1. Cells: The Living Units
Chapter 3

2. Cells
Basic structural and functional units of life.

3. Plasma Membrane: Structure

4. Plasma Membrane
A.K.A. cell membrane

5. The Fluid Mosaic Model Fluid bilayer of lipids Mostly phospholipids
hydrophilic “head”
Charged
Attracted to water
Located on inner and outer sides of membrane
hydrophobic “tail”
Uncharged (nonpolar)
Avoid water
Center of membrane

6. Lipid Bilayer

7. The Fluid Mosaic Model(cont’d)
Cholesterol
Stabilizes membrane
Glycolipid
With attached sugar group

8. The Fluid Mosaic Model(cont’d)
Protein
Responsible for most of specialized functions of membrane

9. The Fluid Mosaic Model(cont’d)
Protein (cont’d)
Integral
At least some portion of their structure within the lipid bilayer
Most are transmembrane proteins
Have both hydrophilic and hydrophobic regions

10. The Fluid Mosaic Model(cont’d)
Protein(cont’d)
Peripheral
Attached to the outside of plasma membrane (attached to integral)

11. The Fluid Mosaic Model(cont’d)
Protein(cont’d)
Functions of proteins in membrane:
Transport
Enzymatic activity
Receptors
Intercellular joining
Cell to cell recognition
Help maintain cell shape

12. Plasma Membrane

13. The Fluid Mosaic Model(cont’d)
Carbohydrates
Glycocalyx
“sugar covering”
At cell surface
Biological markers

14. Specialization of Plasma Membrane
Microvilli
Extensions of plasma membrane that increase its surface area for absorption

15. Plasma Membrane: Function

16. Membrane Functions Physical barrier
Plays a role in cellular communication
Contains receptors
Regulates materials in and out of the cell
Selectively, or differentially permeable
Passive transport – movement w/o energy input from cell – uses kinetic energy of molecules
Active transport - requires ATP

17. Passive Transport No extra input of energy required Simple Diffusion
From greater to lesser concentration (down a concentration gradient)
Net diffusion ceases when reaches equilibrium

18. Passive Transport Simple Diffusion (cont’d)
Lipid soluble molecules diffuse directly through lipid bilayer.
Most water-soluble particles unable to diffuse –charged small molecules or ions, can pass through channel proteins (selective).

19. Simple Diffusion

20. Passive Transport (cont’d)
Diffusion- Facilitated diffusion
Molecules that can’t dissolve in lipid bilayer or are too large to pass through membranes – pass through with help from carrier proteins (integral).
Carriers are selective

21. Facilitated Diffusion

23. Passive Transport (cont’d)
Diffusion - Osmosis
diffusion of water across a selectively permeable membrane

24. Passive Transport (cont’d)
Diffusion- Osmosis (cont’d)
Hypotonic solutions – net gain of water
Concentration of solute less outside cell

25. Passive Transport (cont’d)
Diffusion- Osmosis (cont’d)
Hypertonic solutions – net loss of water
Concentration of solute more outside cell

26. Passive Transport (cont’d)
Diffusion- Osmosis (cont’d)
Isotonic solutions – neither loss nor gain
Concentration equal on both sides

27. Passive Transport (cont’d)
Filtration
Force - difference in the number of collisions that occur among molecules in different regions
Pressure gradient

28. Active Transport Cell uses ATP to move substances across membrane
Materials unable to pass in desired direction by diffusion
Too large
May not be able to move in the fat core
Move uphill against concentration gradient

29. Active Transport(cont’d)
2 important examples of active transport:
Solute pumping
Vesicular transport

30. Active Transport - Solute Pumping
Depend on carrier proteins and ATP
Carries amino acids, some sugars, and most ions
Example: Sodium-Potassium (Na+-K+) Pump

31. Active Transport – Sodium-Potassium (Na+-K+) Pump
Necessary for normal transmission of nerve impulse
Transport Na+ and K+ ions against concentration gradient

32. Active Transport - Na+-K+ Pump (cont’d)
Binding sites for Na+ and ATP on intracellular surface
Binding sites for K+ on extracellular surface
3 Na+ move outward and 2 K+ move inward for each molecule of ATP hydrolyzed

34. Active Transport - Na+-K+ Pump (cont’d)
For normal intracellular Na+ concentration, the pump rate limited by availability of internal Na+
Increased intracellular Na+ concentration increases pump transport activities

35. Active Transport - Vesicular Transport
Large particles and molecules transported across plasma membrane.
Requires use of ATP
2 major types:
Exocytosis – Moves large particles out of cell
Ejects hormones, secretions, wastes

36. Exocytosis

37. Active Transport - Vesicular Transport (cont’d)
Endocytosis – Brings large particles or substances into cell
Phagocytosis
“cell eating”
Large particles, like bacteria or dead body cells
White blood cells – phagocytes

38. Active Transport - Vesicular Transport (cont’d)
Endocytosis (cont’d)
Pinocytosis
“cell drinking”
liquids
Important in cells that function in absorption

40. Generating and Maintaining Resting Membrane Potential
Voltage that exists across the plasma membrane during resting state of cells (inside more negative)
Determined mainly by concentration gradients of Na+ and K+ and selectively permeable membrane
Greater outward diffusion of K+ leads to voltage at membrane
This maintained by operation of Na+-K+ pump.

41. Internal Cell Structure

42. The Cell

43. The Cytoplasm

44. Cytoplasm
Cellular material between the plasma membrane and the nucleus.
Cytosol – fluid
Organelles – metabolic machinery of cell
Inclusions – nonliving stored nutrients

45. Organelles

46. Mitochondria Cellular aerobic respiration (ATP)
“Powerhouse of the cell”

47. Ribosomes Site of protein synthesis
Some float free, some attached to ER.

48. Endoplasmic Reticulum (ER)
Pathways
Rough ER (RER)
Studded w/ ribosomes
Makes all proteins secreted by cells
Membrane factory
Synthesize cholesterol and phospholipids

49. ER (cont’d) Smooth ER (SER)
Continuation of RER, but no protein synthesis (no ribosomes)
Synthesis of cholesterol
Fat metabolism & transport
Detoxification of drugs
Steroid synthesis
Breakdown of glycogen

51. The Cell

52. Golgi Apparatus
Prepares and packages cellular products (proteins, membranes)

53. Lysosomes Intracellular digestion Worn-out organelles and tissues
Viruses, bacteria, toxins
Breakdown bone to release Ca++ into blood

54. Peroxisomes
Protect cells from destructive effects of free radicals and other toxins

55. The Cell

56. Cytoskeleton Rods running through cytosol Microtubules
Determine overall shape of cell and distribution of organelles
Intermediate filaments
Ropelike
Resist mechanical stress
Microfilaments
Movement of cell parts
Produce change in cell shape

58. Centrioles
Form mitotic spindle

59. Centrioles (cont’d) Basis of cilia and flagella
Cilia – whiplike, cellular extensions
Occurs in large numbers in some cells
Moves substances along cell surface

60. Centrioles (cont’d) Flagella – longer extension of cell surface
Used to propel cell

61. The Cell

62. Nucleus Control center of cell Transmit genetic information
Instructions for protein synthesis
Nuclear membrane (envelope)
Large pores
Regulate the passageway into and out of nucleus
Nucleoli
Site of ribosome synthesis
Chromatin
Proteins and DNA
Threadlike
Become coiled chromosomes during cell division

63. The Nucleus

64. The Environment of
the Cell

65. Extracellular Environment
Cellular products
gases, salts, & food particles
proteins, hormones, & vitamins
secretions of the cell
ECF (extracellular fluid)
syrup like substance of water, products, and other substances
plasma (heart & blood vessels)
interstitial (between the cells)

66. Intracellular Environment
The substance of a cell is called protoplasm, which is composed of:
water, proteins, carbohydrates, nucleic acids, lipids, & electrolytes
plasma (cell) membrane
cytoplasm
nucleus

67. Cell Life Cycle

68. Chromosomes

69. Chromosomes Humans - 46 chromosomes.
Homologous chromosomes or homologues
Same size and shape and carry genes for the same traits
One from each parent
22 homologous pairs plus 2 sex chromosomes

70. Human Karyotype

71. Cell Life Cycle From cell formation to cell reproduction
2 major periods:
Interphase
Cell division

72. Cell Life Cycle

73. Interphase Nondividing phase Cytoplasmic growth DNA replication
Prepare for division

74. Interphase

75. Cell Division Essential for body growth and repair 2 major phases:
Mitosis – division of nucleus
Cytokinesis – division of cytoplasm

76. Mitosis Prophase Chromosomes thicken and become visible
Centrioles move to opposite poles
Nuclear membrane disappears
Spindle fibers begin to develop

77. Prophase

78. Mitosis (cont’d) Metaphase Spindle fibers continue to expand
Chromosomes line up along the central plane

79. Metaphase

80. Mitosis (cont’d) Anaphase
Chromatids are separated by the shrinking of spindle fibers

81. Anaphase

82. Mitosis (cont’d) Telophase Chromatids reach opposite poles
Spindle fibers disappear
Nucleus begins to reappear
Chromosomes uncoil - become chromatin
Cytokinesis begins

83. Telophase

84. Cytokinesis Cytoplasm divides
Offspring approximately equal in size and genetically identical

85. Cytokinesis

86. Meiosis Only in reproductive cells 2 consecutive nuclear divisions
Produce 4 cells, each w/ half the chromosome no. of parent
Each division - stages similar to mitotic division, but with certain differences.

87. Meiosis (cont’d)
Interphase - same

88. Meiosis (cont’d) Prophase I –
Homologous chromosomes line up – tetrad (4 strands) – synapsis
Crossing over

89. Crossing Over

90. Meiosis (cont’d) Metaphase I Tetrads line up at central plane
Random orientation

91. Meiosis (cont’d)
Anaphase I
Each homologous chromosome moves to poles

92. Meiosis (cont’d) Telophase I Nuclear membrane forms
Cytokinesis – 2 cells

93. Meiosis (cont’d)
Brief interphase

94. Meiosis (cont’d) Meiosis II Same course as mitotic division
4 phases PMAT II
End result – 4 cells – half the original chromosome no.

95. Prophase II Metaphase II

96. Anaphase II Telophase II

99. DNA Replication

100. DNA Deoxyribonulceic acid Store and transmit genetic information
Directs protein synthesis

101. DNA Nucleotide 3 parts: sugar molecule called deoxyribose
phosphate group
one of four nitrogenous bases:
adenine (A)
guanine (G)
cytosine (C)
thymine (T)

102. Complementary base pairing
Rules for pairing of nitrogenous bases are:
Cytosine - Guanine
Adenine - Thymine

103. Structure of DNA

104. DNA Replication Helix uncoils
Chains separate by enzymes called helicase.
Each chain - template for a new nucleotide chain, using base-pairing rules.
DNA polymerase, an enzyme, helps form new chains.
Product – 2 new exact copies of the original DNA molecule are produced.

107. Protein Synthesis

108. RNA Ribonucleic acid Contains uracil (U), instead of thymine.
Pairs with adenine.
Ribose sugar
Single stranded

109. RNA (cont’d) 3 types of RNA: Messenger RNA (mRNA)
Carries instructions for making proteins from DNA in the nucleus to ribosomes
Each 3 base sequence (codon) calls for a particular amino acid to be built in the protein.

110. RNA (cont’d) Transfer RNA (tRNA)
Transfers amino acids to ribosome and recognizes codons on mRNA strand specifying its amino acid.

111. RNA (cont’d) Ribosomal RNA (rRNA)
Forms ribosomes, where proteins are made

112. Protein Synthesis Transcription
Instructions for protein synthesis are copied from DNA to mRNA.
Base pairing rules:
C-G
A-U
When complete, mRNA leaves the nucleus and goes to the ribosomes.

114. Protein Synthesis (cont’d)
Translation
Occurs at ribosomes
Reading of mRNA (codon) by tRNA (anticodon)
Genetic Code: Each codon codes for a specific amino acid.

116. Protein Synthesis (cont’d)
Translation (cont’d)
tRNA (anticodon) is complementary
Brings amino acid to ribosome
Pairs with mRNA codons
Peptide bonding of the amino acids into protein.

117. Translation

120. Cells and Aging

121. Theories on Aging Little chemical insults
Free radicals causing damages
Antioxidant Vitamins – may prevent damage
Vit C
Vit E
Presence of toxic chemicals in blood
Temporary absence of needed substances
May be cumulative
Finally upsetting balance in body

122. Theories on Aging (cont’d)
External factors
Genetics – aging clock
Disorders of immune system