1. Anatomy and Physiology, Seventh Edition
Rod R. Seeley Idaho State University
Trent D. Stephens Idaho State University
Philip Tate Phoenix College
Chapter 03
Lecture Outline*
*See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. Chapter 3 Cell Structure and Function

3. Basic Structure of the Cell
Plasma membrane
Cytoplasm containing organelles
Nucleus
Functions of the Cell
Basic unit of life
Protection and support through production and secretion of various kinds of molecules
Movement. Various kinds occur because of specialized proteins produced in the cell
Communication. Cells produce and receive electrical and chemical signals
Cell metabolism and energy release
Inheritance. Each cell contains DNA. Some cells are specialized to gametes for exchange during sexual intercourse

4. Plasma Membrane
Separation of intracellular vs. extracellular materials
Production of charge difference (membrane potential) across the membrane by regulation of intracellular and extracellular ion concentrations
Outside of membrane positively charged compared to inside because of gathering ions along outside and inside
Glycocalyx: combinations of carbohydrates and lipids (glycolipids) and proteins (glycoproteins) on outer surface.
Fluid-mosaic model

5. Membrane Lipids Phospholipids and cholesterol predominate
Phospholipids: bilayer. Polar heads facing water in the interior and exterior of the cell (hydrophilic); nonpolar tails facing each other on the interior of the membrane (hydrophobic)
Cholesterol: interspersed among phospholipids. Amount determines fluid nature of the membrane
Fluid nature provides/allows
Distribution of molecules within the membrane
Phospholipids automatically reassembled if membrane is damaged
Membranes can fuse with each other

6. Membrane Proteins Integral or intrinsic
Extend deeply into membrane, often extending from one surface to the other
Can form channels through the membrane
Peripheral or extrinsic
Attached to integral proteins at either the inner or outer surfaces of the lipid bilayer
Functioning depends on 3-D shape and chemical characteristics. Markers, attachment sites, channels, receptors, enzymes, or carriers.

7. Marker Molecules: Glycoproteins and Glycolipids
Allow cells to identify one another or other molecules
Immunity
Recognition of oocyte by sperm cell
Intercellular communication

8. Attachment Sites Integrins, membrane-bound proteins
Attachment sites to other cells or to extra/intracellular molecules.

9. Channel Proteins (Integral): hydrophilic region faces inward; charge determines molecules that can pass through
Nongated ion channels: always open
Responsible for the permeability of the plasma membrane to ions when the plasma membrane is at rest
Gated ion channels can be open or closed
Ligand gated ion channel: open in response to small molecules that bind to proteins or glycoproteins
Voltage-gated ion channel: open when there is a change in charge across the plasma membrane

10. Receptor Molecules Proteins in membranes with an exposed receptor site
Can attach to specific ligand molecules and act as an intercellular communication system
Ligand can attach only to cells with that specific receptor

11. Receptors Linked to Channel Proteins
Receptor molecules linked to channel proteins
Attachment of receptor-specific ligands (e.g., acetylcholine) to receptors causes change in shape of channel protein
Channel opens or closes
Changes permeability of cell to some substances
Cystic fibrosis: defect in genes causes defect(s) in channel proteins
Drugs used to alter membrane permeability through attachment to channel protein-linked receptors

12. A Receptor Linked to a G Protein
Alter activity on inner surface of plasma membrane
Leads to intracellular chemical signals that affect cell function
Some hormones function in this way

13. Enzymes and Carrier Protein
Enzymes: some act to catalyze reactions at outer/inner surface of plasma membrane. Surface cells of small intestine produce enzymes that digest dipeptides
Carrier proteins: integral proteins move ions from one side of membrane to the other
Have specific binding sites
Protein change shape to transport ions or molecules

14. Movement through the Plasma Membrane
Diffusion
Osmosis
Filtration
Mediated transport mechanisms
Facilitated diffusion
Active transport
Secondary active transport

15. Diffusion
Movement of solutes from an area of higher concentration to lower concentration in solution
Concentration or density gradient: difference between two points
Viscosity: how easily a liquid flows

16. Osmosis
Diffusion of water (solvent) across a selectively permeable membrane. Water moves from an area of low concentration of solute to an area of high concentration of solute
Osmotic pressure: force required to prevent water from moving across a membrane by osmosis

17. Osmosis
Comparative terms used to describe osmotic pressures of solutions
Isosmotic: solutions with the same concentrations of solute particles
Solution with a greater concentration of solute is hyperosmotic
Solution with a lesser concentration of solute is hyposmotic

18. Osmosis and Cells
Important because large volume changes caused by water movement disrupt normal cell function
Cell shrinkage or swelling
Isotonic: cell neither shrinks nor swells
Hypertonic: cell shrinks (crenation)
Hypotonic: cell swells (lysis)

19. Filtration Works like a sieve
Depends on pressure difference on either side of a partition
Moves from side of greater pressure to lower
Example: urine formation in the kidneys. Water and small molecules move through the membrane while large molecules remain in the blood

20. Mediated Transport Mechanisms
Involve carrier proteins or channels in the cell membrane
Characteristics
Specificity for a single type of molecule
Competition among molecules of similar shape
Saturation: rate of transport limited to number of available carrier proteins

21. Saturation of a Carrier Protein
When the concentration of x molecules outside the cell is low, the transport rate is low because it is limited by the number of molecules available to be transported.
When more molecules are present outside the cell, as long as enough carrier proteins are available, more molecules can be transported; thus, the transport rate increases.
The transport rate is limited by the number of carrier proteins and the rate at which each carrier protein can transport solutes. When the number of molecules outside the cell is so large that the carrier proteins are all occupied, the system is saturated and the transport rate cannot increase.
Saturation of a Carrier Protein

22. Mediated Transport Mechanisms
Move large, water soluble molecules or electrically charged molecules across the plasma membrane.
Amino acids and glucose in, manufactured proteins out.
Facilitated diffusion: carrier- or channel-mediated. Passive.
Active transport
Secondary active transport

23. Active Transport
Requires ATP. The use of energy allows the cell to accumulate substances
Rate of transport depends on concentration of substrate and on concentration of ATP
Example: Na/K exchange pump that creates electrical potentials across membranes
Insert 1. Animation: The Sodium/Potassium Pump
2. Insert Fig. 3.20

24. Secondary Active Transport
Ions or molecules move in same (symport) or different (antiport) direction.
Is the movement of glucose a symporter example or an antiporter example?
This example shows cotransport of Na+ and glucose.
A sodium-potassium exchange pump maintains a concentration of Na that is higher outside the cell than inside. Active transport.
Na moves back into the cell by a carrier protein that also moves glucose. The concentration gradient for Na provides the energy required to move glucose against its concentration gradient.
Secondary Active Transport

25. Endocytosis Internalization of substances by formation of a vesicle
Types
Phagocytosis
Pinocytosis
Receptor-mediated endocytosis

26. Pinocytosis and Receptor-Mediated Endocytosis

27. Exocytosis Accumulated vesicle secretions expelled from cell Examples
Secretion of digestive enzymes by pancreas
Secretion of mucous by salivary glands
Secretion of milk by mammary glands

28. Cytoplasm Cellular material outside nucleus but inside plasma membrane
Composed of Cytosol, Cytoskeleton, Cytoplasmic Inclusions, Organelles
Cytosol: fluid portion. Dissolved molecules (ions in water) and colloid (proteins in water)

29. Cytoskeleton
Supports the cell but has to allow for movements like changes in cell shape and movements of cilia
Microtubules: hollow, made of tubulin.
Internal scaffold, transport, cell division
Microfilaments: actin.
Structure, support for microvilli, contractility, movement
Intermediate filaments: mechanical strength
Cytoplasmic inclusions: aggregates of chemicals such as lipid droplets, melanin

30. Organelles Small specialized structures with particular functions
Most have membranes that separate interior of organelles from cytoplasm
Related to specific structure and function of the cell

31. Nucleus Membrane-bound Nucleoplasm, nucleolus and nuclear envelope
Much of the DNA in a cell located here

32. Chromosome Structure Chromatin: DNA complexed with proteins (histones)
During cell division, chromatin condenses into pairs of chromatids called chromosomes. Each pair of chromatids is joined by a centromere

33. Centrioles and Spindle Fibers
Located in centrosome: specialized zone near nucleus
Center of microtubule formation
Before cell division, centrioles divide, move to ends of cell and organize spindle fibers

34. Cilia Appendages projecting from cell surfaces Capable of movement
Moves materials over the cell surface

35. Flagella Similar to cilia but longer Usually only one per cell
Move the cell itself in wave-like fashion
Example: sperm cell

36. Microvilli Extension of plasma membrane Increase the cell surface area
Normally many on each cell
One tenth to one twentieth size of cilia
Do not move

37. Ribosomes Sites of protein synthesis
Composed of a large and a small subunit
Types
Free
Attached (to endoplasmic reticulum)

38. Endoplasmic Reticulum
Types
Rough
Has attached ribosomes
Proteins produced and modified here
Smooth
No attached ribosomes
Manufactures lipids
Cisternae: Interior spaces isolated from rest of cytoplasm

39. Golgi Apparatus
Modification, packaging, distribution of proteins and lipids for secretion or internal use
Flattened membrane sacs stacked on each other

40. Function of Golgi Apparatus

41. Action of Lysosomes

42. Peroxisomes and Proteasomes
Smaller than lysosomes
Contain enzymes to break down fatty acids and amino acids
Hydrogen peroxide is a by-product of breakdown
Proteasomes
Consist of large protein complexes
Include several enzymes that break down and recycle proteins in cell

43. Mitochondria Major site of ATP synthesis Membranes
Cristae: Infoldings of inner membrane
Matrix: Substance located in space formed by inner membrane
Mitochondria increase in number when cell energy requirements increase.
Mitochondria contain DNA that codes for some of the proteins needed for mitochondria production.

44. Overview of Cell Metabolism
Production of ATP necessary for life
ATP production takes place in the cytosol (anaerobic) and mitochondria (aerobic)
Anaerobic does not require oxygen. Results in very little ATP production.
Aerobic requires oxygen. Results in large amount of ATP.

45. Overview of Protein Synthesis
Transcription: DNA used to form RNA
Translation: synthesis of a protein at the ribosomes using mRNA, tRNA and rRNA

46. Transcription

47. Post-transcriptional Modification of mRNA

48. Translation

49. Regulation of Protein Synthesis
All nucleated cells except germ cells have the full complement of DNA.
During development, differentiation occurs and some segments of DNA are turned off in some cells while those segments remain “on” in other cells.
During the lifetime of a cell, the rate of protein synthesis varies depending upon chemical signals that reach the cell.
Example: thyroxine from the thyroid causes cells to increase their metabolic rate. More thyroxine, higher metabolic rate; less thyroxine, lower metabolic rate.

50. Cell Life Cycle Interphase: phase between cell divisions
Replication of DNA
Ongoing normal cell activities
Mitosis: series of events that leads to the production of two cells by division of a mother cell into two daughter cells. Cells are genetically identical.
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis: division of cell cytoplasm

51. Mitosis

52. Cellular Aspects of Aging
Cellular clock. After a certain amount of time or certain number of cell divisions, cells die.
Death genes. Turn on late in life, or sometimes prematurely causing cells to deteriorate and die. Apoptosis.
DNA damage. Telomeres at ends of chromosomes TTAGGG. During replication, nucleotides are lost. Telomerase protects telomeres, enzymes seem to be lost with aging.
Free radicals. DNA mutation caused by free radicals (atoms or molecules with an unpaired electron.
Mitochondrial damage. Mitochondrial DNA may be more sensitive to free radicals. Loss of energy, cell death.