1. Chapter 03 Lecture Outline*
Rod R. Seeley Idaho State University
Trent D. Stephens Idaho State University
Philip Tate Phoenix College
*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 Biology and Genetics

3. Basic Structure of the Cell
Plasma membrane
Cytoplasm containing organelles
Nucleus

4. Functions of the Cell Cell metabolism and energy use
Synthesis of molecules
Communication. Cells produce and receive electrical and chemical signals
Reproduction and Inheritance. Each cell contains DNA. Some cells are specialized to gametes for exchange during sexual intercourse

5. 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

6. 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

7. 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.

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

9. Attachment Proteins Cadherins – attach cells to other cells
Integrins – integral proteins that attach to extracellular molecule
Sometimes allow communication due to contact with intracellular molecules

10. Transport Proteins
Hydrophilic region faces inward; charge determines molecules that can pass through
Includes channel proteins, carrier proteins, and ATP-powered pumps.

11. Channel Proteins 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 opened or closed by certain stimuli
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

12. Carrier Proteins Also called transporters
Integral proteins move ions from one side of membrane to the other
Have specific binding sites
Protein changes shape to transport ions or molecules
Resumes original shape after transport

13. Carrier Proteins (cont.)
Carrier proteins come in several forms
Uniporters – moves one particle
Symporters – move two particles in the same direction at the same time
Antiporters – move two particles in opposite directions at the same time

14. ATP-Powered 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

15. Receptor Proteins
Proteins or glycoproteins in membranes with an exposed receptor site
Can attach to specific chemical signal molecules and act as an intercellular communication system
Ligand can attach only to cells with that specific receptor

16. Receptors Linked to Channel Proteins
Receptor molecules linked to channel proteins
Attachment of receptor-specific chemical signals (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

17. Receptors Linked to G Protein Complexes
Alter activity on inner surface of plasma membrane
Leads to intracellular chemical signals that affect cell function
Some hormones function in this way

18. Enzymes in the Plasma Membrane
Enzymes: some act to catalyze reactions at outer/inner surface of plasma membrane. Surface cells of small intestine produce enzymes that digest dipeptides

19. Summary of Membrane Proteins

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

21. 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

22. 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

23. 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

24. 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)

25. 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

26. Mediated Transport
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

27. 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.

28. Mediated Transport – Facilitated Diffusion
Facilitated diffusion: carrier- or channel-mediated. Passive.
Move large, water soluble molecules or electrically charged molecules across the plasma membrane.
Amino acids and glucose in, manufactured proteins out.

29. Mediated Transport – Active Transport
ATP-Powered 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

30. Mediated Transport – 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.

31. Endocytosis Internalization of substances by formation of a vesicle
Types
Phagocytosis (shown)
Pinocytosis
Receptor-mediated endocytosis

32. Pinocytosis and Receptor-Mediated Endocytosis

33. 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

34. 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)

35. 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

36. 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

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

38. 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

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

40. 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

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

42. Function of Golgi Apparatus

43. Action of Lysosomes

44. 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

45. 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.

46. 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

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

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

49. 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

50. Genes and Gene Expression
Functional unit of heredity
Types
Structural: serve as template for mRNA, code for amino acid sequences
Regulatory: control which structural genes transcribed in given tissue

51. Genes and Gene Expression
Transcription: DNA used to form RNA
Translation: synthesis of a protein at the ribosomes using mRNA, tRNA and rRNA

52. Transcription The strands of DNA are separated
RNA polymerase binds at a promoter region
RNA polymerase catalyses the formation of a mRNA chain using the DNA as a template and following the rules of complimentary base pairing
A with U
C with G
Transcription ends at a terminator sequence

53. Posttranscription Processing
The mRNA is modified after transcription and before it can leave the nucleus
Intron removal
Guanosine cap added
Poly-A tail added
The mRNA now contains the genetic code that will be used to manufacture a polypeptide

54. Translation Process that occurs on ribosomes
Turns mRNA into a polypeptide
Involves rRNA, tRNA, and mRNA
tRNA anticodons match with mRNA codons, and the rRNA catalyzes the formation of a peptide bond between the amino acids at the opposite end of the tRNA

55. 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.

56. 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

57. Replication of DNA DNA strands separate
The old strands become the templates for the new (complementary) strands to form
Two identical DNA molecules are formed by semiconservative replication

58. Mitosis Interphase – DNA replication occurs Mitosis
Prophase – nuclear envelope disintegrates, chromatin condenses, spindles attach to kinetochore
Metaphase – chromosomes are aligned at the nuclear equator
Anaphase – spindles separate the chromatids, cytokinesis begins
Telophase – chromosomes decondense, nuclear envelope reforms, cytokinesis continues
Cytokinesis – cytoplasmic division, separate process from mitosis

59. Genetics Study of heredity
Explains how certain characteristics are passed on to offspring

60. Mendalian Genetics
Genotype: actual set of alleles a person has for a given trait
Phenotype: person’s appearance
Dominant and recessive alleles
Dominant masks effects of recessive genes
Sex-linked traits: traits affected by genes on sex chromosomes

61. Mendalian Genetics
Homozygous: Having two of the same alleles for a trait.
Homozygous dominant: AA
Homozygous recessive: aa
Heterozygous: Having one dominant and one recessive allele for a trait Aa

62. Chromosomes Genetics: study of heredity
DNA: hereditary material of cells and controls cell activities
Found in discrete sections called chromosomes
Karyotype or display
Autosomal and sex (X or Y)
Contain thousands of genes
Diploid: two copies of chromosomes
Haploid: one copy of chromosomes, only in gametes
Karyotype: map of chromosomes

63. Inheritance of Sex

64. Chromosomes
Homologous: pairs of chromosome where one is from the father and the other is from the mother
Locus: the location of a gene on a chromosome
Allele: different forms of the same gene
Multiple alleles – sometimes alleles come in more than just dominant and recessive forms

65. Gene Dominance
Complete dominance: the dominant allele covers up the recessive allele and is the only allele expressed
Codominance: both alleles are expressed equally at the same time
Incomplete dominance: the dominant allele and the recessive allele both are expressed, with the recessive being at a much lower level

66. Other Types of Gene Expression
Polygenic traits
Determined by expression of multiple genes on different chromosomes
Height, eye and skin color, intelligence

67. Sex-linked Traits Affected by areas of the X and Y chromosome
X-linked traits more often affect males
Y-linked traits only affect males

68. Meiosis and the Transmission of Genes
Meiosis: DNA replication followed by two cell divisions
Homologous pairs are separated
Resulting gametes (egg, sperm) unite to form a zygote
Homologous pairs are reunited
New pairs are a mixture of DNA from two individuals

69. Genetic Disorders
Cancer: tumor resulting from uncontrolled cell divisions
Oncogenes: genes associated with cancer
Tumor suppressor genes
Carcinogens
Genetic susceptibility or predisposition
Genetic disorders: abnormalities in DNA
Congenital disorders
Birth defects not necessarily genetic
Teratogens: agents that cause birth defects
Mutation
Mutagens: agents that cause mutations