1. Ch. 3a Cells

2. 50 to 100 trillion cells in the Human Body
Generalized Cell
50 to 100 trillion cells in the Human Body
Each one is composed mainly of 4 elements
Carbon, Hydrogen, Oxygen, Nitrogen
Cells have three basic parts:
Plasma membrane—outer boundary regulating movement of material in and out of cell
Cytoplasm—gel-like fluid in cell; contains organelles
Nucleus—contains DNA

3. Chromatin Nuclear envelope Nucleolus Nucleus Smooth endoplasmic
reticulum
Plasma
membrane
Mitochondrion
Cytosol
Lysosome
Centrioles
Centrosome
matrix
Rough
endoplasmic
reticulum
Ribosomes
Golgi apparatus
Secretion being
released from cell
by exocytosis
Cytoskeletal
elements
• Microtubule
• Intermediate
filaments
Peroxisome
Figure 3.2

4. Plasma Membrane
The plasma membrane separates the intracellular fluid (ICF) from extracellular fluid (ECF)
The plasma membrane is semi-permeable which means that some things can cross the membrane and some things cannot

5. Extracellular fluid
Intracellular fluid
Figure 3.3

6. Types of Membrane Transport
A concentration gradient is:
Passive Transport
No cellular energy (ATP) required
Substance moves down its concentration gradient
Active Transport
Energy (ATP) required
Substances are moved or“pumped” against their gradient

7. Passive Transport
What determines whether or not a substance can passively cross the plasma membrane?
Is the substance a lipid (Lipid solubility of substance)
Size of substance passing

8. Three Types of Passive Transport Across Cellular membranes
Simple diffusion
Facilitated diffusion
Osmosis

9. Passive Transport: Simple Diffusion
What types of substances use simple diffusion to cross the plasma membrane?
Small, nonpolar, hydrophobic substances diffuse directly through phospholipid bilayer (O2, CO2)

10. Extracellular fluid
Lipid-
soluble
solutes
Cytoplasm
Figure 3.7a

11. Passive Transport: Facilitated Diffusion
What types of substances use facilitated diffusion to cross the plasma membrane?
Larger, hydrophilic molecules (glucose, amino acids)
Can pass through carriers or channels

12. Hydrophilic molecules
A Carrier Protein
Figure 3.7b

13. Passive Transport: Osmosis
Movement of solvent (water) across a selectively permeable membrane from where it is most concentrated to where it is less concentrated
Water diffuses through plasma membranes:
mainly through channels

14. Water
molecules
A Channel Protein
Lipid
billayer
Aquaporin
Figure 3.7d

15. (a) Membrane permeable to both solutes and water
Solute and water molecules move down their concentration gradients
in opposite directions.
Both solutions have the
same osmolarity: volume
unchanged
H2O
Solute
Solute
(sugar)
Membrane
Figure 3.8a

16. Both solutions have identical osmolarity, increases on the right
(b) Membrane permeable to water, impermeable to solutes
Solute molecules are prevented from moving but water moves by osmosis.
Volume increases in the compartment with the higher osmolarity.
Both solutions have identical
osmolarity, increases on the right
because only water is
free to move
Left
compartment
Right
compartment
H2O
Solute
(sugar)
Membrane
Figure 3.8b

17. Importance of Osmosis
When osmosis occurs, water enters or leaves a cell
A change in cell volume disrupts cell function

18. Tonicity
Defined as: The ability of a solution to cause a cell to shrink or swell
Isotonic: A solution that does not cause a change in cell volume
Hypertonic: A solution that causes a cell to shrink
Hypotonic: A solution that causes a cell to swell.

19. Figure 3.9 (a) Isotonic solutions (b) Hypertonic solutions
(c) Hypotonic solutions
Figure 3.9

20. Active Transport Defined as:
The Sodium-potassium pump (Na+-K+ ATPase) is a specific example of active transport
Located in all plasma membranes
Maintains electrochemical gradients essential for muscle and nerve functions

21. Other Cellular Organelles
Membranous structures
Nucleus with chromatin-
Mitochondria –
Endoplasmic Reticulum (ER) (rough and smooth) –
Golgi Apparatus-
Lysosomes-

22. Nucleus Nuclear envelope Smooth ER Rough ER Vesicle Golgi apparatus
Plasma
membrane
Transport
vesicle
Lysosome
Figure 3.22

23. Smooth ER
Nuclear
envelope
Rough ER
Ribosomes
Figure 3.18a

24. Rough ER ER membrane Phagosome Plasma mem- brane Vesicle becomes
lysosome
Secretory
vesicle
Golgi
apparatus
Secretion by
exocytosis
Extracellular fluid
Figure 3.20

25. Mitochondria Organelle with shelflike folds called cristae
Provide most of cell’s ATP (enzymes for this process are located on cristae)

26. Other Organelles Non-Membranous structures
Centrioles- involved in cell division
Cytoskeleton- protein filaments that help maintain cell shape, cell movement and in cell division (microtubules)

27. Centrosome matrix
Centrioles
(a)
Microtubules
Figure 3.25a

28. Extensions of the plasma membrane
Cilia are: short, hairlike structures; move substances across cell surfaces
Flagella are: Whiplike, tails that move the entire cell
Microvilli are: fingerlike extensions found on absorptive cells

29. Microvillus
Actin
filaments
Terminal
web
Figure 3.28

30. The Cell Cycle Includes: Interphase
Period from cell formation to cell division
Three sub phases of Interphase:
G1 (gap 1)—growth and metabolism
S (synthetic)—DNA replication
G2 (gap 2)—preparation for division
Cell division (mitotic phase or mitosis)
Consists of four sub phases of mitosis (PMAT) and cytokinesis

31. Mitosis (Cell Division)
Purpose:
Does not occur in:

32. S Growth and DNA synthesis
Growth and final
preparations for
division G1
Growth M
Figure 3.31

33. During the S-phase of Interphase DNA is Replicated
Helicase untwists the double helix and exposes complementary chains
Each nucleotide strand serves as a template for building a new complementary strand
DNA polymerase forms new DNA strand

34. DNA Replication
End result: two DNA molecules formed from the original
This process is called semiconservative replication
After DNA has been replicated the cell progresses into mitosis and cytokinesis

35. Template for synthesis of new strand Free nucleotides DNA polymerase
Chromosome
Leading strand
Lleading and lagging strands are
synthesized in opposite directions
Lagging
strand
Old DNA
Helicase unwinds
the double helix and
Exposes bases
Replication
fork
Adenine
Thymine
Cytosine
DNA polymerase
Old (template) strand
Guanine
Figure 3.32

36. Mitosis and Cytokinesis
Mitosis—four stages of nuclear division:
Prophase-
Metaphase-
Anaphase-
Telophase-
Cytokinesis—division of cytoplasm by cleavage furrow

37. S Growth and DNA synthesisM
Figure 3.31

38. Early mitotic Early Prophase spindle Aster Chromosome Centromere
consisting of two
sister chromatids
Centromere
Early Prophase
Figure 3.33

39. Microtubule Late Prophase Fragments of nuclear envelope Microtubule
Figure 3.33

40. Metaphase
Spindle
Metaphase
plate
Metaphase
Figure 3.33

41. Anaphase
Daughter
chromosomes
Anaphase
Figure 3.33

42. Cytokinesis
Begins during late anaphase
Ring of actin microfilaments contracts to form a cleavage furrow
Two daughter cells are pinched apart, each containing a nucleus identical to the original

43. Telophase and Cytokinesis
Nuclear
envelope
forming
Nucleolus
forming
Contractile
ring at
cleavage
furrow
Telophase and Cytokinesis
Telophase
Figure 3.33