1. Physiology of Cells

2. Passive Transport 1.Diffusion –Tendency of small particles to spread out evenly within a given space –Occurs down a concentration gradient until equilibrium is reached Measurable difference between one area to another –Diffusion or permeability dependent upon presence of specified channels –Selectively permeable – channels open and close based on cell’s needs

3. Diffusion

4. Passive Transport 2. Dialysis (fig 4-4, pg. 94) –Selectively permeable membrane separates smaller and larger particles

5. Passive Transport 3. Osmosis (fig 4-5, pg. 95) –Diffusion of water through a selectively permeable membrane

6. Osmotic Pressure Osmotic pressure – pressure that develops in a solution as a result of osmosis –Important concept for maintaining homeostasis Isotonic – two fluids have the same osmotic pressure Hypotonic – lower concentration of solute outside of the cell (ECF) Hypertonic – higher concentration of solute outside of cell (ECF)

7. Effects of Osmosis on a Cell

8. Passive Transport 4. Facilitated Transport –(also carrier-mediated passive transport) –Movement of a molecule is facilitated by a carrier mechanism in the cell membrane –Still requires concentration gradient

9. Passive Transport 5. Filtration –Passing of water and permeable solutes through a membrane by the force of hydrostatic pressure –Hydrostatic pressure: force or weight of a fluid pushing against a surface –Occurs down a hydrostatic pressure gradient –Most often associated with movement across a sheet of cells (ex: capillaries)

10. Active Transport Carrier-mediate process Moves molecules “uphill” (against concentration gradients) Ex: Sodium-potassium pump –Operates in all human cells

11. Sodium-Potassium Pump Transports Na + out of the cell and K + into the cell Requires energy (sodium-potassium ATPase) – made in mitochondria 3 Na + bind on the intracellular side and are exchanged for 2 K + from the ECF

12. Sodium-Potassium Pump

13. Endocytosis 1.Receptors in the plasma membrane bind to molecules in the ECF 2.Cytoskeleton pulls a portion of the membrane inward, creating a pocket 3.Edges of the “pocket” fuse forming a vesicle 4.Vesicle is pulled inside the cell by the cytoskeleton 5.Vesicle fuses with the membrane walls of a lysosome

15. Exocytosis Process by which large molecules (proteins) exit the cell 1.Wastes/proteins enclosed by a membrane vesicle 2.Cytoskeleton moves vesicle to plasma membrane 3.Fuses with membrane & releases contents to ECF

16. Cell Life Cycle Two main processes: –Growth –Reproduction

17. Cell Growth During cell growth additional cytoplasm and plasma membrane are produce through protein synthesis –Includes structural proteins and enzymes –Anabolic process

18. DNA Replication Prior to cell reproduction, DNA must be replicated: 1.DNA unzips 2.Nucleotides attached to exposed base pairs according to base pair rule (A-T; G-C) 3.DNA polymerase binds nucleotides 4.Two identical DNA strands are forms

19. DNA Replication

20. Cell Reproduction One parent cell (diploid) produces two identical daughter cells (also diploid) Two steps: –Mitosis –Cytokinesis

21. Mitosis Cell organizes replicated DNA into two identical sets and distributes one set to each daughter cells 4 phases of mitosis (PMAT) 1.Prophase –Chromosomes shorten & thicken –Centrioles move to poles of cell –Spindle fibers appear –Nuclear membrane disappears

22. Mitosis 2. Metaphase –Chromosomes lined up at the equator (middle) –Spindle fibers attached to centromere 3. Anaphase –Centromeres break apart separating sister chromatids

23. Mitosis 4. Telophase –Spindle fibers disappear –Nuclear envelope reappears Cytokinesis: Completes cellular reproduction by splitting the plasma membrane and cytoplasm into two

25. Meiosis Cell division which occurs in primitive sex cells The end result is mature gametes –Males  sperm –Females  ova (egg) Gametes are haploid (contain half the number of chromosomes of a somatic cell) –Reduction division

27. Deoxyribonucleic Acid (DNA) Double Helix (twisted ladder) Monomer: nucleotide 1.5 Carbon sugar (deoxyribose) 2.Phosphate group 3.Nitrogen base Nitrogen bases: Purines: adenine, guanine Pyrimidines: cytosine, thymine Chargaff’s rule

28. Deoxyribonucleic Acid (DNA)

29. Three base pairs = codon Sequence of base pairs determines each gene Genes control the production of proteins (therefore determine individual traits

30. Ribonucleic Acid (RNA) Single helix Smaller than DNA 5 carbon sugar = ribose Uracil replaces thymine which binds with adenine

31. Protein Synthesis Occurs in 2 steps: –Translation: DNA  RNA –Transcription: RNA  Proteins

32. Translation Occurs in the nucleus DNA “unzips” exposing base pairs RNA nucleotides (already present in the nucleus) attach themselves to the exposed bases along one side of the DNA molecule These RNA nucleotides bind to each other with the help of RNA polymerase The chain that results is called messenger RNA (mRNA)

34. Preparation of mRNA Occurs in the nucleus The mRNA pulles away from the DNA strand The result is a copy or “transcript” of a gene Non-coding portions of mRNA (introns) are removed Remaining portions (exons) are spliced back together mRNA travels to the nucleus via nuclear pores

36. Translation Occurs in the cytoplasm Ribosomal subunits attach to one of the mRNA Transfer RNA (tRNA) bring specific amino acids to the ribosome site –Which amino acid is based upon each mRNA codon –The tRNA must have a complementary anticodon to fit onto the binding site of each condon

37. Translation Amino acids are joined by peptide bonds Forms long molecules called polypeptides Several polypeptides are needed to make a protein

39. After Translation… Enzymes within the endoplasmic reticulum, Golgi apparatus and/or cytosol line polypeptides to form larger structures –May also form lipoproteins or glycoproteins

40. Translation Video http://www.dnatube.com/video/1947/Protein- Synthesis-Translation-1