Biomolecules

What element is the basis for the chemistry of life on Earth?

Carbon.

What property of carbon allows it to form long chains and complex molecules?

Catenation — the ability of carbon to bond with itself.

Which six elements are considered the major macronutrients found in cells?

Hydrogen (H), Carbon (C), Oxygen (O), Nitrogen (N), Phosphorus (P), and Sulfur (S).

What are the building blocks of macromolecules called?

Monomers.

What process links monomers together to form polymers?

Dehydration reaction

What is the name of the reaction where water breaks bonds between monomers?

Hydrolysis.

What type of molecules help speed up chemical reactions in cells?

Enzymes.

The smaller molecules act as building blocks and are called monomers, and the macromolecules that result from their linkage are called?

polymers.

Why are biomolecules typically called macromolecules?

Because they are large molecules made from repeating units (monomers).

Differentiate between organic and inorganic compounds.

Organic compounds contain carbon and are generally larger/complex; inorganic compounds usually do not contain carbon.

How does lactose intolerance demonstrate the role of enzymes in digestion?

People with lactose intolerance lack the enzyme (lactase) needed to hydrolyze lactose, a sugar found in milk.

Why is carbon capable of forming more compounds than any other element?

Because it can form up to four covalent bonds and create stable, varied structures like chains and rings.

Why is carbon the ideal backbone for complex biomolecules rather than another element like nitrogen or oxygen?

Carbon can form four covalent bonds, allowing for flexible and stable molecules with varied shapes and lengths. Nitrogen and oxygen cannot form as many simultaneous bonds.

If a dehydration reaction links glucose molecules into starch, what would hydrolysis do to starch in your digestive system?

Hydrolysis would break starch down into glucose molecules for absorption and energy.

If a scientist discovers a compound in a cell that lacks carbon, what type of compound is it likely to be?

Inorganic compound.

What functional role do groups like hydroxyl (-OH) or carboxyl (-COOH) play in biomolecules?

They determine the molecule’s properties and the types of chemical reactions it can undergo.

Which macromolecule group is primarily involved in genetic information storage?

Nucleic acids.

Why does drinking water while eating help digestion?

Because water is needed for hydrolysis, helping enzymes break down food molecules into absorbable units.

What are the monomers of carbohydrates?

Monosaccharides.

What is the general molecular formula for a monosaccharide?

A multiple of CH₂O.

What is the chemical formula of glucose and fructose?

C₆H₁₂O₆.

What are molecules with the same molecular formula but different structures called?

Isomers.

What sugar is the main fuel for cellular work?

Glucose.

What enzyme breaks down the sugar lactose?

Lactase.

What do most sugar names end with?

-ose.

What do most enzyme names end with?

-ase.

What is formed when two monosaccharides are linked by dehydration reaction?

A disaccharide.

What is the most common disaccharide?

Sucrose.

What are large carbohydrate macromolecules made of hundreds or thousands of monomers called?

Polysaccharides.

How do structural differences in isomers like glucose and fructose affect their properties?

Slight structural differences result in different chemical behaviors; e.g., fructose is sweeter than glucose.

Why are many five- and six-carbon sugars drawn as rings in aqueous solution?

Because they tend to form ring structures rather than staying linear in water.

What does sucrose consist of and how is it used in plants?

Glucose + fructose; it is transported in plant sap to provide energy and raw materials.

How do plants store glucose?

As starch, a polysaccharide that coils into helical chains and may be branched or unbranched.

How do animals store glucose?

As glycogen, stored in liver and muscle cells.

Why is glycogen important to animals?

It can be hydrolyzed to release glucose when energy is needed.

What is cellulose and where is it found?

A polysaccharide that makes up the tough walls of plant cells.

Why is cellulose not a nutrient for humans?

Humans lack enzymes to hydrolyze the bonds in cellulose.

What role does cellulose play in our diet?

It acts as dietary fiber that aids in digestion.

What is chitin and where is it found?

A structural polysaccharide found in insect/crustacean exoskeletons and fungal cell walls.

Why are most carbohydrates hydrophilic?

Because of the many hydroxyl (–OH) groups that attract water.

Cotton towels are water-absorbent. What property of their main component, cellulose, explains this?

Cellulose is hydrophilic due to multiple hydroxyl groups.

If you link many glucose molecules together in plants, what carbohydrate do you get?

Starch.

Why is glucose an ideal energy source for cells?

It has a simple structure that allows quick bond breaking and energy release.

A person eats bread (rich in starch). How does the body turn it into usable energy?

Enzymes hydrolyze starch into glucose, which cells then use for cellular respiration

A scientist finds a compound with a sweet taste and formula C₆H₁₂O₆. What test could distinguish if it’s glucose or fructose?

Structural isomer analysis—since both are isomers, look at structural arrangement using chemical or spectroscopic methods.

Why is cellulose stronger and more rigid than starch, even though both are made of glucose?

Because of the way glucose monomers are arranged—cellulose forms straight, cable-like microfibrils for structure.

Which of the following structures provides strength in plant cells?

Cellulose

How is chitin similar to cellulose?

Both are structural polysaccharides with tough, fibrous forms and made of repeating sugar units.

What shared characteristic defines all lipids?

All lipids are hydrophobic, meaning they do not mix well with water.

What are the three main types of lipids found in biological systems?

Fats, phospholipids, and steroids.

What two building blocks make up a fat molecule?

Glycerol and fatty acids.

What is the main function of fat in animals?

Long-term energy storage.

Which lipid is a key component of cell membranes?

Phospholipids.

What is the structural difference between saturated and unsaturated fatty acids?

Saturated fatty acids have no double bonds; unsaturated fatty acids have one or more double bonds.

What lipid molecule is the precursor for steroid hormones?

Cholesterol.

What is the function of adipose tissue?

Adipose tissue stores fat, cushions organs, and insulates the body.

Why are saturated fats solid at room temperature, while unsaturated fats are liquid?

Saturated fats have straight tails that allow tight packing; unsaturated fats have kinked tails due to double bonds, preventing tight packing.

How do phospholipids form the structure of cell membranes in water?

They form a bilayer with hydrophilic heads facing the water and hydrophobic tails tucked inward, creating a selective barrier.

Why do fats provide more energy than carbohydrates?

Fats have more C-H bonds, which release more energy upon oxidation.

How does the structure of steroids differ from other lipids?

Steroids have a carbon skeleton with four fused rings instead of fatty acid chains.

How do the chemical structures of glycerol and fatty acids allow them to combine into fats?

Glycerol's hydroxyl groups react with the carboxyl groups of fatty acids in dehydration synthesis.

A person consumes large amounts of processed foods containing partially hydrogenated oils. What type of fat is this person consuming and what are the health implications?

Trans fats; they increase the risk of heart disease, high cholesterol, and other health issues.

An organism is found with a membrane composed of tightly packed lipids that remain solid in warm climates. What type of lipids likely make up this membrane?

Saturated fatty acids.

Athletes abusing anabolic steroids may experience which of the following side effects?

Shrunken testicles and mood swings

Why would a polar dye fail to stain fat droplets in a microscope slide?

Because fats are nonpolar (hydrophobic), and polar dyes do not bind well to nonpolar substances.

Which lipid type is directly responsible for forming hormone precursors and regulating body processes like puberty?

Steroids, particularly cholesterol as a precursor.

A cell is unable to form a proper bilayer membrane. Which lipid is most likely deficient?

Phospholipids.

After prolonged starvation, what role do adipose tissues play in survival?

They release stored fat for energy to maintain basic bodily functions.

What are proteins made of?

Amino acids.

What is the bond that connects amino acids in a protein?

Peptide bond.

What is a long chain of amino acids called?

Polypeptide.

What part of an amino acid determines its properties?

The R group (side chain).

What happens to a protein during denaturation?

It unravels, loses its shape, and loses its function.

How many different amino acids are there in proteins?

20.

What type of biomolecule are enzymes?

Proteins.

Why is the shape of a protein important?

Because it determines the protein’s specific function and how it binds to other molecules.

What causes denaturation of proteins?

Factors like heat, pH changes, or chemicals.

How can misfolded proteins cause disease?

They can accumulate and disrupt normal cell function, as seen in diseases like Alzheimer’s and Parkinson’s.

What are prions?

Infectious, misshapen proteins that cause degenerative brain diseases

How does a polypeptide become a functional protein?

By folding into a specific three-dimensional structure influenced by the R groups.

What are the four levels of protein structure?

Primary, secondary, tertiary, and quaternary structures.v

What is the primary structure of a protein?

The specific sequence of amino acids in a polypeptide chain.

A student fries an egg and observes the clear part turning white. What protein process is this an example of?

Denaturation due to heat.

A protein fails to bind to its target molecule. What is most likely the reason?

The protein’s shape is incorrect, possibly due to misfolding or denaturation.

What would happen if a mutation caused the amino acid sequence of a protein to change?

The protein may fold incorrectly and lose its function.

Which protein structure is directly affected by a change in the amino acid sequence?

Primary structure.

Why do hydrophobic amino acids cluster inside globular proteins?

To avoid water and help stabilize the protein’s structure in an aqueous environment.

In a lab, a scientist alters the pH of a solution containing proteins. What is a possible outcome?

The proteins may denature and lose their function.

What are the two main types of nucleic acids?

DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).

What are the building blocks (monomers) of nucleic acids?

Nucleotides.

What are the three components of a nucleotide?

A five-carbon sugar, a phosphate group, and a nitrogenous base.

What sugar is found in DNA? In RNA?

Deoxyribose in DNA; ribose in RNA.

What are the nitrogenous bases in DNA?

Adenine (A), Thymine (T), Cytosine (C), Guanine (G).

What base is found in RNA but not in DNA?

Uracil (U) replaces Thymine (T) in RNA.

What shape does DNA form?

A double-stranded helix.

Which bases pair together in DNA?

A pairs with T; C pairs with G.

Why is the sequence of nitrogenous bases in DNA important?

It encodes genetic instructions that determine the amino acid sequence of proteins.

How does base pairing make DNA replication possible?

Each strand serves as a template for forming a complementary strand, ensuring accurate replication.

What is gene expression?

The process by which DNA instructions are used to synthesize proteins via RNA.

Why is RNA necessary for protein synthesis?

RNA carries the genetic code from DNA to the ribosomes where proteins are made.