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Cells and stem cells

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Which observation directly supports the origin-of-cells statement?

  1. An enzyme removed from a cell still breaks down starch.
  2. One bacterial cell divides into two cells.
  3. A mitochondrion has an inner membrane.
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One bacterial cell divides into two cells.

The new cells arise from an existing cell.

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Which feature best supports identifying a mitochondrion?

  1. A cellulose layer outside the cell surface membrane, giving support.
  2. An enclosing boundary with inward folds of the inner membrane.
  3. A round, dark-staining body with a nucleolus inside it.
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An enclosing boundary with inward folds of the inner membrane.

Cristae are a useful structural clue.

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Which structure is NOT bounded by a membrane?

  1. Lysosome
  2. Nucleus
  3. Ribosome
  4. Mitochondrion
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Ribosome

Ribosomes are made of rRNA and protein with no membrane. They are found in bacteria too.

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Which route suits a protein secreted from a eukaryotic cell?

  1. Rough ER-associated ribosome, ER, Golgi, secretory vesicle.
  2. Golgi-associated ribosome, Golgi, rough ER, secretory vesicle.
  3. Smooth ER, transport vesicle, Golgi, cell surface.
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Rough ER-associated ribosome, ER, Golgi, secretory vesicle.

These structures carry out different stages of production and delivery.

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Why may a plant-cell membrane be difficult to label separately in a light micrograph?

  1. The membrane is thin and may not be resolved separately from the wall.
  2. The membrane and wall are the same structure in a turgid plant cell.
  3. Plant cells have a cell wall in place of a cell surface membrane.
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The membrane is thin and may not be resolved separately from the wall.

Presence and visibility are different claims.

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Which pair is characteristic of a typical bacterium?

  1. 70S ribosomes and a peptidoglycan wall.
  2. A nuclear envelope and Golgi body.
  3. A cellulose wall and no ribosomes.
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70S ribosomes and a peptidoglycan wall.

Both fit the required bacterial model.

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Which statement correctly describes a blood stem cell?

  1. It divides once and cannot keep up its own population.
  2. It can make any cell type, including nerve and muscle cells.
  3. It can self-renew and generate several related blood-cell types.
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It can self-renew and generate several related blood-cell types.

This combines self-renewal with multipotency.

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Which statements are correct? 1: A zygote is totipotent. 2: Embryonic stem cells can form the placenta. 3: Blood stem cells are multipotent. 4: All stem cells can self-renew.

  1. 1 and 3 only
  2. 1, 3 and 4 only
  3. 1, 2, 3 and 4
  4. 1, 2 and 3 only
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1, 3 and 4 only

The zygote is totipotent, blood stem cells are multipotent and all stem cells self-renew. Pluripotent embryonic stem cells do not form the placenta.

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Why must a tissue retain some stem cells during renewal?

  1. Each replacement must remove a complete stem-cell lineage from the tissue.
  2. A continuing source is needed for future replacement cells.
  3. Self-renewal is required only when a tissue contains totipotent cells.
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A continuing source is needed for future replacement cells.

Self-renewal preserves that source while differentiation supplies cells now.

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Question 1 of 7

Explain a growing culture

3 marks

A bacterial culture increases from 200 cells to 400 cells by division. Explain how this illustrates cell theory and identify two structures each new cell needs for protein synthesis. [3]

Link origin of cells to DNA and ribosomes.

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