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AP Bio



Unit 1

1.0 Unit 1 Overview: Chemistry of Life

4 min readjune 10, 2021


Danna Esther Gelfand

Unit 1 Overview

The chemistry of life 🌱connects all the main macromolecules and how their structure relates to their function. This unit is the foundation to understand the chemical basis of life which is needed for the rest of the course.
This unit focuses on the properties of carbohydrates, lipids, proteins, nucleic acids and how they interact with each other and other molecules. Water is an important component to the connections of all living things.
  • Water 💧has covalent bonding, but when bonding to other water molecules use hydrogen bonding. These concepts lead us to understand adhesion, cohesion, and surface tension. Water is a polar molecule which is what leads to the molecule’s ability to have covalent and hydrogen bonding.
Carbon and its versatility are important concepts for this unit, as all macromolecules are made up of carbon. All four macromolecules listed below all use carbon as their building block to make the molecules. The chart below gives a summary of the four main macromolecules and some of their important characteristics.


The four main macromolecules are carbohydrates, lipids, proteins, and nucleic acids. Knowing the functional groups that are associated with each macromolecule is essential, as this leads to the shape of the molecule which leads to the function. ⚙️
  • The functional groups help to determine what the macromolecule will do in the body.
  • The functional groups also help in determining how the monomers are assembled.
  • There are many functional groups that exist, each one giving a different characteristic to the molecule that it is part of. The six main ones that all students should know are:
    ○ Carboxyl
    ○ Carbonyl
    ○ Hydroxyl
    ○ Amino
    ○ Phosphate
    ○ Sulfhydryl
Most macromolecules are made of monomers and linked 🔗 together to make the polymer/macromolecule. This happens through dehydration synthesis. Dehydration synthesis is the process of bringing monomers together by removing water 💧 and forming a covalent bond. The reverse, hydrolysis, occurs if the macromolecule is being broken down. A water 💧 molecule is added that splits the macromolecule into monomers and breaking the covalent bond that had linked them together.


🧁 composed of carbon, hydrogen, and oxygen. They serve as short term energy.☀️


  • 🧈 made of carbon, hydrogen, and oxygen, but not in the same ratio as carbohydrates.
    • They are nonpolar molecules.
    • Lipids have the capability of being unsaturated or saturated depending on if there is a presence of double bonds. Lipids have long chains of hydrocarbons and the double bond, if there is one, is normally found in the hydrocarbon chain. Saturated lipids🍟 do not have a double bond and tend to form solids at room temperature. Unsaturated lipids 🥑 have at least one double bond and will tend to stay a liquid at room temperature.
    • Phospholipids contain a polar and a nonpolar region, which helps in their function in the cell membrane. They serve as long-term energy. ☀️ The head region of the phospholipid is hydrophilic, and is considered "water loving", where as the tail region is hydrophobic and considered "water fearing." The head faces out and the tails face inwards so the bilayer that is formed has the hydrophobic portions in the middle and the hydrophilic portions face out.

Image from Libretexts


🥩 made of carbon, hydrogen, oxygen, nitrogen, and sulfur.
    • The building block is amino acids and linked together serve as the polypeptide chain.
    • They aid in many things in the body including structure, movement, transport, immunity, enzymes, and hormones.
    • The sequence of amino acids determines the overall shape which in return determines the function.
      They must move through at least three folding sequences to be a functional protein.
      • The primary structure is the peptide bonding of amino acids.
      • The secondary structure is through local folding into alpha-helices or beta-sheets.
      • The tertiary structure is what gives the functional shape through R-group bonding.
      • The quaternary structure arises is there is more than one chain bonded together. They are subject to denaturing and the topic of many disruptions in the body.



Image from NewsMedical

Nucleic Acids

🧬compose DNA and RNA. They are made of carbon, hydrogen, oxygen, nitrogen, and phosphorus.
    • The building block is a nucleotide and is made of a 5-carbon sugar, a phosphate group, and one of four nitrogenous bases (adenine, thymine, cytosine, or guanine in DNA and thymine is replaced with uracil in RNA.) They serve as holders of the genetic information composed of nucleotides. DNA is structurally setup in an antiparallel nature, with each strand running in opposite 5’ to 3’ orientation.

Image from ScienceNotes

🎥 Watch: AP Bio Unit 1 Review


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