Unit 4: Area of study 1: Biological macromolecules, cell membranes and organelles.

1. Unit 3 VCE Biology
Cell membranes and organelles

2. Prokaryotic cell

3. Eukaryotic (animal) cell

5. Cell membrane – phospholipid bilayer

6. Cell membrane with embedded proteins

7. Two types of proteins in membranes:
• Integral proteins that are embedded or
inserted into the cell membrane.
• Peripheral proteins that are attached to the
surface of the cell membrane.
• The functions of these proteins include
transportation, enzymes, receptor sites, cell
adhesion and attachment to the cytoskeleton.

8. Through the cell membrane
• Diffusion (passive)
• Osmosis (passive)
• Facilitated diffusion (passive)
• Active transport (requires energy)
• Bulk transport (requires energy)

9. Diffusion
• Passive movement of molecules from an area
of high concentration to low concentration.
• Concentration gradient is the difference in
concentration between the two regions.
• Small, uncharged molecules (CO2, H20 and O2)
move easily through the membrane.
• Works well over short distances, but slows
once molecules enter the cell.
• Limits cell size.

10. Diffusion (passive)

11. Osmosis
• Osmosis is the process by which water moves
through a semi-permeable membrane from an
area of high concentration (of water) to lower
concentrations.
• It is a passive process and therefor does not
require energy.

12. Osmosis – diffusion of water

13. Facilitated diffusion
• Channel mediated - Some substances diffuse
with the assistance of protein channels
• Carrier mediated - Substances move down
the concentration gradient via specific carrier
molecules. Slower than channel-mediated as
the protein carrier has to change shape for
each molecule it transports.

14. Facilitated diffusion - passive

15. Active Transport
• Movement of dissolved substances into or out
of cells against a concentration gradient.
• Active transport requires energy and involves
a carrier protein for each substance that is
actively transported.
• Includes endocytosis (into cell) and exocytosis
(out of cell).
• Transport vesicles fuse with the membrane to
consume or excrete substances.

16. Active Transport
• Pinocytosis is when a liquid is consumed or
excreted.
• Phagocytosis is when a solid substance is
consumed or excreted.
• Cell walls lie outside the plasma membrane in
plant, fungal and prokaryotic cells.
• Endocytosis and exocytosis can occur into and
out of the cell vacuole.

17. Active Transport – requires energy

18. Bulk Transport – requires energy

19. The Nucleus

21. Mitochondrion

22. Ribosomes
• Ribosomes are cell
organelles consisting
of RNA and proteins,
found in the
cytoplasm and
sometimes along
the endoplasmic
reticulum (RER).
• Ribosomes are responsible for assembling the
proteins in a cell.

23. Nucleus with Rough Endoplasmic
Reticulum (RER)

25. Lysosomes

26. Lysosomes
• Lysosomes serve as the cells digestive system.
• They are membrane-bound organelles
containing enzymes that can break down
individual proteins or complete micro-organisms.
• They are released from the golgi apparatus.

27. Chloroplasts in plant cells

30. Cytoskeleton
• The centrosome (in animal cells) creates
microtubules that provide a spindle for mitosis
and meiosis.

31. Image Sources
• http://commons.wikimedia.org/wiki/File:Prokary
ote_cell_diagram.svg
• http://commons.wikimedia.org/wiki/File:Animal_
cell_structure_en.svg
• http://commons.wikimedia.org/wiki/File:Plant_c
ell_structure.png
• http://commons.wikimedia.org/wiki/File:Osmotic
_pressure_on_blood_cells_diagram.svg
• http://commons.wikimedia.org/wiki/File:1215_C
ell_Membrane_Channels.jpg

32. Image Sources
• http://commons.wikimedia.org/wiki/File:Cell_
membrane_detailed_diagram_en.svg
• http://commons.wikimedia.org/wiki/File:Diffu
sion.en.svg
• http://commons.wikimedia.org/wiki/File:Cent
rosome_(standalone_version)-en.svg
• http://commons.wikimedia.org/wiki/File:Endo
cytosis_types.svg