Download T-17 Chapter 2B notes Section 2.3 Carbon Based Molecules To this

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Chapter 2B notes
Section 2.3
Carbon Based Molecules
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To this point in chapter 2, you have studied chemistry that deals with non-life (acids, bases,
salts, atoms….)
The second part of this chapter deals with the chemistry of life or “Organic Chemistry”. Organic
Chemistry is the chemistry that deals with carbon. Carbon forms most of the molecules
necessary for life. What makes carbon so unique is a 2-fold:
o Carbon can bond to itself easily
o Carbon can form up to 4 more bonds with other atoms – these are covalent bonds!
In many carbon-based molecules, smaller subunits are chained together to make large complex
molecules. The subunits are called monomers and the larger molecule is called a polymer.
o a polymer is many monomers put together:
(monomer + monomer + monomer…..=polymer)
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Now, when we talk about making big molecules or polymers, all organisms are made up of 4
basic types:
o Carbohydrates
o Lipids
o Proteins
o Nucleic acids
All 4 of these compounds (polymers) have different structures and functions, but all are made
by chains of carbons.
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A. Carbohydrates
 These are compounds composed of Carbon, Hydrogen, and Oxygen. They include
starches and sugars.
 Carbohydrates are a major source of energy. When you consume carbohydrates, they
are broken down into chemical energy that your cells can use.
 The most basic carbohydrates are simple sugars or monosaccharides. Monosaccharides
are the monomer for carbohydrates. Many of them are put together to make a
polysaccharide, or complex sugar.
 Most all carbohydrates have carbon, hydrogen, and oxygen in a 1-2-1 ratio:
 C6H12O6 (Glucose) or C3H6O3 or C12H24O12
 Starches, glycogen and cellulose are polysaccharides.
 Cellulose is what makes up cell walls in plans and glycogen is what is stored in
an animal’s liver.
 REMEMBER- monomers are put together to make polymers, but monomers and
polymers are just general terms. In each one of the 4 major molecules, they have
specific monomers and polymers.
 Carbs: monosaccharides (monomer) are put together to make polysaccharides
(polymers)
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B. Lipids
 Are non-polar molecules that include fats, oils, and cholesterol. Like the other 3 major
compounds, lipids contain long chains of carbons bonded to oxygen and hydrogen.
 Lipids are used for both energy for the cell and for the cell’s structure.
 Fats and oils are the most familiar type of lipids.
 Fats store large amounts of chemical energy. Animal fats are things like meats
and butter while plant fats come in the form of oils (olive oil and peanut oil).
 All fats are made by taking fatty acids and chaining them together to make a fat.
 Each monomer consists of 3 fatty acids and a glycerol.
 Fatty acid + fatty acid + fatty acid +…..= Lipid
 There are generally 3 different types of fats:
 Saturated fats- fats that have the maximum number of hydrogen atoms.
 Bad Fats
 Unsaturated fats- contain at least one carbon double bond.
 Better fats
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C. Lipids continued:
 Another type of lipid is a Phospholipid. This molecule is the most important part of a cell
membrane. It contains a “non-polar” fatty acid end and a “polar” phosphate end. This is
how cell membranes regulate what enters and leaves the cell.
 Cholesterol is the final fat we will talk about. You hear a lot of bad things about
cholesterol, but your body needs it to function properly.
D. Proteins
 Proteins are the most diverse group of organic compounds. A Protein is a polymer
made up of monomers called amino acids. This compound contains carbon, hydrogen,
oxygen, nitrogen, and sulfur.
 There are exactly 20 amino acids. Your body makes 12 of them and you get the other 8
from the food you eat.
 All amino acids are structurally the same with the exception of what is called the
R-Group.
 All amino acids have a carboxyl, amine, and hydrogen. They all differ in the R-Group.
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C. Proteins Continued.
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Proteins differ from each other by the order in which the amino acids are put together.
Twenty amino acids can form thousands of different combinations which is what makes
the many different types of proteins possible.
One very specific type of protein is called an Enzyme. Enzymes are catalysts. Catalysts
speed up chemical reactions by lowering the amount of energy needed for the reaction
to start.
Every reaction requires a certain amount of energy to build up before the reaction can
start. Enzymes decrease the amount of energy needed to start so the reaction starts
sooner.
Enzymes are involved in almost every reaction in your body. Enzymes are a specialized
protein made up of long chains of amino acids. Enzymes function is affected by
temperature and pH. Enzymes work in a certain pH and temperature range and will not
work properly if conditions change. This is one reason why a high temperature is very
dangerous.
Enzymes work by “binding” or “connecting” to the substrates it is going to affect. Each
enzyme is very “specific” to certain substances, which means certain enzymes only act
upon certain substrates. This is demonstrated by the “Lock and Key Theory”.
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Enzymes Continued:
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Enzymes work on the “Lock and Key” theory. This means that like a lock and key, only
certain enzymes will fit certain interactions. The shape of the enzyme determines which
substance it will affect.
Notice that the enzyme for one reaction would not work for the enzyme of another
reaction because the shapes would not match up.
D. Nucleic Acids
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Where does your body get the instructions to do everything needed to be done? Nucleic
Acids are carbon based molecules that contain hereditary information and instructions
on how things are to work. The monomer is a Nucleotide. These nucleotides are
composed of a sugar, a phosphate, and nitrogen base.
The 2 types are DNA and RNA
 DNA = stores genetic information
 RNA = helps build proteins
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Section 2.4
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Chemical reactions
 Chemical reactions change substances into different substances by breaking and
forming chemical bonds.
 When a reaction occurs, Reactants make Products
Chemical reactions break bonds of the reactants and make bonds in the products.
Breaking and making bonds is difficult. Bond Energy is the energy needed to break
bonds.
All chemical reactions involve changes in energy. Reactions will not start until enough
energy has built up. This is called Activation energy.
 Exothermic Reactions= release more energy than they take in
 Endothermic Reactions= absorb more energy than they release.