Amino Acids 1 Flashcards

Question

what does polar mean

Answer 1

the R-group carries small charge, both positive and negative (hydrogen bonds)

Answer 2

the R-group is ionisable, creating +ve or -ve charge depending on pH and type of R-group (electrostatic/ionic interaction)

Answer 3

carboxyl & amine

Answer 4

Amphoteric

Answer 5

protonated & unprotonated

Answer 6

how well something mops up protons: a low pKa means it is no good at mopping them up

Answer 7

An Amino Group

Answer 8

A Granido group

Answer 9

delocalised

Answer 10

amino acid R-groups that can gain or lose a proton, making them either positively or negatively charged

Answer 11

the R-group is polarised, meaning electrons are drawn to one end

Answer 12

how hydrophobic something is (so something with a high hydropathy value would be highly hydrophobic i.e. oily)

Answer 13

Isoleucine - a hydrocarbon (highly oily)

Answer 14

- Isoleucine - methionine - leucine - valine

Answer 15

- Tyrosine - Phenylalanine - Tryptophan

Answer 16

It's an Imino Acid - its cyclic - it kinks

Answer 17

- disulphide bridges - Thiol group - Thiol group

Answer 18

1. Hydrogen bonds 2. Ionic (electrostatic) interactions 3. Hydrophobic interactions 3. Van der Waals forces - Individually weak - Collectively strong and specific - Responsible for protein structure, DNA base pairing, and molecular recognition

Answer 19

- a specialised type of polar interaction involving a slightly electropositive H atom interacting with an electronegative acceptor atom - most H bonds occur in proteins between H-O/N atoms - Directional and specific Examples: - DNA base pairing (A–T, G–C) - Protein secondary structure (α-helices, β-sheets)

Answer 20

- Provide specificity (correct base pairing) - Strong enough to stabilise structures - Weak enough to be reversibly broken - Most stable in non-aqueous environments (water competes for H-bonds)

Answer 21

- Attraction between oppositely charged groups; Positive (+) and negative (−) - Long-range compared to other non-covalent forces Examples: - Salt bridges in proteins - DNA (− phosphate backbone) interacting with + proteins

Answer 22

- Distance between charges - pH (affects ionisation of groups) - Salt concentration (ions shield charges) - Solvent (weaker in water)

Answer 23

- Non-polar molecules cluster together to avoid water - Driven by entropy, not direct attraction - Water molecules become more disordered when hydrophobic groups cluster Key idea: Hydrophobic interactions are caused by water exclusion

Answer 24

- Main driving force for protein folding - Forms the hydrophobic core of proteins - Stabilises membranes (lipid bilayers) - Critical for molecular recognition

Answer 25

- Very weak, short-range attractions - Caused by temporary dipoles from electron movement - Occur between all atoms

Answer 26

- Individually weak, but additive - Essential for: > Precise molecular fitting > Protein–ligand interactions - Require close contact between molecules

Answer 27

- Hydrogen bonds: Specific, directional - Electrostatic interactions: Strongest, charge-based - Hydrophobic interactions: Entropy-driven, folding force - Van der Waals: Weakest, short-range, additive

Answer 28

- Allow stability + flexibility - Enable reversible interactions - Permit regulation and dynamic changes - Covalent bonds would be too permanent

Answer 29

- Structure: Cα + NH₃⁺ + COO⁻ + H + R - 20 standard amino acids - Classified by R group properties - pKa and pI determine charge - Side chains control protein structure and function

Answer 30

Building block of proteins General structure: - α-carbon (Cα) - Amino group (–NH₃⁺) - Carboxyl group (–COO⁻) Hydrogen (H) - R group (side chain) → determines properties

Answer 31

Central α-carbon bonded to: - –NH₃⁺ (amino group) - –COO⁻ (carboxyl group) - H - R group Exists as a zwitterion at physiological pH (~7.4)

Answer 32

- All amino acids are chiral except glycine - Proteins use L-amino acids only - Chirality is essential for protein structure and function

Answer 33

- Linked by peptide bonds - Formed by condensation reaction: > –COO⁻ of one AA + –NH₃⁺ of another > Releases H₂O - Produces a polypeptide chain

Answer 34

- Nonpolar (hydrophobic) - Polar, uncharged - Positively charged (basic) - Negatively charged (acidic)

Answer 35

- R groups are hydrocarbon-rich - Avoid water - Found in protein cores Examples: Alanine, Valine, Leucine, Isoleucine, Methionine, Phenylalanine

Answer 36

Positively charged (basic): - Lysine, Arginine, Histidine Negatively charged (acidic): - Aspartate, Glutamate - Form ionic interactions (salt bridges)

Answer 37

- R groups can form hydrogen bonds - Hydrophilic but no net charge Examples: Serine, Threonine, Asparagine, Glutamine, Tyrosine, Cysteine

Answer 38

- Glycine: smallest, flexible, achiral - Proline: rigid, breaks α-helices - Cysteine: forms disulfide bonds - Histidine: pKa near physiological pH → good buffer

Answer 39

- Contain ionisable groups - Can donate or accept protons - Buffering strongest near their pKa values

Answer 40

- pH where net charge of amino acid = 0 - Amino acid exists mainly as a zwitterion - No movement in an electric field

Answer 41

- Most soluble when charged - Least soluble at pI - Charge affects protein folding and interactions

Answer 42

- Hydrophobic AAs → protein core - Polar/charged AAs → surface - Side chains drive: > Hydrogen bonds > Ionic interactions > Hydrophobic packing > Disulfide bonds

Answer 43

- A covalent bond linking two amino acids - Forms between: > Carboxyl group (–COO⁻) of one amino acid > Amino group (–NH₃⁺) of the next - Creates a polypeptide chain

Answer 44

- Formed by a condensation reaction - –OH (carboxyl) + –H (amino) → H₂O released - Reaction is catalysed by the ribosome during translation

Answer 45

- The Linkage is: –C(=O)–NH– - Called an amide bond - Connects the carbonyl carbon of one amino acid to the nitrogen of the next

Answer 46

- Always written N-terminus → C-terminus - N-terminus: free –NH₃⁺ - C-terminus: free –COO⁻ - Peptide bonds link amino acids in one direction only

Answer 47

- Peptide bond has partial double-bond character - Due to resonance between C=O and C–N - Prevents free rotation around the peptide bond

Answer 48

Cannot rotate: - peptide (C–N) bond Can rotate: - φ (phi): N–Cα bond - ψ (psi): Cα–C bond These rotations allow protein folding

Answer 49

- Repeating unit: –N–Cα–C(=O)– - Backbone is the same in all proteins - R groups project outward and determine properties

Answer 50

- Peptide bond is usually trans - Minimises steric clash between R groups - Cis is rare (more common with proline)

Answer 51

- C=O → hydrogen bond acceptor - N–H → hydrogen bond donor - Enables formation of: α-helices & β-sheets

Answer 52

- Backbone C=O and N–H form regular hydrogen bonds - Drives formation of: > α-helices > β-pleated sheets - Independent of R groups

Answer 53

- Partial double-bond character - Resonance stabilisation - Requires enzymes (proteases) for hydrolysis in cells

Answer 54

- By hydrolysis (addition of water) - Catalysed by: > Digestive enzymes (e.g. pepsin, trypsin) > Cellular proteases

Answer 55

- Dipeptide: 2 amino acids, 1 peptide bond - Tripeptide: 3 amino acids - Polypeptide: many amino acids - A protein = one or more polypeptides

Answer 56

- Covalent amide bond: –C(=O)–NH– - Formed by condensation - Rigid and planar - Backbone = repeating unit - Direction: N → C - Enables protein folding via H-bonding

Answer 57

the magnitude of the electrostatic force between two point electric charges is directly proportional to the product of the magnitudes of each charge and inversely proportional to the square distance of the distance between the charges

Answer 58

ATPase: - enzymes that hydrolyse ATP are called ATPases - the lysine amino acid R-group bonds ionically to Adenosine Triphosphate

Answer 59

- INCREASE

Amino Acids 1 Flashcards

(85 cards)