1. 3 The Cellular Level of Organization C h a p t e r
PowerPoint® Lecture Slides prepared by Jason LaPres
Lone Star College - North Harris

2. An Introduction to Cells
Cell Theory
Developed from Robert Hooke’s research
Cells are the building blocks of all plants and animals
All cells come from the division of preexisting cells
Cells are the smallest units that perform all vital
physiological functions
Each cell maintains homeostasis at the cellular level
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3. An Introduction to Cells
Sex cells (germ cells)
Reproductive cells
Male sperm
Female oocyte (a cell that develops into an egg)
Somatic cells (soma = body)
All body cells except sex cells
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4. An Introduction to Cells
A cell is surrounded by a watery medium known as the extracellular fluid (interstitial fluid)
Plasma membrane (cell membrane) separates cytoplasm from the extracellular fluid
Cytoplasm
Cytosol = liquid
Intracellular structures collectively known as organelles
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5. An Introduction to Cells
Figure 3–1 The Anatomy of a Model Cell.
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6. Plasma Membrane Functions of the Plasma Membrane Physical isolation
Barrier
Regulates exchange with environment
Ions and nutrients enter
Wastes eliminated and cellular products released
Monitors the environment
Extracellular fluid composition
Chemical signals
Structural support
Anchors cells and tissues
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7. Plasma Membrane Membrane Lipids Double layer of phospholipid molecules
Hydrophilic heads—toward watery environment, both sides
Hydrophobic fatty-acid tails—inside membrane
Barrier to ions and water—soluble compounds
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8. Plasma Membrane Membrane Proteins Integral proteins
Within the membrane
Peripheral proteins
Bound to inner or outer surface of the membrane
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9. Plasma Membrane Membrane Proteins Anchoring proteins (stabilizers)
Attach to inside or outside structures
Recognition proteins (identifiers)
Label cells as normal or abnormal
Enzymes
Catalyze reactions
Receptor proteins
Bind and respond to ligands (ions, hormones)
Carrier proteins
Transport specific solutes through membrane
Channels
Regulate water flow and solutes through membrane
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10. Plasma Membrane Membrane Carbohydrates
Proteoglycans, glycoproteins, and glycolipids
Extend outside cell membrane
Form sticky “sugar coat” (glycocalyx)
Functions of the glycocalyx
Lubrication and protection
Anchoring and locomotion
Specificity in binding (receptors)
Recognition (immune response)
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11. Plasma Membrane Figure 3–2 The Plasma Membrane.
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12. Organelles and the Cytoplasm
All materials inside the cell and outside the nucleus
Cytosol (fluid)
Dissolved materials:
nutrients, ions, proteins, and waste products
High potassium/low sodium
High protein
High carbohydrate/low amino acid and fat
Organelles
Structures with specific functions
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13. Organelles and the Cytoplasm
Nonmembranous organelles
No membrane
Direct contact with cytosol
Includes the cytoskeleton, microvilli, centrioles, cilia, ribosomes, and proteasomes
Membranous organelles
Covered with plasma membrane
Isolated from cytosol
Includes the endoplasmic reticulum (ER), the Golgi apparatus, lysosomes, peroxisomes, and mitochondria
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14. Organelles and the Cytoplasm
Nonmembranous Organelles
The Cytoskeleton — structural proteins for shape and strength
Microfilaments
Intermediate filaments
Microtubules
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15. Organelles and the Cytoplasm
The Cytoskeleton
Microfilaments—thin filaments composed of the protein actin
Provide additional mechanical strength
Interact with proteins for consistency
Pair with thick filaments of myosin for muscle movement
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16. Organelles and the Cytoplasm
The Cytoskeleton
Intermediate filaments—mid-sized between microfilaments and thick filaments
Durable (collagen)
Strengthen cell and maintain shape
Stabilize organelles
Stabilize cell position
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17. Organelles and the Cytoplasm
The Cytoskeleton
Microtubules—large, hollow tubes of tubulin protein
Attach to centrosome
Strengthen cell and anchor organelles
Change cell shape
Move vesicles within cell (kinesin and dynein)
Form spindle apparatus
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18. Organelles and the Cytoplasm
Figure 3–3 The Cytoskeleton.
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19. Organelles and the Cytoplasm
Figure 3–3 The Cytoskeleton.
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20. Organelles and the Cytoplasm
Microvilli
Increase surface area for absorption
Attach to cytoskeleton
Centrioles in the Centrosome
Centrioles form spindle apparatus during cell division
Centrosome: cytoplasm surrounding centriole
Cilia
Small hair-like extensions
Cilia move fluids across the cell surface
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21. Organelles and the Cytoplasm
Figure 3–3 The Cytoskeleton: Microtubules in a Living Cell.
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22. Organelles and the Cytoplasm
Figure 3–4 Centrioles and Cilia.
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23. Organelles and the Cytoplasm
Figure 3–4 Centrioles and Cilia.
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24. Organelles and the Cytoplasm
Ribosomes
Build polypeptides in protein synthesis
Two types
Free ribosomes in cytoplasm:
manufacture proteins for cell
Fixed ribosomes attached to ER:
manufacture proteins for secretion
Proteasomes
Contain enzymes (proteases)
Disassemble damaged proteins for recycling
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25. Organelles and the Cytoplasm
Membranous Organelles
Five types of membranous organelles
Endoplasmic reticulum (ER)
Golgi apparatus
Lysosomes
Peroxisomes
Mitochondria
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26. Organelles and the Cytoplasm
Endoplasmic reticulum (ER)
Endo- = within, plasm = cytoplasm, reticulum = network
Cisternae are storage chambers within membranes
Functions
Synthesis of proteins, carbohydrates, and lipids
Storage of synthesized molecules and materials
Transport of materials within the ER
Detoxification of drugs or toxins
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27. Organelles and the Cytoplasm
Endoplasmic reticulum (ER)
Smooth endoplasmic reticulum (SER)
No ribosomes attached
Synthesizes lipids and carbohydrates:
phospholipids and cholesterol (membranes)
steroid hormones (reproductive system)
glycerides (storage in liver and fat cells)
glycogen (storage in muscles)
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28. Organelles and the Cytoplasm
Endoplasmic reticulum (ER)
Rough endoplasmic reticulum (RER)
Surface covered with ribosomes:
active in protein and glycoprotein synthesis
folds polypeptides protein structures
encloses products in transport vesicles
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29. Organelles and the Cytoplasm
Figure 3–5 The Endoplasmic Reticulum.
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30. Organelles and the Cytoplasm
Figure 3–5 Rough Endoplasmic Reticulum.
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31. Organelles and the Cytoplasm
Membranous Organelles
Golgi apparatus
Vesicles enter forming face and exit maturing face:
secretory vesicles:
modify and package products for exocytosis
membrane renewal vesicles:
add or remove membrane components
lysosomes:
carry enzymes to cytosol
Functions of the Gogi Apparatus
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32. Organelles and the Cytoplasm
Figure 3–6 The Golgi Apparatus.
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33. Organelles and the Cytoplasm
Figure 3–6 The Golgi Apparatus.
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34. Organelles and the Cytoplasm
Figure 3–7 Functions of the Golgi Apparatus.
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35. Organelles and the Cytoplasm
Membranous Organelles
Lysosomes
Powerful enzyme-containing vesicles:
lyso- = dissolve, soma = body
Primary lysosome:
formed by Golgi apparatus and inactive enzymes
Secondary lysosome:
lysosome fused with damaged organelle
digestive enzymes activated
toxic chemicals isolated
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36. Organelles and the Cytoplasm
Functions of Lysosomes
Clean up inside cells
Break down large molecules
Attack bacteria
Recycle damaged organelles
Eject wastes by exocytosis
Autolysis
Auto- = self, lysis = break
Self-destruction of damaged cells:
lysosome membranes break down
digestive enzymes released
cell decomposes
cellular materials recycle
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37. Organelles and the Cytoplasm
Figure 3–8 Lysosome Functions.
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38. Organelles and the Cytoplasm
Membranous Organelles
Peroxisomes
Are enzyme-containing vesicles:
break down fatty acids, organic compounds
produce hydrogen peroxide (H2O2)
replicate by division
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39. Organelles and the Cytoplasm
Membranous Organelles
Membrane flow
A continuous exchange of membrane parts by vesicles:
all membranous organelles (except mitochondria)
allow adaptation and change
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40. Organelles and the Cytoplasm
Membranous Organelles
Mitochondria
Have smooth outer membrane and inner membrane with numerous folds (cristae)
Matrix:
fluid around cristae
Mitochondrion takes chemical energy from food (glucose):
produces energy molecule ATP
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41. Organelles and the Cytoplasm
Mitochondria
Aerobic metabolism (cellular respiration)
Mitochondria use oxygen to break down food and produce ATP
glucose + oxygen + ADP  carbon dioxide + water + ATP
Glycolysis:
glucose to pyruvic acid (in cytosol)
Tricarboxylic acid cycle (TCA cycle):
pyruvic acid to CO2 (in matrix)
Electron transport chain
inner mitochondrial membrane
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42. Organelles and the Cytoplasm
Figure 3–9 Mitochondria.
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43. The Nucleus Nucleus Nuclear envelope Perinuclear space Nuclear pores
Largest organelle
The cell’s control center
Nuclear envelope
Double membrane around the nucleus
Perinuclear space
Between the two layers of the nuclear envelope
Nuclear pores
Communication passages
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44. The Nucleus Figure 3–10 The Nucleus
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45. The Nucleus Figure 3–10 The Nucleus
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46. The Nucleus Contents of the Nucleus DNA Nucleoplasm Nuclear matrix
All information to build and run organisms
Nucleoplasm
Fluid containing ions, enzymes, nucleotides, and some RNA
Nuclear matrix
Support filaments
Nucleoli
Are related to protein production
Are made of RNA, enzymes, and histones
Synthesize rRNA and ribosomal subunits
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47. The Nucleus Contents of the Nucleus Nucleosomes Chromatin Chromosomes
DNA coiled around histones
Chromatin
Loosely coiled DNA (cells not dividing)
Chromosomes
Tightly coiled DNA (cells dividing)
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48. The Nucleus Figure 3–11 The Organization of DNA within the Nucleus.
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49. The Nucleus Information Storage in the Nucleus DNA Gene Genetic code
Instructions for every protein in the body
Gene
DNA instructions for one protein
Genetic code
The chemical language of DNA instructions:
sequence of bases (A, T, C, G)
Triplet code:
3 bases = 1 amino acid
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50. Organelles Review
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51. Organelles Review
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52. Protein Synthesis The Role of Gene Activation in Protein Synthesis
The nucleus contains chromosomes
Chromosomes contain DNA
DNA stores genetic instructions for proteins
Proteins determine cell structure and function
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53. Protein Synthesis Transcription Translation Processing
Copies instructions from DNA to mRNA (in nucleus)
Translation
Ribosome reads code from mRNA (in cytoplasm)
Assembles amino acids into polypeptide chain
Processing
By RER and Golgi apparatus produce protein
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54. Protein Synthesis The Transcription of mRNA
A gene is transcribed to mRNA in three steps
Gene activation
DNA to mRNA
RNA processing
Transcription and Translation
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55. Protein Synthesis The Transcription of mRNA Step 1: Gene activation
Uncoils DNA, removes histones
Start (promoter) and stop codes on DNA mark location of gene:
coding strand is code for protein
template strand used by RNA polymerase molecule
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56. Protein Synthesis The Transcription of mRNA Step 2: DNA to mRNA
Enzyme RNA polymerase transcribes DNA:
binds to promoter (start) sequence
reads DNA code for gene
binds nucleotides to form messenger RNA (mRNA)
mRNA duplicates DNA coding strand, uracil replaces thymine
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57. Protein Synthesis The Transcription of mRNA Step 3: RNA processing
At stop signal, mRNA detaches from DNA molecule:
code is edited (RNA processing)
unnecessary codes (introns) removed
good codes (exons) spliced together
triplet of three nucleotides (codon) represents one amino acid
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58. Protein Synthesis Figure 3–12 mRNA Transcription.
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59. Protein Synthesis Translation mRNA moves
From the nucleus through a nuclear pore
To a ribosome in cytoplasm
Surrounded by amino acids
mRNA binds to ribosomal subunits
tRNA delivers amino acids to mRNA
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60. Protein Synthesis Translation tRNA anticodon binds to mRNA codon
1 mRNA codon translates to 1 amino acid
Enzymes join amino acids with peptide bonds
Polypeptide chain has specific sequence of amino acids
At stop codon, components separate
Protein Synthesis: Sequence of Amino Acids in the Newly Synthesized Polypeptide
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61. Protein Synthesis Figure 3–13 The Process of Translation.
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62. Protein Synthesis Figure 3–13 The Process of Translation.
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63. Protein Synthesis How the Nucleus Controls Cell Structure and Function
Direct control through synthesis of
Structural proteins
Secretions (environmental response)
Indirect control over metabolism through enzymes
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64. Membrane Transport The plasma (cell) membrane is a barrier, but
Nutrients must get in
Products and wastes must get out
Permeability determines what moves in and out of a cell, and a membrane that
Lets nothing in or out is impermeable
Lets anything pass is freely permeable
Restricts movement is selectively permeable
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65. Membrane Transport Plasma membrane is selectively permeable
Allows some materials to move freely
Restricts other materials
Selective permeability restricts materials based on
Size
Electrical charge
Molecular shape
Lipid solubility
Membrane Transport: Fat-and Water-Soluble Molecules
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66. Membrane Transport Transport through a plasma membrane can be
Active (requiring energy and ATP)
Passive (no energy required)
Diffusion (passive)
Carrier-mediated transport (passive or active)
Vesicular transport (active)
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67. Membrane Transport All molecules are constantly in motion
Molecules in solution move randomly
Random motion causes mixing
Concentration is the amount of solute in a solvent
Concentration gradient
More solute in one part of a solvent than another
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68. Diffusion Diffusion is a Function of the Concentration Gradient
Molecules mix randomly
Solute spreads through solvent
Eliminates concentration gradient
Solutes move down a concentration gradient
Membrane Transport: Diffusion
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69. Diffusion Figure 3–14 Diffusion.
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70. Carriers and Vesicles Figure 3–20 Secondary Active Transport.
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