The four molecules of life: carbohydrates, lipids, proteins, nucleic acids
Grade 9 Science Worksheet
Circle the best answer.
Building-block drawing, not to scale. Bo reads about molecule M, which has four linked carbon rings and a short tail. Which statement about M is correct?
- M is a steroid, a lipid that is not a polymer
- M is a nucleic acid, because bases are rings
- M is a protein, because rings join like amino acids
- M is a steroid, a lipid that is a polymer of rings
Building-block chain, not to scale. Esme reads about molecule M, used when cells build proteins. M is a chain of beads, each with a sugar, a phosphate group and a base. What is M?
- Carbohydrate, because each bead has a sugar
- Protein, because it helps build proteins
- Nucleic acid, because its beads are nucleotides
- Lipid, because it holds phosphate groups
Every sample also contains carbon, hydrogen and oxygen. Jun reads a lab’s atom report. Which sample is most likely a nucleic acid?
- Sample D: it has phosphorus
- Sample C: it has nitrogen and phosphorus
- Sample A: it has no nitrogen, phosphorus or sulfur
- Sample B: it has nitrogen and sulfur
Sample Z also contains carbon, hydrogen and oxygen. Kira reads the atom report for sample Z. Which pair of classes can be ruled out?
- Carbohydrates and lipids
- Proteins and nucleic acids
- Lipids and nucleic acids
- Proteins and carbohydrates
Both samples also contain carbon, hydrogen and oxygen. Luz compares samples E and F in the atom report. Which statement is correct?
- E is likely a nucleic acid, since both have nitrogen
- E is a protein, but F cannot be one without sulfur
- Neither can be a protein, since both lack phosphorus
- E is likely a protein, and F could be a protein too
Noah studies molecule M, which makes up the outer layer of cell membranes. Which statement about M is correct?
- M is a nucleic acid, since it contains phosphate
- M is a polymer of many identical lipid units
- M is a lipid with a phosphate-containing head
- M is a protein that forms channels in membranes
Pia learns that saliva contains amylase, an enzyme. Amylase is a folded chain of beads joined by peptide bonds. Which statement is correct?
- It is a food nutrient, so it cannot work inside the body
- It is a carbohydrate, because it acts on starch
- It is a protein that works as an enzyme
- It is a nucleic acid, because it directs a reaction
Read this first
Results card (model data)
Tube Sample Test Result Tube P glucose solution Benedict’s solution, heated by a teacher turned orange-red Tube Q plain water Benedict’s solution, heated by a teacher stayed blue A teacher ran this Benedict’s test while Ren’s class watched. What does the result in tube P show?
- Protein, which is made of amino acids
- A fat, which is a lipid
- Starch, which stores glucose
- A simple sugar, a carbohydrate
Tube R holds potato extract. A teacher ran two tests on potato extract while Tala’s class watched. Which conclusion fits both results?
- No carbohydrate, since Benedict’s stayed blue
- Protein, since iodine changed color
- Starch and a simple sugar, since iodine changed
- Starch is present, but no simple sugar was found
Sample S is a seed extract. A teacher ran two tests on a seed extract while Zee’s class watched. Which conclusion fits both results?
- Protein and a lipid are both present
- A lipid is present, and violet shows DNA, a protein
- Protein is present, and the spot shows a carbohydrate
- A lipid is present, and violet shows starch