Biology  by Bradford
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B2.2 Organelles and compartmentalization: revision map

The subtopic in the middle and nine tasks round it: label four diagrams, complete a table, put two processes in order and fill 40 gaps. Every standard level statement has a box; the four boxes for higher level only are dashed and badged HL, and drop off for an SL class. Type into the blanks and check them, or print it on A4, Letter or A3 with an answer key.

B2.2 practice questionsThe whole B2 map

B2.2

Organelles and compartmentalization

Cells ยท Form and functionName

B2.2.2One cell, two compartments

prokaryoteeukaryote1234
  1. 1
  2. 2
  3. 3
  4. 4

In the prokaryote, translation can begin before has finished. In the eukaryote, translation waits until the message has moved out to the .

B2.2.5Built for photosynthesisHL

1234
  1. 1
  2. 2
  3. 3
  4. 4

Stacks of flattened membrane sacs give a large area for the that absorb light. The fluid inside each sac has a small , so protons pumped in build a steep gradient fast. The enzymes and substrates of the cycle are kept together in the fluid round the stacks.

B2.2.6A double envelopeHL

Two membranes wrap the nucleus, keeping its DNA apart from the cytoplasm. So that mRNA can get out and proteins can get in, the double membrane is crossed by . At the start of mitosis and meiosis it breaks up into , letting the chromosomes be separated; afterwards these to rebuild a covering round each new nucleus.

B2.2.1Organelle or not?

An organelle is a discrete subunit of a cell, adapted to its own job. Nuclei and vesicles count, and so do , although they have no membrane, and the round the cell. The cell wall does not, nor does the network of protein fibres called the , nor the that the organelles sit in.

B2.2.7, B2.2.8, B2.2.9A protein for exportHL

Number the steps in order.

  1. A vesicle buds off the ER and carries the protein to the Golgi apparatus.
  2. The Golgi apparatus modifies the protein, for example by adding carbohydrate.
  3. Ribosomes on the rough ER make a polypeptide, feeding it into the ER as it grows.
  4. The vesicle fuses with the plasma membrane, releasing the protein by exocytosis.
  5. A vesicle carrying the finished protein buds off the Golgi apparatus.

Proteins to be kept in the cytoplasm are made instead by ribosomes. Many vesicles bud with the help of , a protein that coats a patch of membrane and pulls it into a sphere.

B2.2Organelles and compartmentalization

B2.2 examA cell as it appears in an electron micrograph

A cell as it appears in an electron micrograph1234
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B2.2.1Cell fractionation

Number the steps in order.

  1. Spin it at low speed until the biggest organelles settle as a pellet.
  2. Filter the mixture to remove debris and unbroken cells.
  3. Spin that liquid faster, so smaller organelles settle out, and repeat at rising speeds.
  4. Pour the liquid above the pellet into a fresh tube.
  5. Grind the tissue in a cold, isotonic buffer to break the cells open.

The first pellet is mostly . The highest speeds need an : its invention let biologists study one kind of organelle at a time, a case of progress in science following a new .

B2.2.2, B2.2.3Kept apart, kept together

CompartmentHoldsBenefit
NucleusDNAtranscripts before translation
Lysosome enzymesthe rest of the cell is not digested
Phagocytic vacuolea bacterium, with lysosome enzymesenzymes and substrate at a high

So compartments speed up reactions and keep processes separate.

B2.2.4Built for ATPHL

1234
  1. 1
  2. 2
  3. 3
  4. 4

The space between the two membranes is , so protons pumped into it quickly build a steep gradient. The folded inner membrane gives a large for the electron transport chain. The fluid inside keeps the enzymes and substrates of the cycle together.

Word bank Calvincell wallchloroplastclathrinconcentrationcristacytoplasmcytoskeletondigestiveDNAdouble membranefreefusegranumincompatibleintermembrane spaceKrebsmatrixmodifiedmRNAnuclear envelopenucleinucleusouter membranephotosystemsplasma membraneporesribosomeribosomessmallstromasurface areatechniquethylakoidtranscriptionultracentrifugevacuolevesiclesvolume

Answer key

Every box on the sheet with its gaps filled in, as the subtopic reads in full.

  1. GapsOrganelle or not?

    An organelle is a discrete subunit of a cell, adapted to its own job. Nuclei and vesicles count, and so do ribosomes, although they have no membrane, and the plasma membrane round the cell. The cell wall does not, nor does the network of protein fibres called the cytoskeleton, nor the cytoplasm that the organelles sit in.

  2. OrderCell fractionation

    1. Grind the tissue in a cold, isotonic buffer to break the cells open.
    2. Filter the mixture to remove debris and unbroken cells.
    3. Spin it at low speed until the biggest organelles settle as a pellet.
    4. Pour the liquid above the pellet into a fresh tube.
    5. Spin that liquid faster, so smaller organelles settle out, and repeat at rising speeds.

    The first pellet is mostly nuclei. The highest speeds need an ultracentrifuge: its invention let biologists study one kind of organelle at a time, a case of progress in science following a new technique.

  3. LabelOne cell, two compartments

    1. nuclear envelope
    2. DNA
    3. mRNA
    4. ribosome

    In the prokaryote, translation can begin before transcription has finished. In the eukaryote, translation waits until the message has moved out to the cytoplasm.

  4. TableKept apart, kept together

    CompartmentHoldsBenefit
    NucleusDNAtranscripts modified before translation
    Lysosomedigestive enzymesthe rest of the cell is not digested
    Phagocytic vacuolea bacterium, with lysosome enzymesenzymes and substrate at a high concentration

    So compartments speed up reactions and keep incompatible processes separate.

  5. LabelBuilt for ATP HL

    1. outer membrane
    2. intermembrane space
    3. crista
    4. matrix

    The space between the two membranes is small, so protons pumped into it quickly build a steep gradient. The folded inner membrane gives a large surface area for the electron transport chain. The fluid inside keeps the enzymes and substrates of the Krebs cycle together.

  6. LabelBuilt for photosynthesis HL

    1. double membrane
    2. thylakoid
    3. granum
    4. stroma

    Stacks of flattened membrane sacs give a large area for the photosystems that absorb light. The fluid inside each sac has a small volume, so protons pumped in build a steep gradient fast. The enzymes and substrates of the Calvin cycle are kept together in the fluid round the stacks.

  7. GapsA double envelope HL

    Two membranes wrap the nucleus, keeping its DNA apart from the cytoplasm. So that mRNA can get out and proteins can get in, the double membrane is crossed by pores. At the start of mitosis and meiosis it breaks up into vesicles, letting the chromosomes be separated; afterwards these fuse to rebuild a covering round each new nucleus.

  8. OrderA protein for export HL

    1. Ribosomes on the rough ER make a polypeptide, feeding it into the ER as it grows.
    2. A vesicle buds off the ER and carries the protein to the Golgi apparatus.
    3. The Golgi apparatus modifies the protein, for example by adding carbohydrate.
    4. A vesicle carrying the finished protein buds off the Golgi apparatus.
    5. The vesicle fuses with the plasma membrane, releasing the protein by exocytosis.

    Proteins to be kept in the cytoplasm are made instead by free ribosomes. Many vesicles bud with the help of clathrin, a protein that coats a patch of membrane and pulls it into a sphere.

  9. Exam diagramA cell as it appears in an electron micrograph

    1. cell wall
    2. chloroplast
    3. vacuole
    4. nucleus