the carboxyl end of
  another. Removal of water allows formation of a
  type of covalent bond known as a peptide bond.

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Primary Structure

• Amino acids are linked together into a
  polypeptide, the primary structure is the
  sequence of amino acids in a polypeptide.

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Secondary Structure

• The secondary structure is the tendency of the
  polypeptide to coil or pleat due to H-bonding
  between R-groups.

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Tertiary Structure

• The tertiary structure is controlled by bonding
  (or in some cases repulsion) between R-groups.
• The protein tends to fold upon itself.

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Quaternary Structure

• Many proteins, such as hemoglobin, are formed
  from one or more polypeptides. Such structure is
  termed quaternary structure.

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Nucleic Acids

• Nucleic acids are polymers composed of units
  known as nucleotides.
• The main functions of nucleotides are information
  storage (DNA), protein synthesis (RNA), and
  energy transfers (ATP and NAD).

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Nucleic Acids Contd

• Nucleotides consist of a sugar, a nitrogenous
  base, and a phosphate. The sugars are either
  ribose or deoxyribose.
• There are five nitrogenous bases. Purines
  (Adenine and Guanine) are double-ring structures,
  while pyrimidines (Cytosine, Thymine and Uracil)
  are single-ringed.

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DNA

• Deoxyribonucleic acid (better known as DNA) is
  the physical carrier of inheritance for 99 of
  living organisms. The bases in DNA are C, G, A
  and T.

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RNA

• RNA functions in protein synthesis.
• There are three types of RNA, each is involved in
  protein synthesis.
• Messenger RNA (mRNA) is the blueprint for
  construction of a protein.
• Ribosomal RNA (rRNA) is the construction site
  where the protein is made.
• Transfer RNA (tRNA) is the truck delivering the
  proper amino acid to the site at the right time.

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