Structure of eukaryotic cellsAQA A-Level Biology: Subtopic test

1. 1
   A phagocyte is a white blood cell that engulfs bacteria and digests them using hydrolytic enzymes. The enzymes are proteins that the cell makes itself.

   (a)

   Which organelle contains the hydrolytic enzymes that digest the engulfed bacteria?

   [1 mark]

   • AGolgi apparatus
   • BNucleolus
   • CRough endoplasmic reticulum
   • DLysosome

   (b)

   Which row correctly matches an organelle with its function in the phagocyte?

   [1 mark]

   • ASmooth endoplasmic reticulum: protein synthesis on attached ribosomes
   • BGolgi apparatus: aerobic respiration
   • CRough endoplasmic reticulum: folds and transports proteins made on its ribosomes
   • DLysosome: release of ATP

   (c)

   Suggest why the hydrolytic enzymes of the phagocyte are enclosed inside lysosomes, rather than free in the cytoplasm.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Chlorella is a single-celled green alga that lives in freshwater ponds. Its cells have a cell wall, a chloroplast, a nucleus and a cell vacuole, and are surrounded by dilute pond water.

   (a)

   Which pair of structures is found in Chlorella cells but not in human cells?

   [1 mark]

   • AMitochondria and ribosomes
   • BChloroplast and cell wall
   • CNucleus and Golgi apparatus
   • DLysosomes and cell-surface membrane

   (b)

   Which statement about the cell wall of Chlorella is correct?

   [1 mark]

   • AIt lies outside the cell-surface membrane and supports the cell, preventing it from bursting
   • BIt contains the chromosomes of the cell
   • CIt is the site of photosynthesis
   • DIt is a selectively permeable layer that controls which substances enter the cell

   (c)

   Water tends to enter Chlorella cells from the dilute pond water, but the cells do not burst. Explain why.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   The liver is an organ of the digestive system. Its main cells, hepatocytes, have a high metabolic rate and carry out many functions, including the synthesis of lipids. Under the electron microscope hepatocytes show many mitochondria and a large amount of smooth endoplasmic reticulum.

   (a)

   Explain how the large number of mitochondria and the large amount of smooth endoplasmic reticulum adapt the hepatocyte to its functions.

   [3 marks]

   (b)

   Hepatocytes are specialised cells. Using the liver as an example, describe how specialised cells are organised in a complex multicellular organism.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Palisade mesophyll cells in a leaf carry out photosynthesis. Exocrine cells in the pancreas make digestive enzymes and secrete them from the cell. Both are eukaryotic cells, and their organelles are suited to their different functions.

   (a)

   Explain how the organelles of a palisade mesophyll cell adapt it to carry out photosynthesis and to remain supported in the leaf.

   [6 marks]

   (b)

   Explain how the organelles of a pancreatic exocrine cell adapt it to make and secrete digestive enzymes.

   [6 marks]

   Total for question 4: 12 marks

End of questions