Biology (Grades 9–10) Midterm — Units 1–2

Science Grades 9–10 20 multiple choice + 1 written

Free printable Biology midterm (Grades 9–10): 20 multiple-choice questions plus 1 written response covering Biochemistry, Cells & Cell Transport. Answer key included — customize it in the Midterm Maker.

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Directions: Read each question carefully and choose the best answer. Answer the written response in complete sentences.

Covers: Biochemistry · Cells & Cell Transport

Part 1: Multiple Choice

Why does an enzyme stop working at very high temperatures?
1. A. It gains extra amino acids
2. B. Its shape changes, so the active site no longer fits the substrate
3. C. Its substrate becomes an enzyme
4. D. It turns into a carbohydrate
Water molecules stick to one another mainly because of which type of attraction?
1. A. Peptide bonds between water molecules
2. B. Ionic bonds between water molecules
3. C. Attraction between nonpolar molecules
4. D. Hydrogen bonds between polar molecules
Simple carbohydrates are made of which elements?
1. A. Carbon, oxygen, and phosphorus
2. B. Carbon, hydrogen, and nitrogen
3. C. Carbon, hydrogen, and oxygen
4. D. Nitrogen, oxygen, and sulfur
What are the monomers (building blocks) of proteins?
1. A. Nucleotides
2. B. Amino acids
3. C. Monosaccharides
4. D. Fatty acids
A solution with pH 3 has how many times more hydrogen ions than a solution with pH 5?
1. A. 1,000
2. B. 2
3. C. 20
4. D. 100
How do enzymes speed up chemical reactions?
1. A. By being used up as reactants
2. B. By raising the temperature of the cell
3. C. By lowering the activation energy
4. D. By increasing the activation energy
What are the monomers of nucleic acids such as DNA and RNA?
1. A. Monosaccharides
2. B. Glycerol molecules
3. C. Amino acids
4. D. Nucleotides
Glucose belongs to which class of macromolecules?
1. A. Proteins
2. B. Lipids
3. C. Nucleic acids
4. D. Carbohydrates
The basic structure of a cell membrane is a bilayer of which molecules?
1. A. Phospholipids
2. B. Nucleotides
3. C. Carbohydrates
4. D. Proteins
When two monomers are joined by dehydration synthesis, which molecule is released?
1. A. Oxygen
2. B. Carbon dioxide
3. C. Water
4. D. Glucose
A white blood cell surrounds and takes in a bacterium by folding its membrane around it. What is this process called?
1. A. Exocytosis
2. B. Endocytosis
3. C. Diffusion
4. D. Osmosis
Which organelle modifies, sorts, and packages proteins for transport?
1. A. Golgi apparatus
2. B. Nucleolus
3. C. Lysosome
4. D. Mitochondrion
Which process uses energy to move substances against their concentration gradient?
1. A. Simple diffusion
2. B. Active transport
3. C. Facilitated diffusion
4. D. Osmosis
What is osmosis?
1. A. Engulfing of large particles
2. B. Pumping of glucose against its gradient
3. C. Movement of salt using ATP
4. D. Diffusion of water across a selectively permeable membrane
An animal cell is placed in a solution saltier than its cytoplasm. What happens?
1. A. Salt leaves the cell and it bursts
2. B. Nothing changes in the cell
3. C. Water leaves the cell and it shrinks
4. D. Water enters the cell and it swells
Glucose moves into a cell through a carrier protein, down its gradient, without using ATP. What is this called?
1. A. Exocytosis
2. B. Active transport
3. C. Facilitated diffusion
4. D. Endocytosis
What is a key difference between eukaryotic and prokaryotic cells?
1. A. Eukaryotic cells lack ribosomes
2. B. Prokaryotic cells lack DNA
3. C. Prokaryotic cells have mitochondria
4. D. Eukaryotic cells have a membrane-bound nucleus
A plant cell placed in pure water swells but does not burst. Why?
1. A. Water cannot enter plant cells
2. B. Its cell wall resists the pressure
3. C. It has no cell membrane
4. D. Its chloroplasts absorb the water
A cube-shaped cell has sides of 2 µm. What is its surface area-to-volume ratio?
1. A. 1:3
2. B. 6:1
3. C. 2:1
4. D. 3:1
Diffusion is the movement of particles in which direction?
1. A. From low concentration to high concentration
2. B. Only into the nucleus
3. C. From high concentration to low concentration
4. D. Only when ATP is used

Part 2: Written Response

A slice of potato is placed in very salty water and another in distilled water. Predict what happens to each and explain using osmosis and tonicity.

Answer Key — Biology (Grades 9–10) Midterm — Units 1–2

B — Its shape changes, so the active site no longer fits the substrate Heat denatures proteins by disrupting their folded shape.
D — Hydrogen bonds between polar molecules Water's polarity allows hydrogen bonding, causing cohesion.
C — Carbon, hydrogen, and oxygen Sugars such as glucose (C₆H₁₂O₆) contain only C, H, and O.
B — Amino acids Proteins are chains of amino acids joined by peptide bonds.
D — 100 Each pH unit is a tenfold change: 10 × 10 = 100.
C — By lowering the activation energy Enzymes lower the energy barrier and are not consumed.
D — Nucleotides Each nucleotide has a sugar, phosphate, and nitrogen base.
D — Carbohydrates Glucose is a simple sugar, a carbohydrate monomer.
A — Phospholipids Phospholipid heads face water; tails face inward.
C — Water Dehydration synthesis removes a water molecule to form a bond.
B — Endocytosis Endocytosis brings large materials in using membrane vesicles.
A — Golgi apparatus The Golgi processes proteins received from the endoplasmic reticulum.
B — Active transport Active transport requires ATP to move from low to high concentration.
D — Diffusion of water across a selectively permeable membrane Osmosis is specifically the passive movement of water.
C — Water leaves the cell and it shrinks In a hypertonic solution, water moves out by osmosis.
C — Facilitated diffusion Transport proteins help, but no cellular energy is spent.
D — Eukaryotic cells have a membrane-bound nucleus Prokaryotes have DNA in a nucleoid region, not a nucleus.
B — Its cell wall resists the pressure The rigid cell wall creates turgor pressure that prevents bursting.
D — 3:1 Surface area 24 µm² ÷ volume 8 µm³ = 3:1.
C — From high concentration to low concentration Particles spread out down their concentration gradient.

Written Response — Look-Fors

Salty (hypertonic): water leaves cells, slice becomes limp/loses mass; distilled (hypotonic): water enters, slice becomes firm/gains mass; water moves from high to low water concentration; cell wall prevents bursting.

Biology (Grades 9–10) Midterm — Units 1–2

Part 1: Multiple Choice

Part 2: Written Response

Written Response — Look-Fors

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