bio101 lecture-2 jan 23, 2013.pdf
TRANSCRIPT
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Lecture 2
1. Molecules of Life2. Cells & Biodiversity
BIO101 Introductory Biology
January 23, 2013
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Generic Definition
An organized genetic unit that is capable ofmetabolism,
reproduction and division
http://rds.yahoo.com/_ylt=A0WTb_3YOzlNlCwAv0ejzbkF/SIG=13bq3pq5u/EXP=1295682904/**http:/faculty.biu.ac.il/~gariniy/images/What%20is%20life%20-%20Schrodinger.jpg -
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Proteins (summary)
Amino acids - 20
Peptide bonds
Polymer of amino acids
(hencepolypeptide)
1, 2, 3 and 4 structures 2: a-helix and b-sheet
Different shapes
Function is associated with structure
Most enzymes are proteins
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Carbohydrates
Different forms of glucose
Act as source of energy
Serve as building blocks of other molecules
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Simple sugars(Monosaccharides)
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Disaccharides
Maltose can be hydrolyzed by the human body but not cellobiose!
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Polysaccharides
Starch & glycogen
Glucose polymers witha-linkages
CelluloseGlucose polymers with
b-linkages
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Modified Carbohydrates
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Lipids
Hydrophobic (water hating) Energy reservoirs
Serve as thermal insulation
Repel water on surfaces of skin, fur and feathers
Play important structural role in membranes
Help capture light energy
Act as electrical insulator in nerve cells
Steroids and vitamins
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Simple lipids- Triglycerides (made up of glycerol + fatty acid)
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Fatty acids can be saturated or unsaturated
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Phospholipids
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Carotenoids & Steroids
- Produced from covalent linking and modification of isoprene units
Carotenoids
Pigments that trap light energy
Found in plants and animals
Vitamin-A Rhodoprin
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Steroids
Signal molecules
Similar chemical skeleton
Different types
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Some Lipids are Vitamins
Vitamin-A (precursor of -carotene)
Part of rhodopsin (required for vision)
Vitamin-D
Regulates absorption of calcium from small intestine
Vitamin-E
Protects cells from damaging effects of redox reactions
Vitamin-KInvolved in blood clotting
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Rhodopsin
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Nucleic Acids
Deoxyribonucleic (DNA) & Ribonucleic (RNA)
Basic unit: Nucleotide
Nucleotide has three components:
1. Sugar: Ribose (RNA) or Deoxyribose (DNA)
2. Base:
Purines: Guanine (G) and Adenine (A)
Pyrimidines: Thymine (T), Cytosine (C) & Uracil (U)3. Phosphate
Polymers of nucleotides (polynucleotides)
DNA is a double-helix
Complimentarity (G:C and A:T or A:U pairing)
Polarity (i.e., direction)
Store/carry genetic information
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http://upload.wikimedia.org/wikipedia/commons/8/81/ADN_animation.gif -
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Figure 4-3 Molecular Biology of the Cell( Garland Science 2008)
DNA
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RNA
Mostly single-stranded Uracil (instead of thymine)
Ribose
Sequence
Structure
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Life (7th Ed)
Chapter 2: Small Molecules; p15-34
Chapter 3: Large Molecules; p35-60
Reading
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Cells
Fundamental units of life All organisms are composed of cells
All cells come from pre-existing cells
Require energy
Two types:- Prokaryotic (lacking nucleus)
- Eukaryotic (eu = true karyon= kernel)
Jargon: unicellular; multicellular
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The Scale of Life
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Visualizing
Cells by
Microscopy
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Features of Prokaryotic & Eukaryotic cells
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Prokaryotic Cells - Features
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Flagella and Pili
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Eukaryotic
Cells
Types
Animal cells
Plant cells
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Plant
Cells
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Nucleus- Contains DNA
- DNA is bound
to proteins
- Careful packaging!
- Nucleosomes
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Chromatin and Chromosomes
Heterochromatin Condensed chromosomal regions
Euchromatin Loose chromosomal regions
Endoplasmic Reticulum
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Endoplasmic Reticulum
Inside area Lumen
~1/10 volume of cell
Extensive surface area
Types
1. Rough protein intake & modification; transport
2. Smooth lipid & steroid synthesis; glycogen hydrolysis
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Golgi Apparatus- Cisternae (cis and trans)
- Receives proteins from ER for further modification
- Concentrates and packages proteins to destinations within and outside the cell
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Lysosomes- 1 mM diameter with featureless interior
- Contain digestive enzymes
- Sites where macromoleculesare broken down
- Process phagocytosed (i.e., eaten) stuff
- Primary and secondary
- Acidic environment
- Tay Sachs disease
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Mitochondria
- Powerhouse
- Bacterial origin
- ~1000 / liver cell- Outer & inner membranes
- Cristae
- Respiration
- Have their own ribosomes and DNA
- mtDNA is maternally inherited
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Chloroplasts Contain chlorophyll
Site of photosynthesis
outer & inner membrane
Origin of Mitochondria
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Figure 1-34 Molecular Biology of the Cell, Fifth Edition ( Garland Science 2008)
Origin of Mitochondria
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Peroxisomes
- Degrade hydrogen peroxide
Fractionating
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Fractionating
Cells and Cellular
Components
C t k l t
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Cytoskeleton
- Maintains cell
shape & support
-Ropes
- Framework for
transport
Composed of:
1. Microfilaments
(actin)
2. Intermediate
filaments
(fibrous proteins)
3. Microtublues
(tubulin)
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Molecular MotorsDynein and kinesin
- Move along microtubules
Plant Cell Wall
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Plant Cell Wall
Composed largely
of cellulose
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CellsThis and That
Require free energy
Are surrounded by membranes
Contain informational and non-informational
macromolecules
Need to sense and communicate with their environment Depend on pathways for processing nutrients and waste,
and synthesis/breakdown of small/large molecules
Life-begets-life!
Synthetic cells? (not yet, possible, never)
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Tree of Life!
Microbes Rule!
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B t i C i Diff t Sh
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Bacteria Come in Different Shapes
Spherical
Rod-shaped
Spiral
Some bacteria
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Some bacteria
use flagella
for locomotion
i d i l ll ll
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Gram Stain and Bacterial Cell Wall
Gram stain is used for classifying bacteria!
E S
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ORGANISM TYPE ENERGY SOURCE CARBON SOURCE
Photoautotrophs Light Carbon dioxide(found in A, B & E)
Photoheterotrophs Light Organic compounds(some Bacteria)
Chemolithotrophs Inorganic substances Carbon dioxide(some B; most A)
Chemoheterotrophs Organic compounds Organic compounds(found in A, B & E)
Energy Sources
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Highly diverse group
Autoheterotrophs
Look like corkscrews
Extremely small
Mostly Gram-positive
Some form endospores
Live in hot & acidic places
Some methanogens;
Salt lovers (halophiles)
Charateristics
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Life (7th Ed)
Chapter 4: Cells (p61-84)
Chapter 27: Bacteria & Archaea (p524-540)
Reading