physiology: Cell notes
NOTES: Cell Structure and Function
1. Cell: structural and functional unit of living things
2. Organelles: specialized sub-cellular structures that perform a specific task
Unicellular: one celled organisms (bacteria, Protists, such as algae, etc.)
Multicellular: many-celled organisms (higher plants and animals)
3. Prokaryote: organism without a nuclear membrane; nucleus is called a nucleoid;
These belong to a separate Kingdom: Monera; they consist of bacteria.
Eukaroyte: organism with a true nuclear membrane; they consist of all the
remaining organisms above the bacteria.
4. Cell membrane (plasma membrane): determines what enters and leaves the cell.
Has phospholipid bilayer, cholesterol molecules, protein channels.
a. Membrane proteins: channels, enzymes, receptors, markers
b. Integral proteins: embedded into the membrane; may be transmembranal or only on one surface.
c. Glycoproteins: proteins that contain sugars for markers; glycocalyx
d. Peripheral proteins: proteins found on the outside attached to integral
proteins or lipids
5. Five functions of membrane proteins:
6. Fluid mosaic: liquid phospholipid membrane consisting of embedded proteins
a. nucleus: control center for most cells; houses DNA, RNA, genes that are responsible for heredity
b. nuclear envelope: double membrane surrounding the nucleus; contains pores
c. nuclear pore complex: proteins that regulate the passage of materials into and out of the nucleus
d. endoplasmic reticulum: channel of membranes; cisternae=fluid filed cavities
Rough: holds the ribosomes; where protein synthesis occurs
Smooth: involved in lipid metabolism; where steroid hormones are made; detoxification of drugs; glycogen to glucose in liver
e.golgi apparatus: flattened sacs; storage of proteins; refines proteins; secretory vesicles for transport
f. mitochondria: where ATP energy is produced; cristae are inner membranes; matrix: inner cavity
g. lysosomes: sac-like structures that contain digestive enzymes; autolysis
h. peroxisomes; contain oxidases and catalases; neutralize free radicals; found in liver and kidney
8. Cytoskeleton: mesh-like lattice found in the cytosol.
9. Microtubules: hollow tubes; produce spindle fibers for cell division; also regulate the movement of organelles within the cell.
10. Cilia: small hair-like structures responsible for cell movement
Flagella: longer whip-like structures responsible for movement
11. Diffusion: movement of molecules from a higher concentration to a lower concentration.
12. Concentration gradient: slope indicating the difference in two concentrations of materials.
13. Polar molecules: cannot generally cross the membrane (hydrophobic tails); they use protein channels to enter the cell
Non-polar molecules” can dissolve in the fatty layers of the membrane and enter
the cell more easily
14. Osmosis: diffusion of water through a semipermeable membrane
15. Osmotic pressure: cells tendency to resist entry of water due to lower solute
Tonicity: state of water volume within the cell
16. Isotonic: equal concentration of solutes both inside and outside the cell
Hypotonic: lower concentration of solute present outside the cell
Hypertonic: higher concentration of solute present outside the cell
17. Facilitated diffusion: passive movement of materials from high to lower
concentration assisted by membrane proteins
18. Active transport: movement of materials against the concentration gradient;
requires energy in the form of ATP
19. Sodium-potassium pump: mechanism of active transport that pumps sodium out
of the cell and potassium into the cell.
20. Coupled transport: as one molecule (Na+) enters the cell, another molecule (K+) leaves the cell (antiport); if 2 molecules come in together (glucose and sodium) it is symport.
21. Exocytosis: cell membrane actively deposits excreted materials outside the cell
Endocytosis: cell membrane captures large proteins to enter the cell.