b1.2 proteins Flashcards
1
Q
diagram of generic amino acid
A
amino grp
r grp
carboxyl grp
notes
2
Q
why does R-group differ
A
differs in each of the 20 amino acids
3
Q
polar
A
hydrophilic
4
Q
non-polar
A
hydrophobic
5
Q
formation of dipeptide
A
condensation
6
Q
put water back in
A
hydrolysis
7
Q
diagram of condensation
A
- peptide bond formed
notes
8
Q
source of essential amino acids
A
- must be obtained form the diet
- cannot be synthesised by the body or other amino acids
9
Q
source of non-essential amino acids
A
can be made form other amino acids
10
Q
why does vegan diet require attention
A
ensure essential amino acids are consumed
11
Q
why infinite variety of possible peptide chains
A
- 20 amino acids coded for in the genetic code
- peptide chains can have any number of amino acids
- amino acids can be in any order
12
Q
polypeptide with 4 polypeptide chains
A
haemoglobin
13
Q
protein denaturation by heat
A
increased kinetic energy and stronger vibrations that break intermolecular bonds
14
Q
protein denaturation by pH
A
affects positive and negative charges on the R-groups of the amino acids, causing ionic bonds within protein to break
> changes 3d formation
15
Q
denaturation
A
when the quaternary, tertiary, secondary structures are disturbed by external stress and results in a change in active site and loss of function
16
Q
why is denaturation usually irreversible
A
- very hard to reform the disulphide bond once its broken
water has access to it and water wouldnt want it to fold back to its original shape
17
Q
primary structure
A
- order ofhow the amino acids are composed in the protein
- formed by covalent peptide bonds between adjacent amino acids
- controls all subsequent levels of structure
18
Q
secondary structure
A
- held by h bonds
- alpha helix and beta sheets
19
Q
tertiary structure
A
- 3 dimensional bc of r group interactions
- hydrophobic and hydrophilic side chains affecting the folding of the polypeptide
20
Q
quaternary structure
A
- made of more than one polypeptide chain
- interaction between multiple polypeptides
21
Q
what do R-groups determine
A
properties of assembled polypeptides
22
Q
non-conjugated proteins egs [2]
A
- insulin
- collagen
23
Q
conjugated protein eg [1]
A
haemoglobin
24
Q
why does the structure have to be 3d
A
so hydrophobic elements would be protected inside
25
2 types of protein
fibrous or globular
26
fibrous protein eg
collagen
27
non-conjugated protein
only made up of polypeptides
28
conjugated proteins
has non-polypeptide component
29
polypeptide chains
separate chains held together using disulphide chains between R groups
30
difference between fibrous and globular proteins [5]
fibrous protein- have repeating sequence
shape: elongated and rounded in shape
fibrous proteins: do not (may have extended secondary structure)
globular proteins: tertiary structure
fibrous: insoluble
globular proteins: generally soluble
31
how does amine and carboxyl groups in R-groups become +ve or -ve charged
binding or dissociation of hydrogen ions- can participate in ionic bonding
32
what structure mediates and controls the formation of polypeptides
ribosome
33
how many natural amino acids are synthesised by ribosomes
none
- made into chains by ribosomes but amino acids not produced
34
3 examples of amino acids synthesised by ribosomes
collagen
enzymes
antibodies
35
why is primary structure maintained after denaturation
energy was not enough to break the peptide bonds
36
examples of what is broken during denaturation
disulphide bridges
37
primary (polypeptide) fibrous or globular
neither (will fold to become later)
38
secondary fibrous or globular
can be both
39
tertiary fibrous or globular
can be both
40
quaternary fibrous or globular
can be both
41
what does amino acid sequence determine
the three-dimensional conformation of a protein
42
what does a protein must consist of
single polypeptide or more than one polypeptide linked together
43
what bonds do pairs of cysteines form
disulfide bonds
44
how many molecules of water are required to completely hydrolyse a polypeptide made up of 23 amino acids
22
45
3 eg of fibrous proteins
collagen, keratin, myosin
46
2 eg of globular proteins
enzymes, antibodies
47
characteristics of polar amino acids
- soluble
- stable interactions in water
- strongly hydrophilic
48
characteristics of non-polar amino acids
- soluble
- stable interactions in the lipid bilayer
- hydrophobic
49
where does process of forming dipeptide by condensation occur
ribosomes
50
similarities of fibrous and globular protein [3]
- polypeptides
- chains of amino acids joined by peptide bonds
- have primary structure
51
non polar amino acids interactions w the membrane
retain protein in position in the membrane
52
polar amino acids interaction w the membrane
form hydrophilic channels in the membrane
53
where are polar amino acids on transmembrane proteins
on either side on the transmembrane protein
54
proteins in the membrane + position/egs [8]
1. peripherial proteins: on the surface
2. some integral proteins (transmembrane proteins): extend from one side of the membrane to the other
3. hormone binding sites: insulin
4. enzymes: sucrase
5. pumps for active transport
6. electron carriers: etc
7. neurotransmitters: acetylcholine
8. pigments: in rods/cones
55
how do non-polar amino acids help channel proteins + enzymes [2]
1. help channel proteins + enzymes to be embedded in a membrane
2. non-polar amino acids at active site attract non-polar substrate
56
how do polar amino acids help channel proteins + enzymes [4]
1. retain protein position in membrane
2. lining pore allow polar particles to pass through
3. on surface of enzyme allow it to dissolve in water
4. active site of enzyme attract polar substrates
57
how do polar + non-polar amino acids help enzymes
polar and non-polar amino acids contribute to the specificity of
an enzyme
58
byproduct of condensation
h2o
59
bond formed between sulphur-containing amino acids
disulphide bridges
60
bond between r groups
ionic bond
61
hydrophilic amino acid(s)
glutamic acid
62
hydrophobic amino acid(s)
valine, cysteine, methlonine
63
what bonds can be broken during denaturation
1. hydrogen bonds
2. disulphide bridges
64
ribosomes
form dipeptide by condensation
65
role of glycoproteins
recognise and bind to carbohydrate receptors on adjacent cells
> cell to cell attachment
> intracellular responses in the reacting cells
66
glycoprotein eg
ABO antigens in blood
67
haemoglobin (no. of polypeptides + type of protein)
4 polypeptides
globular protein
68
how to calc no. of peptide bonds
no. of amino acids - no. of disulphide bridges
69
products of condensation
dipeptide + h2o
70
process of protein denaturation by heat
increase in kinetic energy → increase vibration → break bonds
71
why is denaturation mostly irreversible
water has access to it → cant fold back to original shape
72
definition of conjugated proteins
have components other than amino acids
73
non-conjugated proteins eg [2]
collagen
insulin
74
fibrous proteins eg [3]
collagen
keratin
myosin
75
amino acids synthesised by ribosomes
collagen
antibodies
enzymes
76
how are polypeptide chains held tgt
using disulphide bridges between R grps
77
what does the positive or negative dissociation of H ions allow proteins to do
participate in ionic bonding
78
bond between pairs of cystines
disulphide bonds
79
similarities of fibrous + globular proteins
- polypeptides
- amino acids joined by peptide bonds
- have primary structure
80
y can amino acids dissolve in water
polar amino acids on the surface of enzymes
81
function of polar amino proteins inside channel proteins
allow substances that are polar (eg. glucose, sodium ions) to pass through
82
eg(s) of hydrophilic amino acids
glutamic acid
83
eg(s) of hydrophobic amino acids
valine
cystine
methlonine
84
