1. Cell Structure and Function

2. Definition of a cell: basic structural and functional unit of life
the smallest units that display the characteristics of life, i.e. reproduction, metabolism, response to stimuli

3. General Subdivisions of a Cell
Plasma Membrane = selectively permeable boundary between the cell and the environment
Nucleus = regulatory center of the cell
Cytoplasm = everything between the plasma membrane and the nucleus (fluid + organelles)

4. Plasma Membrane Structure phospholipd bilayer
proteins embedded in, and attached to, the inner (intracellular) and outer (extracellular) surfaces
phospholipids are liquid at body temperature, so proteins float around in the membrane

5. Plasma Membrane Function
Main responsibility: ensure the composition of extracellular fluid is not the same as the composition of the intracellular fluid
Selectively permeable barrier controls what enters and leaves the cell

6. Plasma Membrane Function
Water-soluble substances (salts, nutrients) cross membrane with aid of protein channels, which are selective about what can pass through
Lipids can pass directly through bilayer by diffusion (movement from area of high pressure to area of low pressure)
Attachment site of cytoskeleton, the internal support of the cell

7. Plasma Membrane

8. Nucleus Nuclear Envelope (membrane)
Phospholipid bilayer with nuclear pores
Controls what enters/leaves the nucleus
things only go in or out by passing through Protein channels, which are selective
Encloses all the chromosomes

9. Nucleus
Chromatin
All the chromosomes, which are long strands of the molecule DNA
DNA regulates all cell activities, yet never leaves the nucleus;
produces RNA, short messenger molecules that exit through nuclear pores
RNA carries instructions out into the cytoplasm

10. Nucleus Nucleolus Site of ribosome synthesis
Compartment in the nucleus where ribsomes are assembled
Ribosomes are then moved out into cytoplasm through nuclear pores
Ribosomes and RNA work together outside the nucleus, to build all the proteins in the cell

11. Nuclear Compartment

12. Ribosomes Ribosomes = site of protein synthesis
--assembled in the nucleolus
--exported into the cytoplasm
Free – unbound in the fluid cytoplasm, produce
proteins for use in the cell
Bound – attached to the endoplasmic reticulum
(ER), produce proteins for export, or for the
plasma membrane

13. Cytoplasm Fluid portion = “cytoplasm”
Water with dissolved salts, nutrients and enzymes (= proteins that do a particular job)
Site of many metabolic reactions

14. Cytoskeleton
Network of protein fibers extending throughout the fluid cytoplasm
Support and structure for the cell
Very dynamic, always remodeling itself
Critical for cells to divide and copy themselves

15. Cell Structure

16. Organelles
Separate compartments within the cytoplasm formed by membranes
Mitochondrion – “thread granule”
major source of cell’s energy
energy is taken from sugar, stored in molecule called ATP (adenosine triphosphate)
requires oxygen to make this exchange (aerobic metabolism)
contained within double membrane

17. Mitochondrion

18. Organelles Cytomembrane System
system of tubes and chambers formed by membranes
extensively distributed throughout the fluid cytoplasm
involved in synthesis, modification, processing & packaging of cellular lipids and proteins

19. Cytomembrane System
Endoplasmic Reticulum (ER) = “within the cytoplasm network”
system of tubes and sacs formed by membranes (an enclosed space)

20. Cytomembrane System Two Types Rough = with bound ribosomes
modifies proteins produced by the ribosomes
Smooth = without bound ribosomes
doesn’t modify proteins
functions in lipid synthesis, drug detoxification, carbohydrate metabolism

21. Cytomembrane System Golgi Apparatus
series of flattened sacs formed by membranes,
functions in final protein processing prior to use by the cell
proteins get shuttled from the ER to one end of the Golgi

22. Cytomembrane System Golgi Apparatus
in each sac, different modifications are made (proteins get individually tailored)
proteins get sorted and shipped off to their destination (like the post office of the cell)

23. Cytomembrane System Vesicles
small membrane-bound structures that transport proteins and lipids around the cell
little transporters that shuttle their contents from one organelle to another
when they contact the appropriate organelle, they fuse with its outer membrane and dump their contents inside
same for plasma membrane, allowing the export of materials from the cell (exocytosis)

24. Vesicles move from ER to Golgi

25. Cytomembrane System Lysosome
membrane-bound vesicle that contains digestive enzymes or toxic chemicals
merges with vesicles containing food particles, invading bacteria
harsh chemicals and enzymes degrade the food or bacteria, without harming rest of cell