Biology: Biochemistry: Carbohydrates, Proteins, Lipids, Nucleic Acids Worksheet

Question 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?

Accepted Answer

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.

Question 2

Complete the relationship: monosaccharide is to carbohydrate as amino acid is to which macromolecule?

Accepted Answer

Amino acid is to protein. Amino acids are the monomers that join together to form proteins.

Question 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?

Accepted Answer

The reaction shown is dehydration synthesis, also called a condensation reaction. Monomers are joined together while water is removed.

Question 4

Explain the difference between a monosaccharide, a disaccharide, and a polysaccharide. Give one example of each.

Accepted Answer

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.

Question 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.

Accepted Answer

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.

Question 6

A protein is made when amino acids are joined together. What type of bond connects one amino acid to another in a protein?

Accepted Answer

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.

Question 7

List the four levels of protein structure in order from simplest to most complex, and briefly describe the primary level.

Accepted Answer

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.

Question 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?

Accepted Answer

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.

Question 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?

Accepted Answer

A lipid is likely present. Lipids can store long-term energy, form cell membranes, provide insulation, and help with chemical signaling.

Question 10

Compare saturated and unsaturated fatty acids in terms of carbon-carbon bonds and physical shape.

Accepted Answer

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.

Question 11

A phospholipid has a hydrophilic head and two hydrophobic tails. Explain how this structure helps form cell membranes.

Accepted Answer

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.

Question 12

What are the three parts of a nucleotide?

Accepted Answer

A nucleotide is made of a phosphate group, a five-carbon sugar, and a nitrogenous base. Nucleotides are the monomers of nucleic acids.

Question 13

In DNA, a strand has the base sequence A T G C C A. Write the complementary DNA strand.

Accepted Answer

The complementary DNA strand is T A C G G T. In DNA, adenine pairs with thymine, and cytosine pairs with guanine.

Question 14

Explain two key differences between DNA and RNA.

Accepted Answer

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.

Question 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.

Accepted Answer

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.

Biology: Biochemistry: Carbohydrates, Proteins, Lipids, Nucleic Acids

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