The Central Dogma: DNA to proteins (an animated lecture video)
Summary
TLDREl guion ofrece una introducción a cómo el ADN da forma a nuestras características al codificar proteínas. Se explica el proceso de transcripción y traducción que convierte la información génica en proteínas, así como la estructura molecular de ácidos nucleicos y proteínas. Se utiliza una analogía de imprimir un ensayo para ilustrar la transcripción y traducción. Además, se discuten los distintos niveles de estructura de las proteínas y cómo la secuencia de aminoácidos determina su forma y función. El guion también explora la importancia de las bases nitrogenadas en el ADN y cómo su combinación afecta la forma de las proteínas, con ejemplos como el anemia falciforme causada por una única variación en una proteína.
Takeaways
- 🧬 La genética se basa en el ADN, que actúa como un almacén de información y es capaz de replicarse.
- 📚 El 'Dogma Central' de la biología molecular describe cómo el ADN se convierte en ARN mensajero (mRNA) y luego en proteínas.
- 🔠 El lenguaje genético se basa en cuatro letras: adenina (A), timina (T), citosina (C) y guanina (G).
- 🌐 El ADN es una molécula de doble helix, compuesta por dos cadenas antiparalelas conectadas por pares de bases.
- 🔄 El proceso de transcripción convierte la información del ADN en mRNA, mientras que la traducción convierte el mRNA en proteínas.
- 📝 La estructura primaria de un ARN o ADN es la secuencia de nucleótidos que determina su función.
- 🧬 Las proteínas son polímeros de aminoácidos y su forma tridimensional es crucial para su función.
- 🔗 La estructura secundaria de las proteínas se compone de alfahélices y betaplacas, formadas por enlaces de hidrógeno.
- 🌀 La estructura terciaria de una proteína es el resultado de las interacciones entre los grupos laterales (R) de los aminoácidos.
- 🤝 La estructura cuaternaria se refiere a las proteínas que están compuestas de múltiples polipeptidos.
- 🌐 La variación en una sola base del ADN puede causar cambios significativos en la estructura y función de una proteína, como en el anemia falciforme.
Q & A
¿Qué es la molécula de ADN y qué función cumple en la biología?
-La molécula de ADN, o ácido desoxirribonucleico, es una molécula de información que almacena los datos genéticos en todas las formas de vida. Sirve como plantilla para la síntesis de ARN mensajero (mRNA), que a su vez se traduce en proteínas, esenciales para la función y estructura de las células.
¿Qué es la hipótesis central de la biología molecular y quiénes la propusieron?
-La hipótesis central de la biología molecular fue propuesta por Francis Crick y describe cómo la información de la ADN se transfiere y se traduce en proteínas. Esto implica dos procesos principales: la transcripción, donde la ADN se copia en ARNm, y la traducción, donde el ARNm se traduce en una cadena de aminoácidos para formar proteínas.
¿Cómo se describe el proceso de transcripción en el script?
-El proceso de transcripción es cuando la información del ADN se copia en una molécula de ARN mensajero (mRNA). Este proceso es crucial ya que permite que la información genética se utilice para la síntesis de proteínas en el ribosoma.
¿Qué es el ARN mensajero (mRNA) y qué papel juega en la síntesis de proteínas?
-El ARN mensajero es una molécula que actúa como intermediario entre la ADN y las proteínas. Se genera a partir de una secuencia específica de la ADN y lleva la información codificada para la síntesis de una cadena específica de aminoácidos en el ribosoma.
¿Qué son las proteínas y cómo se relacionan con la función celular?
-Las proteínas son grandes moléculas que sirven como máquinas celulares y participan en una amplia variedad de procesos biológicos, como la señalización celular, la catalización de reacciones químicas y el transporte molecular. Cada proteína tiene una forma tridimensional específica que determina su función.
¿Cómo se describe la estructura primaria de una molécula de ADN?
-La estructura primaria de una molécula de ADN se compone de una secuencia de nucleótidos que determina la información genética. Los nucleótidos están conectados por enlaces fosfodiesteros, formando una doble helix donde las cadenas se encuentran opuestas en sentido antiparalelo.
¿Cuáles son las diferencias entre los nucleótidos de la ADN y los de la RNA?
-Los nucleótidos de la ADN, llamados deoxyribonucleótidos, tienen un azúcar llamado desoxirribosa y cuatro bases nitrogenadas: adenina, timina, citosina y guanina. Mientras tanto, los nucleótidos de la RNA, ribonucleótidos, tienen un azúcar llamado ribosa y una quinta base nitrogenada, uracilo, en lugar de timina.
¿Qué es la estructura secundaria de la ADN y cómo se descubrió?
-La estructura secundaria de la ADN es la forma en que los nucleótidos se organizan en una doble helix. Este descubrimiento fue posible gracias a los estudios de Rosalind Franklin y Maurice Wilkins, quienes usaron cristalografía de rayos X para determinar la forma molecular de la ADN.
¿Cómo se describe la relación entre las bases nitrogenadas en la estructura de la ADN?
-Las bases nitrogenadas en la ADN se unen a través de emparejamiento base por base, donde la adenina (A) se une a la timina (T) y la citosina (C) se une a la guanina (G), manteniendo la información genética y dando forma a la doble helix.
¿Qué son las proteínas y cuántos tipos de aminoácidos hay en las proteínas de los seres vivos?
-Las proteínas son polímeros formados por cadenas de monómeros llamados aminoácidos. Hay más de 500 aminoácidos conocidos, pero solo 20 de ellos son utilizados en las proteínas de los seres vivos.
¿Cómo se relaciona la estructura primaria de una proteína con su función?
-La estructura primaria de una proteína, que es la secuencia de aminoácidos, determina su forma tridimensional, que a su vez define su función. Cualquier cambio en la secuencia de aminoácidos puede afectar la forma y, por lo tanto, la función de la proteína.
Outlines
🧬 Fundamentos de la Bioquímica Molecular
Este párrafo introduce los conceptos básicos de cómo la DNA da forma a las proteínas y explora la estructura molecular de ácidos nucleicos y proteínas. Se menciona que todos los organismos vivos comparten un código genético y que Francis Crick propuso que la DNA es una molécula de almacenamiento informativo capaz de replicarse y transmitir información a través de ARN mensajero (mRNA) para sintetizar proteínas. La analogía de imprimir un ensayo en una computadora se utiliza para explicar el proceso de transcripción y traducción, donde la información de la DNA se transcribe a mRNA y luego se traduce a una cadena específica de aminoácidos en el ribosoma para formar proteínas. Además, se describe la importancia de la forma tridimensional de las proteínas en su función.
🌟 Composición y Estructura de ADN y ARN
Se describe la composición de los ácidos nucleicos, el ADN y el ARN, enfocándose en las diferencias entre ellos. El ADN es una molécula doblamente enroscada compuesta por monómeros llamados deoxirribonucleótidos, que consisten en un grupo fosfato, un azúcar (desoxirribosa) y una de cuatro bases nitrogenadas. Por otro lado, el ARN es una cadena sencilla compuesta por ribonucleótidos, que difieren en el azúcar (ribosa) y una de las bases nitrogenadas (uracilo en lugar de timina). Se explica cómo estos monómeros están conectados mediante enlaces fosfodiester y se proporciona información sobre la direcciónalidad de las cadenas nucleicas, marcada por los extremos 5' y 3'.
🎓 Estructura Secundaria de la DNA y Descubrimientos Clave
Este párrafo detalla la estructura secundaria de la DNA, que fue un hito en la biología del siglo XX. Se menciona el trabajo pionero de Erwin Chargaff, que descubrió la relación de paridad entre las bases, y la hipótesis de Watson y Crick sobre la doble helice de la DNA con base par. Se describe cómo la evidencia de Rosalind Franklin y Maurice Wilkins, mediante cristalografía de rayos X, ayudó a determinar la forma molecular de la DNA. La base par se establece a través de un enlace de hidrógeno, lo que explica la forma y estabilidad de la doble helice.
🛠 Funciones y Estructura de las Proteínas
Se explora el papel de las proteínas como máquinas celulares y su importancia en los procesos biológicos. Las proteínas son polímeros formados por cadenas de monómeros llamados aminoácidos, y solo 20 de los más de 500 aminoácidos conocidos aparecen en las proteínas de los organismos vivos. Se describe la estructura de los aminoácidos y cómo las diferencias en sus grupos laterales (R) afectan la forma y la función de las proteínas. Además, se explica cómo las enzimas catalizan reacciones químicas y cómo las proteínas pueden ser transportadoras moleculares, con la forma tridimensional de las proteínas siendo crucial para su función.
🔍 Estructura de los Aminoácidos y Enfermedades Genéticas
Este párrafo se enfoca en la estructura primaria de las proteínas, donde la secuencia de aminoácidos es crucial para su función. Se utiliza la anemia falciforme como ejemplo de una enfermedad causada por una variación en la estructura primaria de una proteína, específicamente la hemoglobina. Se discute cómo una sustitución de un solo amino ácido puede cambiar drásticamente la forma y la función de una proteína, y cómo esto puede tener consecuencias médicas significativas. También se menciona cómo ciertas condiciones genéticas pueden ser ventajosas en ciertos entornos, como la resistencia a la malaria en el caso de la anemia falciforme.
🌀 Estructuras Secundaria y Terciaria de las Proteínas
Se describen las estructuras secundaria y terciaria de las proteínas, que son esenciales para su forma y función. La estructura secundaria se compone de patrones regulares como el alfa hélice y las hojas plegada, que se forman a través de enlaces de hidrógeno entre los grupos amine y carboxilo de los aminoácidos vecinos. La estructura terciaria se define por cómo los grupos R de los aminoácidos vecinos interactúan, lo que resulta en patrones de plegado específicos que estabilizan la forma tridimensional de la polipeptídica. Además, se mencionan las interacciones entre los grupos R, incluyendo enlaces de hidrógeno, iones y otras fuerzas no covalentes, que contribuyen a la estabilidad y forma de las proteínas.
🧬 Codigo Genético y Procesos de Transcripción y Traducción
Este párrafo concluye el script con una breve mención de los temas que se abordarán en una próxima lección, que incluyen el código genético y los detalles específicos de la transcripción y traducción. Aunque no se proporcionan detalles en este párrafo, se establece el contexto para una discusión más profunda sobre cómo la información genética se convierte en proteínas y cómo se regula este proceso en las células.
Mindmap
Keywords
💡DNA
💡Proteínas
💡Transcripción
💡Traducción
💡ARN mensajero (mRNA)
💡ARN de transferencia (tRNA)
💡Ribosoma
💡Aminoácidos
💡Esfera de Chargaff
💡Doblingue helicoidal
Highlights
DNA como molécula de almacenamiento de información y su capacidad de replicación.
El concepto del 'dogma central' de la biología molecular.
Proceso de transcripción de ADN a ARNmessenger (mRNA).
La traducción de mRNA a proteínas a través del ribosoma y el ARN de transferencia (tRNA).
La estructura tridimensional de las proteínas y su importancia en la función celular.
Analogía entre la transcripción y traducción y el proceso de imprimir un ensayo desde una computadora.
La síntesis de proteínas y su comparación con el lenguaje de nucleótidos y aminoácidos.
La diferencia entre el azúcar de ribosa en ARN y deoxirribosa en ADN y su importancia.
La base de uracilo en ARN en lugar de timina en ADN y su implicación en la diferenciación de los dos tipos de ácidos nucleicos.
La formación de enlaces fosfodiester por condensación en la creación de ácidos nucleicos.
La direcciónalidad de los ácidos nucleicos y su notación secuencial.
La estructura secundaria del ADN y la hipótesis de la doble hélice propuesta por Watson y Crick.
La relación entre la paridad de bases y la estructura del ADN según las reglas de Chargaff.
El papel del ácido ribonucleico en la síntesis activa de proteínas.
La diferencia entre los ácidos nucleicos y las proteínas en términos de sus monómeros y estructura.
La estructura primaria de las proteínas y su relación con la secuencia de aminoácidos.
La anemia falciforme como un ejemplo de cómo una variación en la estructura primaria de una proteína puede causar un trastorno heredado.
La ventaja evolutiva de la anemia falciforme en áreas donde predomina la malaria.
La estructura secundaria de las proteínas, incluyendo las helicias alfa y las hojas plegada beta.
La estructura terciaria de las proteínas y cómo las interacciones de los grupos laterales de los aminoácidos afectan su forma.
La estructura cuaternaria de las proteínas y cómo múltiples polipeptídos pueden interactuar para formar una proteína funcional completa.
Transcripts
[Music]
genetically you are who you are because
of DNA but how does DNA make you you in
this lecture you will learn the basics
of how DNA makes proteins and
investigate the molecular structure of
nucleic acids and proteins
as our understand
biological molecules increased in the
20th century researchers discovered that
all living organisms share a genetic
code in 1956 Francis Crick proposed that
DNA is an informational storage molecule
capable of replicating itself further he
proposed that the information that was
transmitted had to be read by a
manufacturing body within the cell which
puts amino acids together in a specific
sequence ultimately synthesizing a
protein this became known as the central
dogma of molecular biology specifically
DNA serves as a template for the direct
synthesis of a messenger RNA molecule
also known as mRNA in a process known as
transcription secondly mRNA is read at a
ribosome by transfer RNAs also known as
T RNAs which work together to assemble a
specific chain of amino acids which
collectively assembled to generate a
protein in a process known as
translation proteins are the cells
internal machinery similar to parts of a
car each protein has a specific
three-dimensional shape that determines
its function any change in the shape
potentially changes the function of the
protein consider an analogy of
transcription and translation to
printing an essay from a computer once
your essay is complete you store the
document to the hard drive similar to
DNA the hard drive stores information
DNA is a genetic storage molecule data
and computer is stored in a binary
language when it's time to print your
essay you send a command to the computer
to send a message to the printer this
message is akin to mRNA a genetic
messaging molecule similar to the binary
message sent to the printer DNA and RNA
share a chemical language based on
nucleotides hence why the information
exchanged from DNA to RNA is called
transcription an exchange of information
in the same language once the
information is received at the printer
it is translated from a binary language
into a different language a language of
ink analogously mrna is read by the
ribosome and translated into the
language of proteins which are made up
of amino acids thus the process from RNA
to protein
is known as translation translating from
the language of nucleotides to amino
acids the ribosome is akin to the
printer serving as a facility for the
process of translation the molecules
that actually translate the mRNA at the
ribosome are a different kind of RNA
transfer RNA or tRNA in the process of
translation a tRNA reads the mRNA and
links a specific amino acid to a growing
protein for your essay to represent your
idea the ink must be physically arranged
in a specific manner any malfunctioning
the positioning of the letters would not
convey the same idea
similarly proteins have a specific
three-dimensional shape that determines
their function any change in that shape
can potentially alter its function in
our analogy DNA is the stored file in
the hard drive mRNA is the message sent
to the printer the printer is the
ribosome the SI is the protein in the
letters represent the amino acids DNA
indirectly codes for proteins DNA
directly creates all of the intermediate
players of transcription and translation
DNA's day to day function is the
production of RNA molecules messenger
RNA is directly generated by a specific
segment of DNA that segment of DNA is
known as a gene the mRNA travels to a
ribosome which is made up of a protein
and another type of RNA ribosomal RNA or
rRNA at the ribosome the mRNA serves as
a code for the synthesis of protein by
linking specific amino acids in an exact
sequence the overall collection of an
amino acid chain is the protein Dena is
also capable of self replication
necessary for the creation of new cell's
DNA and RNA are biological molecules
known as nucleic acids nucleic acids as
well as proteins are polymers or
molecules made up of a linking chain of
repeating molecules the repeating
components are known as monomers the
monomers when nucleic acids are
nucleotides which are composed of three
components
hey sugar a phosphate group and in that
raja'na space DNA or deoxyribonucleic
acid is a double-stranded nucleic acid
composed of monomers known as
deoxyribonucleotides a
deoxyribonucleotide is made up of three
components a phosphate group the sugar
deoxyribose and one of four nitrogenous
bases while the phosphate group and
deoxyribose are identical in the varying
deoxyribonucleotides
DNA houses for different nitrogenous
bases adenine known as a thymine T
cytosine C and guanine G these four
different nucleotides serve as the
letters of the genetic informational
storage which are transcribed into mRNA
and eventually read at the ribosome to
create a protein all of the biological
diversity on earth in the world is based
on the language of life which only has
four letters
these nitrogenous bases can be placed
into categories based on their shape
thymine and cytosine are each composed
of a single carbon ring skeleton and are
known as parameters whereas adenine and
guanine are composed of two carbon ring
skeletons connected together once
excited in yellow and five sided and
these are known as purines ribonucleic
acids RNAs are single-stranded nucleic
acid polymers made up of the monomers
ribonucleotides ribonucleotides are
identical to deoxyribonucleotides with
two exceptions first ribonucleotides are
made of the sugar ribose which has a
hydroxide at the two prime carbon
whereas deoxyribose has a hydrogen atom
at that location the carbons of ribose
and deoxyribose are notated moving
clockwise from the oxygen ring one prime
to five prime the 1 prime carbon
connects to the nitrogenous base the
atoms attached to the two prime carbon
differ between ribose and deoxyribose
clockwise from the two prime carbon is
the 3 prime carbon followed by the four
prime carbon and the five prime carbon
attaches to the phosphate group so
relative to RNA sugar ribose DNA sugar
deoxyribose lacks an oxygen at the two
prime carbon
hence deoxy ribose that single
difference allows cells to differentiate
between those two nucleotides second
ribonucleotides differ in their suite of
nitrogenous bases 3 ribonucleotides have
the same nitrogenous base as the
deoxyribonucleotides cytosine guanine
and adenine while the fourth
ribonucleotide is composed of the
nitrogenous base uracil
your SIL is very similar to the thymine
except that there is a hydrogen atom at
the three prime location of uracil while
thymine has a methyl or ch3 group there
the phosphate group is identical for
both ribonucleotides and
deoxyribonucleotides nucleotides linked
together in long chains to form a
nucleic acid individual nucleotides are
connected by a covalent bond that forms
between the three prime carbon of the
sugar molecule of one nucleotide and a
phosphorus of the phosphate group of an
adjacent nucleotide in this reaction a
hydrogen atom is removed from the three
prime carbon and hydroxyl is removed
from the phosphate these byproducts
combine forming water and a reaction
known as a condensation reaction
following this reaction the two
nucleotides are connected by a
phosphodiester bond in which a phosphate
group is linked to the five prime carbon
of its original nucleotide and the three
prime carbon of an adjacent nucleotide
adding a third nucleotide the nucleic
acid begins to take shape in this
developing nucleic acid a phosphate is
attached to a sugar which is attached to
a phosphate attached to a sugar and so
on
a phosphodiester linkage involves two of
the three components of a nucleotide a
phosphate and a sugar hanging off to the
side of the nucleic backbone are the
nitrogenous bases this repeating pattern
forms the backbone of nucleic acids one
end of a nucleic acid strand is bound by
a phosphate group while the opposite end
is bound by a sugar giving DNA and RNA
directionality the phosphate group
terminus of a nucleic acid is referred
to as the five prime end of the Strand
as the five prime carbon is the closest
carbon to the end of that molecule the
opposite end of the nucleic backbone
contains a sugar terminus called the
three prime end the sequence of
nucleotides in a nucleic acid is known
as its primary structure scientists have
standardized the notation of nucleic
acids primary structure by listing the
nucleotides from the five prime end to
the three prime end five prime to three
prime for example a segment of RNA
adenine guanine guanine uracil adenine
cytosine would be notated a g g u a c
RNA or ribonucleic acid is a
single-stranded nucleic acid composed of
ribonucleotides the nucleic backbone of
RNA is bound by a phosphate group at the
five prime terminus and ribose a sugar
on the three prime terminus each
ribonucleotide has one of four
nitrogenous bases adenine uracil
cytosine and guanine RNA molecules are
predominantly responsible for actively
synthesizing proteins DNA synthesizes
messenger RNA mRNA which transmits
genetic information from DNA to arrived
ISM the primary sequence of the mRNA
determines the sequence of amino acid
and the resultant protein ribosomes are
hybrid complexes made up of proteins and
a different type of RNA ribosomal RNA
are RNA at the ribosome the mRNA is read
and decoded by a third
RNA transfer RNA or tRNA and eukaryotes
a different are in a small nuclear RNA s
in RNA is involved in modifying the mRNA
after transcription and before
translation DNA is the double-stranded
nucleic acid composed of
deoxyribonucleotides which vary from
ribonucleotides by having a different
five carbon sugar called deoxyribose in
living organisms there are four
deoxyribonucleotides that vary in their
nitrogenous bases adenine thymine
cytosine and guanine once the primary
structure of DNA was solidified the next
question was how are the nucleotides
arranged to create the DNA molecule or
the secondary structure of DNA the
discovery of DNA secondary structure was
one of the most important biological
discoveries of the 20th century one of
the first Clues came from analyses
conducted in the early 1950s by erwin
chargaff comparing the relative
abundances of deoxyribonucleotides
across a variety of organisms chargaff
discovered that the relative abundance
of guanine equal cytosine and the
relative abundance of adenine equals
thymine and what is most interesting
about this is that he found this
relationship across many different
species of organisms chargaff's
discovery was instrumental to scientist
uncovering DNA secondary structure James
Watson and Francis Crick suggested shar
graphs evidence strongly supports base
pairing in DNA in which
deoxyribonucleotides of adenine attached
a thymine and guanine attaches to
cytosine in addition Watson and Crick
hypothesized that base pairing of
deoxyribonucleotides suggests that DNA
was most likely double-stranded
acquire evidence of the actual molecular
shape of DNA rosalind Franklin and
Maurice Wilkins bombarded DNA with
x-rays and analyzed how the radiation
scattered a technique known as x-ray
chromatography analysis of the scatter
plots from this technique allowed them
to measure the distance between atoms
and DNA and they were able to conclude
three things one DNA has a consistent
width to within DNA as a repeating
pattern in three the molecule must be
helical in collaboration with Franklin
and Wilkins
Watson and Crick used the measurements
to define the geometry of the components
of the deoxyribonucleotides creating
physical models of the nucleotides
literally paper cutouts Watson and Crick
tinkered with the different arrangements
of the nucleotides to explain one
chargaff's rule to a consistent width 3
the repeating pattern of the nucleotides
and for the helical shape of the DNA by
arranging base pairing nucleotides a
with T and C with G side-by-side and
strands running in opposite directions
all of the discoveries could be
explained in other words Watson and
Crick suggested that DNA is composed of
two strands one running five prime to
three prime connected to a second strand
running three prime to five prime this
orientation is called anti parallel the
nucleic backbone is composed of
alternating phosphate and deoxyribose
sugar molecules with a phosphate on the
five prime end of the Strand
and a deoxyribose on the three prime end
the strands twist to form a double helix
a spiral bounded on the outside by two
nucleic backbones running in opposite
directions with a nitrogenous bases
facing inward based on chargaff's
findings Watson and Crick determined
that the nitrogenous bases from adjacent
DNA strands connect according to base
pairing the discovery of a consistent
width of the DNA also supported the 80
and CG base pairing while adenine and
guanine are different molecules they're
both purines and approximately the same
size and shape the same is also true of
the perimeters cytosine and thymine
however purines consist of a figure 8
structure which is larger than the
search
Euler structure of the parameters for
the width of DNA to be consistent with
the variety of shapes found in the
nitrogenous bases purines must connect
with perimeters a purine purine base
pairing creates a larger molecule width
and observed and a perimeter perimeter
would be too small if a purine
pyrimidine base pairing explains a
consistent width of a double-stranded
DNA molecule why does guanine a purine
always appear to bind with cytosine a
pyrimidine but never thymine also a
perimeter
why doesn't adenine a purine bind with
cytosine with their physical models of
the nucleotides Watson and Crick deduced
the nitrogenous bases of the adjacent
strands were held together by hydrogen
bonding due to the differential in
electronegativities the hydrogen's of
the nitrogenous bases are partially
positive and the oxygens and nitrogen's
are partially negative hydrogen bonds
form between the partially positive and
partially negative atoms of adjacent
nitrogenous bases investigating the
shapes and interactions of these four
nitrogenous bases they discovered that
guanine and cytosine were geometrically
complements of each other and held
together by three hydrogen bonds well I
hadn't even finding are held together by
two hydrogen bonds essentially the AAT
and ceg pairing are more stable than any
other combination due the
complementarity of the molecular shape
of the hydrogen bond orientation alright
let's take a closer look at proteins
proteins are biological molecules that
serve as cellular machines and living
organisms these large molecules are
specific three-dimensional structures
involved in biological processes such as
cellular signaling catalyzing chemical
reactions molecular transportations as
well as many other functions proteins
are polymers consisting of long chains
of monomers amino acids of the more than
500 amino acids known only 20 appear in
proteins of living organisms
an amino acid is a relatively simple
organic molecule attached to a central
carbon by single covalent bonds are one
a hydrogen atom to an amine group in
three plus three a carboxylic acid group
Co Oh minus and for an R group also
known as a sidechain around pH seven as
in water the amine group of an amino
acid attracts a proton becoming nh3 plus
and acts as a base the carboxyl group is
negatively charged in water due to the
high electronegativity of both oxygens
pulling electrons from the hydrogen and
losing the proton different amino acids
vary in their are group of the protein
building amino acids the R groups can
vary in their size shape and polarity
proteins being made up of chains of
amino acids vary based on the
interactions of the atoms within the
amino acids and water these interactions
dictate the shape of the protein which
in turn determines its function R groups
vary in their polarity nonpolar
molecules have relatively equal
distribution of electrons via covalent
bonding while polar molecules have
unequal distribution of electrons the
unequal distribution of electrons and
polar molecules creates partially
charged atoms polar R groups are
hydrophilic meaning they have an
affinity for water due to the hydrogen
bonds between the partial charges of the
R group and water molecules nonpolar R
groups are repelled by water or
hydrophobic therefore in a chain of
amino acids ones with the polar R groups
will bend towards water and nonpolar R
groups will bend away
affecting the eventual shape of a
protein proteins are polymers of amino
acids chained together by covalent bonds
known as peptide bonds a peptide bond is
a condensation reaction in which the
oxygen ion of the carboxylic acid from
one amino acid is removed becoming
carboxyl and combines with two hydrogen
atoms from the amine group of an
adjacent amino acid to produce water a
covalent bond forms between the two
amino acids when the carbon of the
carboxyl group that lost the OAH during
the condensation reaction combines with
the adjacent nitrogen of another amino
acid that lost the hydrogen atoms
bonding to adjacent amino acids this is
a peptide bond amino acids linked via
peptide bonds forming long-chain
molecules or polypeptides
proteins have four levels of structure
the three-dimensional shape of a protein
determines its function and the shape of
proteins are ultimately dependent upon a
sequence of amino acids coded for by DNA
the unique amino acid sequence is of
proteins primary structure in humans
sickle-cell Denia is an inherited
condition in which blood cells have a
variant of the oxygen binding protein
hemoglobin sickle cell anemia is
considered a disease of the primary
structure of proteins as it is caused by
the variation of a single amino acid in
hemoglobin a valine instead of a
glutamate in the sixth position of a
hundred and forty six amino acid protein
while normal blood cells are rounded
humans with this variant produced sickle
shape red blood cells normal blood cells
are elastic and flow freely through
veins but sick old red blood cells are
rigid and tend to get stuck where the
veins branch this blockage starves
downstream tissues of oxygen resulting
in a host of medical issues including
lower life expectancy the body
identifies the cells when they get stuck
and destroys them healthy red blood
cells typically live between 90 and 120
days whereas sick old red blood cells
have a 10 to 20 day lifespan therefore
people with sickle cell Dyneema must
produce much more blood which is rich in
iron leading to an overall iron
deficiency or anemia interestingly
sickle cell anemia is an evolutionary
advantage in certain circumstances prior
to globalization the highest rates of
sickle cell anemia occur in tropical
Africa the Middle East and India all
malaria dominated areas malaria is a
single-celled eukaryotic parasite
transmitted by mosquitoes that some
considered the most deadly human disease
ever
however in sick old red blood cells the
malaria parasites caused a cell to
rupture before they can successfully
reproduce therefore people with sickle
cell anemia have an evolutionary
advantage over people with normal blood
cells in these areas Nerys absent of
malaria sick old red blood cells are
highly disadvantageous due to the host
of medical conditions associated with
this variant
all of this is caused by a single
different amino acid in one protein an
alteration of the proteins primary
structure when amino acids are grouped
into polypeptide chains neighboring
amino acids can interact via hydrogen
bonding these interactions can form a
regular pattern which increases the
molecular stability of the polypeptide
chain these patterns are known as the
proteins secondary structure and form
either corkscrew shaped structures known
as alpha helix ease or folded ribbon
shaped structures known as beta pleated
sheets recall oxygen has a high
electronegativity while hydrogen has low
electronegativity this differential in
electronegativity results in hydrogen
bonding between neighboring amino acids
within a polypeptide backbone the
hydrogen bonds can occur between amine
groups and carboxyls the partially
negative oxygen of the carboxyl combined
with the hydrogen of the amine groups of
other amino acids in alpha helixes and
beta pleated sheets hydrogen bonding
occurs between amine and carboxyl groups
of different amino acids how the
hydrogen bonding occurs between amino
acids determines which of the two shapes
emerges within a single amino acid of an
alpha helix polypeptide chain the
hydrogen's of the amine groups face the
opposite directions relative to the
oxygens of the carboxyl groups down the
entire alpha helix the hydrogen's of the
amine group face the same direction and
oxygens of the carboxyl group orient in
the opposite direction within the Alpha
helix the hydrogen bonds forms when an
oxygen of the carboxyl faces the
hydrogen of a different amino acid
further down the polypeptide chain this
accumulation of multiple hydrogen bonds
stabilizes the polypeptide chain beta
pleated sheets are also formed by
hydrogen bonding between the amine and
carboxyl groups of different amino acids
however the orientation of these groups
differs in a single amino acid beta
pleated sheet the oxygen of a carboxyl
and the hydrogen of the amine group face
in the same direction in the adjacent
amino acid the oxygen and hydrogen both
face the opposite direction relative to
the first in beta pleated sheets
hydrogen bonds also occur between the
carboxyl oxygen and the a mean hydrogen
between neighboring amino acids however
the orientation of these atoms causes
the structures to bend in a folded
ribbon shape or beta pleated sheet while
the secondary structure of proteins is
determined by the interactions between
amine groups and the carboxyl groups of
neighboring acids tertiary structure is
defined by how the R groups of
neighbouring amino acids interact these
interactions result in a very specific
folding patterns eventually helping to
stabilize the specific three-dimensional
structure of the polypeptide several
types of interactions occur between
neighboring R groups while the hydrogen
bonding determines the secondary
structure of proteins hydrogen bonding
can also occur between R groups of a
polypeptide chain the 20-yard groups of
amino acids are either polar or nonpolar
polar R groups have oxygen or nitrogen
atoms which characteristically have high
electronegativity
due to their high affinity for electrons
these polar R groups tend to bond with
hydrogen atoms of neighboring nonpolar R
groups or the hydrogen of the amine
group of the peptide backbone nonpolar R
groups can also form hydrogen bonds with
the peptide backbone either by
interacting with the oxygen of the
carboxyl group or the nitrogen of the
amine group while hydrogen bonding is
relatively weak the overarching
abundance of these interactions forms
very stable polypeptide structures in
living organisms proteins are surrounded
by water polar R groups are hydrophilic
and been to turn towards water whereas
nonpolar R groups are hydrophobic and
turn away from water
hydrophobic R groups tend to amass in
the internal section of a protein
forming globular masses while hydrogen
bonding is facilitated by the
interactions of partial charges
certain R groups have full charges and
are involved in ionic bonding this
happens when completely positive R
groups form ionic bonds with neighboring
are groups that are completely negative
the overall structure of a fully
functional protein is known as the
quaternary structure most proteins are
composed of several polypeptides a
polypeptide is composed of either a
series of alpha helixes with tertiary
level interactions or a series of beta
pleated sheets with tertiary level
interactions in the next lecture you're
going to learn about the genetic code
and the specifics of transcription and
translation
you
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