1. Ch. 3 Cells!

2. Introduction Cell theory
Cells are the smallest living subunit of an organism
All cells arise from pre-existing cells
Bacteria, amoebas are unicellular and function independently
Human cells work interdependently
Vary in size, shape, function
Mostly microscopic
More than 200 kinds

3. Cell Structure Cell membrane (plasma membrane) Nucleus Cytoplasm
Forms outer boundary of cell
Nucleus
Absent in mature red blood cells
Cytoplasm
Organelles

4. Cell Membrane Plasma membrane (PM)
Made of phospholipids, cholesterol, proteins (Fig. 3-1)
Phospholipid bilayer
Permit lipid-soluble materials to enter/leave cell via diffusion
Cholesterol makes membrane more stable
Proteins
Form channels or pores to permit passage of materials
Carrier enzymes (transporters) help substances enter cell
Antigens identify cells as “self”
Receptor sites for hormones

6. Cell Membrane (cont.) Active, dynamic membrane Selectively permeable
Certain substances can pass through, others cannot

8. Nucleus Within cytoplasm Bounded by 2-layered, porous nuclear membrane
Contains 1 or more nucleoli, chromosomes (Fig. 3-2)
Nucleolus – small sphere of DNA, RNA, protein
Form ribosomal RNA (rRNA); becomes part of ribosomes; involved in protein synthesis

9. Nucleus (cont.) Control center
Contains 46 chromosomes in long threads called chromatin
Before cell division, chromatin coils into visible chromosomes (made of DNA, protein)
Nucleus contains the same genetic information, but only a small number of genes are active “switched on”
Active genes code for proteins

10. Cytoplasm
Watery solution of minerals, gases, organic molecules, organelles
Cytosol
Water portion of cytoplasm; where many rxns take place

11. Organelles Intracellular structures, often membrane-bound
Have specific functions in cell metabolism (Fig. 3-2)
Endoplasmic reticulum (ER)
Extensive tubular network extending from nuclear membrane to PM
Rough ER has ribosomes on surface, smooth ER does not
Passageway for proteins, lipids

12. Organelles (cont.) Ribosomes Not membrane-bound
Very small structures made of protein and rRNA
Some on Rough ER, others in cytoplasm
Site of protein synthesis

13. Organelles (cont.) Golgi apparatus (GA)
Flat, membranous sacs stacked on top one another
Carbohydrate synthesis, packaging for secretion from the cell

14. Organelles (cont.) Golgi Apparatus Secretion
Small sacs of Golgi membrane break off & fuse with PM
Substance is released to cell exterior (exocytosis)

15. Organelles (cont.) Mitochondria
Oval or spherical organelles bounded by double membrane
Inner membrane has folds (cristae)
Site of ATP production
Contain own genes in a single DNA molecule
Duplicate themselves when cell divides
Many mitochondria in muscle cells

16. Organelles (cont.) Lysosomes Single-membrane digestive structures
Have enzymes that digest bacteria, old cell parts and dead cells

17. Organelles (cont.) Centrioles Cilia Flagella
Pair of rod-shaped structures just outside the nucleus
Organize spindle fibers during cell division
Cilia
Short, hair-like structures covering surface of cell
Beat in unison and sweep materials across cell’s surface
Cilia in fallopian tubes sweep egg toward the uterus
Flagella
Whip-like tail
Provides motility for sperm

18. Organelles (cont.) Microvilli Table 3-1
Folds of cell membrane on the free surface of a cell
Greatly increase surface area of membrane
Part of cells lining organs that absorb material
Small intestine
Kidney tubules
Table 3-1

19. Cellular Transport Mechanisms
Enable cells to move materials into or out of cell
Diffusion
Osmosis
Facilitated diffusion
Active transport
Filtration
Phagocytosis
Pinocytosis

20. Diffusion
Movement of molecules from an area of high to low concentration along a concentration gradient
Oxygen and CO2 move by diffusion (Fig. 3-3)

22. Osmosis Diffusion of H2O through a selectively permeable membrane
Water moves from an area with more to an area with less water
Water will move to an area with more solutes
If a 2% salt solution and a 6% salt solution are separated by a membrane, allowing only water to pass through, in which direction will water diffuse?
See Box 3-1

23. Facilitated Diffusion
Molecules move through a membrane from an area of high to low concentration with assistance
Use a carrier enzyme (transporter)

24. Active Transport
Requires ATP to move molecules from a low to high concentration against a concentration gradient
Nerve and muscle cells have sodium pumps to move sodium ions out of cells (Fig. 3-3)

25. Filtration Requires energy of mechanical pressure
Water, dissolved materials are forced through a membrane from an area of high to low pressure
Formation of tissue fluid; first step in urine formation

26. Phagocytosis & Pinocytosis
Forms of endocytosis
Phagocytosis
White blood cell engulfs bacteria (Fig. 3-3)
Digestion using enzymes in lysosomes
Pinocytosis
Stationary cells take in small molecules adsorbed or attached to their membranes
Kidney tubules reabsorb small proteins (Fig. 3-3)
Table 3-2

27. Cell Division Process by which cell reproduces itself 2 types Mitosis
Meiosis

28. Mitosis
One cell with a diploid (2N) # of chromosomes divides into 2 identical cells, each with the diploid number
2N = 46
Interphase
DNA replication enables each chromosome (chromatin) to copy itself
Resting (non-dividing) stage
Stores energy in ATP

29. Mitosis (cont.) Long, thin, invisible chromatin begins to coil
Each looks like a letter X because original DNA molecule & its copy (chromatids) are attached
Mitosis stages (PMAT); see Table 3-4; Fig. 3-5
Prophase
Metaphase
Anaphase
Telophase

30. Mitosis (cont.) Essential to replace damaged or dead cells
Occurs constantly in epidermis, stomach lining, red bone marrow
Does not occur in most muscle cells & neurons
Skeletal muscle cells have limited mitosis
Research has found some potential for mitosis in the CNS and heart
At present, mitosis does not take place sufficiently enough to replace dead cells

32. Meiosis More complex Results in gamete (egg, sperm) formation
One diploid cell (2N) divides twice to form 4 haploid cells (N)
Meiosis takes place in ovaries (oogenesis) and testes (spermatogenesis)
“reduction division”
During fertilization, the egg joins with the sperm to restore the diploid number of 46 in the fertilized egg (zygote)