Biology: Biochemistry: Carbohydrates, Proteins, Lipids, Nucleic Acids
Structure and function of the four major biological macromolecules
Biology: Biochemistry: Carbohydrates, Proteins, Lipids, Nucleic Acids
Structure and function of the four major biological macromolecules
Biology - Grade 9-12
- 1
A student finds a molecule made of carbon, hydrogen, and oxygen in about a 1:2:1 ratio. The molecule is used by cells for quick energy. Which macromolecule group does it most likely belong to, and why?
Think about the general formula for many simple sugars.
The molecule most likely belongs to the carbohydrate group because carbohydrates often have a carbon, hydrogen, and oxygen ratio near 1:2:1 and are commonly used for quick energy. - 2
Complete the relationship: monosaccharide is to carbohydrate as amino acid is to which macromolecule?
Amino acid is to protein. Amino acids are the monomers that join together to form proteins. - 3
A diagram shows glucose molecules joining together to form a long starch molecule while water molecules are released. What type of chemical reaction is shown?
Look for whether water is being removed or added.
The reaction shown is dehydration synthesis, also called a condensation reaction. Monomers are joined together while water is removed. - 4
Explain the difference between a monosaccharide, a disaccharide, and a polysaccharide. Give one example of each.
A monosaccharide is one sugar unit, such as glucose. A disaccharide is two sugar units joined together, such as sucrose. A polysaccharide is a long chain of sugar units, such as starch, glycogen, or cellulose. - 5
Cellulose and starch are both made of glucose monomers, but animals can digest starch more easily than cellulose. Explain why two molecules made from the same monomer can have different properties.
In biology, structure and function are closely related.
Cellulose and starch have different bonds and shapes even though they are both made of glucose. Their different structures affect how enzymes interact with them, so they have different properties and functions. - 6
A protein is made when amino acids are joined together. What type of bond connects one amino acid to another in a protein?
A peptide bond connects one amino acid to another in a protein. Peptide bonds form between the amino group of one amino acid and the carboxyl group of another amino acid. - 7
List the four levels of protein structure in order from simplest to most complex, and briefly describe the primary level.
Primary means first and refers to the order of building blocks.
The four levels of protein structure are primary, secondary, tertiary, and quaternary. The primary structure is the specific sequence of amino acids in a polypeptide chain. - 8
A protein loses its normal three-dimensional shape after being exposed to very high heat. What is this process called, and how can it affect the protein's function?
This process is called denaturation. Denaturation can change the shape of the protein so that it no longer works properly, because protein function depends on protein shape. - 9
A food sample leaves a translucent spot on brown paper after drying. Which macromolecule is likely present, and what is one major function of this macromolecule group?
Fats and oils often leave greasy spots.
A lipid is likely present. Lipids can store long-term energy, form cell membranes, provide insulation, and help with chemical signaling. - 10
Compare saturated and unsaturated fatty acids in terms of carbon-carbon bonds and physical shape.
Saturated fatty acids have only single bonds between carbon atoms, so their chains are usually straight. Unsaturated fatty acids have one or more double bonds, which often create bends or kinks in the chain. - 11
A phospholipid has a hydrophilic head and two hydrophobic tails. Explain how this structure helps form cell membranes.
Hydrophilic means water-loving, and hydrophobic means water-fearing.
Phospholipids form a bilayer because the hydrophilic heads face the watery environments inside and outside the cell, while the hydrophobic tails point inward away from water. This arrangement creates the basic structure of the cell membrane. - 12
What are the three parts of a nucleotide?
A nucleotide is made of a phosphate group, a five-carbon sugar, and a nitrogenous base. Nucleotides are the monomers of nucleic acids. - 13
In DNA, a strand has the base sequence A T G C C A. Write the complementary DNA strand.
Use the base-pairing rules A with T and C with G.
The complementary DNA strand is T A C G G T. In DNA, adenine pairs with thymine, and cytosine pairs with guanine. - 14
Explain two key differences between DNA and RNA.
Think about sugar type, bases, and number of strands.
DNA usually has deoxyribose sugar and RNA has ribose sugar. DNA uses thymine while RNA uses uracil. DNA is usually double-stranded, while RNA is usually single-stranded. - 15
A lab table lists four unknown samples: Sample A tests positive with Benedict's solution after heating, Sample B tests positive with Biuret solution, Sample C tests positive with Sudan stain, and Sample D contains a polymer of nucleotides. Identify the main macromolecule in each sample.
Sample A contains a reducing sugar, which is a carbohydrate. Sample B contains protein because Biuret solution detects peptide bonds. Sample C contains lipid because Sudan stain detects fats and oils. Sample D contains a nucleic acid because it is made of nucleotides.