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Cells and the cycling of matter

Ten questions of mixed difficulty, covering Cells. Print it, or work through it on screen — the answer key starts on its own page.

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Cells and the cycling of matter

Science 10 · maddyhelps.com

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Circle the best answer for each question. Show your work in the space provided.

  1. Active transport differs from diffusion in that it

    1. a) only moves water
    2. b) moves substances against a concentration gradient and uses ATP
    3. c) needs no membrane
    4. d) is faster

  2. Osmosis is the diffusion of

    1. a) salt across a membrane
    2. b) water across a selectively permeable membrane
    3. c) gases only
    4. d) any substance through a cell wall

  3. Of these structures, the one found in plant cells but not animal cells is the

    1. a) cell membrane
    2. b) nucleus
    3. c) mitochondrion
    4. d) cell wall

  4. Diffusion is the movement of particles

    1. a) from higher to lower concentration, without energy
    2. b) only in living things
    3. c) from lower to higher concentration, using energy
    4. d) only through a membrane

  5. Most of a cell's ATP is produced in the

    1. a) nucleus
    2. b) chloroplast
    3. c) mitochondrion
    4. d) cell wall

  6. A cell's surface area to volume ratio limits its size because

    1. a) the membrane gets thicker
    2. b) DNA runs out
    3. c) large cells have no nucleus
    4. d) volume grows faster than surface area, so exchange cannot keep up

  7. Photosynthesis and cellular respiration are closely linked because

    1. a) the products of each are the reactants of the other
    2. b) neither uses oxygen
    3. c) both destroy energy
    4. d) both happen in the chloroplast

  8. The basic unit of life is the

    1. a) tissue
    2. b) cell
    3. c) organ
    4. d) molecule

  9. The organelle that controls a cell's activities and holds its DNA is the

    1. a) ribosome
    2. b) nucleus
    3. c) mitochondrion
    4. d) vacuole

  10. The overall equation for photosynthesis is

    1. a) 6O₂ + 6H₂O → C₆H₁₂O₆
    2. b) 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
    3. c) C₆H₁₂O₆ → 6CO₂
    4. d) C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

Answer key · Cells and the cycling of matter

Science 10 · maddyhelps.com

  1. b) moves substances against a concentration gradient and uses ATP — Diffusion can only even things out. Concentrating a substance where it is already plentiful is uphill, so it has to be paid for with energy.
  2. b) water across a selectively permeable membrane — Water moves towards the more concentrated solution — that is, towards where there is proportionally less water. It is diffusion with a specific substance named.
  3. d) cell wall — Plant cells add a rigid cell wall, chloroplasts and a large central vacuole. Both kinds of cell have a membrane, a nucleus and mitochondria.
  4. a) from higher to lower concentration, without energy — Random motion spreads particles out until they are evenly distributed. It is passive, which means no ATP is spent — a rule that holds for non-living systems too.
  5. c) mitochondrion — Mitochondria carry out the later stages of cellular respiration. Chloroplasts do photosynthesis and are found only in plants and algae — plant cells have both.
  6. d) volume grows faster than surface area, so exchange cannot keep up — Doubling a cell's width gives four times the surface and eight times the volume. Beyond a certain size the membrane cannot supply the interior fast enough, so cells divide instead of growing.
  7. a) the products of each are the reactants of the other — Matter cycles round the pair indefinitely; energy passes through once, entering as light and leaving as heat. That asymmetry is the key idea of the whole unit.
  8. b) cell — All living things are made of one or more cells, all cells come from existing cells, and the cell is the smallest thing that carries out all the functions of life. That is the cell theory in one sentence.
  9. b) nucleus — Mitochondria release energy, ribosomes build proteins, and vacuoles store things. Prokaryotes such as bacteria have DNA but no nucleus to keep it in.
  10. b) 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ — Carbon dioxide and water in, glucose and oxygen out, with light supplying the energy. The second option is cellular respiration, which is the same equation reversed.