Connect the structure of carbohydrates, lipids, proteins, and nucleic acids to their biological jobs.
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Carbon can form four covalent bonds. Carbon skeletons can branch, form rings, and have different lengths. Attached functional groups help determine how a molecule behaves.
Two molecules can contain the same types and numbers of atoms but differ in structure. A shape change can change how a molecule interacts with an enzyme or receptor.
Which process joins monomers by removing water, and which process splits a polymer by adding water?
Dehydration synthesis joins them; hydrolysis splits them.
In dehydration synthesis, parts of a water molecule are removed as a bond forms. Hydrolysis uses water to break a bond. Both processes are guided by enzymes in cells.
Starch stores glucose in plants. Glycogen stores it in animals. Cellulose supports plant cell walls. Their different linkages give them different shapes and functions.
Humans can digest starch but lack enzymes to break the main bonds in cellulose. Cellulose is still useful as dietary fiber. A molecule’s connections matter as much as its ingredients.
A large molecule is made of glucose, but humans cannot digest it. It provides strength to a plant cell wall. What is it?
Cellulose.
Both starch and cellulose contain glucose. Different bond arrangements make cellulose tough and resistant to human digestive enzymes.
Fats contain glycerol joined to three fatty acids. They store substantial energy and can cushion or insulate. Lipids are mostly hydrophobic and are not true polymers made from repeating monomers.
Saturated fatty acids lack carbon-carbon double bonds. Unsaturated fatty acids have at least one; many cis double bonds introduce bends that reduce close packing.
Why do phospholipids form a bilayer when surrounded by water?
Their hydrophilic heads face water, while their hydrophobic tails cluster away from water inside the bilayer.
A phospholipid typically has two fatty acid tails and a phosphate-containing head. This arrangement creates a stable barrier with water on both sides.
Proteins are chains of amino acids linked by peptide bonds. Their amino acid sequence influences folding. A folded protein’s shape helps it perform jobs such as catalysis, transport, defense, or signaling.
Primary structure is the sequence; secondary structure includes local coils and folds; tertiary structure is the overall shape of one chain; quaternary structure involves multiple chains.
Heat changes an enzyme’s shape so its substrate no longer fits. What happened, and why does activity fall?
The enzyme denatured. Its active site lost the shape and chemical conditions needed for the reaction.
Heat or extreme pH can disrupt interactions that maintain a protein’s shape. Denaturation often leaves the amino acid chain intact while damaging its functional folding.
DNA and RNA are nucleotide polymers. Each nucleotide contains a sugar, a phosphate group, and a nitrogenous base. DNA uses deoxyribose and A, T, C, G; RNA uses ribose and A, U, C, G.
DNA usually stores inherited instructions. RNA has many roles in using and regulating those instructions, including carrying messages and helping build proteins.
Match each material to its main small unit: protein, DNA, starch. Choose from amino acid, nucleotide, and glucose.
Protein → amino acids; DNA → nucleotides; starch → glucose.
A molecule’s building blocks help predict its function and the enzymes needed to make or break it. Fat uses glycerol and fatty acids but is not a repeating-unit polymer like these examples.