How does the structure of each macromolecule suit the job it does in a cell?
Relate the structure of the four macromolecules (carbohydrates, lipids, proteins, nucleic acids), their monomers, and their functions in carrying out cellular processes (GSE SB1.c).
A Georgia Milestones Biology EOC answer on the four biological macromolecules: carbohydrates, lipids, proteins, and nucleic acids, their monomers and elements, their functions, and how structure relates to function in cellular processes.
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What this topic is asking
Standard SB1.c asks you to relate the structure of macromolecules to their functions in cellular processes. For the Georgia Milestones Biology EOC you must know the four macromolecules (carbohydrates, lipids, proteins, nucleic acids), their monomers (building blocks), and the jobs each does, then explain how a macromolecule's makeup suits that job. The recurring skill is matching a function to the right macromolecule.
The four macromolecules
Learn each as elements, monomer, and function:
- Carbohydrates. Made of carbon, hydrogen, and oxygen; monomer is the monosaccharide (simple sugar, such as glucose). Function: quick energy (glucose) and short-term energy storage (starch in plants, glycogen in animals); also structure (cellulose in plant cell walls).
- Lipids. Made mostly of carbon and hydrogen; not a single repeating monomer (fats are built from glycerol and fatty acids). Function: long-term energy storage, membranes (phospholipids), insulation, and some hormones.
- Proteins. Made of carbon, hydrogen, oxygen, and nitrogen; monomer is the amino acid (about 20 kinds). Function: the most varied class, including enzymes (speed up reactions), structure (such as collagen), transport (such as membrane channels), and defense (antibodies).
- Nucleic acids. Made of carbon, hydrogen, oxygen, nitrogen, and phosphorus; monomer is the nucleotide. Function: DNA stores genetic information and RNA carries it to build proteins.
Structure relates to function
The standard stresses the structure-function link, so be ready to explain it, not just recall the function.
- A protein folds into a specific three-dimensional shape determined by its amino-acid sequence, and that shape is what lets an enzyme fit its substrate or a channel let a specific ion through. Change the shape (by heat or pH) and the protein stops working.
- A phospholipid has a hydrophilic (water-loving) head and two hydrophobic (water-fearing) tails. In water, phospholipids automatically arrange into a bilayer, heads out and tails in, which is exactly the structure of the cell membrane.
- Glucose is a small, soluble sugar that is quick to break down for energy, while starch is a coiled polymer of glucose that packs many sugars into a compact, insoluble store.
Monomers and polymers
Cells build polymers by joining monomers and break them down by splitting the bonds. Joining monomers releases a water molecule (dehydration synthesis); breaking a polymer adds a water molecule (hydrolysis). You do not need the reaction names in depth for most EOC items, but you should know that the macromolecule's properties come from the kind and arrangement of its monomers: the same amino acids in a different order make a completely different protein.
Try this
Q1. Name the monomer of each: carbohydrate, protein, nucleic acid. [3 points]
- Cue. Carbohydrate: monosaccharide; protein: amino acid; nucleic acid: nucleotide.
Q2. Explain why a phospholipid's structure suits it to form the cell membrane. [2 points]
- Cue. Its hydrophilic head faces water and its hydrophobic tails avoid water, so in water phospholipids form a bilayer with heads out and tails in, which is the membrane structure.
Exam-style practice questions
Practice questions written in the style of GaDOE exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Milestones (style)1 marksWhich macromolecule is the main source of quick energy and includes sugars and starches? (A) protein (B) lipid (C) carbohydrate (D) nucleic acidShow worked answer →
A 1-point selected-response item on macromolecule function.
The correct answer is C. Carbohydrates (sugars and starches), built from monosaccharide monomers, are the main source of quick energy for cells. Lipids store energy long term and form membranes, proteins build structures and act as enzymes, and nucleic acids store genetic information. Matching the function (quick energy) to the macromolecule (carbohydrate) is the skill being tested.
Milestones (style)2 marksDrag and drop. Match each macromolecule to its monomer (building block): carbohydrate, protein, nucleic acid. Monomers: amino acid, monosaccharide, nucleotide.Show worked answer →
A 2-point technology-enhanced (drag-and-drop) matching item.
The correct matches are: carbohydrate to monosaccharide, protein to amino acid, and nucleic acid to nucleotide. Carbohydrates are polymers of monosaccharides (simple sugars), proteins are polymers of amino acids, and nucleic acids (DNA and RNA) are polymers of nucleotides. Lipids are the exception: they are not built from a single repeating monomer, which is why the item lists only the three polymer macromolecules.
Related dot points
- Construct an explanation of how cell structures and organelles (nucleus, cytoplasm, cell membrane, cell wall, chloroplasts, lysosome, Golgi apparatus, endoplasmic reticulum, vacuoles, ribosomes, mitochondria) interact as a system to maintain homeostasis (GSE SB1.a).
A Georgia Milestones Biology EOC answer on the eukaryotic organelles as a structure-and-function system: the nucleus, ribosomes, endoplasmic reticulum, Golgi apparatus, mitochondria, chloroplasts, lysosomes, vacuoles, membrane, and cell wall, and how they work together to maintain homeostasis.
- Explain how enzymes (a type of protein) lower activation energy and carry out cellular processes, and how temperature, pH, and substrate fit affect enzyme activity (GSE SB1.c).
A Georgia Milestones Biology EOC answer on enzymes: how they lower activation energy, the lock-and-key specificity of the active site, the effect of temperature, pH, and substrate concentration, and what denaturation does to enzyme activity.
- Describe the structure of DNA and RNA, including the double helix, nucleotides, and complementary base pairing, and compare DNA and RNA (GSE SB2.a).
A Georgia Milestones Biology EOC answer on the structure of DNA and RNA: the double helix, nucleotides (sugar, phosphate, base), complementary base pairing (A-T, C-G, A-U), the antiparallel strands, and the key differences between DNA and RNA.
- Explain the roles of photosynthesis and cellular respiration in the cycling of matter and the flow of energy, including their reactants, products, and how the two processes connect (GSE SB1.e).
A Georgia Milestones Biology EOC answer on photosynthesis and cellular respiration: the reactants and products of each, where they occur, how energy flows and matter cycles, and why the two processes are reverse complements that link plants and animals.
- Determine the role of cellular transport (diffusion, osmosis, facilitated diffusion, and active transport) across the selectively permeable membrane in maintaining homeostasis (GSE SB1.d).
A Georgia Milestones Biology EOC answer on cellular transport: the selectively permeable membrane, passive transport (diffusion, osmosis, facilitated diffusion) versus active transport, predicting water movement in hypotonic, hypertonic, and isotonic solutions, and how transport maintains homeostasis.
Sources & how we know this
- Biology Georgia Standards of Excellence (GSE) — Georgia Department of Education (2024)
- Georgia Milestones Biology EOC Assessment Guide — Georgia Department of Education (2024)