AP Bio Unit 1: MCQ + FRQ

What role do DNA molecules play?

the hereditary material in all living organisms, stores genetic info in the sequence of nitrogenous bases (A, T, G, C), provides instructions for protein synthesis

What happens when you change the deoxyriboses to riboses by adding (-OH) groups?

changes DNA into RNA; ribose makes the molecule less stable, more reactive, and usually single-stranded, allowing RNA to function in protein synthesis (mRNA, tRNA, rRNA) instead of long-term information storage.

What is starch?

a carbohydrate (polysaccharide) made of α-glucose monomers used to store energy; easily broken down by enzymes for energy, CAN BE DIGESTED BY HUMANS

What is cellulose?

a carbohydrate (polysaccharide) made of β-glucose monomers that forms straight fibers; it is the main structural component of plant cell walls and provides rigidity and support, NOT DIGESTED BY HUMANS

Phosphodiester bonds in DNA

strong covalent bonds that link the 3′ hydroxyl group of one deoxyribose sugar to the 5′ phosphate group of the next nucleotide. They form the sugar-phosphate backbone of DNA, giving the molecule stability and direction from 5′ to 3′.

Glycosidic bonds in DNA

In DNA and RNA, glycosidic bonds are the covalent bonds that connect a nitrogenous base (A, T, G, C) to the sugar (deoxyribose in DNA)

Hydrogen bonds in DNA

weak bonds that form between complementary nitrogenous bases on opposite strands of DNA. (holds the two strands in a helix together)

Van de Waals interactions in DNA

weak attractive forces between stacked nitrogenous bases inside the helix. help stabilize the DNA structure by keeping the bases tightly packed in the hydrophobic core of the molecule.

Which of the following statements best describes the different functions of starch and cellulose in plants?

Starch functions as an energy storage molecule in plants because its glucose monomers are linked in a way that can be easily broken down for energy, while cellulose provides structural support in plant cell walls because its glucose chains form rigid fibers that most organisms cannot digest.

Which of the following describes the process that adds a monosaccharide to an existing polysaccharide?

dehydration (condensation) synthesis reaction. –OH group from the monosaccharide and an –H from the polysaccharide are removed to form water, and a glycosidic bond is created that links the new sugar into the chain.

What would happen if animals lost the ability to maintain a colony of microorganisms in their digestive tracts? 

animals would lack the enzymes needed to break down cellulose and other complex plant materials. This would prevent them from fully digesting their food and obtaining enough energy for survival. (ex. cows breaking down the cellulose in their diets)

What is the elemental makeup of carbohydrates?

C,H,O

What is the elemental makeup of lipids?

C,H,O

What is the elemental makeup of proteins?

C,H,O,N,_(s)

What is the elemental makeup of nucleic acids?

C,H,O,N,P

What atom do plants require to grow?

Phosphorus, essential element used to build nucleic acids (DNA + RNA), ATP, and phospholipids in cell membranes. Without phosphorus, plants cannot grow properly because they lack the molecules needed for energy transfer, genetic material, and cell structure.

What do amino acids bond to? How?

amino acids form peptide bonds with their amino group and their carboxyl group. The amino group (NH₂) of one amino acid bonds with the carboxyl group (COOH) of another through a dehydration reaction, linking them together into proteins.

Reactants Process Product(s)

Reactants→ undergo chemical process → products

How do R groups (side chains) work in amino acids?

R groups are the variable side chains attached to the central carbon of amino acids that determine their chemical properties. They can be nonpolar, polar, acidic, or basic, which affects how the amino acid interacts with other molecules and how a protein folds and functions.

What are the nitrogenous bases in DNA?

four nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G). Adenine pairs with thymine (A–T) and cytosine pairs with guanine (C–G) through hydrogen bonds, forming the rungs of the DNA double helix.

What are the nitrogenous bases in RNA?

RNA contains four nitrogenous bases: adenine (A), uracil (U), cytosine (C), and guanine (G). Uracil replaces thymine, so adenine pairs with uracil (A–U) instead of thymine.

RNA structure?

single-stranded and can fold into complex 3D shapes. Its sugar is ribose; involved in protein synthesis and gene regulation

DNA structure?

double-stranded, forming a double helix. Its sugar is deoxyribose; strands are held together by hydrogen bonds between complementary bases.

What do all proteins contain that nucleic acids do not?

Sulfur, even though it is a very small amount ALL proteins contain it

Dehydration Synthesis Reaction

the process of joining two molecules together by removing a water molecule. It is used to build macromolecules like polysaccharides, proteins, and nucleic acids by forming covalent bonds between monomers.

What is the role of phospholipids?

the main component of cell membranes, forming a bilayer that separates the inside of the cell from the outside environment. Their hydrophilic heads face outward toward water, while their hydrophobic tails face inward, creating a selective barrier that controls what enters and leaves the cell.

How does the structure of phospholipids relate to their function in cell membranes?

Phospholipids have hydrophilic heads and hydrophobic tails, which causes them to spontaneously form a bilayer, (structure made of two layers of molecules), in water. This arrangement creates a selectively permeable barrier, protecting the cell and controlling the movement of substances in and out.

What is the role of carbon in biological functions?

Carbon forms the backbone of all macromolecules, including carbohydrates, lipids, proteins, and nucleic acids. Its ability to make four covalent bonds allows complex structures needed for growth, energy storage, and biological functions. Carbon from nutrients provides the building blocks for cell growth.

How are the cell membranes are fused?

Cell membranes are fused using chemicals or electrical pulses that temporarily disrupt the lipid bilayer. This allows the phospholipids from two cells to merge, combining the cytoplasm and cellular components into a single hybrid cell.

How do the phospholipids interact?

The polar heads of phospholipids interact with water and with the heads from the other membrane via hydrogen bonding. The nonpolar tails interact through hydrophobic interactions, forming a stable interior. These interactions allow the bilayer to merge without breaking the barrier.

What is the most immediate effect on fused B-cancer cells that lack nitrogen, and why?

The most immediate effect is that the cells cannot synthesize nucleotides, so they cannot produce DNA or RNA. This happens because nitrogen is an essential component of nitrogenous bases, which are required to build nucleic acids. Without these macromolecules, the cells cannot replicate or make proteins, halting growth and function.

What is the process used to form covalent peptide bonds that join amino acids into polypeptides?

The process is called dehydration synthesis. During this process, the carboxyl group (–COOH) of one amino acid reacts with the amino group (–NH₂) of another, releasing a water molecule and forming a covalent peptide bond that links the amino acids into a polypeptide chain.