Organic Molecules: Lipids and Carbohydrates

Carbon-Based Life Form  Carbon is the backbone for all life on Earth.  Carbon forms the compounds that make up all cells and organisms.

Carbon-Based Life Form  Organic molecules make up living things.  These molecules are composed of carbon and hydrogen.  Sometimes they also will have oxygen, nitrogen, phosphorus & other elements

The Uniqueness of Carbon  Atoms create molecules by forming covalent bonds – sharing electrons.  The number of covalent bonds depends upon the atoms that are interacting.  Hydrogen – can only create one bond since it only has one electron to share.

The Uniqueness of Carbon  Carbon is unique because it readily makes four bonds with other atoms!

The Uniqueness of Carbon  Be aware with the state asking a question that looks like this: What does the X represent in this molecule? H2NH2N H X H X O OH

The Uniqueness of Carbon  Carbon atoms are most stable when they have all four bonds filled.  Typically, carbon makes single bonds – like that in methane.  However, carbon can also form double and triple bonds. Carbon Dioxide Acetylene

The Uniqueness of Carbon  Carbon’s unique structure permits the formation of four different important macromolecules: 1. Lipids 2. Nucleic Acids 3. Carbohydrates 4. Proteins

Lipids: Fats and Oils  Lipids include oils, waxes, fats and sterols. Sterols include cholesterol.

Lipids: Fats and Oils  Fats and oils share the same monomer: fatty acids attached to a single glycerol molecule. Monomers are basic structures of macromolecules!

Lipids: Fats and Oils  Fatty acids are long chains of carbon atoms connected to each other with double or single bonds.  Lipids are mostly composed of carbon and hydrogen with a few oxygen atoms. Fatty acids Glycerol

Lipids: Fats and Oils  Two forms of fatty acids: saturated (bad) and unsaturated (better).  Saturated fats has carbon atoms held together with the maximum number of single bonds and hydrogen atoms.  Unsaturated fats has carbon atoms held together with single and double bonds with hydrogen atoms.

Lipid Functions  Long-term energy storage: In animals, such as us, we store lipids in adipose tissue.  Adipose tissue contains special cells for lipid storage.

Lipid Functions  Cell Membranes: Phospholipids help to form the cell membrane and the organelles membranes in cells.  Phospholipids are composed of a polar phosphate group attached to a non-polar glycerol. Polar Non-Polar Cell membranes are also called plasma membranes!

Lipid Functions  Chemical Messengers:  Sterols act as chemical messengers.  Cholesterol is the monomer of estrogen, progesterone, and testosterone.

Phospholipids  The cell membrane (plasma membrane) is made up of phospholipids.  Two fatty acid make up the non-polar tails.  The phosphate group connects the two fatty acids and makes the polar head.

Phospholipids  The lipids in cell membranes make them impermeable to water.  Water can not freely cross the cell membrane.  Water must pass through special protein channels.

Phospholipids When we talk about the cell membrane we say that the polar heads are hydrophilic and the non-polar tails are hydrophobic. 1. What is hydrophilic? 2. What is hydrophobic?

Phospholipids The plasma membrane is made up with a phospholipid bilayer, or two sheets of phospholipids. Given the structure of a phospholipid, how are these sheets arranged in the plasma membrane? 1. head*tail – head*tail 2. head*tail – tail*head 3. tail*head – tail*head 4. tail*head – head*tail ?*? - ?*? Exterior of cell Cell Membrane Cytoplasm

Carbohydrates  Carbohydrates consist of carbon, hydrogen and oxygen with a 1:2:1 ratio.  Examples:  Glucose: C 6 H 12 O 6  Sucrose: C 12 H 22 O 11

Carbohydrates  The simplest form of a carbohydrate is glucose.  The carbohydrate’s monomer is called a monosaccharide – glucose is a monosaccharide.  Monosaccharides tend to be single rings. Monosaccharide Single ring

Carbohydrates  Table sugar (sucrose) is a disaccharide formed by bonding two monosaccharides in a double ring structure. Monosaccharide Single ring Disaccharide Double ring

Carbohydrates  Many monosaccharides tend to be isomers.  Isomers are molecules that have the same chemical formula but different arrangement of atoms.

Polysaccharides  Monosaccharides can be linked together to form long chains known as polysaccharides.  Polysaccharides are known as polymers.  Many glucose molecules link together to form starch, glycogen and cellulose.

Polysaccharides  Starch is a polysaccharide produced by plants to store energy.  Starch is found in wheat, rice and potatoes.

Polysaccharides  Cellulose is a polysaccharide that composes the plant’s cell wall.  It strengthens and supports the plant cell.  It can only be broken down by very few organisms.

Many Functions of Carbohydrates  Cellular respiration : all carbohydrates are broken down into glucose to be used in cellular respiration for ATP production. Any time you see energy production in cells … immediately think ATP !

Many Functions of Carbohydrates  Energy storage : Plants and animals store energy in the form of carbohydrates called glycogen and starch.  Structure : plant cell walls are strengthened by cellulose.

Carbohydrate Reactions  Organisms depend upon chemical reactions to join monomers together and break polymers apart.  Dehydration synthesis joins two monomers together.  Hydrolysis breaks down polymers into monomers

Dehydration Synthesis  Dehydration synthesis links two monosaccharides such as glucose and fructose into larger molecules.  When this occurs, glucose loses a hydrogen and fructose loses a oxygen and a hydrogen.  Along with the new disaccharide being formed, a water molecule is formed. H + + OH - = H 2 O AWAY FROMWATERPROCESS

Dehydration Synthesis  When dehydration synthesis occurs repeatedly longer chains of carbohydrates are formed.  Dehydration synthesis also joins fatty acids to the glycerol molecule in lipids. CARBSCARBS LIPIDSLIPIDS

Hydrolysis  Hydrolysis breaks down polysaccharides into monosaccharides.  Water is used to add back the –OH group and H+ atom to the monomers.  Hydrolysis is the reverse reaction of dehydration synthesis ProcessBreakdownWater

Carbohydrate Reactions  In a cell, 132 glucose monomers are joined to form a straight chain of starch. Remember, for dehydration synthesis to occur, water is formed. How many water molecules are formed in this situation?