Macromolecules

Macromolecules

Middle School

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Learning Objectives

• Define monomers and polymers and understand their relationship.

• Identify the four major types of macromolecules: carbohydrates, lipids, proteins, and nucleic acids.

• Describe the basic structure and function of each of the four macromolecules.

• Explain how dehydration synthesis and hydrolysis build and break down macromolecules.

Key Vocabulary

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Macromolecule

A large organic molecule, essential for life, made of smaller repeating subunits called monomers.

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Monomer

The basic building block or single unit of a larger molecule known as a polymer.

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Polymer

A large molecule formed by the linking of many smaller molecules called monomers together.

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Carbohydrate

A macromolecule used for quick energy and structural support, made of monosaccharide monomers.

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Lipid

A macromolecule used for long-term energy storage and insulation, made of fatty acids and glycerol.

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Protein

A macromolecule with many functions, like speeding up reactions, made of amino acid monomers.

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What Are Macromolecules?

• Macromolecules are large organic molecules, also known as biomolecules, essential for life.

• These large polymers are built from smaller, repeating units called monomers.

• They are composed of Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), and Phosphorus (P).

• The four major classes are carbohydrates, lipids, proteins, and nucleic acids.

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Multiple Choice

What is the relationship between monomers and polymers?

• Polymers are the building blocks of monomers.

• Monomers are large molecules made by linking polymers together.

• Polymers are large molecules made by linking many monomer units together.

• Monomers and polymers are two completely unrelated types of molecules.

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What Are Carbohydrates?

• Carbohydrates are made of carbon (C), hydrogen (H), and oxygen (O) atoms.

• They provide quick, short-term energy and structural support for cells.

• The monomer is a monosaccharide, like glucose (C₆H₁₂O₆).

• Monosaccharides link to form polymers like starch, glycogen, and cellulose.

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Multiple Choice

What is the primary function of carbohydrates in living organisms?

• To store genetic information

• Long-term energy storage and insulation

• To provide quick, short-term energy

• To speed up chemical reactions

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What Are Lipids?

• Lipids are made of C, H, and O, with fewer oxygen atoms than carbohydrates.

• ​They are hydrophobic, meaning they do not mix with water.

• Lipids are made of glycerol and fatty acids, forming molecules such as triglycerides, but they are not considered true polymers.

• Functions include energy storage, insulation, and forming cell membranes.

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Multiple Choice

Which of the following is a key characteristic of lipids?

• They are the main source of quick energy.

• They are composed of amino acids.

• They are hydrophobic and do not mix with water.

• They store and transmit genetic information.

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What Are Proteins?

• Proteins are large molecules made of C, H, O, and N.

• The building blocks of proteins are monomers called amino acids.

• A chain of amino acids linked together is a polypeptide.

• Proteins act as enzymes, provide structure, and help transport materials.

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Multiple Choice

What are the monomers that build proteins called?

• Monosaccharides

• Nucleotides

• Fatty acids

• Amino acids

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Nucleic Acids

DNA

• ​DNA, or deoxyribonucleic acid, is shaped like a double helix.

• ​​It stores the genetic blueprint for an organism to develop and function.

• ​Its nucleotides contain the sugar deoxyribose, a key part of its structure.

RNA

• ​RNA, or ribonucleic acid, is usually a single-stranded molecule.

• ​​It helps carry out the genetic instructions from DNA to build proteins.

• ​Its nucleotides have the sugar ribose, which is different from the sugar in DNA.

Multiple Choice

What is the main function of nucleic acids like DNA and RNA?

• To provide structural support to cells

• To store and express genetic information

• To act as the main source of quick energy

• To insulate the body and store energy long-term

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Building and Breaking Down Macromolecules

Dehydration Synthesis

• Dehydration synthesis is a chemical reaction in which two molecules (monomers) are joined together, forming a larger molecule, such as a dimer or polymer, with the release of a water molecule.

• This is the primary way that large biological molecules are built inside living organisms.

Hydrolysis

• Large molecules known as polymers are broken down into their smaller monomer subunits.

• A molecule of water (H₂O) is added, which causes the chemical bond to break apart.

• This reaction is important for processes like digestion, where food is broken down.

Multiple Choice

What is the main difference between dehydration synthesis and hydrolysis?

• Dehydration synthesis adds water to break a bond, while hydrolysis removes water to form a bond.

• Dehydration synthesis removes water to form a bond, while hydrolysis adds water to break a bond.

• Both processes add water to form larger molecules.

• Both processes remove water to break down molecules.

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Common Misconceptions

Misconception	Correction
Carbohydrates are only in unhealthy foods like bread and candy.	Carbohydrates from healthy foods are the body's main source of quick energy.
All fats (lipids) are bad for you.	Your body needs healthy fats for long-term energy and building cell membranes.
Proteins are only important for building muscles.	Proteins also act as enzymes and help the immune system.

Multiple Choice

How do the primary functions of carbohydrates and lipids differ regarding energy for the body?

• Carbohydrates provide long-term energy, while lipids provide quick energy.

• Carbohydrates provide quick energy, while lipids are used for long-term energy storage.

• Both provide the exact same type of energy for the same duration.

• Carbohydrates store genetic information, while lipids provide energy.

Multiple Choice

Which two macromolecules contain the element Nitrogen (N)?

• Carbohydrates and Lipids

• Lipids and Nucleic Acids

• Proteins and Nucleic Acids

• Carbohydrates and Proteins

Multiple Choice

What happens during a hydrolysis reaction?

• Monomers join together to form polymers, releasing water

• Polymers are broken down into monomers, with water added

• Energy is always absorbed without breaking bonds

• Polymers are formed without involving water

Multiple Choice

A scientist discovers an organism that cannot perform dehydration synthesis. How would this inability affect the organism?

• It would be unable to break down large polymers into smaller monomers.

• It would be unable to build large polymers, like proteins and starches, from small monomers.

• It would be unable to store genetic information in its DNA.

• It would have too much water in its cells due to an inability to perform hydrolysis.

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Summary

• Living things are made of four major macromolecules: carbohydrates, lipids, proteins, and nucleic acids.

• Macromolecules are very large molecules essential to life, made up of smaller subunits, and include carbohydrates, proteins, lipids, and nucleic acids.

• Carbohydrates provide quick energy and structure, while lipids store long-term energy.

• Proteins have many functions, and nucleic acids store genetic information.

Poll

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