The cell membrane: a selective barrier
Grade 9 Science Worksheet
Circle the best answer.
Membrane drawing (model, not to scale). No proteins are drawn. Esme lists three particles near a cell: carbon dioxide, potassium ions and glucose. Which can cross the bilayer on its own, with no protein?
- Potassium ions, because they are small
- Each of the three, because the bilayer is open
- Carbon dioxide, because it has no charge
- No particle can, because gases need a protein too
No proteins are drawn. Oxygen, carbon dioxide and chloride ions are outside Bo’s cell. Which one needs a transport protein to cross the bilayer?
- No particle needs one, because the membrane is open
- Oxygen, because gases need a protein to cross
- Carbon dioxide, because it is the largest of the three
- Chloride ions, because they carry a charge
Membrane drawing (model, not to scale). Phospholipid heads face the watery fluid on both sides of the membrane. Jun wants to know why. Which explanation fits?
- The heads are water-fearing, so they stay near the water
- The membrane is a solid wall, so heads are pressed outward
- The heads are water-loving, so they form hydrogen bonds with water
- The tails are water-loving, so they pull the heads outward
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Phospholipids in water (model, not to scale). Each phospholipid has one round head and two thin tails. Water fills the space above and below a double layer of phospholipids.
Luz reads that phospholipids placed in water form a double layer. Which prediction describes how the two layers line up?
- Heads and tails lock together in one solid layer
- Tails face the water on both sides; heads meet in the middle
- Heads face the water on both sides; tails meet in the middle
- Heads face the water above; tails face the water below
Membrane drawing (model, not to scale). The tails in Milo’s drawing meet in the middle, away from both fluids. Which explanation fits?
- The tails are charged, so ions pull them into the middle
- The tails are water-loving, so they gather in the middle
- The membrane is a solid wall, so the tails are locked in
- The tails are water-fearing, so they pack together away from water
Membrane drawing in two steps (model, not to scale). Noah reads about a protein that binds one glucose molecule, changes shape and releases the glucose inside the cell. What kind of protein is it?
- A carrier protein, which changes shape to carry glucose
- A channel protein, which forms an open tunnel for glucose
- A surface protein, which rests on top of the bilayer
- A phospholipid, which lets sugars slip through the tails
Use this
Membrane drawing (model, not to scale).
Pia’s drawing shows a protein that reaches across the bilayer and forms a tunnel shaped to fit sodium ions. What kind of protein is it?
- A carrier protein, which changes shape to carry ions
- A phospholipid, which lets sodium ions slip through
- A carbohydrate chain, which marks the cell’s outside
- A channel protein, which forms a tunnel for ions
A protein uses ATP energy to move sodium ions out of a cell and potassium ions in. What kind of protein is it, according to Ren’s drawing?
- A surface protein, which rests on top of the bilayer
- A gap in the tails, which lets ions slip across
- A channel protein, which needs no energy
- A pump, which uses ATP energy
Glycoproteins and glycolipids carry sugar chains. In Tala’s drawing, where are such chains found?
- On the outside surface, facing away from the cell
- On the inside surface, facing the cell’s inside
- In the middle, among the thin tails
- On both surfaces of the membrane equally
Letter K points to cholesterol in Ari’s animal cell drawing. Where does it lie, and what does it do?
- Alongside the phospholipids, helping keep the membrane fluid
- Inside a channel, helping ions cross the bilayer
- Alongside the phospholipids, making the membrane a solid wall
- On the outside surface, helping cells recognize each other