1. The Cell
Chapter 3

2. Cell Diversity

3. Cell Theory
Cells are the smallest unit to demonstrate the properties of life
Cells are produced from existing cells
Organismal activity depends on cells individually and collectively
Subcellular structures dictate cellular activity

4. Typical Animal Cell Plasma membrane Nucleus Cytoplasm (cytosol)
Outer limiting barrier
Detect chemical signals, and recognize self from not
Nucleus
Control center
Cytoplasm (cytosol)
Intracellular fluid including organelles (excluding)

5. Plasma Membrane’s Role
Physical isolation
Separates intracellular from extracellular environment
Regulates exchange with environment
Selective permeability
Polarity (hydrophobic vs. hydrophilic)
Charge (charged vs. uncharged)
Size (large vs. small)
Ions & nutrient enter, wastes & secretions exit
Allows a concentration gradient to develop
Maintains homeostasis

6. The Fluid Mosaic Model Integral proteins Peripheral proteins
Channels, carriers, and signal transduction
Peripheral proteins
Enzymes, cell-cell recognition, and structure
Phospholipid bilayer (unsaturated)
Hydrophilic ends
Hydrophobic ends
Cholesterol

7. Types of Transport Passive Active Energy not required
Movement ‘down’ a concentration gradient
Specific types
Diffusion
Simple
Facilitated
Osmosis
Filtration
Energy required
Movement against a concentration gradient

8. Simple Diffusion
Movement of MOLECULES ‘down’ their concentration gradient
Small, nonpolar molecules
E.g. O2 in and CO2 out in red blood cells
Each substance is independent
Continues until equilibrium = no NET movement

9. Osmosis Movement of WATER ‘down’ its concentration gradient
Water binds to solute in solution
More solute = less free water = less water available to move
Depends on TOTAL solute concentration
Selective permeability has a role too
water
molecules
glucose
molecules

10. Tonicity Ability of a solution to cause a cell to gain or lose water
Depends on [solutes] that can’t cross PM relative to those in the cell
Hypotonic solutions have a ___?__ [solute] than the cell
Water moves in
Cells lyse
Hypertonic solutions have a ___?__ [solute] than the cell
Water moves out
Cells crenate
Isotonic solutions have ___?__ [solute] as the cell
Water shows no NET movement

11. Other Passive Transport Types
Facilitated diffusion
Filtration
Movement same as simple
Larger, water soluble substances
Glucose, water, & ions
Protein carriers or channels
Water and solutes move ‘down’ a pressure gradient
Water forced, solutes chosen by size
Bulk movement

12. Active Transport
Movement of MOLECULES against their concentration gradient
ATP is energy source
Maintains disequilibrium

13. Vesicular Transport Exocytosis: removes from inside the cell
Golgi vesicles to PM
Endocytosis: brings into the cell
PM pinches in to form vesicles
3 types
Phagocytosis
Pinocytosis
Receptor-mediated

14. Plasma Membrane Specializations
Microvilli
Folds of PM to increase surface area
Membrane Junctions
Tight junctions
Integral proteins fuse the PM’s of 2 cells together = impermeable
E.g. digestive enzymes from blood
Desmosomes
Protein filaments anchor cells in places of high tension
E.g. skin and heart muscle
Gap junctions
Integral proteins form communication channels for ions and small molecules
E.g. heart and smooth muscle

15. Organelles Within Cytosol
Membranous
Nonmembranous
Mitochondria
Produces ATP
Lysosomes
Produced by golgi apparatus
Endoplasmic reticulum (ER)
Rough – proteins to Golgi
Smooth – lipids & carb production; detoxification
Golgi apparatus
Modify and package secretory vesicles
Digestive processes
Peroxisomes
Detoxification
Cytoskeleton
Microtubules, microfilaments, & intermediate filaments
Centrioles
Formed by microtubules, 9 triplets
Microtubules originate in mitosis
Ribosomes
Small and large subunits
Free or attached = dynamic
Cilia
Move substances or organism
Flagella
9 + 2 orientation

16. Nucleus Control center of the cell Nuclear envelope Nucleoli Chromatin
Double membrane continuous with
rough ER
Maintains shape
Nuclear pores for transport; selectively permeable
Nucleoli
Build ribosome subunits
Chromatin
DNA and protein
Coils/condenses to become visible = chromosomes

17. The Cell Cycle (IPMATC)
Interphase about 90%
Chromosomes not visible yet
G1 phase
S phase = DNA replication occurs
G2 phase
Mitotic (M phase) cell division
Mitosis is nuclear division
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis is cytoplasm division
Repeat as needed

18. DNA Replication Helicase DNA polymerase Daughter strands
2 templates formed
DNA polymerase
Complementary base pairing
Daughter strands
Leading strand
Lagging strand
DNA ligase
Semiconservative model
Chromatid  sister chromatids

19. Prophase Sister chromatids condense
Nuclear envelope begins to disappear
Mitotic spindles form

20. Metaphase Sister chromatids line up with centromere on metaphase plate
Microtubules attached to each chromatid at the centromere

21. Anaphase Sister chromatids separate
Single chromosomes move toward opposite ends of the cell
Microtubule ‘tug of war’

22. Telophase Daughter nuclei form Nuclear envelope reforms
Chromosomes begin to uncoil
Mitosis is complete

23. Cytokinesis Division of cytoplasm Cleavage furrow forms
Begins at the end of telophase (late anaphase too)
Cleavage furrow forms
Pinch plasma membrane in 2
2 identical daughter cells formed

24. Meiosis Similar to mitosis
Reduces genetic material of each daughter cell by half
Diploid (2n) adult produces haploid (n) gametes
n = # different chromosomes, paired = homologous
Autosomes (22) and sex chromosome (X or Y)
Event occurs in 2 cycles
Meiosis I
Most variation from mitosis
Meiosis II

25. Protein Synthesis DNA  RNA  protein
Genes instruct, but don’t build
Nucleotides and amino acids are different ‘languages’
RNA connects them
Transcription: same language
Translation: different language

26. Reviewing DNA and RNA DNA RNA Sugar is ribose Sugar is deoxyribose
Has -OH
Bases are A, C, G, and U
Single-stranded
Not confined to nucleus
Lots of processing and modifications
3 types (mRNA, tRNA, rRNA)
Sugar is deoxyribose
Has –H
Bases are A,C, G, and T
Double-stranded helix
Only in nucleus
Modified only by mutations
1 type
Reviewing DNA and RNA

27. Transcription Similar to replication RNA polymerase Steps Processing
Only 1 template used
Occurs in the nucleus
RNA polymerase
Complementary bases added
Steps
Initiation at promoter
Elongation
Terminator sequence reached
Pre-mRNA
Processing
Introns spliced out by spliceosomes
Exons rejoined
mRNA

28. Decoding Genes 4 nucleotide bases to specify 20 amino acids
Genetic instructions are based on triplet code called codons
43 = 64 (plenty)
Demonstrates redundancy, but not ambiguity
Nearly universal across species

29. Translation Ribosome binds mRNA
In cytoplasm
tRNA with complementary anticodon binds
Carries start AA (from chart) into P site
2nd tRNA to A site
Peptide bond forms
Ribosome translocates
New tRNA to A site
P site with 1st & 2nd AA
Stop codon terminates
Polypeptide folds = protein

30. Summary of Protein Synthesis