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Bioquímica I > Tema 2: aminoacidos > Flashcards

Tema 2: aminoacidos Flashcards

(56 cards)

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1
Q

¿Qué son las proteínas?

A

Son polímeros lineales de aminoácidos.

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2
Q

Define un aminoácido.

A

Es una molécula biológica con 3 grupos funcionales: grupo amino, grupo ácido y cadena lateral, unida a un carbono alfa.

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3
Q

¿Cuántos aminoácidos conforman las proteínas en los seres vivos?

A

20 aminoácidos.

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4
Q

Clasifica los aminoácidos en grupos.

A
  • Alifáticos (6)
  • Aromáticos (3)
  • Hidroxilados (2)
  • Azufrados (2)
  • Básicos (3)
  • Ácidos y amidas (2 y 2)
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5
Q

Menciona los aminoácidos alifáticos.

A
  • Glicina (Gly, G)
  • Alanina (Ala, A)
  • Valina (Val, V)
  • Leucina (Leu, L)
  • Isoleucina (Ile, I)
  • Prolina (Pro, P)
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6
Q

¿Cómo se comportan los aminoácidos en diferentes pH?

A
  • pH=1: COOH y NH3+
  • pH=7: COO- y NH3+
  • pH=11: COO- y NH2
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7
Q

¿Qué relación existe entre la fuerza de un ácido, su Ka y su pKa?

A

Cuanto mayor es la fuerza de un ácido, mayor es su Ka y menor es su pKa.

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8
Q

¿Qué indica la ecuación de Henderson-Hasselbalch?

A

Permite conocer la proporción de base y ácido en una disolución.
*pH=pKa –> el ácido está disociado un 50%
*pH<pKa –> mayor parte del ácido sin disociar
*pH>pKa –> mayor parte del ácido disociado

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9
Q

¿Qué es el punto isoeléctrico (pI)?

A

Es el valor de pH para el cual la molécula presenta carga neutra.

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10
Q

¿Qué mide la hidropatía en aminoácidos?

A

Es una medida de la hidrofobicidad e hidrofilicidad.

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11
Q

Clasifica los aminoácidos según su polaridad.

A
  • Polares con carga: His, Lis, Arg (positivos, básicos), Asp, Glu (negativos, ácidos)
  • Polares sin carga: Ser, Thr, Cys, Asn, Gln, Tyr
  • Apolares: Gly, Ala, Val, Leu, Ile, Pro, Phe, Trp, Met (alifáticos y aromáticos)
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12
Q

¿Qué es la estereoisomería?

A

Es la disposición de los átomos en una molécula con un carbono quiral.

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13
Q

¿Qué son los enlaces peptídicos?

A

Se forman cuando el grupo amino de un aminoácido reacciona con el grupo carbonilo de otro, desprendiendo una molécula de agua.

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14
Q

¿Cómo se describe la estructura primaria de una proteína?

A

Es la secuencia de aminoácidos que conforman la cadena.

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15
Q

Define estructura secundaria en proteínas.

A

Describe la distribución espacial local de la cadena principal sin tener en cuenta las cadenas laterales.

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16
Q

¿Qué caracteriza a la hélice alfa?

A
  • Elevación de 0.15 nm
  • Repite cada 10 vueltas y 36 aminoácidos
  • Ángulos fi y psi: -57º y -47º respectivamente
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17
Q

¿Qué son las estructuras supersecundarias?

A

Son combinaciones de estructuras secundarias que aparecen en diferentes proteínas, que suelen estar relacionadas con una función

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18
Q

¿Qué indica la longitud de la cadena lateral unida al carbono alfa?

A

Limita el movimiento y plegamiento de los planos.

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19
Q

¿Qué es un ángulo diedro?

A

Es un ángulo que forma dos planos.

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20
Q

¿Qué es el diagrama de Ramachandran?

A

Establece que no todos los valores de ángulos fi y psi son posibles debido a choques estéricos.

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21
Q

¿Cómo se clasifican las proteínas?

A
  • Globulares: solubles en agua, compactas
  • Fibrosas: soporte estructural, largas hebras u hojas
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22
Q

What stabilizes the structure of proteins?

A

Hydrogen bonds between amino and carbonyl groups of the backbone

Hydrogen bonds are crucial for maintaining the secondary structure of proteins.

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23
Q

What does ‘p = n x h’ represent in the context of helices?

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A

p: pitch of the helix; n: number of residues per turn; h: rise

This equation relates the spatial arrangement of residues in a helical structure.

24
Q

Define the 3’613 helix.

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A

A helix where the carbonyl group of a residue forms a hydrogen bond with the amino group of a residue 4 positions ahead, forming a cycle of 13 atoms

It is the most stable helix due to its wider structure.

25
What is a 310 helix?
A helix formed when the hydrogen bond is with the amino group of the residue 3 positions ahead, creating a cycle of 10 atoms with 3 residues per turn.
26
What characterizes bipolar helices?
Distribution of polar residues on one side of the helix ## Footnote This structure allows for functional specialization despite non-consecutive residues in primary structure.
27
What is a leucine zipper?
A supersecondary structure that dimerizes through hydrophobic interactions between parallel helices formed by repeating leucines every 7 residues.
28
Describe the beta conformation in proteins.
The polypeptide backbone is extended in a zig-zag pattern with a separation of 6.5-7 Å between consecutive residues.
29
What are the angles phi (φ) and psi (ψ) for parallel and antiparallel beta sheets?
Parallel: φ=-119º, ψ=113º; Antiparallel: φ=-139º, ψ=135º.
30
Which is more stable: parallel or antiparallel beta sheets?
Antiparallel beta sheets ## Footnote Antiparallel sheets have better hydrogen bond alignment, enhancing stability.
31
What are beta turns?
Changes in direction of the polypeptide chain involving approximately 4 residues, with specific types based on residue positions.
32
What defines a Type I beta turn?
Any amino acid except Proline at position 3.
33
What defines a Type II beta turn?
Glycine at position 2 and Proline at position 3.
34
What are supersecondary structures?
Combinations of secondary structures appearing in unrelated proteins, usually linked to function.
35
What is the tertiary structure of a protein?
The three-dimensional arrangement of all atoms in a protein, allowing interactions between distant residues.
36
What is the quaternary structure of a protein?
The arrangement of multiple polypeptide chains into a biologically active protein.
37
Classify proteins based on structure.
Fibrous proteins provide structural support; Globular proteins are soluble and compact.
38
What is a modular structure in proteins?
Proteins composed of repeated basic domains fulfilling functional requirements.
39
What is alpha-keratin?
Structural protein with two right-handed alpha helices forming a left-handed superhelix.
40
Describe fibroin.
Protein made of antiparallel beta sheets with a sequence rich in glycine, allowing high packing density.
41
What is collagen?
Most abundant protein in mammals, comprising 3 polypeptide chains with a unique collagen helix structure.
42
What stabilizes collagen structures?
Hydroxylation of proline and glycine residues, forming hydrogen bonds for stability.
43
Define the hydrophobic effect in protein structure.
Folding of the protein to keep hydrophobic residues away from water.
44
What are coordination bonds in proteins?
Metal ions binding to amino acids through coordination, forming specific structures.
45
What are the roles of electrostatic interactions in proteins?
Interactions between charged amino acids that help maintain protein structure.
46
What do disulfide bridges involve?
Cysteine amino acids linking via sulfur chains.
47
How are angles phi (φ) and psi (ψ) calculated?
φ: nitrogen covers alpha carbon; ψ: alpha carbon covers carbonyl carbon.
48
Menciona los aminoácidos aromáticos
Fenilalanina (Phe, F), tirosina (Tyr, Y), triptófano (Trp, W)
49
Menciona los aminoácidos hidroxilados
Serina (Ser, S), Treonina (Thr, T)
50
Menciona los aminoácidos azufrados
Cisteína (Cys, C), Meteonina (Met, M)
51
Menciona los aminoácidos básicos
Histidina (His, H), Lisina (Lys, K), Arginina (Arg, R)
52
Menciona los aminoácidos ácidos
Aspartato (Asp, D), Glutamato (Glu, E)
53
Menciona los aminoácidos amidas
Asparragina (Asn, N), Glutamina (Gln, Q)
54
Qué aminoácido puede generar la descarboxilación del glutamato?
el Gamma-aminobutírico, y es un neurotransmisor
55
Qué características tienen las cadenas laterales ácidas?
Tienen grupos que pueden donar protones, no tienen carga cuando están protonadas, y tienen carga negativa cuando están desprotonadas
56
Qué características tienen las cadenas laterales básicas?
Tienen carga positiva cuando están protonados y carga neutra cuando están desprotonados

Bioquímica I (6 decks)

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