Bleeding Beets and Bendy Carrots

Use kitchen tests to model how cell parts keep a vegetable firm.

Part 1: The beet and carrot tests

Read the passage and both tables. Use them to answer questions 1–5.

Prep Night for the Family Dinner

1Caleb Nakamura's school culinary club is cooking a vegetable dinner for families. Their volunteer chef, Rhoda Esposito, warned the club about two problems: beets bleed red juice onto everything once they are cooked, and carrots that boil too long go limp and mushy. When Caleb asked why, she said the answer is inside the vegetables' cells. Beets and carrots are roots, and their cells are still alive when they come from the store.

2Each root cell has a thin cell membrane that controls what moves in and out. Inside the membrane, the cell stores water, sugar and, in a beet, a red pigment. Around the membrane is a stiff cell wall. The wall has tiny openings that let water and dissolved substances pass through, but it is strong. When a living cell is full of water, it presses outward against its wall, a little like an inflated ball inside a box.

3For the beet test, Chef Esposito cut a raw beet into cubes of the same size and rinsed them in cold water to wash off juice from the cells the knife had cut open. She put one cube into each of four cups holding 50 mL of water at 20 °C, 40 °C, 60 °C and 80 °C. She prepared the hot cups herself and kept each cup at its temperature for 10 minutes. Then she lifted out the cubes, and the club compared the color of each cup with a chart that runs from 0 (clear) to 10 (deep red).

4For the carrot tests, the club used carrot sticks of the same size. They clamped one end of each stick at the edge of a table, hung a 50 g weight from the other end and measured how far the tip bent. The chef boiled some sticks and let them cool before testing, and the club looked at a thin slice of each stick under a microscope.

5Last, the chef set the cut-off top of a raw carrot in a dish of water on a sunny windowsill. Within a week, new green leaves were sprouting from it. A carrot top cut from a carrot boiled for 20 minutes sat beside it and grew nothing.

Table 1: Beet Cubes After 10 Minutes
Water temperature (°C)	Color score (0–10)
20	1
40	2
60	7
80	10

Table 2: Carrot Stick Tests
Stick	Tip bend (mm)	Cells at 400×
Raw, fresh	3	Plump, pressed tightly together
Raw, left on the counter 2 days	15	Smaller and wrinkled, still joined
Raw, 2 days, then cold water 2 h	4	Plump again, pressed tightly together
Boiled 5 min	9	Less plump, still joined
Boiled 10 min	16	Shrunken, still joined
Boiled 20 min	31	Many pulled apart from their neighbors
Boiled 20 min, then cold water 2 h	30	Same as before soaking

Use Table 1.

The color score rose by points from the 40 °C cup to the 60 °C cup.

Use paragraph 2 and Table 1. What does the beet test show about the cell membrane?

A. The membranes made extra red pigment in hot water, which flowed out of the cubes into the cup.
B. The cell walls held the pigment in until 60 °C, and then the heat melted holes in the walls.
C. The membranes let out more pigment in cool water, since cool water has more room for color.
D. Up to 40 °C the membranes kept most pigment in; by 60 °C heat had damaged them, so pigment leaked out.

Why did Chef Esposito rinse the beet cubes before the test?

A. So the color in each cup would come from cells leaking during the test, not from cut cells
B. To fill the cells with extra water, so they would hold on to more of their pigment
C. So the cubes would weigh the same, since water would soak into each cube equally
D. To cool the cubes down, so the hot cups would warm them at the same speed

Use Table 2.

The stick boiled for 20 minutes bent mm farther than the fresh raw stick.

Use Table 2. The limp raw carrot firmed up again in cold water, but the stick boiled for 20 minutes did not. Which is the best explanation?

A. The boiled stick was already full of water from the pot, so no more water could fit inside its cells.
B. The living cells' membranes took water back in and pressed out on the walls; the boiled cells' could not.
C. The raw stick had more cell walls than the boiled stick, since boiling turns cell walls into water.
D. The cold water closed the openings in the boiled cells' walls, so water could not pass into them.

Part 2: A model of a living root cell

Use the passage, both tables and what you know about cell parts to answer questions 6–10.

Match each cell part to the job it does in a living carrot, as described on this page.

Nucleus
Mitochondria
Cell membrane
Cell wall
Chloroplasts

A. Holds the instructions for building new cells in the top
B. Makes sugar using light, in the new green leaves on the top
C. Releases energy from stored sugar so the top can grow
D. Gives a stiff layer that the water-filled cell presses against
E. Keeps water, sugar and pigment inside the living cell

After 5 minutes of boiling, the carrot cells were still joined, yet the stick bent 3 times as far as a fresh one. Which explanation fits the model best?

A. The boiling water pushed into the cells and made them too full, so the stick turned soft.
B. The heat began to damage the membranes, so cells lost water and pressed less on their walls.
C. The heat used up the cells' sugar, and the sugar was the part that held the stick stiff.
D. The heat made the walls thinner, which softened the stick before the membranes changed.

Suppose the chef had also tested a beet cube in water at 50 °C. Which color score is most likely?

A. About 1, the same as the 20 °C cup, since 50 °C is still cooler than 60 °C
B. About 10, the same as the 80 °C cup, since 50 °C is hot water too
C. From 2 to 7, since 50 °C falls between the 40 °C and 60 °C cups
D. Higher than 10, since the cube sits between two of the warmest cups

Use paragraph 5. The raw carrot top grew new leaves, but the top from the boiled carrot grew nothing. Which statement explains this best?

A. The raw top's cells were alive, so their parts could work together to build new cells.
B. The raw top grew because the water in the dish gave it the energy for its new leaves.
C. The boiled top needed more sunlight, since cooking had removed its green chloroplasts.
D. The boiled top had no nucleus left in its cells, but its membranes and mitochondria still worked.

10.

A club member says, "Cooking makes carrots soft just because the heat melts the cell walls." Do you agree? Write a claim, give evidence from both tables, and explain your reasoning using a model of how the membrane and the wall work together.