Читать книгу Cell Biology - Stephen R. Bolsover - Страница 53

1 Membranes are made of phospholipids, protein, and cholesterol.

2 Cells are bounded by membranes, while cell functions are compartmentalized into membrane‐bound organelles.

3 Solutes with a significant solubility in hydrophobic solvents can pass across biological membranes by simple diffusion. Charged molecules cannot.

4 The nucleus and mitochondrion are bounded by double‐membrane envelopes. In the case of the nucleus, this is perforated by nuclear pores. Both organelles contain DNA.

5 Mitochondria produce the energy currency ATP.

6 Peroxisomes carry out a number of reactions, including the destruction of hydrogen peroxide.

7 The ER is a major site of protein synthesis. Cell stimulation can often cause calcium ions stored in the ER to be released into the cytosol.

8 The Golgi apparatus is concerned with the modification of proteins after they have been synthesized.

9 Lysosomes contain powerful degradative enzymes that degrade material.

10 Organelles form membrane contact sites with other organelles and the plasma membrane to allow information flow.

11 Tight junctions prevent the passage of extracellular water or solute between the cells of an epithelium.

12 Gap junctions allow solute and electrical current to pass from the cytosol of one cell to the cytosol of its neighbor.

13 Anchoring junctions form a strong physical link between cells.