Biochemistry Chapter 1.1 and 1.2 2009
Transcript of Biochemistry Chapter 1.1 and 1.2 2009
chap 1.1 to 1.2
1
chap 1.1 to 1.2 1
自然科學自然科學自然科學自然科學 數學數學數學數學
1.1.1.1.物理科學物理科學物理科學物理科學
requirerequirerequirerequire
((((研究物質及能量研究物質及能量研究物質及能量研究物質及能量))))
地質學
地質學
地質學
地質學
物理學
物理學
物理學
物理學
天文學
天文學
天文學
天文學
化學化學化學化學
跨領域跨領域跨領域跨領域
跨領域跨領域跨領域跨領域
分析化學
分析化學
分析化學
分析化學
物理化學
物理化學
物理化學
物理化學
有機化學
有機化學
有機化學
有機化學
無機化學
無機化學
無機化學
無機化學
物理化學物理化學物理化學物理化學
化學物理化學物理化學物理化學物理
原子分子原子分子原子分子原子分子 生物物理化學生物物理化學生物物理化學生物物理化學
醫學化學醫學化學醫學化學醫學化學
生物化學生物化學生物化學生物化學
2.2.2.2.生物生物生物生物科學科學科學科學
動動動動物學物學物學物學
植植植植物學物學物學物學
微生物學
微生物學
微生物學
微生物學
生態學
生態學
生態學
生態學
遺傳學
遺傳學
遺傳學
遺傳學
生理學
生理學
生理學
生理學
科學的範疇科學的範疇科學的範疇科學的範疇
chap 1.1 to 1.2 2
化學與物理化學與物理化學與物理化學與物理
量子力學量子力學量子力學量子力學(quantum mechanics)
本世紀初本世紀初本世紀初本世紀初,,,,量子力學肇始並宣稱已解決量子力學肇始並宣稱已解決量子力學肇始並宣稱已解決量子力學肇始並宣稱已解決所有的化學問題及一半的物理問題所有的化學問題及一半的物理問題所有的化學問題及一半的物理問題所有的化學問題及一半的物理問題
Schrodinger Equation::::ΗΨΗΨΗΨΗΨ=ΕΨΕΨΕΨΕΨΗΗΗΗ::::Hamiltonian operator
ΨΨΨΨ::::wavefunction
ΕΕΕΕ::::energy
所有的分子性質所有的分子性質所有的分子性質所有的分子性質、、、、化學反應皆可由此化學反應皆可由此化學反應皆可由此化學反應皆可由此Schrodinger Equation推測推測推測推測
然而現今只能成功地推測小分子然而現今只能成功地推測小分子然而現今只能成功地推測小分子然而現今只能成功地推測小分子!!!!!!!!
chap 1.1 to 1.2 3
化學與應用化學化學與應用化學化學與應用化學化學與應用化學
•材料科學材料科學材料科學材料科學::::金屬材料金屬材料金屬材料金屬材料
高分子材料高分子材料高分子材料高分子材料
電子工程電子工程電子工程電子工程::::電子材料電子材料電子材料電子材料
化學工程化學工程化學工程化學工程::::將化學實驗室的製程放大將化學實驗室的製程放大將化學實驗室的製程放大將化學實驗室的製程放大
食品食品食品食品::::食品添加物食品添加物食品添加物食品添加物
生化及藥化產業生化及藥化產業生化及藥化產業生化及藥化產業::::製藥製藥製藥製藥、、、、生物科技生物科技生物科技生物科技
chap 1.1 to 1.2 4
Chapter 1Foundations of Biochemistry
What is Chemistry????This science that tries to understand::::(A)The properties of substances
(B)The changes that substances undergo
The realm of substances::::(A)Natural substances::::e.g.water, air, element, salt...
(B)New compounds created by chemists
e.g.polymer ,nylon...
(C)Chemicals found in living creatures::::e.g.DNAs, proterins, carbohydrates...
Biochemistry tries to understand::::(A)The properties of biomolecules
(B)The changes that biomolecules undergo
chap 1.1 to 1.2 5
1. A high degree of chemicail complexity &
microscopic organization
2. Living organisms extract, transform,and use
“energy” from their environments, usually in the
form of chemical nutrients or sunlight.
3. Defined functions for each of an organism’s
components and regulated interactions among
them
4. Mechanisms for sensing and responding to
alterations in their surrounding
5. Living organisms are capable of “self-assemby”
and self-replication
6. A capacity to change over time by gradual
evolution
The differences between livings and inanimate objects
chap 1.1 to 1.2 6
Biochemistry explains diverse forms of life in
unifying chemical terms::::
Living organisms are remarkably alike at the
cellular and chemical levels
Living organisms are enormously diverse::::
animals、、、、plants
同同同同((((微觀微觀微觀微觀))))異異異異((((巨觀巨觀巨觀巨觀))))
Biochemistry describes::::1.The structures, mechanisms, and chemical processes
shared by all organisms in “molecular terms”
2.Provides organization principles that underlie life
The molecular logic of life
chap 1.1 to 1.2
2
chap 1.1 to 1.2 7
The molecular logic of life
• Consider the properties of living organisms
• Describe a set of principles that characterize
all living organism
Diverse living organisms
share common chemical
features chap 1.1 to 1.2 8
Cells:
1. Plasma membrane::::
defines the periphery of the
cell, separating its contents
from the surroundings.
It is composed of lipid and
protein molecules that form
a thin, tough, pliable,
hydrophobic barrier
around the cell.
1.1 Cellular Foundations
Cells are the structural and functional units of all living organisms
chap 1.1 to 1.2 9
2. Cytoplasm::::
composed of cytosol and
suspended particles
Cytosols::::
enzymes, RNA molecules,
monomeric subunits (amino
acids and nucleotides),
metabolites (small organic
molecules), coenzymes.
suspended particles::::
Supramolecular structures
(like ribosomes and
proteasomes)chap 1.1 to 1.2 10
3. Nucleus or Nucleoid::::
Complete set of genes (genome)
Eukaryotes (真核生物真核生物真核生物真核生物)::::
Cells with nuclear envelopes
Prokaryotes (原核生物原核生物原核生物原核生物)::::without nuclear envelopes
chap 1.1 to 1.2 11
• Animal and plant cells are 5 to 100 µµµµm in diameter
• many bacteria are only 1 to 2 µµµµm long
• the smallest cells::::mycoplasmas (黴漿菌黴漿菌黴漿菌黴漿菌), ~300nm in
diameter, and ~10-14 ml in volume
•Upper limit of cell size::::defined by the rate of diffusion
of solute molecules in aquaous systems
•Lower limit of cell size::::Set by the minimum number of
each type of biomolecule (supramolecules and organelles)
required by the cell (e.g. ribosome,,,,~20nm long)
Cellular Dimensions Are Limited by Oxygen
Diffusion
chap 1.1 to 1.2 12
There Are Three Distinct Domains of Life
1. bacteria (真細菌真細菌真細菌真細菌)inhabits soils, surface waters, tissues.
e.g. E. Coli
2. Archaea (古細菌古細菌古細菌古細菌)inhabits more extreme environments (salt lakes, hot
springs…) e.g. methanococcus jannasch
3.Eukaryotes (真核生物真核生物真核生物真核生物)
chap 1.1 to 1.2
3
chap 1.1 to 1.2 13
prokaryotes包含兩個包含兩個包含兩個包含兩個Groups
1. bacteria(真細菌真細菌真細菌真細菌)
2. archaea (古細菌古細菌古細菌古細菌)
There Are Three Distinct Domains of Life
chap 1.1 to 1.2 14
Organisms can be classified according to their
energy source (sunlight or oxidizable chemicals)
chap 1.1 to 1.2 15
Escherichia coli (大腸大腸大腸大腸桿菌桿菌桿菌桿菌) is the most-studied
prokaryotic cell : 5 µµµµm in length; 2 µµµµm in diameter
ribosomes
membrane 伸伸伸伸
出出出出::::
Pili, flagella
chap 1.1 to 1.2 16
Escherichia coli is the most-studied
prokaryotic cell
•cytoplasm::::Ribosomes (15,000個個個個), enzymes (1000種種種種),
metabolites, and cofactors
•Nucleoid::::A single, circular molecule of DNA. 1000x
length(v.s. cell),,,,packed 成成成成1 µµµµm左右大小左右大小左右大小左右大小•Plasmid::::Few smaller, circular molecule of DNA
Resistance to toxins and antibiotics.Amenable
to manipulation for molecular genetic study
chap 1.1 to 1.2 17
Cell envelopes::::
• Gram-negative bacteria (e.g. E. Coli, cyanobacteria氰氰氰氰
菌菌菌菌, etc)
with outer membrane
peptidoglycan layer
extensive inner membrane system
• Gram-postive bacteria (e.g. Bacillus subbtilis桿菌桿菌桿菌桿菌,
staphylococcus aureus葡萄球菌葡萄球菌葡萄球菌葡萄球菌, archaebacteria, etc.)
without outer membrane
pseudopeptidoglycan layer thicker
inner membrane
Escherichia coli is the most-studied
prokaryotic cell
chap 1.1 to 1.2 18
Cell envelopesGram negative and positive bacteria
chap 1.1 to 1.2
4
chap 1.1 to 1.2 19
Typical Eukaryotic cells
5-100 μμμμm
Eukaryotic Cells Have a Variety of Membranous
Organelles, Which Can Be Isolated for Study
核仁核仁核仁核仁
chap 1.1 to 1.2 20
Plant cell
Eukaryotic Cells Have a Variety of Membranous
Organelles, Which Can Be Isolated for Study
堆疊堆疊堆疊堆疊
葉綠體葉綠體葉綠體葉綠體
澱粉細粒澱粉細粒澱粉細粒澱粉細粒
類囊體類囊體類囊體類囊體
chap 1.1 to 1.2 21
Eukaryotic Cells Have a Variety of Membranous
Organelles, Which Can Be Isolated for Study
chap 1.1 to 1.2 22
Plasma membrane::::Lipid bilayer, contains transporter and receptors
1.Transporters::::proteins that span the membrane and
carry nutrients into the cell and products out
2.Signal receptors::::bind with extra-cellular signaling
molecules (ligands): receptors recognize ligands (can be small
molecules or macromolecules).
e.g. drugs – receptor
virus/bacteria/protein – receptors
antigens - antibody
•Higher plants have cell wall(rigid, protective shell)
formed by cellulose & carbohydrate polymers outside
the plasma membrane
Eukaryotic Cells Have a Variety of Membranous
Organelles
補充
chap 1.1 to 1.2 23
Endoplasmic reticulum(ER)::::
Highly convoluted, three-dimensional network of
membrane-enclosed spaces throughout the cytoplasm
and enclosing a subcellular compartment(the lumen of
the ER)
Rough ER::::
Granular appearance (because ribosomes attached)
Smooth ER::::
1. the site for lipid synthesis
2. metabolism of certain drugs and toxic compound
3. In some tissues(e.g skeletal muscle), storage and
release Ca+2
Cellular Components of Eukaryotic Cells補充
chap 1.1 to 1.2 24endocytosis exocytosis
Rough ER
Golgi complex
smooth ER
補充
chap 1.1 to 1.2
5
chap 1.1 to 1.2 25
Golgi complex::::
• Cis side::::face rough ER
• Medial element
• Trans side::::face plasma membrane
• Proteins will be modified (e.g. adding sulfate, lipid,
carbohydrate groups)
補充
chap 1.1 to 1.2 26Proteins(during the synthesison ribosomes on rough ER)
Inserted into rough ER lumen
Move to the Golgi complex(Proteins will be modified e.g. adding sulfate, lipid, carbohydrate groups)
Bud
1.Targeted for intracellular organelles(e.g. lysosomes)2.Released from the cell byexocytosis3.Incorporate into plasma membrane
Small membrane vesicles(Transport vesicles)
補充
chap 1.1 to 1.2 27
Ribosome::::
• Synthesis of proteins
• Ribosomes attached ER synthesis protein that will
be::::
1.Released from the cell(secretory proteins)
2.Targeted for intracellular organelle(e.g. lysosome)
3.Inserted into nuclear or plasma membranes
• Cytoplasmic ribosomes synthesize proteins that will
remain and function in cytosol
補充
chap 1.1 to 1.2 28
Lysosomes(溶溶溶溶酶酶酶酶體體體體)::::(Only in animal cells)
• contain enzymes, capable of digesting proteins,
polysaccharides, nucleic acids, and lipids.
• act as recycling centers
分解分解分解分解::::complex molecules carried from endocytosis
foreign cell fragment carried from phagocytosis
organelles carried from cell’s cytoplasm
分解成分解成分解成分解成 a.a, monosaccharides, fatty acids.
• pH of lysosomal compartment < 5
enzymes inside are more active in acidic pH
補充
chap 1.1 to 1.2 29
Peroxisomes(過氧化氫過氧化氫過氧化氫過氧化氫酶酶酶酶體體體體):::: contain catalase
2H2O2 2H2O +O2
catalase
Glyoxysomes(乙醛酸循環體乙醛酸循環體乙醛酸循環體乙醛酸循環體)::::
• specialized peroxisomes in certain plant cells
• contain high conc. of enzymes of glyoxylate cycle
fats Carbohydrates
enzymes
Lysosomes, peroxisomes, and glyoxysomes
稱稱稱稱為為為為 microbodies
補充
chap 1.1 to 1.2 30
Vacuoles of plant cells
• plant cells have no lysosomes.
• vacuoles carry similar “degradative” rx
•Tonoplast (the membrane surrounding the vacuole):
regulate the entry of ions, metabolites etc. for
degradation.
•Vacuole (at acidic pH) : degrade and recycle
biomolecules 的的的的enzymes
•Vacuoles also provide physical support to the plant
cell.(因因因因salt含量比含量比含量比含量比cytosol高高高高,,,,產生產生產生產生osmotic pressure or
call turgor pressure 將將將將cell撐起撐起撐起撐起)
•Vacuoles 含染料含染料含染料含染料,,,,會使花果有顏色會使花果有顏色會使花果有顏色會使花果有顏色
補充
chap 1.1 to 1.2
6
chap 1.1 to 1.2 31
Nuclear Pore
Nucleolus
補充
chap 1.1 to 1.2 32
Nucleus::::contains the genome
•Nuclear pores(~~~~90 nm in diameter) associated with
nuclear pore complexes specific transporters
Chromatin(染色質染色質染色質染色質)::::contain DNA and proteins (histones)
bound tightly together
Nucleolus::::在在在在nucleus中中中中,,,,含含含含many copies of the genes
coding ribosomal RNAs (有效地有效地有效地有效地transcribe into ribosomal
RNA!!!!)以備有效產生許多以備有效產生許多以備有效產生許多以備有效產生許多ribosomes!!!!
enzymes for
DNA replication
DNA repair
transcription
RNA processing
to nucleoplasm to cytoplasm
mRNA precursors
and associated proteins
補充
chap 1.1 to 1.2 33
Mitosis::::Nuclear division 有絲分裂有絲分裂有絲分裂有絲分裂
Cytokinesis::::細胞分裂細胞分裂細胞分裂細胞分裂, 胞質分裂胞質分裂胞質分裂胞質分裂(cell division)
Double helix
Nucleosomes (DNA + histones) 1::::1 ratio(重量比重量比重量比重量比)
Chromatin fiber
Chromatid
正在正在正在正在mitosis時時時時,,,,mitotic chromosome
(含含含含two identical chromatid)
106個個個個帶帶帶帶----電電電電 帶帶帶帶++++電的電的電的電的protein
補充
chap 1.1 to 1.2 34
Somatic cells(體細胞體細胞體細胞體細胞)::::
have two copies of each chromosome (diploid,雙倍的雙倍的雙倍的雙倍的)
Gametes(配子配子配子配子) (egg, sperm 生殖細胞生殖細胞生殖細胞生殖細胞):
•have only one copy of each chromosome (haploid, 單倍的單倍的單倍的單倍的)
•有性生殖時與不同性的配子合成有性生殖時與不同性的配子合成有性生殖時與不同性的配子合成有性生殖時與不同性的配子合成 zygate (合子合子合子合子)
DNA of a single diploid human cell
拉長時拉長時拉長時拉長時:~:~:~:~2m
packed時時時時:~:~:~:~200μμμμm
104差別差別差別差別
補充
chap 1.1 to 1.2 35
•1μμμμm in size
•數百數百數百數百~~~~1000個個個個 mitochondria / eukaryotic cell
•含含含含two membrane::::
outer membrane
inner membrane (called cristae)::::
內含物內含物內含物內含物(matrix)::::enzymes involving in the energy-
yielding metabolism.
利用利用利用利用oxidation of organic nutrients
製造製造製造製造ATP
Mitochondria are the power plants of
Aerobic Eukaryotic cells
產生能量產生能量產生能量產生能量
補充
chap 1.1 to 1.2 36
• mitochondria are produced only by division of
previously existing mitochondria.
• mitochondria contains its own DNA, RNA, and
ribosomes.
• mitochondria DNA codes for certain proteins specific
the mitochondria inner membrane.
Mitochondria are the power plants of
Aerobic Eukaryotic cells
補充
chap 1.1 to 1.2
7
chap 1.1 to 1.2 37
Pigment molecules (chlorophyll,葉綠素葉綠素葉綠素葉綠素)
adsorb solar light
make ATP
reduce CO2 to carbohydrates::::
在在在在chloroplast的的的的inner membranes (thylakoid類粒體類粒體類粒體類粒體)
Mitochondria and chloroplast probably evolved from
endosymbiotic bateria (內共生菌內共生菌內共生菌內共生菌).
Chloroplast(葉綠體葉綠體葉綠體葉綠體)::::power plants of plant cells
補充
chap 1.1 to 1.2 38
Cytoskeleton::::
1. actin filaments 6nm
(又叫又叫又叫又叫microfilament 肌動蛋白絲肌動蛋白絲肌動蛋白絲肌動蛋白絲)
2. microtubules 22nm
(微管微管微管微管)
3. intermediate filaments 6-22nm
Cytoskeletal components
Simple protein subunits that polymerize
(location in cells, not rigidly fixed, change during
mitosis, cytokinesis….)
The Cytoplasm is organized by the
cytoskeleton and is highly dynamic
constantly disassemble & reassemble
chap 1.1 to 1.2 39
Microtubules radiating
from the cell centers
Intermediate filaments
Extended throught the
cytoplasm
Actin filaments
bundled together to
form ‘stress fibers’chap 1.1 to 1.2 40
The Cytoplasm is organized by the cytoskeleton and
is highly dynamic
cytoskeletal filaments:
1. Actin filaments (in red)
2. Microtubules (in green)
nucleus (in blue)
(A)
chap 1.1 to 1.2 41
The Cytoplasm is organized by the cytoskeleton and
is highly dynamic(B)
cytoskeletal filaments:
2. Microtubules (in green)
3. Intermediate filaments
( in red)
Chromosome (in blue)
chap 1.1 to 1.2 42
Actin sununits
actin thin filament
parallelly-linked(by fordin)
cross-linked(by filamin)
++++filamin ++++fordin
actin filament
Actin filament
head(binds to actin filament)
tail(binds to the membrane of a
cytoplasmic organelle)
+Myosin
+ ATP
move cytoplasmic organelle or vesicle along the actin
filament (called cytoplasmic streaming)
(1) Actin(肌動蛋白肌動蛋白肌動蛋白肌動蛋白) filament (or microfilament): 6-7nm
chap 1.1 to 1.2
8
chap 1.1 to 1.2 43
*muscle contraction 亦相似亦相似亦相似亦相似
Actin filament+
Myosin+
ATP
muscle contraction
(See figure 5-31)
(2)microtubles (22nm)
subunits::::αααα- & ββββ- tubulin
(throughout the cell, but concentrated around nucleus)
mitosis時時時時, microtubules 會會會會 highly organized & help
the separation of chromosomes (可能可能可能可能provide motive
force)chap 1.1 to 1.2 44
Microtubules+
kinesin
dynesin+
ATP
move organelle along microtubules (以以以以1μμμμm/s移動移動移動移動)
e.g. cilia
flagella beating motion
e.g.
•contraction of muscle
propelling action of cilia
and flagella
• intracellular transport
of organelles
reason::::myosin, kinesin,dynesin
splitting “ATP”
driving sliding motion along
microtubules and
microfilaments
chap 1.1 to 1.2 45
(3)Intermediate filaments (8-10nm)::::provide internal mechanical support for the cell and
to position its organelles
subunit:::: vimentin, keratin,desmin等等等等
e.g. 在在在在endothelial cells(內皮細胞內皮細胞內皮細胞內皮細胞), vimentin
fibers anchor nucleus and fat droplets in
the specific location
• The cytoplasm is crowded, highly organize and dynamic!!
• Cytoplasm::::meshwork of structural fibers (protein fibers)
membrane-bound organelles locate在其中在其中在其中在其中
chap 1.1 to 1.2 46
Endocytosis and Exocytosis carry traffic across
the plasma membrane
Endocytosis(胞飲胞飲胞飲胞飲)::::
A mechanism for transporting components of the
surrounding medium deep into the cytoplasm
Phagocytosis(吞噬吞噬吞噬吞噬)::::
One kind of endocytosis,,,,but carry cell fragment or
other smaller cells
Exocytosis (胞吐胞吐胞吐胞吐)::::
A vesicle in the cytoplasm moves to the inside surface
of the plasm membrane fuses with it, then release the
contents outside the membrane
chap 1.1 to 1.2 47
Cells Build Supramolecular Structures
(A)Protein::::
20種種種種amino acids as building blocks
chap 1.1 to 1.2 48
Cells Build Supramolecular Structures
(B)DNA::::4 possibilities
5’ 3’
chap 1.1 to 1.2
9
chap 1.1 to 1.2 49
+ Fatty acids
(C)Lipids
e.g. Oleate
palmitate
Glycerol
R1
R2
R3
可形成可形成可形成可形成Lipid bilayer
chap 1.1 to 1.2 50
(D)Polysaccharides
Most abundant polysaccharides::::starches, glycogen and
cellulose
Monomeric subunit::::主要為主要為主要為主要為glucose
chap 1.1 to 1.2 51
Structural hierarchy in the molecular organization of
cells
chap 1.1 to 1.2 52Building blocks
Covalent bonds
Macromolecules
Supramolecular assemblies
Organelles
Cell
Amino acids
Nucleotides
Sugars
ProteinsDNARNAPolysaccharides
MembranesRibosomes
Chromatin
Microtubules
Nucleus
Mitochondria
Golgi body
E.R
etc
Non-covalent interactions
Hydrogen bondIonic interaction
Hydrophobic interaction
Structural hierarchy in the molecular organization of cells
Van der Waals forces
chap 1.1 to 1.2 53
Complexity of life Simplicity of “element”world
1.2 Chemical Foundations
Bulk elements::::required in gram(only H, C, N, O, Na,
P, S, Cl, K, Ca, in red) 佔佔佔佔99%99%99%99%
Trace elements::::required much less (colored in yellow)
如如如如Mg, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Se, Mo, Ichap 1.1 to 1.2 54
組成組成組成組成biomolecule的骨架的骨架的骨架的骨架Covalent bonding
O
H
H H
N
H H
C
H
H
H
H
S
H
H P
O
O
H
O
H
O
H
Geometry of
Carbon Bonding
C CBond length
1.54A
chap 1.1 to 1.2
10
chap 1.1 to 1.2 55
Biomolecules Are Compounds of Carbon
with a Variety of Functional Groups
Some common functional
groups of biomolecules
Multi-functionalMany biomolecules
“reactivity (chemical properties) of
biomolecules determined by: (1) functional
groups, (2) 3-dimensional structure
e.g. glycine(R=H)
amino
carboxylchap 1.1 to 1.2 56
chap 1.1 to 1.2 57
• In cytosol:a collection of a thousand of small
molecules (Mr ~ 100 to 500), the central
metabolites in the major pathway in cells.
• including amino acids, nucleotides, sugars, etc.
Polar or charged, in µµµµM to mM
• may contain secondary metabolites (in specific
plant cells that gives plants characteristic scents,
e.g morphine, caffeine etc)
Cells contain a universal set of small
molecules
chap 1.1 to 1.2 58
Macromolecules Are the Major Constituents of Cells
Proteins and nucleic acids are informational
macromolecules
chap 1.1 to 1.2 59
Three-Dimensional Structure Is Described
by Configuration and Conformation
Three ways to represent the structure of Biomolecules::::
(a) Structure Formula
(b) Ball-and-stick model (shows relative bond length and
bond angles
(c) Space-filling model (shows correct 電子密度的電子密度的電子密度的電子密度的bond length)chap 1.1 to 1.2 60
Configuration ----changed only by bond-breaking
Configuration ::::fixed spatial arrangement of atoms in a
molecule
In the presence of (1) double bonds (2) chiral center
configurational isomers
chap 1.1 to 1.2
11
chap 1.1 to 1.2 61
respected to
double bond
geometric
isomers
or cis-trans
chiral centers
enantiomers
diastereomers
stereoisomersR/S form
D/L form
(mirror images)
(non-mirror images)
n 個個個個 Chiral carbons 2n個個個個 stereoisomers
Configurational isomers can be isolated (if use proper
separating methods)有有有有chiral center,,,,表四個不同的表四個不同的表四個不同的表四個不同的atom,,,,C的四周圍電子密度不的四周圍電子密度不的四周圍電子密度不的四周圍電子密度不均勻均勻均勻均勻,,,,使電磁波偏移使電磁波偏移使電磁波偏移使電磁波偏移• Enantiomers will notate the plane of plane-polarized light
• Racemic mixtures(equimolar mixture of two enantiomers)
will not rotate the plane-polarized light chap 1.1 to 1.2 62
Molecular Conformation is Changed by Rotation
about Single Bonds
Molecular conformation
The spatial arrangement
of substituent groups can
be changed by “free
rotation”(w/o any bond
breaking)
See figure 1-21
Potential energy differences of
many conformations of ethane
Energy differences are two
small conformational isomers
can be interconverted
Cannot be separated
chap 1.1 to 1.2 63
Configuration and conformation define biomolecular
Structures
Molecular recognition::::related to their three-dimensional
structures (結構上的互補性結構上的互補性結構上的互補性結構上的互補性, complementarity)
e.g. Hormone molecule with receptor
Antigen with a specific antibody
Substrate with the catalytic site of an enzyme
TAR region of HIV
genome w/arginine
Example: Fig. 1-22
chap 1.1 to 1.2 64
Interactions between Biomolecules are stereospecific
In vivo, biomolecules are usually present in only one
of their chiral forms.
Glucose Only D form
Amino acids Only L isomerse.g.
Enzymes have the ability to distinguish between
isomers. (Enzymes are stereospecific!!!!)
Example: Fig. 1-23
chap 1.1 to 1.2 65
(a)Carvone::::Smell as spearmint (R form)
caraway香菜香菜香菜香菜 (S form)
Smell sensory receptor can
distinguish!!!!
(b) aspartame::::Taste sweet
taste receptor can distinguish!!!!
aspartame